Effects of Soybean Planting Date on Yield Loss From Defoliation.

Soybean, Glycine max (L.) Merr., is planted during 3.5-4 mo across the Mid-South United States. Currently, no information exists regarding the effects of planting date on soybean yield loss from early season defoliation. In 2015 and 2016, to evaluate the effects of planting date on yield loss from defoliation, soybean were planted in field plots 2 wk apart from early April to mid-June, for a total of six planting dates. Each planting date included a nondefoliated control and a 100% defoliation treatment where leaves were manually excised at the V4 growth stage. Mean yield loss from defoliation varied across planting dates, with mid-April plantings having the least amount yield reduction, 573 kg/ha, and early-June plantings having the greatest yield reduction, 904 kg/ha. Percent yield reduction from defoliation increased as planting was delayed, suggesting that defoliation thresholds might need adjustment based on planting date and yield potential. However, more research is needed at lower levels of defoliation to accurately delineate such thresholds.

Elucidating the genetic basis of biomass accumulation and radiation use efficiency in spring wheat and its role in yield potential.

One of the major challenges for plant scientists is increasing wheat (Triticum aestivum) yield potential (YP). A significant bottleneck for increasing YP is achieving increased biomass through optimization of radiation use efficiency (RUE) along the crop cycle. Exotic material such as landraces and synthetic wheat has been incorporated into breeding programmes in an attempt to alleviate this; however, their contribution to YP is still unclear. To understand the genetic basis of biomass accumulation and RUE, we applied genome-wide association study (GWAS) to a panel of 150 elite spring wheat genotypes including many landrace and synthetically derived lines. The panel was evaluated for 31 traits over 2 years under optimal growing conditions and genotyped using the 35K wheat breeders array. Marker-trait association identified 94 SNPs significantly associated with yield, agronomic and phenology-related traits along with RUE and final biomass (BM_PM) at various growth stages that explained 7%-17% of phenotypic variation. Common SNP markers were identified for grain yield, BM_PM and RUE on chromosomes 5A and 7A. Additionally, landrace and synthetic derivative lines showed higher thousand grain weight (TGW), BM_PM and RUE but lower grain number (GM2) and harvest index (HI). Our work demonstrates the use of exotic material as a valuable resource to increase YP. It also provides markers for use in marker-assisted breeding to systematically increase BM_PM, RUE and TGW and avoid the TGW/GM2 and BM_PM/HI trade-off. Thus, achieving greater genetic gains in elite germplasm while also highlighting genomic regions and candidate genes for further study.

Genome-Wide Association Analyses Identify QTL Hotspots for Yield and Component Traits in Durum Wheat Grown under Yield Potential, Drought, and Heat Stress Environments.

Understanding the genetic bases of economically important traits is fundamentally important in enhancing genetic gains in durum wheat. In this study, a durum panel of 208 lines (comprised of elite materials and exotics from the International Maize and Wheat Improvement Center gene bank) were subjected to genome wide association study (GWAS) using 6,211 DArTseq single nucleotide polymorphisms (SNPs). The panel was phenotyped under yield potential (YP), drought stress (DT), and heat stress (HT) conditions for 2 years. Mean yield of the panel was reduced by 72% (to 1.64 t/ha) under HT and by 60% (to 2.33 t/ha) under DT, compared to YP (5.79 t/ha). Whereas, the mean yield of the panel under HT was 30% less than under DT. GWAS identified the largest number of significant marker-trait associations on chromosomes 2A and 2B with p-values 10-06 to 10-03 and the markers from the whole study explained 7-25% variation in the traits. Common markers were identified for stress tolerance indices: stress susceptibility index, stress tolerance, and stress tolerance index estimated for the traits under DT (82 cM on 2B) and HT (68 and 83 cM on 3B; 25 cM on 7A). GWAS of irrigated (YP and HT combined), stressed (DT and HT combined), combined analysis of three environments (YP + DT + HT), and its comparison with trait per se and stress indices identified QTL hotspots on chromosomes 2A (54-70 cM) and 2B (75-82 cM). This study enhances our knowledge about the molecular markers associated with grain yield and its components under different stress conditions. It identifies several marker-trait associations for further exploration and validation for marker-assisted breeding.

Características agronômicas produtivas, qualidade e custo de produção de forragem em pastagem de azevém (Lolium multiflorum Lam) fertilizada com dois tipos de adubo

One experiment was conducted, with the purpose to evaluate the production, quality and the production cost of forage of ryegrass, in continuous grazing, fertilized with two types of fertilizer: Organic-mineral (FOM) and chemical (FC) applied as top dressing. The pasture was implanted in 04/24/1999, with top-seeding, and the level of fertilizer was300kg ha-1 of FOM formula 06-08-08 or FC formula 10-18-20. No significant interaction between fertilizer and evaluation period was observed for the variables studied. The fertilizer sources did not affect the percentage of dry matter (DM) in the residue (22.6 vs 22.2%), the accumulation rate of dry matter (72.3 vs 63.2kg ha-1 of DM), the total forage production (7518 vs 6801 kg ha-1 of DM), the percentage of crude protein (12.8 vs 12.7%), the neutral detergent fiber (57.4 vs 57.4%) and acid detergent fiber (31.0 vs 32.3%), for FOM and FC, respectively. The total cost of the pasture was of 225.90 and 253.50 R$ ha-1, where the fertilizer represented 37.6 and 44.4%, respectively, for FOM and FC. The production cost of the pasture DM was 0.030 and 0.037 R$ kg-1, for FOM and FC, respectively.

Um experimento foi conduzido, com o objetivo de avaliar o comportamento produtivo e qualitativo, bem como, o custo de produção de forragem da pastagem de azevém comum, em pastejo contínuo, fertilizada com dois tipos de adubos: Organo-mineral (AOM) e Químico (AQ). O estabelecimento da pastagem foi em 24/04/1999, com semeadura a lanço e o nível de adubação, em cobertura, foi de 300kg ha-1 do AOM na fórmula 06-08-08 ou do AQ na fórmula 10-18-20. Não houve interação significativa entre os fertilizantes e período de avaliação para as variáveis estudadas. A fonte de nutrientes, para os valores médios, não afetou significativamente o teor de matéria seca (MS) no resíduo (22,6 vs 22,2%), a taxa de acumulação diária (72,3 vs 63,3kg ha-1 de MS), a produção total de forragem (7.518 vs 6.801kg ha-1 de MS), o teor de proteína bruta (12,8 vs 12,7%), a fibra em detergente neutro (57,4 vs 57,4%) e a fibra em detergente ácido (31,0 vs 32,3%), respectivamente, para o AOM e AQ. O custo total da pastagem foi de 225,90 e 253,50 R$ ha-1, e a fonte de nutrientes representou 37,6 e 44,4%, respectivamente, para o AOM e AQ. Para o custo de forragem produzida, os valores foram de 0,030 e 0,037 R$ kg-1 de MS para a pastagem fertilizada com AOM e AQ, respectivamente.

Características agronômicas produtivas, qualidade e custo de produção de forragem em pastagem de azevém (Lolium multiflorum Lam) fertilizada com dois tipos de adubo

One experiment was conducted, with the purpose to evaluate the production, quality and the production cost of forage of ryegrass, in continuous grazing, fertilized with two types of fertilizer: Organic-mineral (FOM) and chemical (FC) applied as top dressing. The pasture was implanted in 04/24/1999, with top-seeding, and the level of fertilizer was300kg ha-1 of FOM formula 06-08-08 or FC formula 10-18-20. No significant interaction between fertilizer and evaluation period was observed for the variables studied. The fertilizer sources did not affect the percentage of dry matter (DM) in the residue (22.6 vs 22.2%), the accumulation rate of dry matter (72.3 vs 63.2kg ha-1 of DM), the total forage production (7518 vs 6801 kg ha-1 of DM), the percentage of crude protein (12.8 vs 12.7%), the neutral detergent fiber (57.4 vs 57.4%) and acid detergent fiber (31.0 vs 32.3%), for FOM and FC, respectively. The total cost of the pasture was of 225.90 and 253.50 R$ ha-1, where the fertilizer represented 37.6 and 44.4%, respectively, for FOM and FC. The production cost of the pasture DM was 0.030 and 0.037 R$ kg-1, for FOM and FC, respectively.

Um experimento foi conduzido, com o objetivo de avaliar o comportamento produtivo e qualitativo, bem como, o custo de produção de forragem da pastagem de azevém comum, em pastejo contínuo, fertilizada com dois tipos de adubos: Organo-mineral (AOM) e Químico (AQ). O estabelecimento da pastagem foi em 24/04/1999, com semeadura a lanço e o nível de adubação, em cobertura, foi de 300kg ha-1 do AOM na fórmula 06-08-08 ou do AQ na fórmula 10-18-20. Não houve interação significativa entre os fertilizantes e período de avaliação para as variáveis estudadas. A fonte de nutrientes, para os valores médios, não afetou significativamente o teor de matéria seca (MS) no resíduo (22,6 vs 22,2%), a taxa de acumulação diária (72,3 vs 63,3kg ha-1 de MS), a produção total de forragem (7.518 vs 6.801kg ha-1 de MS), o teor de proteína bruta (12,8 vs 12,7%), a fibra em detergente neutro (57,4 vs 57,4%) e a fibra em detergente ácido (31,0 vs 32,3%), respectivamente, para o AOM e AQ. O custo total da pastagem foi de 225,90 e 253,50 R$ ha-1, e a fonte de nutrientes representou 37,6 e 44,4%, respectivamente, para o AOM e AQ. Para o custo de forragem produzida, os valores foram de 0,030 e 0,037 R$ kg-1 de MS para a pastagem fertilizada com AOM e AQ, respectivamente.

Rendimento de grãos e componentes do rendimento de cultivares de milho em duas épocas de semeadura

The experiment was carried out in Passo Fundo-RS, Brazil, in order to evaluate the interaction between cultivars and planting dates for corn yield and yield components. The experiment was conducted under irrigated, during the 1991/92 growing season. Two planting dates (September 13, 1991 and January 3, 1992) and nine com cultivars (C 805, C 901, P 3069, SR 100, AG 303, AG 513, XL 560, XL 605 and G 5555) were tested. Plants were harvested on March 4, 1992 and May 26, 1992 for the planting dates of September and January, respectively. There were differences in the grain yield and yield components among the cultivars for the two planting dates tested. In September, the sowing of the C 901 and C 805 cultivars showed the highest grain yield. In January, the cultivar C 901 showed the highest grain yield. The average grain yield varied from 9.69t ha-1, in the first planting date to 4.05t ha-1 in the second planting date. The average grain yield was reduced in 58.2%. from the first to the second planting date. The grain yield decreased more than 60% in XL 560, P 3069 and SR 100 cultivars as a result of the delay in the planting date. The sowing in September favoured more kernel weight and number of kernels per ear than the sowing in January.

Este experimento teve como objetivo verificar a existência de interação entre cultivares e épocas de semeadura para rendimento de grãos e componentes do rendimento em milho. O experimento, realizado em Passo Fundo, RS, foi conduzido sob condições de suplementação hídrica, durante o ano agrícola 1991/92. Os tratamentos constaram de duas épocas de semeadura (13 de setembro de 1991 e 03 de janeiro de 1992) e nove genótipos de milho (C 805, C 901, P 3069, SR 100, AG 303, AG 513, XL 560, XL 605 e G 5555), em quatro repetições. A colheita foi realizada nos dias 04 de março e 26 de maio de 1992, para as semeaduras de setembro e janeiro, respectivamente. Houve resposta diferencial dos genótipos à época de semeadura, para rendimento de grãos e componentes do rendimento. Na semeadura realizada em setembro, as cultivares C 901 e C 805 apresentaram maiores rendimentos de grãos. Na semeadura de janeiro, destacou-se a cultivar C 901. O rendimento médio de grãos foi de 9,69t ha-1, na primeira época de semeadura e de 4,05t ha-1 na semeadura em janeiro. A redução média do rendimento de grãos com o atraso da semeadura foi de 58,2%, atingindo valores acima de 60% para as cultivares XL 560, P 3069 e SR 100. A semeadura realizada em setembro propiciou maior peso de mil grãos e número de grãos por espiga em relação a semeadura em janeiro.

RENDIMENTO DE GRÃOS E COMPONENTES DO RENDIMENTO DE CULTIVARES DE MILHO EM DUAS ÉPOCAS DE SEMEADURA

The experiment was carried out in Passo Fundo-RS, Brazil, in order to evaluate the interaction between cultivars and planting dates for corn yield and yield components. The experiment was conducted under irrigated, during the 1991/92 growing season. Two planting dates (September 13, 1991 and January 3, 1992) and nine com cultivars (C 805, C 901, P 3069, SR 100, AG 303, AG 513, XL 560, XL 605 and G 5555) were tested. Plants were harvested on March 4, 1992 and May 26, 1992 for the planting dates of September and January, respectively. There were differences in the grain yield and yield components among the cultivars for the two planting dates tested. In September, the sowing of the C 901 and C 805 cultivars showed the highest grain yield. In January, the cultivar C 901 showed the highest grain yield. The average grain yield varied from 9.69t ha-1, in the first planting date to 4.05t ha-1 in the second planting date. The average grain yield was reduced in 58.2%. from the first to the second planting date. The grain yield decreased more than 60% in XL 560, P 3069 and SR 100 cultivars as a result of the delay in the planting date. The sowing in September favoured more kernel weight and number of kernels per ear than the sowing in January.

Este experimento teve como objetivo verificar a existência de interação entre cultivares e épocas de semeadura para rendimento de grãos e componentes do rendimento em milho. O experimento, realizado em Passo Fundo, RS, foi conduzido sob condições de suplementação hídrica, durante o ano agrícola 1991/92. Os tratamentos constaram de duas épocas de semeadura (13 de setembro de 1991 e 03 de janeiro de 1992) e nove genótipos de milho (C 805, C 901, P 3069, SR 100, AG 303, AG 513, XL 560, XL 605 e G 5555), em quatro repetições. A colheita foi realizada nos dias 04 de março e 26 de maio de 1992, para as semeaduras de setembro e janeiro, respectivamente. Houve resposta diferencial dos genótipos à época de semeadura, para rendimento de grãos e componentes do rendimento. Na semeadura realizada em setembro, as cultivares C 901 e C 805 apresentaram maiores rendimentos de grãos. Na semeadura de janeiro, destacou-se a cultivar C 901. O rendimento médio de grãos foi de 9,69t ha-1, na primeira época de semeadura e de 4,05t ha-1 na semeadura em janeiro. A redução média do rendimento de grãos com o atraso da semeadura foi de 58,2%, atingindo valores acima de 60% para as cultivares XL 560, P 3069 e SR 100. A semeadura realizada em setembro propiciou maior peso de mil grãos e número de grãos por espiga em relação a semeadura em janeiro.