Drought is currently a major constraint to soybean [Glycine max (L.) Merr.] production worldwide and is becoming more widespread due to increased aridity and warmer temperatures in the context of global climate change. In this context, breeding for soybean varieties more tolerant to drought stress is critical and requires efficient screening techniques. To find traits associated with drought tolerance at the vegetative stage that are still present at the reproductive stage, we evaluated morphological, physiological, and biochemical traits in two soybean genotypes contrasting in their response to drought stress. Under drought stress at the vegetative stage, the tolerant A 5009 RG genotype showed higher proline and chlorophyll contents, and early activation of the enzymatic antioxidant system compared with well‐watered plants. On the other hand, the sensitive ADM 50048 genotype increased malondialdehyde (oxidative damage marker) and nonenzymatic antioxidant response under stress. Manipulative field assays under contrasting levels of water availability at the reproductive stage mimicked the biochemical patterns observed in the greenhouse tests for the sensitive and tolerant genotypes. A principal component analysis of parameters from vegetative and reproductive stages revealed proline and chlorophyll contents as drought tolerance traits in soybean. We found those traits useful to classify 14 genotypes from the Instituto Nacional de Tecnologia Agropecuaria (INTA) germplasm bank, identifying two new drought‐tolerant genotypes (PI 548510 and PI 200492). We propose proline and chlorophylls as useful tools to classify soybean genotypes according to their drought responses in early developmental stages, potentially reducing breeding times.

The tomato [Solanum lycopersicum (Sl)] phosphatidylinositol-phospholipase C (PI-PLC) gene family is composed of six members, named SlPLC1 to SlPLC6, differentially regulated on pathogen attack. We have previously shown that the fungal elicitor xylanase induces a raise of SlPLC2 and SlPLC5 transcripts and that SlPLC2, but not SlPLC5, is required for xylanase-induced expression of defense-related genes. In this work we studied the role of SlPLC2 in the interaction between tomato and the necrotrophic fungus Botrytis cinerea. Inoculation of tomato leaves with B. cinerea increases SlPLC2 transcript levels. We knocked-down the expression of SlPLC2 by virus-induced gene silencing and plant defense responses were analyzed upon B. cinerea inoculation. SlPLC2 silenced plants developed smaller necrotic lesions concomitantly with less proliferation of the fungus. Silencing of SlPLC2 resulted as well in a reduced production of reactive oxygen species. Upon B. cinerea inoculation, transcript levels of the salicylic acid (SA)-defense pathway marker gene SlPR1a were diminished in SlPLC2 silenced plants compared to non-silenced infected plants, while transcripts of the jasmonic acid (JA)-defense gene markers Proteinase Inhibitor I and II (SlPI-I and SlPI-II) were increased. This implies that SlPLC2 participates in plant susceptibility to B. cinerea.

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Plant-associated microbiomes confer fitness advantages to the plant host by growth promotion through different mechanisms including nutrient uptake, phytohormones production, resistance to pathogens, and stress tolerance. These effects of the potentially beneficial microbes have been used in a diversity of biotechnological approaches to improve crop performance applying individual bacterial cultures. However, healthy plants host a diversity of microorganisms (microbiota). Next-generation sequencing technologies have offered insights into the relative abundances of different phylogenetic groups in a community and the metabolic and physiological potential of its members. In the last decade, researchers have started to explore the possibilities to use temporal and functional combinations of those bacteria in the form of synthetic communities. In this chapter, we review the benefits of using endophytic bacteria in legumes, the available methodological approaches to study the effects of bacterial communities, and the most recent findings using synthetic communities to improve the performance of legume crops.