Cashew gum hydrogel as an alternative to minimize the effect of drought stress on soybean.

The use of hydrogels helpsthe production of plants in drought-stress environments. Thus, this work evaluated using different hydrogels to minimize drought stress in soybean cultivation. The treatments employed two different hydrogels, one already commercialized and the other produced with cashew gum (Anacardium occidentale), five levels (0, 30, 60, 120, and 240 mg pot-1) of the hydrogels, and two levels of drought stress in sandy soil. The growth and yield of soybeans and the levels of macro- and micronutrients in soybeans were evaluated.growth. The use of CG hydrogel promoted 12% increase in protein content in the seeds in the when soybean plants were subjected to drought stress. The levels of 30 mg pot-1, corresponding to 7.5 kg ha-1, improved the 'morphological and productive parametersof the soybeans. The increasing levels of hydrogel promoted the increase in P, K, Ca, Mg, and Fe and reduced S and Cu on an exponential scale. The use of cashew gum hydrogel increased the K and Ca contents in soybean seeds compared to commercial hydrogel.

Selection of forage grasses for cultivation under water-limited conditions using Manhattan distance and TOPSIS.

Extreme weather events, such as severe droughts, pose a threat to the sustainability of beef cattle by limiting the growth and development of forage plants and reducing the available pasture for animals. Thus, the search for forage species that are more tolerant and adapted to soil water deficit conditions is an important strategy to improve food supply. In this study, we propose utilizing the mathematical concept of the Manhattan distance to assess the variations in the morphological variables of tropical forage grasses under water-limited conditions. This study aimed to select genotypes of tropical forage grasses under different water stress levels (moderate or severe) at this distance and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). Nine varieties from five species were examined. Forage grasses were grown in 12-L pots under three soil irrigation regimes [100% pot capacity-PC (well-irrigated control), 60% PC (moderate drought stress), and 25% PC (severe drought stress)] with four replicates. Drought stress treatments were applied for 25 days during the forage grass tillering and stalk elongation phases. After exposure to drought stress, the growth and morphological traits of forage plants were evaluated. The results show that the use of the Manhattan distance combined with TOPSIS helps in the genotypic selection of more stable tropical forage grass varieties when comparing plants exposed to moderate and severe drought conditions in relation to the nonstressful environment (control). The 'ADR 300', 'Pojuca', 'Marandu', and 'Xaraés' varieties show greater stability when grown in a greenhouse and subjected to water stress environments. The selected forage varieties can be used as parents in plant breeding programs, allowing us to obtain new drought-resistant genotypes.

Magnesium supplementation alleviates drought damage during vegetative stage of soybean plants.

Our working hypothesis was that magnesium (Mg) supplementation modulates plant performance under low water availability and improves drought tolerance in soybean genotypes. Plants of Bônus 8579, M8808 and TMG1180 genotypes were grown under field conditions and subjected to three water stress treatments (control, moderate and severe stress) and three Mg levels [0.9 (low), 1.3 (adequate) and 1.7 cmolc dm-³ (supplementation)]. After 28 days of drought imposition, the growth parameters, osmotic potential, relative water content, leaf succulence, Mg content and photosynthetic pigments were assessed. In general, drought drastically decreased the growth in all genotypes, and the reductions were intensified from moderate to severe stress. Under adequate Mg supply, TMG1180 was the most drought-tolerant genotype among the soybean plants, but Mg supplementation did not improve its tolerance. Conversely, although the M8808 genotype displayed inexpressive responses to drought under adequate Mg, the Mg-supplemented plants were found to have surprisingly better growth performance under stress compared to Bônus 8579 and TMG1180, irrespective of drought regime. The improved growth of high Mg-treated M8808-stressed plants correlated with low osmotic potential and increased relative water content, as well as shoot Mg accumulation, resulting in increased photosynthetic pigments and culminating in the highest drought tolerance. The results clearly indicate that Mg supplementation is a potential tool for alleviating water stress in M8808 soybean plants. Our findings suggest that the enhanced Mg-induced plant acclimation resulted from increased water content in plant tissues and strategic regulation of Mg content and photosynthetic pigments.

Soil and foliar Si fertilization alters elemental stoichiometry and increases yield of sugarcane cultivars.

Silicon (Si) fertilization is widely recognized to improve the development of crops, especially in tropical soils and cultivation under dryland management. Herein, our working hypothesis was that Si stoichiometry favors the efficient use of carbon (C), nitrogen (N), and phosphorus (P) in sugarcane plants. Therefore, a field experiment was carried out using a 3 × 3 factorial scheme consisting of three cultivars (RB92579, RB021754 and RB036066) and three forms of Si application (control without Si; sodium silicate spray at 40 mmol L-1 in soil during planting; sodium silicate spray at 40 mmol L-1 on leaves at 75 days after emergence). All Si fertilizations altered the elemental C and P stoichiometry and sugarcane yield, but silicon-induced responses varied depending on sugarcane cultivar and application method. The most prominent impacts were found in the leaf Si-sprayed RB92579 cultivar, with a significant increase of 7.0% (11 Mg ha-1) in stalk yield, 9.0% (12 Mg ha-1) in total recoverable sugar, and 20% (4 Mg ha-1) in sugar yield compared to the Si-without control. In conclusion, our findings clearly show that silicon soil and foliar fertilization alter C:N:P stoichiometry by enhancing the efficiency of carbon and phosphorus utilization, leading to improved sugarcane production and industrial quality.

Weed-Hoeing Periods in Cowpea Cultivation under Direct and Conventional Systems.

Weed coexistence with an agricultural crop can negatively affect its growth, development, and yield. From this perspective, this study aimed to evaluate weed management strategies and their effect on the agronomic parameters of cowpea cultivation in direct (SPD) and conventional (SPC) planting systems. The experiment was set up in a completely randomized block design with a split-plot arrangement with four replications. The plots received a source of variation referring to the planting systems (direct and conventional planting), and the subplots corresponded to ten weed management strategies (manual hoeing 18 days after planting (DAP); at 36 DAP; at 54 DAP; at 18 and 36 DAP; at 18 and 54 DAP; at 18 and 72 DAP; at 36 and 54 DAP; at 36-72 DAP; at 18, 36, and 54 DAP; and a control with no hoeing). Density and dry mass evaluations of the cowpea plants were performed at harvest (72 DAP) by determining the number of pods per plant, pod length, number of grains per pod, 1000-grain mass, and yield. A total of 28 species distributed in 12 botanical families were identified in the two cultivation systems. The family Poaceae showed the highest frequency, with 25% of the species identified. At the end of the assay, treatment 20 had the highest positive influence and provided significant quantitative gains to the complex of traits related to cowpea production (SPD and hoeing at 18, 36, and 54 DAP). UPGMA cluster analysis and canonical discriminant analysis were performed and allowed a better classification of the evaluated treatments. It was observed that the first two canonical variables explained 90.8% of the total variance contained in the original variables. The use of SPD with weeding at 18, 36, and 54 days after planting provides greater weed control and significant quantitative gains for the complex of characteristics related to cowpea production. The results underscore the importance of choosing the correct cropping system and implementing effective weeding practices to optimize weed control and improve crop performance.

Physicochemical Evaluation of Cushuro (Nostoc sphaericum Vaucher ex Bornet & Flahault) in the Region of Moquegua for Food Purposes.

The cyanobacterium Nostoc sp. contains considerable amounts of protein, iron, and calcium that could mitigate the problems of anemia and malnutrition in humans. However, the nutritional value of the edible species Nostoc sphaericum Vaucher ex Bornet & Flahault, which grows in the Moquegua region, is unknown. Descriptive research was developed, and samples were obtained from the community of Aruntaya, located in the region of Moquegua. Water samples were taken at two different points (spring and reservoir), and samples of the cyanobacteria were taken in the reservoir. The design used was completely randomized, with three repetitions. Sixteen characteristics associated with the water collected at two points were evaluated, and from the nutritional point of view, seven characteristics were evaluated in the collected algae. The physicochemical characteristics were determined using methods established in the Codex Alimentarius. For the morphological characterization at the macroscopic level, it was observed that the seaweed collected was spherical in shape, grayish-green in color, soft to the touch, and palatable. After carrying out the physicochemical and morphological characterization of the collected samples, it was verified that all were of N. sphaericum. When comparing the sixteen characteristics related to water at the two collection sites, highly significant differences (p < 0.01) were observed for most of the variables evaluated. The average data of the characteristics of the algae showed protein values of 28.18 ± 0.33%, carbohydrates of 62.07 ± 0.69%, fat of 0.71 ± 0.02%, fiber of 0.91 ± 0.02%, ash of 7.68 ± 0.10%, and moisture of 0.22 ± 0.01%. Likewise, calcium reported an average value of 377.80 ± 1.43 mg/100 g and iron of 4.76 ± 0.08 mg/100 g. High correlations (positive and negative) were obtained by evaluating seven characteristics associated with the reservoir water where the algae grew in relation to eight nutritional characteristics of the algae. In relation to the nutritional value, the amounts of protein, iron, and calcium exceed the main foods of daily intake. Therefore, it could be considered a nutritious food to combat anemia and malnutrition.

First Report on the Genetic Diversity of Populations of Gossypium barbadense L. and Gossypium hirsutun L. in the Amazonian Native Communities, Cusco-Peru.

The genus Gossypium has important ethnobotanical and economic value for Amazonian Native Communities (A.N.C.). However, little research has been undertaken on the distribution and genetic diversity of cotton populations maintained in the Peruvian rainforest. This work aims to present the first report on the genetic diversity of Gossypium spp. populations in the A.N.C. of the province of La Convención, Cusco-Peru. The methodology was based on exploring, collecting, identifying, and characterizing the Gossypium populations present in the A.N.C. Twenty-six descriptors were evaluated (9 quantitative and 17 qualitative), and with this information, distribution, correlation, and principal component (PC) analyses were carried out. As a result, plants of two species [G. barbadense L. (44 samples) and G. hirsutum L. (19 samples)], one variety [G. barbadense var. brasiliensis (75 samples)], and three previously unidentified variations (9 samples) were identified. Altogether, 147 samples were collected. G. barbadense var. brasiliensis, which was always found in association with other economic crops within an altitude range of 338 to 1086 m, was the most predominant (51%), distributed in eleven A.N.C. and always in small plots (up to 2 ha). G. barbadense L. was cultivated between 397 and 1137 m of altitude in eight A.N.C. in plots of up to 3 ha in marginal lands. G. hirsutum L., with a smaller distribution (13%), was found between 334 and 497 m of altitude in only three communities; this species is cultivated in marginal areas throughout the year. The variability found for the first two PCs when considering the quantitative and qualitative descriptors was high (74.7%) and moderate (48.2%), respectively. When combining all the descriptors, the analysis showed that the first two PCs accounted for 51.8% of the total variability of the data. The PCs of the two types of data and their combination confirmed that the three populations found were grouped. The nine undefined samples were close to or intermediate between the described ones, showing that these samples may be the result of spontaneous crosses; as such, these samples need to be better evaluated with other tools for further definition. The information obtained shows that in the A.N.C. of Cusco-Peru, there is variability conserved by the inhabitants, who have been able to maintain and use these genotypes, even from their Amazonian indigenous ancestry, and the environment has been able to generate variability among the species, as will be highlighted in future works.

Selection of Soybean Genotypes under Drought and Saline Stress Conditions Using Manhattan Distance and TOPSIS.

The search for soybean genotypes more adapted to abiotic stress conditions is essential to boost the development and yield of the crop in Brazil and worldwide. In this research, we propose a new approach using the concept of distance (or similarity) in a vector space that can quantify changes in the morphological traits of soybean seedlings exposed to stressful environments. Thus, this study was conducted to select soybean genotypes exposed to stressful environments (saline or drought) using similarity based on Manhattan distance and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method. TOPSIS is a multi-criteria decision method for selecting the best alternative using the concept of distance. The use of TOPSIS is essential because the genotypes are not absolutely similar in both treatments. That is, just the distance measure is not enough to select the best genotype simultaneously in the two stress environments. Drought and saline stresses were induced by exposing seeds of 70 soybean genotypes to -0.20 MPa iso-osmotic solutions with polyethylene glycol-PEG 6000 (119.6 g L-1) or NaCl (2.36 g L-1) for 14 days at 25 °C. The germination rate, seedling length, and seedling dry matter were measured. We showed here how the genotypic stability of soybean plants could be quantified by TOPSIS when comparing drought and salinity conditions to a non-stressful environment (control) and how this method can be employed under different conditions. Based on the TOPSIS method, we can select the best soybean genotypes for environments with multiple abiotic stresses. Among the 70 tested soybean genotypes, RK 6813 RR, ST 777 IPRO, RK 7214 IPRO, TMG 2165 IPRO, 5G 830 RR, 98R35 IPRO, 98R31 IPRO, RK 8317 IPRO, CG 7464 RR, and LG 60177 IPRO are the 10 most stable genotypes under drought and saline stress conditions. Owing to high stability and gains with selection verified for these genotypes under salinity and drought conditions, they can be used as genitors in breeding programs to obtain offspring with higher resistance to antibiotic stresses.

Yield of soybean genotypes identified through GGE biplot and path analysis.

Genotype × environment (G×E) interaction is an important source of variation in soybean yield, which can significantly influence selection in breeding programs. This study aimed to select superior soybean genotypes for performance and yield stability, from data from multi-environment trials (METs), through GGE biplot analysis that combines the main effects of the genotype (G) plus the genotype-by-environment (G×E) interaction. As well as, through path analysis, determine the direct and indirect influences of yield components on soybean grain yield, as a genotype selection strategy. Eight soybean genotypes from the breeding program of Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) were evaluated in field trials using a randomized block experimental design, in an 8 x 8 factorial scheme with four replications in eight different environments of the Cerrado of Northeastern Brazil during two crop seasons. Phenotypic performance data were measured for the number of days to flowering (NDF), height of first pod insertion (HPI), final plant height (FPH), number of days to maturity (NDM), mass of 100 grains (M100) and grain yield (GY). The results revealed that the variance due to genotype, environment, and G×E interaction was highly significant (P < 0.001) for all traits. The ST820RR, BRS 333RR, BRS SambaíbaRR, M9144RR and M9056RR genotypes exhibited the greatest GY stability in the environments studied. However, only the BRS 333RR genotype, followed by the M9144RR, was able to combine good productive performance with high yield stability. The study also revealed that the HPI and the NDM are traits that should be prioritized in the selection of soybean genotypes due to the direct and indirect effects on the GY.

Selected Indices to Identify Water-Stress-Tolerant Tropical Forage Grasses.

Periods of soil water stress have been recurrent in the Cerrado region and have become a growing concern for Brazilian tropical pasture areas. Thus, the search for forage grasses more tolerant to water stress has intensified recently in order to promote more sustainable livestock. In a greenhouse experiment, the degree of water stress tolerance of nine tropical forage grass cultivars was studied under different soil water regimes. The investigation followed a 9 × 3 factorial design in four randomized blocks. Nine cultivars from five species of perennial forage grasses were tested: Urochloa brizantha ('BRS Piatã', 'Marandu', and 'Xaraés'), Panicum maximum ('Aruana', 'Mombaça', and 'Tanzânia'), Pennisetum glaucum ('ADR 300'), Urochloa ruziziensis ('Comum'), and Paspalum atratum ('Pojuca'). These cultivars were grown in pots under three soil water regimes (high soil water regime-HSW (non-stressful condition), middle soil water regime-MSW (moderate water stress), and low soil water regime-LSW (severe water stress)). Plants were exposed to soil water stress for 25 days during the tillering and stalk elongation phases. Twelve tolerance indices, including tolerance index (TOL), mean production (MP), yield stability index (YSI), drought resistance index (DI), stress tolerance index (STI), geometric mean production (GMP), yield index (YI), modified stress tolerance (k1STI and k2STI), stress susceptibility percentage index (SSPI), abiotic tolerance index (ATI), and harmonic mean (HM), were calculated based on shoot biomass production under non-stressful (YP) and stressful (YS) conditions. Soil water stress decreased leaf area, plant height, tillering capacity, root volume, and shoot and root dry matter production in most cultivars, with varying degrees of reduction among tropical forage grasses. Based on shoot biomass production under controlled greenhouse conditions, the most water-stress-tolerant cultivars were P. maximum cv. Mombaça and cv. Tanzânia under the MSW regime and P. maximum cv. Aruana and cv. Mombaça under the LSW regime. P. maximum cv. Mombaça has greater adaptability and stability of shoot biomass production when grown under greenhouse conditions and subjected to soil water stress. Therefore, this forage grass should be tested under field conditions to confirm its forage production potential for cultivation in tropical regions with the occurrence of water stress. The MP, DI, STI, GMP, YI, k2STI, and HM tolerance indices were the most suitable for identifying forage grass cultivars with greater water stress tolerance and a high potential for shoot biomass production under LSW regime.

Understanding the contribution of soybean crop residues inoculated with Bradyrhizobium spp. and not harvested on nitrogen supply in off-season corn cultivars.

Excessive rainfall in the soybean preharvest period can make mechanized crop harvesting technically and economically unfeasible, causing 100% losses in soybean grain yield. An alternative to reduce the economic losses of farmers would be using unharvested soybean crop residues as a source of nitrogen (N) for the subsequent corn crop. However, a question that still needs to be understood is whether the amount of N released from unharvested soybean residues (straw and grains) is sufficient to meet all the nutritional demand for this nutrient in the off-season corn. Therefore, this study investigated the impact of unharvested soybean crop residue persistence on the yield response of off-season corn crop (Zea mays L.) to the application of N fertilizer rates when grown in tropical Cerrado soils of medium and high fertility. Four simple corn hybrids (SYN7G17 TL, 30F53VYHR, B2433PWU, and AG 8700 PRO3) were grown in soils of medium fertility and medium acidity level (UFMS 1) and high fertility and low acidity level (UFMS 2) and fertilized with five of N fertilizer rates (0, 40, 80, 120, and 160 kg ha-1 of N) applied at 30 days after emergence (DAE). Canonical correlation analysis (CCA) was used to investigate the interrelationships between the groups of independent (agricultural production areas, corn cultivars, and N application rates) and dependent (corn agronomic traits) variables. Crop residues remaining on the soil surface from soybeans not harvested and inoculated with Bradyrhizobium spp. can supply most of the nitrogen requirement of off-season corn grown in succession, especially in tropical soils of medium fertility. However, in high-fertility tropical soils, the maximum grain yield potential of off-season corn cultivars can be obtained with the application of mineral N fertilizer in supplement the amount of nitrogen released from unharvested soybean residues. Therefore, the N requirement depends on the corn cultivar and the agricultural production area. However, our results show that when off-season corn is grown on unharvested soybean residues, nitrogen fertilization in topdressing can be dispensed. The agricultural area with high fertility soil (UFMS 2) enhances the grain yield of the off-season corn crop. The corn cultivar AG 8700 PRO3 has a higher thousand-grain mass and high grain yield potential under Brazilian Cerrado conditions.

Zinc - rooting cofactor in rubber tree mini-cuttings / Zinco - cofator de enraizamento em miniestacas de seringueira

The rubber tree (Hevea brasiliensis Müell. Arg.) is a species of significant economic interest in the natural rubber industry in Brazil and the world. This species presents recalcitrance to rooting, and its cuttings are difficult to propagate. This study aimed to evaluate the effect of the pre-conditioning of rubber tree mini-cuttings with zinc on the improvement of the adventitious rooting of rootstocks. Mini-cuttings were standardized with 45 mm length and submitted to preconditioning by immersion of the mini-cutting base in solutions containing 0.00; 0.04; 0.08; 0.16; 0.32 and 0.64 mg L-1 of Zn, for 24 hours. The experimental design was randomized blocks with six treatments and four replicates of 10 mini-cuttings. The rubber tree mini-cuttings were placed in a fitotron-type growth chamber, at 25 °C, with 12-hour photoperiod, 5,000 K intensity, and 95% of relative air humidity, for 60 days. The survival rate, number of buds, percentage of mini-cuttings that had leaf abscission, the percentage of mini-cuttings with callogenesis in the root meristem, the percentage of rooted mini-cuttings, the number of primary roots and root length were evaluated. The highest values of survival rate, the number of buds, the number of primary roots, the percentage of mini-cuttings with callogenesis in the root meristem, the percentage of rooted mini-cuttings and root length were observed with 0.16 to 0.26 Mg L-1 of Zn. The use of zinc in the mini-cuttings of rubber tree reduces linearly the percentage of mini-cuttings that had leaf abscission and the formation of callogenesis in the root meristem.

A seringueira (Hevea brasiliensis Müell. Arg.) é uma espécie de importância econômica para a indústria da borracha natural do Brasil e do mundo. Esta espécie apresenta recalcitrância ao enraizamento e suas estacas são difíceis de se propagar. Este trabalho objetivou avaliar o efeito do pré-condicionamento de miniestacas de seringueira com zinco na melhoria do enraizamento adventício de porta-enxertos. As miniestacas foram padronizadas com 45 mm de comprimento e submetidas ao pré-condicionamento por imersão da miniestaca em soluções contendo 0.00; 0,04; 0,08; 0,16; 0,32 e 0,64 mg L-1 de Zn, por 24 horas. O delineamento experimental foi em blocos ao acaso, com seis tratamentos e quatro repetições de 10 miniestacas. As miniestacas de seringueira foram colocadas em câmara de crescimento tipo fitotron, a 25 °C, com fotoperíodo de 12 horas, intensidade de 5.000 K e umidade relativa do ar de 95% por 60 dias. Foram avaliadas a taxa de sobrevivência, o número de gemas, a porcentagem de miniestacas que apresentaram abscisão foliar, o percentual de miniestacas com calogênese no meristema radicular, o percentual de miniestacas enraizadas, o número de raízes primárias e o comprimento das raízes. Os maiores valores de taxa de sobrevivência, o número de gemas, o número de raízes primárias, a porcentagem de miniestacas com calogênese no meristema radicular, o percentual de miniestacas enraizadas e o comprimento radicular foram verificados com 0,16 a 0,26 Mg L-1 de Zn. O uso de zinco nas miniestacas de seringueira reduz linearmente a porcentagem de miniestacas que tiveram abscisão foliar e a formação de calogênese no meristema radicular

Correlations and path analysis in agronomic traits of soybeans under defoliation / Correlações e análise de trilha em caracteres agronômicas de soja sob desfolha

Stress events or leaf damage can alter the redistribution of photoassimilates and modify the morphological traits directly related to grain yield. This study aimed to evaluate the influence of agronomic traits on grain yield in soybean crop in function of leaf defoliation. The experiment consisted of a randomized block design with three replications, arranged in a 6 x 3 + 1 factorial scheme. The factors were composed by six reprodutive stages (R1, R2, R3, R4, R5, and R6) and three defoliation levels (33%, 66%, and 99%), and one additional treatment without defoliation (control). The following traits were evaluated: plant height, number of pods per plant, number of grains per pod, thousand grain weight, and grain yield. The magnitudes of the correlations between the same traits showed high oscillation according to the defoliation level. Results revealed the potential for the indirect selection for grain yield by the traits plant height and number of grains per pods under 0% of defoliation and by the trait number of pods per plant under 33% of defoliation.

Ocorrências de estresse ou danos foliares podem levar a alteração na redistribuição de fotoassimilados e modificar os caracteres morfológicos envolvidos diretamente na produtividade dos grãos. Portanto, objetivou-se avaliar por meio da análise de trilha, a influência de caracteres agronômicos na produtividade de grãos na cultura da soja em função de níveis desfolha da planta. O delineamento experimental utilizado foi o de blocos casualizados com três repetições, dispostos em esquema fatorial 6 x 3 + 1. O primeiro fator foi composto por seis estádios reprodutivos de desfolha (R1, R2, R3, R4, R5, R6) x três níveis de desfolha (33%, 66%, 99%) e um tratamento adicional sem desfolha (controle). Os caracteres avaliados foram: altura de plantas, número de legumes por planta, número de grãos por legume, peso de mil grãos e produtividade de grãos. As magnitudes das correlações entre os mesmos caracteres apresentaram alta oscilação de acordo com o nível de desfolha, sendo que, que existe potencial da seleção indireta para produtividade de grãos por meio da altura de plantas e número de grãos por legumes sob 0% desfolha e do número de legumes por planta sob 33% de desfolha.

Potassium supplying capacity of some lowland soils under potassium fertilization and successive croppings / Capacidade de suprimento de potássio de alguns solos de várzea sob fertilização com potássio e plantações sucessivas

The effects of intense cropping and potassium fertilization on potassium (K) dynamics and non-exchangeable K release from three lowland soils of Paraná State, Brazil, were investigated in this study. Samples of three lowland soils were fertilized or not with K and subjected to six successive croppings (soybeans, pearl millet, wheat, common beans, soybeans, and maize). The crops were grown in 8-L pots for 45 days, and at the end of the sixth cropping, the soil from each pot was sampled to the determination of soil K pools. The lowland soils differ in the ability to K supply to the plants in the short to medium term due to the wide range of origin material and the concentration of K in solution, exchangeable K, non-exchangeable K, and structural K. When the soils were not fertilized with K, the successive cropping resulted in continuous depletion process of non-exchangeable and exchangeable K; however, this depletion was less pronounced in soils with a higher potential buffer capacity of K. Non-exchangeable and exchangeable K concentrations were increased with the addition of K fertilizer, indicating the occurrence of K fixation in soil. The non-exchangeable K contribution to K nutrition of plants ranged from 44 to 69% in the treatments without the addition of K fertilizer, reporting the importance of non-exchangeable K pools in the supply of this nutrient to plants in agricultural production systems.

Os efeitos dos cultivos sucessivos e da adubação potássica na dinâmica de potássio (K) do solo e na mobilização do K não-trocável para às plantas em três solos de varzea do Estado do Paraná, Brasil, foram investigados neste estudo. Amostras dos três solos de várzea foram submetidas à adição ou não de fertilizante potássico e a seis cultivos sucessivos de plantas (soja, milheto, trigo, feijão, soja e milho). As culturas foram cultivadas em vasos de 8-L por 45 dias e, ao final do sexto cultivo, foram coletadas amostras de solos para a deteminação das diferentes formas de K do solo. Os solos de vázea diferenciaram-se na capacidade de suprir K às plantas a curto e médio prazo, devido à ampla variação do material de origem e dos teores de K na solução, K trocável, K não-trocável e K estrutural. Quando os solos não foram adubados com K, o cultivo sucessivo de plantas resultou em um processo contínuo de esgotamento das formas de K não-trocável e K trocável, sendo menos acentuada nos solos com maior poder tampão de potássio. Os teores de K não-trocável e K trocável aumentaram com a adição de fertilizantes potássicos, indicando a ocorrência de fixação de K pelo solo. A contribuição do K não-trocável para a nutrição das plantas durante os seis cultivos variou de 44 a 69% no tratamento sem adição de fertilizante potássico. Estes resultados reportam a importância das formas de K não-trocável para o suprimento deste nutriente às plantas nos sistemas de produção agrícolas.

Can co-inoculation of Bradyrhizobium and Azospirillum alleviate adverse effects of drought stress on soybean (Glycine max L. Merrill.)?

Harnessing the beneficial potential of plant growth-promoting rhizobacteria may be an alternative strategy to improve plant tolerance to drought stress. The effect of inoculation with Bradyrhizobium japonicum and Azospirillum brasilense either alone or in combination on the plant growth and drought tolerance of soybean [Glycine max (L.) Merrill.] was investigated in this study in greenhouse conditions. Treatments were arranged in a randomized block design in a 3 × 4 factorial: three irrigation regimes [100% of pot capacity-PC (well-watered control), 50% of PC (moderate stress) and 25% of PC (severe stress)] and four inoculation treatments [control (non-inoculated), inoculation with B. japonicum, inoculation with A. brasilense, and co-inoculation with B. japonicum and A. brasilense]. Leaf relative water content, cell membrane stability, root nodulation, plant growth, and morphophysiological indexes were recorded. The inoculation of soybean plants with B. japonicum and A.brasilense either alone or in combination improved leaf membrane stability under drought stress conditions when compared to non-inoculated plants; however, this lower damage to cell membranes was not sufficient to maintain the leaf water content of the plant under drought stress. Plants co-inoculated with B. japonicum and A.brasilense improved the root nodulation under severe drought conditions. Inoculation of B. japonicum and A. brasilense either alone or in combination reduced the pod abortion rate under moderate drought stress, but had no effect under severe drought stress. In summary, the co-inoculation of A. brasilense and B. japonicum alleviate adverse effects limited by drought stress to the growth of soybeans.Author: Please check and confirm that the authors [Elijanara Raissa Silva, Carlos Eduardo Silva Oliveira, Alan Mario Zuffo, Eduardo Pradi Vendruscolo] and their initials have been correctly identified and amend if necessary.The authors were correctly identified.

Drought tolerance of four vegetable crops during germination and initial seedling growth / Tolerância de quatro espécies de hortaliças ao déficit hídrico durante a germinação e crescimento inicial das plântulas

Seeds of arugula (Eruca sativa Miller, cv. Cultivada), carrot (Daucus carota L., cv. Nantes), eggplant (Solanum melongena L., cv. Embú) and watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai cv. Crimson Sweet] were submitted to different osmotic potentials induced by polyethylene glycol(PEG) with the objective of evaluate the effects of drought stress on seed germination and initial seedling growth. Seeds were distributed in plastic boxes containing blotter paper, soaked with PEG solutions prepared with osmotic potentials 0.0 (control), ­0.2, ­0.4, and ­0.8 MPa and kept into a seed germinator, at 25 °C for 14 days. A completely randomized design in a 4 × 4 factorial scheme with four replicates of 50 seeds each was used. The results showed that by increasing of the osmotic potential level, germinated seeds number, germination rate index, root and shoot length, shoot and root dry matter, and seedling vigor indices decreased, while mean germination time and root: shoot ratio increased in all four vegetable crops. Additionally, the carrot and watermelon are more susceptible than arugula and eggplant to drought stress, with germination response declining more rapidly with the rise of osmotic potential level. Arugula and eggplant crops tolerate water stress of up to ­0.2 MPa, without reducing germination of the seeds; however, the growth of shoots and roots are inhibited. The germination process of eggplant and watermelon seeds are completely inhibited at ­0.8 MPa osmotic potential, whereas germination of carrot seeds is completely inhibited at ­0.4 MPa osmotic potential. Severe drought stress limits the process of seed germination and initial seedling growth of vegetable crops.

Sementes de rúcula (Eruca sativa Miller, cv. Cultivada), cenoura (Daucus carota L., cv. Nantes), berinjela (Solanum melongena L., cv. Embú) e melancia [Citrullus lanatus (Thunb.) Matsum. & Nakai cv. Crimson Sweet] foram submetidas a diferentes potenciais osmóticos simulados com polietileno glicol (PEG 6000) com o objetivo de avaliar os efeitos do estresse hídrico na germinação e no crescimento inicial das plântulas. As sementes foram distribuídas em caixas plásticas tipo Gerbox® contendo papel mata-borrão, o qual foi umedecido com diferentes soluções de PEG preparadas com quatro níveis de potenciais osmótico [0 (controle); ­0,2; ­0,4; e ­0,8 MPa]. As caixas plásticas foram então mantidas em câmara de germinação à 25 °C por 14 dias. O delineamento utilizado foi o inteiramente casualizado, em esquema fatorial 4 × 4, com quatro repetições de 50 sementes cada. Os resultados mostraram que o aumento do nível de potencial osmótico da solução reduziu a porcentagem de germinação das sementes, o índice de velocidade de germinação, o comprimentos da parte aérea e da raiz principal, a produção de matéria seca da parte aérea e das raízes e os índices de vigor das plântulas, enquanto que o tempo médio de germinação e a relação entre a matéria seca da raiz/parte aérea aumentou em todas as quatro espécies de hortaliças. As culturas de cenoura e melancia são mais susceptível que a rúcula e a berinjela ao estresse hídrico, com resposta de germinação declinando mais rapidamente com o aumento do nível de potencial osmótico. A rúcula e a berinjela toleram estresse hídrico de até ­0,2 MPa, sem reduzir o processo de germinação das sementes; no entanto, o crescimento da parte aérea e das raízes são inibidos. O processo de germinação das sementes de berinjela e melancia são completamente inibidos em potencial osmótico de ­0.8 MPa, ao passo que a germinação das sementes de cenoura é completamente inibida em potencial osmótico de ­0.4 MPa. O estresse hídrico severo limita o processo de germinação das sementes e crescimento inicial de plântulas das quatro espécies de hortaliças.

Correlations and selection of parents to technological traits of upland cotton / Correlações e seleção de genitores para caracteres tecnológicos em algodoeiro herbáceo

ABSTRACT: Technological traits improvement of cotton fiber is a constant demand by textile industry. This research aimed to identify the potential of improved materials with high lint percentage to contribute with alleles that increase the lint percentage in Extra long staple fiber (ELS) upland cotton. Two contrasting materials for lint percentage (LP) and fiber length (FL) were used, one with long fiber and a low lint percentage (parent A) and another with high lint percentage and medium length (parent B). The following variables were evaluated: lint percentage (LP), upper half mean length (UHML), fiber uniformity (FU), fiber strength (FS), and elongation (EL). Diallel analysis was performed using the Griffing's Method 4 adapted to partial diallel. Additive effects were predominant over non-additive effects. The mean LP was higher when using parent B. The opposite occurred for UHML. A negative correlation was detected between LP and UHML, showing the difficulty of obtaining genetic gain for both traits at the same time.

RESUMO: O aprimoramento das características tecnológicas da fibra de algodão é uma demanda constante da indústria têxtil. Este trabalho teve como objetivo identificar o potencial de materiais melhorados com alta porcentagem de plumas para contribuir com alelos que aumentam a porcentagem de plumas com fibra extra longa (ELS) no algodão de terras altas. Dois materiais contrastantes para porcentagem de fibra (LP) e comprimento de fibra (FL) foram usados, um com fibra longa e uma baixa porcentagem de fibra (pai A) e outro com alta porcentagem de fibra e comprimento médio (pai B). As seguintes variáveis foram avaliadas: porcentagem de fibra (LP), comprimento médio da metade superior (UHML), uniformidade da fibra (FU), resistência da fibra (FS) e alongamento (EL). A análise dialélica foi realizada utilizando o Método 4 de Griffing adaptado para dialelo parcial. Os efeitos aditivos foram predominantes em relação aos efeitos não aditivos. O LP médio foi maior quando se usou o pai B. O oposto ocorreu para o UHML. Uma correlação negativa foi detectada entre LP e UHML, mostrando a dificuldade de obter ganho genético para ambas as características ao mesmo tempo.

Seed priming improves the germination and growth rate of melon seedlings under saline stress / Condicionamento de sementes melhora a germinação e a taxa de crescimento das plântulas de melão sob estresse salino

ABSTRACT: The germination and growth of melon (Cucumis melo L.) plants can be severely affected by excess salts in the soil or irrigation water; however, negative effects of salt stress can be attenuated using appropriate methods of seed priming. Thus, effects of osmopriming as inducer of salt stress tolerance in melon seeds exposed to salinity levels were investigated in this study. Seeds were soaked for 22 h at 25 °C in the dark in distilled water (hydropriming) or 0.5% KNO3 solution (osmopriming), and after drying, were distributed in plastic boxes with blotter paper containing different NaCl solutions prepared with osmotic pressure of 0.0 MPa (control), -0.3 MPa (mild stress), and -0.6 MPa (severe stress). Unprimed dry seeds were taken as control. The plastic boxes were kept into a seed germinator, at 25 °C for 14 days. A completely randomized design in a 3 × 3 factorial schemes with four replicates of 25 seeds was used. Results showed that the seed priming with water and KNO3 may be successfully applied on melon seeds to alleviate the adverse effects of saline stress in initial stages of plant growth. However, under severe salt stress conditions, hydropriming should be used because it results in higher germination and initial growth rate of the seedlings when compared to the osmopriming. Use of unprimed seeds should not be adopted in cultivation areas affected by salinity because they result in low germination rate and reduced initial plant growth.

RESUMO: A germinação e o crescimento de plantas de melão (Cucumis melo L.) podem ser severamente afetadas pelo excesso de sais no solo ou na água de irrigação. No entanto, os efeitos negativos do estresse salino podem ser amenizados com o uso de métodos adequados de condicionamento das sementes. Assim, este estudo objetivou investigar os efeitos do osmocondicionamento como indutor da tolerância ao estresse salino em sementes de melão expostas à níveis de salinidade. As sementes foram imersas por 22 h à 25 °C em água destilada (hidrocondicionamento) ou em solução de 0,5% de KNO3 (osmocondicionamento). Após secagem, as sementes foram distribuídas em caixas plásticas com papel mata-borrão contendo as diferentes soluções de NaCl preparadas com potencial osmótico de 0,0 MPa (controle), -0,3 MPa (estresse suave) e -0,6 MPa (estresse severo). Um tratamento com sementes secas não condicionadas foi utilizado como controle. As caixas plásticas foram mantidas em germinador de sementes, a 25 °C por 14 dias. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 3 × 3, com quatro repetições de 25 sementes. Os resultados mostraram que o condicionamento de sementes com água e KNO3 pode ser aplicado com sucesso em sementes de melão para amenizar os efeitos adversos do estresse salino durante o estágio inicial de crescimento das plantas. No entanto, sob estresse salino severo, o hidrocondicionamento deve ser utilizado por resultar em maior percentagem de germinação e maior taxa de crescimento inicial das plântulas quando comparado ao osmocondicionamento. O uso de sementes de melão sem condicionamento prévio não deve ser adotado em áreas de cultivo afetadas pela salinidade, pois resultam em baixa taxa de germinação e reduzido crescimento inicial das plantas.

Productive performance of soybean cultivars grown in different plant densities / Desempenho produtivo de cultivares de soja cultivadas em diferentes densidades de plantas

ABSTRACT: Plants density in soybean cultivation is an important management practice to achieve high grain yield. In this way, the objective was to evaluate the agronomic traits and grain yield in soybean in different plant densities, in two locations in the south of Minas Gerais. The experimental design was in randomized blocks, arranged in a split plot design, with three replications. Plots were composed of four population densities (300, 400, 500 and 600 thousand plants per hectare) and the subplots were composed of six cultivars (‘BMX Força RR’, ‘CD 250 RR’, ‘FMT 08 - 60.346/1’, ‘NA 5909 RR’, ‘TMG 7161 RR’ and ‘V - TOP RR’) grown in Lavras and Inconfidentes, both in Minas Gerais. At the time of harvest was determined the plant height, lodging, insertion of the first pod, harvest index, number of pods per plant, number of grains, number of grains per pod and yield. Regardless of the soybean cultivar, the plant density of up to 600,000 per ha does not affect grain yield, plant height, lodging, harvest index, and number of grains per pod. The cultivars ‘V-TOP RR’ and ‘BMX FORÇA RR’ showed high grain yield and good agronomic traits in Lavras and Incofidentes.

RESUMO: A densidade de plantas no cultivo de soja é uma prática de manejo relevante para o alcance de alta produtividade de grãos. Dessa forma, objetivou-se avaliar os caracteres agronômicos e produtividade dos grãos na soja em diferentes densidades de plantas. O delineamento experimental utilizado foi o de blocos casualizados, dispostos em esquema de parcelas subdivididas, com três repetições. As parcelas foram compostas por quatro densidades populacionais (300, 400, 500 e 600 mil plantas por hectare) e, as subparcelas foram compostas por seis cultivares (‘BMX Força RR’, ‘CD 250 RR’, ‘FMT 08 - 60.346/1’, ‘NA 5909 RR’, ‘TMG 7161 RR’ e ‘V - TOP RR’) cultivados em Lavras e Incofidentes, ambos em Minas Gerais. Na ocasião da colheita determinou-se a altura de plantas, o acamamento, a inserção do primeiro legume, o índice de colheita, o número de vagens por planta, o número de grãos, o número de grãos por vagem e a produtividade. Independentemente da cultivar de soja, a densidade de plantas de até 600.000 por ha, não afeta o rendimento de grãos, altura da planta, acamamento, índice de colheita e número de grãos por vagem. As cultivares ‘V-TOP RR’ e ‘BMX FORÇA RR’ apresentaram alto rendimento de grãos e boas características agronômicas em Lavras e Incofidentes.