Luiz Henrique Saes Zobiole

Glyphosate Affects Seed Composition in Glyphosate-Resistant Soybean

The cultivation of glyphosate-resistant (GR) soybeans has continuously increased worldwide in recent years mainly due to the importance of glyphosate in current weed management systems. However, not much has been done to understand eventual effects of glyphosate application on GR soybean physiology, especially those related to seed composition with potential effects on human health. Two experiments were conducted to evaluate the effects of glyphosate application on GR soybeans compared with its near-isogenic non-GR parental lines. Results of the first experiment showed that glyphosate application resulted in significant decreases in shoot nutrient concentrations, photosynthetic parameters, and biomass production. Similar trends were observed for the second experiment, although glyphosate application significantly altered seed nutrient concentrations and polyunsaturated fatty acid percentages. Glyphosate resulted in significant decreases in polyunsaturated linoleic acid (18:2n-6) (2.3% decrease) and linolenic acid (18:3n-3) (9.6% decrease) and a significant increase in monounsaturated fatty acids 17:1n-7 (30.3% increase) and 18:1n-7 (25% increase). The combined observations of decreased photosynthetic parameters and low nutrient availability in glyphosate-treated plants may explain potential adverse effects of glyphosate in GR soybeans.

Resistance to toxin-mediated fungal infection: role of lignins, isoflavones, other seed phenolics, sugars, and boron in the mechanism of resistance to charcoal rot disease in soybean

Charcoal rot disease in soybean is caused by the fungus Macrophomina phaseolina, which is believed to infect plants from soil through the roots by a toxin-mediated mechanism. Soybean genotypes exist which are susceptible (S) or moderately resistant (MR) to charcoal rot, but the mechanism of resistance is not known. Significantly (p ≤ 0.05) higher levels of phenolics, seed coat lignin, isoflavones, sugars, and total boron were observed in MR genotype than in S genotype seeds under irrigated and nonirrigated and under experimental M. phaseolina infested and noninfested conditions, indicating a possible association of these substances with resistance to toxin-mediated infection.

Efficacy of Soybean’s Event DAS-81419-2 Expressing Cry1F and Cry1Ac to Manage Key Tropical Lepidopteran Pests Under Field Conditions in Brazil

Abstract Bacillus thuringiensis (Bt) event DAS-81419-2 (Conkesta technology) in soybean, Glycine max (L.) Merrill, expresses Cry1F and Cry1Ac proteins to provide protection from feeding by several lepidopteran pests. A total of 27 field experiments across nine locations were conducted from 2011 to 2015 in southern and central Brazil to characterize the efficacy of DAS-81419-2 soybean infested with Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae), Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae), Heliothis virescens (F.) (Lepidoptera: Noctuidae), and Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) during vegetative (V4) and reproductive (R2 and R4) crop developmental stages. The efficacy of DAS-81419-2 was compared to that of a non-Bt isogenic variety managed with or without applications of commercial foliar insecticides for lepidopteran control. DAS-81419-2 soybean consistently experienced defoliation levels of 0.5% or less (compared with 20.05–56.74% in the non-Bt, nonsprayed treatment) and larval survival of < 0.1% in all four species across the vegetative and reproductive plant stages evaluated. The efficacy of DAS-81419-2 was significantly higher than commercial foliar insecticides applied to the non-Bt variety. DAS-81419-2 soybeans containing two highly effective Bt proteins are expected to be a more robust IRM tool compared to single-trait Bt technologies. The consistent efficacy of DAS-81419-2 soybeans across years, locations, and crop stages suggests that it will be a valuable product for management of hard-to-control key lepidopteran pests in South American soybean production.

Phomopsis Seed Infection Effects on Soybean Seed Phenol, Lignin, and Isoflavones in Maturity Group V Genotypes Differing in Phomopsis Resistance

Research on factors controlling production and quality of soybean seed phenolics is very limited. The objective of this research was to evaluate phenolic compounds (total phenol, lignin, and isoflavones), and cell wall boron (B) in seed of susceptible (S), moderately resistant (MR), and resistant (R) soybean genotypes to phomopsis seed decay disease under irrigated and non-irrigated conditions. Seeds were evaluated at harvest maturity stage (R8) and 15 days after harvest maturity to test for weathering effects. Results showed that the concentration of seed phenolic compounds was significantly (P ≤ 0.05) higher in R and MR genotypes than S genotypes under irrigated and non-irrigated conditions. Cell wall boron percentage was significantly higher and total boron was significantly lower in S genotypes than MR and R genotypes. The current research demonstrated that genotypes with higher phomopsis seed infection had lower phenolic compounds, indicating a possible association of these compounds with disease defense mechanism. The higher cell wall B percentage in S genotypes indicated a possible involvement of boron in phenolic metabolism and phomopsis resistance. The decrease in phenolic compounds concentrations in S genotypes in seed collected 15 days after R8 indicated the weathering effects on seed coat and cell wall deterioration. Soybean breeders may be able to use phenolics as phenotypic trait and biomarkers for selecting soybean genotypes for higher resistance and for higher seed nutritional qualities.

Glyphosate na produção e qualidade das sementes de soja RR

O presente trabalho teve como objetivo avaliar os componentes de producao e a qualidade das sementes de soja RR, em funcao da aplicacao de doses crescentes de glyphosate. Os experimentos foram instalados em campo, no municipio de Mandaguari, Parana, durante as safras 2006/2007 e 2007/2008. Os tratamentos foram compostos por cinco doses de glyphosate. Todas as aplicacoes foram realizadas em modalidade unica entre o estadio V4 e V5. O delineamento experimental utilizado foi em blocos casualizados com quatro repeticoes. Os dados foram submetidos a analise de variância e; quando significativos, aplicou-se o teste t e analise de regressao aos tratamentos. Foram avaliadas a qualidade fisiologica e sanitaria das sementes, a produtividade e a massa de mil sementes. Os resultados indicam que a qualidade das sementes pode ser afetada negativamente pelo glyphosate e, tambem, demonstram provavel reducao nos componentes de produtividade com incrementos na dose.

Role of Boron Nutrient in Nodules Growth and Nitrogen Fixation in Soybean Genotypes Under Water Stress Conditions

Boron is an essential nutrient for plant growth, development, and seed quality [1-4]. Previous research indicated the involvement of B in cell wall structure [5,6]; cell membrane integrity [2, 7]; sugar metabolism [2], especially sugar alcohols [3,8]; nitrogen assimilation and fixation [9, 10]; nodules [11,12], nodullin protein (ENOD2) and malfunction of oxygen diffusion barrier [13]; phenolic metabolism [2,14,15]; ion uptake [2,16]; and plasma membrane-bount H+ ATPase [7,17,18].