Yellow Leaf Disease Resistance and Melanaphis sacchari Preference in Commercial Sugarcane Cultivars.

Sugarcane yellow leaf disease (YLD) caused by sugarcane yellow leaf virus (ScYLV) is a major threat for the sugarcane industry worldwide, and the aphid Melanaphis sacchari is its main vector. Breeding programs in Brazil have provided cultivars with intermediate resistance to ScYLV, whereas the incidence of ScYLV has been underestimated partly due to the complexity of YLD symptom expression and identification. Here, we evaluated YLD symptoms in a field assay using eight sugarcane genotypes comprising six well-established commercial high-sucrose cultivars, one biomass yield cultivar, and a susceptible reference under greenhouse conditions, along with estimation of virus titer through RT-qPCR from leaf samples. Additionally, a free-choice bioassay was used to determine the number of aphids feeding on the SCYLV-infected cultivars. Most of the cultivars showed some degree of resistance to YLD, while also revealing positive RT-qPCR results for ScYLV and virus titers with non-significant correlation with YLD severity. The cultivars IACSP01-5503 and IACBIO-266 were similar in terms of aphid preference and ScYLV resistance traits, whereas the least preferred cultivar by M. sacchari, IACSP96-7569, showed intermediate symptoms but similar virus titer to the susceptible reference, SP71-6163. We conclude that current genetic resistance incorporated into sugarcane commercial cultivars does not effectively prevent the spread of ScYLV by its main aphid vector.

Leaf transcriptome profiling of contrasting sugarcane genotypes for drought tolerance under field conditions.

Drought is the most detrimental abiotic stress to sugarcane production. Nevertheless, transcriptomic analyses remain scarce for field-grown plants. Here we performed comparative transcriptional profiling of two contrasting sugarcane genotypes, 'IACSP97-7065' (drought-sensitive) and 'IACSP94-2094' (drought-tolerant) grown in a drought-prone environment. Physiological parameters and expression profiles were analyzed at 42 (May) and 117 (August) days after the last rainfall. The first sampling was done under mild drought (soil water potential of -60 kPa), while the second one was under severe drought (soil water potential of -75 kPa). Microarray analysis revealed a total of 622 differentially expressed genes in both sugarcane genotypes under mild and severe drought stress, uncovering about 250 exclusive transcripts to 'IACSP94-2094' involved in oxidoreductase activity, transcriptional regulation, metabolism of amino acids, and translation. Interestingly, the enhanced antioxidant system of 'IACSP94-2094' may protect photosystem II from oxidative damage, which partially ensures stable photochemical activity even after 117 days of water shortage. Moreover, the tolerant genotype shows a more extensive set of responsive transcription factors, promoting the fine-tuning of drought-related molecular pathways. These results help elucidate the intrinsic molecular mechanisms of a drought-tolerant sugarcane genotype to cope with ever-changing environments, including prolonged water deficit, and may be useful for plant breeding programs.

Genome-wide approaches for the identification of markers and genes associated with sugarcane yellow leaf virus resistance.

Sugarcane yellow leaf (SCYL), caused by the sugarcane yellow leaf virus (SCYLV) is a major disease affecting sugarcane, a leading sugar and energy crop. Despite damages caused by SCYLV, the genetic base of resistance to this virus remains largely unknown. Several methodologies have arisen to identify molecular markers associated with SCYLV resistance, which are crucial for marker-assisted selection and understanding response mechanisms to this virus. We investigated the genetic base of SCYLV resistance using dominant and codominant markers and genotypes of interest for sugarcane breeding. A sugarcane panel inoculated with SCYLV was analyzed for SCYL symptoms, and viral titer was estimated by RT-qPCR. This panel was genotyped with 662 dominant markers and 70,888 SNPs and indels with allele proportion information. We used polyploid-adapted genome-wide association analyses and machine-learning algorithms coupled with feature selection methods to establish marker-trait associations. While each approach identified unique marker sets associated with phenotypes, convergences were observed between them and demonstrated their complementarity. Lastly, we annotated these markers, identifying genes encoding emblematic participants in virus resistance mechanisms and previously unreported candidates involved in viral responses. Our approach could accelerate sugarcane breeding targeting SCYLV resistance and facilitate studies on biological processes leading to this trait.

Biomass Accumulation and Cell Wall Structure of Rice Plants Overexpressing a Dirigent-Jacalin of Sugarcane (ShDJ) Under Varying Conditions of Water Availability.

A sugarcane gene encoding a dirigent-jacalin, ShDJ, was induced under drought stress. To elucidate its biological function, we integrated a ShDJ-overexpression construction into the rice Nipponbare genome via Agrobacterium-mediated transformation. Two transgenic lines with a single copy gene in T0 were selected and evaluated in both the T1 and T4 generations. Transgenic lines had drastically improved survival rate under water deficit conditions, at rates close to 100%, while WT did not survive. Besides, transgenic lines had improved biomass production and higher tillering under water deficit conditions compared with WT plants. Reduced pectin and hemicellulose contents were observed in transgenic lines compared with wild-type plants under both well-watered and water deficit conditions, whereas cellulose content was unchanged in line #17 and reduced in line #29 under conditions of low water availability. Changes in lignin content under water deficit were only observed in line #17. However, improvements in saccharification were found in both transgenic lines along with changes in the expression of OsNTS1/2 and OsMYB58/63 secondary cell wall biosynthesis genes. ShDJ-overexpression up-regulated the expression of the OsbZIP23, OsGRAS23, OsP5CS, and OsLea3 genes in rice stems under well-watered conditions. Taken together, our data suggest that ShDJ has the potential for improving drought tolerance, plant biomass accumulation, and saccharification efficiency.

Resistance mechanisms of sugarcane cultivars to spittlebug Mahanarva fimbriolata

The spittlebug Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae) is one of the most important pests of sugarcane in Brazil. Measures for population control are currently restricted to the use of chemical insecticides and fungus Metarhizium anisopliae, in part because very little information exists regarding resistance of sugarcane cultivars. Therefore, the aim of this study was to evaluate resistance mechanisms of 12 different sugarcane cultivars to M. fimbriolata to provide information for growers for pest management. Isolated buds of each cultivar were planted in pots and kept in a greenhouse for approximately three months. The pots were then moved to climate test chambers (26 ± 1 ºC; 70 ± 10 % relative humidity; 12 h photoperiod) to carry out laboratory tests to evaluate adult feeding and female oviposition preferences (using both free-choice and no-choice tests) as well as the effects of cultivars on nymph development and cultivars tolerance to pest attack. The least attractive cultivars for adult feeding were IACSP96-2042 and IAC91-1099. Cultivars IACSP96-2042, IACSP96-3060 and IACSP94-2101 received the fewest eggs in the free-choice and no-choice oviposition tests and exhibited some level of antixenosis resistance. Cultivar IAC91-1099 showed the highest level of antibiosis resistance with a nymph survival rate in the roots of only 20 %. Finally, cultivar IACSP94-2094 appears to be tolerant to M. fimbriolata, as it did not show significant reductions in aboveground biomass weight, despite showing reduced leaf chlorophyll levels following pest attack.

Resistance mechanisms of sugarcane cultivars to spittlebug Mahanarva fimbriolata

The spittlebug Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae) is one of the most important pests of sugarcane in Brazil. Measures for population control are currently restricted to the use of chemical insecticides and fungus Metarhizium anisopliae, in part because very little information exists regarding resistance of sugarcane cultivars. Therefore, the aim of this study was to evaluate resistance mechanisms of 12 different sugarcane cultivars to M. fimbriolata to provide information for growers for pest management. Isolated buds of each cultivar were planted in pots and kept in a greenhouse for approximately three months. The pots were then moved to climate test chambers (26 ± 1 ºC; 70 ± 10 % relative humidity; 12 h photoperiod) to carry out laboratory tests to evaluate adult feeding and female oviposition preferences (using both free-choice and no-choice tests) as well as the effects of cultivars on nymph development and cultivars tolerance to pest attack. The least attractive cultivars for adult feeding were IACSP96-2042 and IAC91-1099. Cultivars IACSP96-2042, IACSP96-3060 and IACSP94-2101 received the fewest eggs in the free-choice and no-choice oviposition tests and exhibited some level of antixenosis resistance. Cultivar IAC91-1099 showed the highest level of antibiosis resistance with a nymph survival rate in the roots of only 20 %. Finally, cultivar IACSP94-2094 appears to be tolerant to M. fimbriolata, as it did not show significant reductions in aboveground biomass weight, despite showing reduced leaf chlorophyll levels following pest attack.(AU)

Molecular and Pathogenic Diversity Among Brazilian Isolates of Xanthomonas albilineans Assessed with SSR Marker Loci.

Leaf scald is one of the most important diseases of sugarcane in Brazil. Despite its importance, little is known about the genetic and pathogenic variability of its causal agent, Xanthomonas albilineans. The genetic diversity of 44 X. albilineans isolates from diverse geographic regions of Brazil was assessed using 15 newly developed short sequence repeat (SSR) loci designed from the genome sequence of X. albilineans strain GPE PC73. In addition, the aggressiveness of each isolate was evaluated by inoculating on a susceptible sugarcane cultivar and scoring the disease severity. Of the 15 SSR loci, 12 were polymorphic and produced 54 polymorphic alleles. The average number of polymorphic alleles per locus was 4.5, and ranged from 2 to 12 alleles. Phenetic analysis based on Nei's unbiased genetic distance, clustered the isolates into two major groups. Group I included 32 isolates from all four geographic regions studied, whereas group II included 9 isolates from two regions. Three isolates did not cluster within these groups. Analysis of disease severity data also revealed variability in aggressiveness among isolates but no correlation could be established with either SSR haplotypes or phenetic groups. Isolates with identical haplotypes differed in aggressiveness and vice versa. However, single marker-trait analysis revealed two markers associated with this trait.

Genetic divergence of sugar cane cultivars for resistance to Diatraea saccharalis / Divergência genética de cultivares de cana-de-açúcar quanto à resistência a Diatraea saccharalis

The objective was to evaluate the genetic diversity of cultivars in sugar cane for resistance to D. saccharalis. The experiment was carried out in the laboratory in completely randomized design with 11 treatments (one control and 10 treatments) in ten replications. The replications were made from artificial diets (food and refood) made with dry steam crushed from sugar cane cultivars stems, except for one of them considered standard diet. The cultivars used were: RB867515, RB855453, RB855536, CTC 15, CTC 9, SP80-1842, SP79-1011, SP89-1115, SP81-3250 and SP87-365. In the evaluation biological characteristics of the insect considered were: larval development (days), larval viability (%), pupal development (days), pupal weight (g), pupal viability (%), period of hatched larvae to adults emergence (days), total viability (%) and adults longevity without food (days). The generalized Mahalanobis distance (D2) for the cluster analysis by the method of average linkage between groups (UPGMA) and Tochers method optimization was determined. Four and five groups were formed, respectively, by the method of average linkage between groups (UPGMA) and Tochers method optimization. We concluded that the cultivar CTC 15 standed out as highly susceptible to D. saccharalis, while the cultivar SP87- 365 behaved as moderately resistant by antibiosis to D. saccharalis.

O objetivo do trabalho foi avaliar a divergência genética de cultivares de cana-de-açúcar quanto à resistência a D. saccharalis. O experimento foi conduzido em laboratório em delineamento inteiramente casualizado, com 11 tratamentos (uma testemunha e dez cultivares) em dez repetições. As repetições foram constituídas a partir de dietas artificiais (alimentação e realimentação) elaboradas com colmo seco triturado de cada cultivar de cana-de-açúcar, com exceção de uma delas considerada dieta padrão. As cultivares utilizadas foram: RB867515, RB855453, RB855536, CTC 15, CTC 9, SP80-1842, SP79-1011, SP89-1115, SP81-3250 e SP87-365. Na avaliação foram considerados os seguintes parâmetros biológicos do inseto: período larval (dias), viabilidade larval (%), período pupal (dias), peso de pupas (g), viabilidade pupal (%), período da eclosão da larva à emergência do adulto (dias), viabilidade total (%) e a longevidade dos adultos de D. saccharalis sem alimento (dias). Determinou-se a distância generalizada de Mahalanobis (D2) para a análise de agrupamento pelo método da ligação média entre grupo (UPGMA) e otimização de Tocher. Foram formados quatro e cinco grupos, respectivamente, pelo método da ligação média entre grupo (UPGMA) e otimização de Tocher. Conclui-se que a cultivar CTC 15 apresentou comportamento análogo à testemunha destacando-se como altamente suscetível a D. saccharalis, e

Genetic divergence of sugar cane cultivars for resistance to Diatraea saccharalis / Divergência genética de cultivares de cana-de-açúcar quanto à resistência a Diatraea saccharalis

The objective was to evaluate the genetic diversity of cultivars in sugar cane for resistance to D. saccharalis. The experiment was carried out in the laboratory in completely randomized design with 11 treatments (one control and 10 treatments) in ten replications. The replications were made from artificial diets (food and refood) made with dry steam crushed from sugar cane cultivars stems, except for one of them considered standard diet. The cultivars used were: RB867515, RB855453, RB855536, CTC 15, CTC 9, SP80-1842, SP79-1011, SP89-1115, SP81-3250 and SP87-365. In the evaluation biological characteristics of the insect considered were: larval development (days), larval viability (%), pupal development (days), pupal weight (g), pupal viability (%), period of hatched larvae to adults emergence (days), total viability (%) and adults longevity without food (days). The generalized Mahalanobis distance (D2) for the cluster analysis by the method of average linkage between groups (UPGMA) and Tochers method optimization was determined. Four and five groups were formed, respectively, by the method of average linkage between groups (UPGMA) and Tochers method optimization. We concluded that the cultivar CTC 15 standed out as highly susceptible to D. saccharalis, while the cultivar SP87- 365 behaved as moderately resistant by antibiosis to D. saccharalis.

O objetivo do trabalho foi avaliar a divergência genética de cultivares de cana-de-açúcar quanto à resistência a D. saccharalis. O experimento foi conduzido em laboratório em delineamento inteiramente casualizado, com 11 tratamentos (uma testemunha e dez cultivares) em dez repetições. As repetições foram constituídas a partir de dietas artificiais (alimentação e realimentação) elaboradas com colmo seco triturado de cada cultivar de cana-de-açúcar, com exceção de uma delas considerada dieta padrão. As cultivares utilizadas foram: RB867515, RB855453, RB855536, CTC 15, CTC 9, SP80-1842, SP79-1011, SP89-1115, SP81-3250 e SP87-365. Na avaliação foram considerados os seguintes parâmetros biológicos do inseto: período larval (dias), viabilidade larval (%), período pupal (dias), peso de pupas (g), viabilidade pupal (%), período da eclosão da larva à emergência do adulto (dias), viabilidade total (%) e a longevidade dos adultos de D. saccharalis sem alimento (dias). Determinou-se a distância generalizada de Mahalanobis (D2) para a análise de agrupamento pelo método da ligação média entre grupo (UPGMA) e otimização de Tocher. Foram formados quatro e cinco grupos, respectivamente, pelo método da ligação média entre grupo (UPGMA) e otimização de Tocher. Conclui-se que a cultivar CTC 15 apresentou comportamento análogo à testemunha destacando-se como altamente suscetível a D. saccharalis, e

Minimizing inter-genotypic competition effects to predict genetic values and selection in forestry genetic tests

The effect of competition is an important source of variation in breeding experiments. This study aimed to compare the selection of plants of open-pollinated families of Eucalyptus with and without the use of competition covariables. Genetic values were determined for each family and tree and for the traits height, diameter at breast height and timber volume in a randomized block design, resulting in the variance components, genetic parameters, selection gains, effective size and selection coincidence, with and without the use of covariables. Intergenotypic competition is an important factor of environmental variation. The use of competition covariables generally reduces the estimates of variance components and influences genetic gains in the studied traits. Intergenotypic competition biases the selection of open-pollinated eucalypt progenies, and can result in an erroneous choice of superior genotypes; the inclusion of covariables in the model reduces this influence.

Minimizing inter-genotypic competition effects to predict genetic values and selection in forestry genetic tests

The effect of competition is an important source of variation in breeding experiments. This study aimed to compare the selection of plants of open-pollinated families of Eucalyptus with and without the use of competition covariables. Genetic values were determined for each family and tree and for the traits height, diameter at breast height and timber volume in a randomized block design, resulting in the variance components, genetic parameters, selection gains, effective size and selection coincidence, with and without the use of covariables. Intergenotypic competition is an important factor of environmental variation. The use of competition covariables generally reduces the estimates of variance components and influences genetic gains in the studied traits. Intergenotypic competition biases the selection of open-pollinated eucalypt progenies, and can result in an erroneous choice of superior genotypes; the inclusion of covariables in the model reduces this influence.

Comparação de ambientes na germinação de cariopses de cana-de-açúcar / Environment comparison in the germination of sugarcane seeds

A obtenção de cariopses de cana-de-açúcar por meio de cruzamento de parentais é de primordial importância para os programas de melhoramento de cultivares. Objetivou-se, neste trabalho comparar o ambiente de germinação de cariopses da casa de vegetação do Programa Cana IAC com um ambiente de condições controladas, a fim de avaliar sua eficiência, no período de 30/09 a 09/10/2004. Foram desenvolvidos dois experimentos, em delineamento experimental de blocos casualizados com quatro repetições, em Jaú, SP. Um deles foi montado sob condições de laboratório em câmara de germinação e outro em casa de vegetação em condições não controladas, sendo cada tratamento constituído por 100 cariopses por repetição, provenientes de seis cruzamentos. Foram realizadas avaliações do índice de velocidade de germinação (IVG), da porcentagem ( por centoG) e dos dias para emergência (DE), em intervalos de 24 horas, após a instalação dos testes. A massa de 100 sementes de cada cruzamento também foi avaliada com o propósito de verificar sua influência nos demais atributos da germinação. Os resultados foram submetidos à análise de variância e a comparação de médias foi feita pelo teste de Tukey, a 0,05 de significância. A massa de 100 sementes foi diferente entre os cruzamentos, e interferiu, de maneira geral, nos atributos IVG e por cento G. Concluiu-se que a casa de vegetação utilizada pelo Programa Cana IAC proporciona porcentagens de germinação semelhantes às da câmara de germinação, porém condições controladas favorecem o IVG e os DE.

The production of true seeds of sugarcane through parental crossing is primordial for the breeding programs of cultivars. With the objective of comparing the efficiency of the environment greenhouse used for seed germination in the IAC Sugarcane Program with an environment with controlled conditions (germination chamber), two experiments were carried out in a completely randomized block with four replicates of 100 seeds each, in Jaú (SP), from 09/30 to 10/09/2004. In both places the treatments were composed of seeds from six crossings. The evaluations accomplished were speed of germination index (SGI), germination percentage ( percent G) and days for emergence (DE) in 24 h intervals after set up treatments. The mass of 100 seeds of each crossing was also evaluated with the purpose of measuring its influence on other germination attributes. The data were submitted to the analysis of variance and averages were compared by the Tukey test at 0.005 significance. The weight of 100 seeds differed among the crossings, and, in general, it interfered with the attributes SGI and percent G. It was concluded that the greenhouse used by the IAC Sugarcane Program provides germination percentages similar to the germination chamber; however, controlled conditions improve SGI and DE.

Efeitos por comparações e por experimento em interações de experimentos fatoriais / Comparisonwise and experimentwise effects in fatorial experiments interactions

Avaliar efeitos de interações é um dos principais objetivos dos experimentos fatoriais. Em experimentos com dois fatores A e B, com m e n níveis de cada fator, respectivamente, há m x n possíveis interações e (m-1)(n-1) graus de liberdade associados. Freqüentemente somente parte dessas interações contribui efetivamente para a Soma de Quadrados da Interação e pode ser interessante examiná-las. O uso de nível de significância menos rigoroso para interpretação do efeito da interação "por experimento", em relação às demais fontes de variação da análise de variância, pode captar efeitos importantes. Recomenda-se o uso de p = 0,25 para a interpretação do efeito da interação "por experimento", mantendo-se o usual p = 0,05 para efeitos "por comparações". Mesmo no caso de interações significativas, comparações selecionadas, em lugar de apenas "cortes", podem auxiliar a interpretação de interações complexas.

To evaluate interaction is one of the most important objectives of fatorial experiments. In experiments with two factors A and B, with m and n levels of each factor, there are m x n possible interactions and (m-1)(n-1) degrees of freedom associated. Frequently just a part of these interactions contributes effectively to the sum of squares of interaction and must be interesting to evaluate them. The use of less rigorous level of significance for interpretation of the interaction "for experiment", in relation to sources of variation of the variance analysis, may catch important effect. One recommends the use of p = 0.25 for the interpretation of the effect of the interaction "for experiment" remaining usual p = 0.05 for effect "for comparisons". Even in the case of significant interactions, selected comparisons, instead of "cuts" only, may assist the interpretation of complex interactions.

Electrical conductivity as an indicator of pea seed aging of stored at different temperatures

Research on soybean seed has revealed that conductivity test results may be influenced by storage temperature and that an apparent direct relationship between deterioration at low temperatures and loss of cellular membrane integrity is not evident. The objective of this study was to verify the influence of low storage temperatures on electrical conductivity results in other species, such as seeds of two pea cultivars studied temperatures were: 10, 20, 25, 20/10 and 25/10ºC. The physiological potential of the seeds was evaluated every three months during an 18 month storage period using germination, accelerated aging and electrical conductivity tests. The electrical conductivity test was not a good indicator for the degree of seed deterioration stored at low temperatures. Seed deterioration at 10ºC did not seem to be directly related to the loss of membrane integrity, possibly due to membrane repair or reorganization during storage at this temperature.

Pesquisas com sementes de soja têm revelado que os resultados do teste de condutividade elétrica podem ser influenciados pela temperatura de armazenamento, sugerindo que a deterioração das sementes em temperaturas baixas parece não estar relacionada diretamente com a perda da integridade das membranas celulares. O presente estudo foi conduzido com o objetivo de verificar se a influência de baixas temperaturas de armazenamento nos resultados da condutividade elétrica ocorre também para outra espécie, sendo utilizadas para tanto, sementes de dois cultivares de ervilha. O efeito das seguintes temperaturas foi estudado: 10, 20, 25, 20/10 e 25/10ºC. A cada três meses, num total de 18 meses de armazenamento, foi avaliado o potencial fisiológico das sementes usando-se os testes de germinação, envelhecimento acelerado e condutividade elétrica. O teste de condutividade elétrica não se mostrou um bom indicador da intensidade do processo de deterioração de sementes armazenadas a baixas temperaturas. A deterioração das sementes a 10ºC parece não estar relacionada diretamente com a perda da integridade das membranas, possivelmente devido ao reparo ou à reorganização das mesmas durante o período de armazenamento nesta temperatura.

Electrical conductivity as an indicator of pea seed aging of stored at different temperatures

Research on soybean seed has revealed that conductivity test results may be influenced by storage temperature and that an apparent direct relationship between deterioration at low temperatures and loss of cellular membrane integrity is not evident. The objective of this study was to verify the influence of low storage temperatures on electrical conductivity results in other species, such as seeds of two pea cultivars studied temperatures were: 10, 20, 25, 20/10 and 25/10ºC. The physiological potential of the seeds was evaluated every three months during an 18 month storage period using germination, accelerated aging and electrical conductivity tests. The electrical conductivity test was not a good indicator for the degree of seed deterioration stored at low temperatures. Seed deterioration at 10ºC did not seem to be directly related to the loss of membrane integrity, possibly due to membrane repair or reorganization during storage at this temperature.

Pesquisas com sementes de soja têm revelado que os resultados do teste de condutividade elétrica podem ser influenciados pela temperatura de armazenamento, sugerindo que a deterioração das sementes em temperaturas baixas parece não estar relacionada diretamente com a perda da integridade das membranas celulares. O presente estudo foi conduzido com o objetivo de verificar se a influência de baixas temperaturas de armazenamento nos resultados da condutividade elétrica ocorre também para outra espécie, sendo utilizadas para tanto, sementes de dois cultivares de ervilha. O efeito das seguintes temperaturas foi estudado: 10, 20, 25, 20/10 e 25/10ºC. A cada três meses, num total de 18 meses de armazenamento, foi avaliado o potencial fisiológico das sementes usando-se os testes de germinação, envelhecimento acelerado e condutividade elétrica. O teste de condutividade elétrica não se mostrou um bom indicador da intensidade do processo de deterioração de sementes armazenadas a baixas temperaturas. A deterioração das sementes a 10ºC parece não estar relacionada diretamente com a perda da integridade das membranas, possivelmente devido ao reparo ou à reorganização das mesmas durante o período de armazenamento nesta temperatura.

Geostatistical characterization of the spatial distribution of Xylella fastidiosa sharpshooter vectors on citrus / Caracterização geoestatística da distribuição espacial de cigarrinhas vetores de Xylella fastidiosa em citrus

A distribuição espacial das espécies de cigarrinhas (Dilobopterus costalimai Young, Acrogonia sp. e Oncometopia facialis Signoret), vetoras da Xylella fastidiosa, agente causal da Clorose Variegada dos Citros, foi estudada com o uso da geoestatística. As avaliações foram feitas em um pomar comercial de laranja 'Pêra' (Citrus sinensis [L.] Osb.), objetivando estabelecer meios para melhor controle dos vetores e da doença. O monitoramento da ocorrência das cigarrinhas no pomar foi feito através de amostragens mensais, utilizando-se armadilhas adesivas amarelas de 3" x 5", distribuídas uniformemente em 50 pontos na área, dispostas em laranjeiras à altura de 1,5 m do solo e substituídas mensalmente. Acrogonia sp. foi a espécie prevalente nas amostragens. Os resultados possibilitaram ajustar modelos aos semivariogramas da distribuição espacial das três espécies no pomar estudado. Durante os três anos consecutivos de amostragem, as populações de Acrogonia sp., D. costalimai e O. facialis apresentaram modelos de distribuição agregada somente nos meses de verão, inverno e primavera, respectivamente, mostrando a necessidade de monitoramento constante desses vetores para reduzir a sua população em épocas favoráveis ao seu desenvolvimento. Através de parâmetros geoestatísticos foi possível calcular a área de agregação das cigarrinhas no pomar. A espécie Acrogonia sp. apresentou área média de agregação de 15.760 m², enquanto para O. facialis e D. costalimai foi possível constatar áreas médias de agregação de 11.555 m² e 10.980 m², respectivamente. Esses resultados indicaram que para um levantamento seguro de cigarrinhas é necessário pelo menos dispor de uma armadilha por hectare.

The spatial distribution of the three principal species of sharpshooter (Dilobopterus costalimai Young, Acrogonia sp. e Oncometopia facialis Signoret), vectors of Xylella fastidiosa causal agent of Citrus Variegated Chlorosis, was studied by using geostatistics. The evaluations were carried out in a commercial 'Pera' sweet orange (Citrus sinensis [L.] Osb.) grove budded on Rangpur lime (Citrus limonia Osb.) located at Bebedouro, São Paulo state, aiming to establish better means for vector and disease control. The sharpshooters were monitored using with 50 uniformly distributed 3" x 5" yellow sticky traps hanging down in branches at 1.5 m up to the ground, which were replaced monthly. Acrogonia sp. was the prevalent species sampled. The results were used to adjust population models to semivariograms of the spatial distribution of the three sharpshooters species in the grove. During the three consecutive years of sampling, the population of Acrogonia sp., D. costalimai and O. facialis showed an aggregated distribution only during summer, winter and spring, respectively, showing that intensive monitoring of these vectors is necessary to control their population in periods favorable to their development. The aggregation area of the sharpshooters within the orange grove was determined using geostatistic parameters. Acrogonia sp. showed a mean aggregation area of 15,760 m², whereas for O. facialis and D. costalimai, the corresponding areas were 11,555 m² and 10,980 m², respectively. Therefore, in order to obtain a reliable estimate of sharpshooter populations, at least one trap should be used per hectare.

Oxisol subsurface chemical attributes related to sugarcane productivity

In spite of the great homogeneity found in the morphological characteristics of Oxisols, there is great chemical diversity in subsurface layers of these soils. Studies indicate that crop yield presents significant correlation with the chemical attributes of the subsurface, which, are more stable than attributes found in the plough layer, subject to greater alterations as a consequence of agricultural exploration. This work evaluated the effects of subsurface chemical attributes of Oxisols of the South Central region of Brazil, on the yield of sugarcane clones and of variety RB72454, during the first, second and third cropping cycles. Productivity data were obtained between 1993 and 1998. Soils were characterized in terms of their mechanical analysis and chemical traits at 0.8 to 1.0 m; correlation studies between these attributes and mean daily productivity as well as multiple regression analysis were also carried out; variables were selected based on their R² values by means of the stepwise procedure. The subsurface chemical traits of the Oxisols influenced sugarcane productivity, especially the 3rd harvest; the clone productivity model for the 3rd harvest as a function of base saturation and phosphorus content presented R² = 0.31, i.e., 31% of the variation in sugarcane yield (t ha-1 day-1) can be explained by these two attributes. For variety RB72454, 47% of that variation is explained by the sum of bases and contents of calcium and organic matter. Variations on productivity at 1st and 2nd harvests can be better explained by pHwater.

Embora haja homogeneidade nas características morfológicas na classe dos Latossolos, existe grande diversidade química na subsuperfície. Trabalhos indicam que a produção agrícola apresenta correlação significativa com atributos químicos de subsuperfície, que são mais estáveis que na camada arável, sujeita a alterações decorrentes da exploração agrícola. Pelo exposto, o presente estudo avaliou os efeitos dos atributos químicos de subsuperfície de Latossolos da região Centro-Sul do Brasil na produtividade agrícola dos três primeiros cortes de clones de cana-de-açúcar e da variedade RB72454. Utilizaram-se os dados de produtividade agrícola correspondentes ao período de 1993 a 1998. Os solos foram caracterizados sob o ponto de vista granulométrico e químico na profundidade entre 0,8 e 1,0 m e foram feitos estudos de correlação entre tais atributos e as médias de produtividade agrícola diária durante o ciclo dos clones de cada ensaio e da variedade RB72454 e análise de regressão múltipla, com as variáveis selecionadas pelo procedimento "stepwise" em função do R². As características químicas de subsuperfície dos Latossolos influenciaram na produtividade agrícola da cana-de-açúcar, principalmente no 3º corte. Para as médias dos clones, o modelo de produtividade do 3º corte em função de saturação por bases e fósforo, mostra R² = 0,31, ou seja, que 31% da variação de TCH dia-1 pode ser explicada por esses dois atributos. No caso da variedade RB72454, essa mesma variação no 3º corte é explicada em 47% pelos atributos soma de bases e teores de cálcio e matéria orgânica. As variações de produtividade de 1º e 2º cortes foram melhor explicadas pelo pHágua.

Oxisol subsurface chemical attributes related to sugarcane productivity

In spite of the great homogeneity found in the morphological characteristics of Oxisols, there is great chemical diversity in subsurface layers of these soils. Studies indicate that crop yield presents significant correlation with the chemical attributes of the subsurface, which, are more stable than attributes found in the plough layer, subject to greater alterations as a consequence of agricultural exploration. This work evaluated the effects of subsurface chemical attributes of Oxisols of the South Central region of Brazil, on the yield of sugarcane clones and of variety RB72454, during the first, second and third cropping cycles. Productivity data were obtained between 1993 and 1998. Soils were characterized in terms of their mechanical analysis and chemical traits at 0.8 to 1.0 m; correlation studies between these attributes and mean daily productivity as well as multiple regression analysis were also carried out; variables were selected based on their R² values by means of the stepwise procedure. The subsurface chemical traits of the Oxisols influenced sugarcane productivity, especially the 3rd harvest; the clone productivity model for the 3rd harvest as a function of base saturation and phosphorus content presented R² = 0.31, i.e., 31% of the variation in sugarcane yield (t ha-1 day-1) can be explained by these two attributes. For variety RB72454, 47% of that variation is explained by the sum of bases and contents of calcium and organic matter. Variations on productivity at 1st and 2nd harvests can be better explained by pHwater.

Embora haja homogeneidade nas características morfológicas na classe dos Latossolos, existe grande diversidade química na subsuperfície. Trabalhos indicam que a produção agrícola apresenta correlação significativa com atributos químicos de subsuperfície, que são mais estáveis que na camada arável, sujeita a alterações decorrentes da exploração agrícola. Pelo exposto, o presente estudo avaliou os efeitos dos atributos químicos de subsuperfície de Latossolos da região Centro-Sul do Brasil na produtividade agrícola dos três primeiros cortes de clones de cana-de-açúcar e da variedade RB72454. Utilizaram-se os dados de produtividade agrícola correspondentes ao período de 1993 a 1998. Os solos foram caracterizados sob o ponto de vista granulométrico e químico na profundidade entre 0,8 e 1,0 m e foram feitos estudos de correlação entre tais atributos e as médias de produtividade agrícola diária durante o ciclo dos clones de cada ensaio e da variedade RB72454 e análise de regressão múltipla, com as variáveis selecionadas pelo procedimento "stepwise" em função do R². As características químicas de subsuperfície dos Latossolos influenciaram na produtividade agrícola da cana-de-açúcar, principalmente no 3º corte. Para as médias dos clones, o modelo de produtividade do 3º corte em função de saturação por bases e fósforo, mostra R² = 0,31, ou seja, que 31% da variação de TCH dia-1 pode ser explicada por esses dois atributos. No caso da variedade RB72454, essa mesma variação no 3º corte é explicada em 47% pelos atributos soma de bases e teores de cálcio e matéria orgânica. As variações de produtividade de 1º e 2º cortes foram melhor explicadas pelo pHágua.

Morfologia floral e biologia reprodutiva de genótipos de aceroleira

Flower morphology and reproductive biology knowledge of fruit crops may contribute to the development of castration and pollination tecniques. With this objective, flower structure and the biology of West Indian cherry genotypes were studied at Jaboticabal, SP, Brazil. Flower morphology was evaluated by characterization, quantification and reproductive biology, from flower bud beginning until opening. West Indian Cherry flower is hermaphrodite with a calix of six or seven sepals, corolla of five petals, nine or ten glands in the lower region, ten stamen androecium and gyneceum with three or four pistils. The flowers are distributed in bunches of 3 to 13 units each, on the same year or on the latest year branches. Plants flower 6 to 7 times per year, mainly from January to May and August to December periods, with about 7 days elapsed from flower bud appearance to anthesis, wich occurs from 5h00 to 8h00 AM and from 2h00 to 4h00 PM. The flowering period endures from 22.1 to 29.4 days. The fruit ripeness occurs 22 days after flowering and the crop lasts 19.7 to 28.8 days.

Estudos sobre morfologia floral e biologia reprodutiva de uma cultura contribuem para o desenvolvimento de técnicas de castração e polinização. Com este propósito, estudaram-se a estrutura e a biologia floral em cinco genótipos de aceroleira (Malpighia emarginata), em Jaboticabal, SP; no período de dezembro/97 a janeiro/99. Foi avaliada a morfologia floral, por caracterização e quantificação, e a biologia reprodutiva, desde o aparecimento dos primórdios do botão floral até a abertura. As flores da aceroleira são monóclinas, com cálice composto por seis a sete sépalas, corola de cinco pétalas, nove a dez glândulas presentes na base, androceu com dez estames e gineceu com três a quatro pistilos e distribuem-se em cimeiras axilares com 3 a 13 flores nos ramos do ano anterior e do mesmo ano. Verificaram-se de 6 a 7 floradas por ano, principalmente de janeiro a maio e de agosto a dezembro, registrando-se que desde o aparecimento do botão floral à antese decorrem 6,9 a 7 dias, com abertura floral entre 5h00 e 8h00 e das 14h00 às 16h00, com floração de 22,1 a 29,4 dias, decorrendo do florescimento à maturação do fruto 22 dias e duração da colheita de 19,7 a 28,8 dias.

Morfologia floral e biologia reprodutiva de genótipos de aceroleira

Flower morphology and reproductive biology knowledge of fruit crops may contribute to the development of castration and pollination tecniques. With this objective, flower structure and the biology of West Indian cherry genotypes were studied at Jaboticabal, SP, Brazil. Flower morphology was evaluated by characterization, quantification and reproductive biology, from flower bud beginning until opening. West Indian Cherry flower is hermaphrodite with a calix of six or seven sepals, corolla of five petals, nine or ten glands in the lower region, ten stamen androecium and gyneceum with three or four pistils. The flowers are distributed in bunches of 3 to 13 units each, on the same year or on the latest year branches. Plants flower 6 to 7 times per year, mainly from January to May and August to December periods, with about 7 days elapsed from flower bud appearance to anthesis, wich occurs from 5h00 to 8h00 AM and from 2h00 to 4h00 PM. The flowering period endures from 22.1 to 29.4 days. The fruit ripeness occurs 22 days after flowering and the crop lasts 19.7 to 28.8 days.

Estudos sobre morfologia floral e biologia reprodutiva de uma cultura contribuem para o desenvolvimento de técnicas de castração e polinização. Com este propósito, estudaram-se a estrutura e a biologia floral em cinco genótipos de aceroleira (Malpighia emarginata), em Jaboticabal, SP; no período de dezembro/97 a janeiro/99. Foi avaliada a morfologia floral, por caracterização e quantificação, e a biologia reprodutiva, desde o aparecimento dos primórdios do botão floral até a abertura. As flores da aceroleira são monóclinas, com cálice composto por seis a sete sépalas, corola de cinco pétalas, nove a dez glândulas presentes na base, androceu com dez estames e gineceu com três a quatro pistilos e distribuem-se em cimeiras axilares com 3 a 13 flores nos ramos do ano anterior e do mesmo ano. Verificaram-se de 6 a 7 floradas por ano, principalmente de janeiro a maio e de agosto a dezembro, registrando-se que desde o aparecimento do botão floral à antese decorrem 6,9 a 7 dias, com abertura floral entre 5h00 e 8h00 e das 14h00 às 16h00, com floração de 22,1 a 29,4 dias, decorrendo do florescimento à maturação do fruto 22 dias e duração da colheita de 19,7 a 28,8 dias.