Common bean is the most important staple grain legume for direct human consumption and nutrition. It complements major sources of carbohydrates, including cereals, root crop, or plantain, as a source of dietary proteins. It is also a significant source of vitamins and minerals like iron and zinc. To fully play its nutritional role, however, its robustness against stresses needs to be strengthened. Foremost among these is drought, which commonly affects its productivity and seed quality. Previous studies have shown that photosynthate remobilization and partitioning is one of the main mechanisms of drought tolerance and overall productivity in common bean. In this study, we sought to determine the inheritance of pod harvest index (PHI), a measure of the partitioning of pod biomass to seed biomass, relative to that of grain yield. We evaluated a recombinant inbred population of the cross of ICA Bunsi and SXB405, both from the Mesoamerican gene pool, to determine the effects of intermittent and terminal drought stresses on the genetic architecture of photosynthate allocation and remobilization in pods of common bean. The population was grown for two seasons, under well-watered conditions and terminal and intermittent drought stress in one year, and well-watered conditions and terminal drought stress in the second year. There was a significant effect of the water regime and year on all the traits, at both the phenotypic and QTL levels. We found nine QTLs for pod harvest index, including a major (17% of variation explained), stable QTL on linkage group Pv07. We also found eight QTLs for yield, three of which clustered with PHI QTLs, underscoring the importance of photosynthate remobilization in productivity. We also found evidence for substantial epistasis, explaining a considerable part of the variation for yield and PHI. Our results highlight the genetic relationship between PHI and yield and confirm the role of PHI in selection of both additive and epistatic effects controlling drought tolerance. These results are a key component to strengthen the robustness of common bean against drought stresses.

Arbuscular mycorrhizal fungi (AMF) colonization in plants promotes both local and systemic changes in the gene expression profiles of the host that might be relevant for drought-stress perception and response. Drought-tolerant common bean plants (cv. BAT 477), colonized by a mixture of AMF (Glomus clarum, Acaulospora scrobiculata, and Gigaspora rosea), were exposed to a water deprivation regime of 96 h during pre-flowering. Root transcriptomes were accessed through RNA-Seq revealing a set of 9,965 transcripts with significant differential regulation in inoculated plants during a water deficit event, and 10,569 in non-inoculated. These data include 1,589 transcripts that are exclusively regulated by AMF-inoculation, and 2,313 under non-inoculation conditions. Relative gene expression analyses of nine aquaporin-related transcripts were performed in roots and leaves of plants harvested at initial stages of treatment. Significant shifts in gene expression were detected in AM water deficit-treated roots, in relation to non-inoculated, between 48 and 72 h. Leaves also showed significant mycorrhizal influence in gene expression, especially after 96 h. Root cortical cells, harboring or not arbuscules, were collected from both inoculation treatments through a laser microdissection-based technique. This allowed the identification of transcripts, such as the aquaporin PvPIP2;3 and Glucan 1,3 β-Glucosidase, that are unique to arbuscule-containing cells. During the water deficit treatment, AMF colonization exerted a fine-tune regulation in the expression of genes in the host. That seemed to initiate in arbuscule-containing cells and, as the stressful condition persisted, propagated to the whole-plant through secondary signaling events. Collectively, these results demonstrate that arbuscular mycorrhization leads to shifts in common bean’s transcriptome that could potentially impact its adaptation capacity during water deficit events.

We analyzed the nucleotide variability and the expression profile ofDREBgenes from common bean, a crop of high economic and nutritional value throughout the world but constantly affected by abiotic stresses in cultivation areas. AsDREBgenes have been constantly associated with abiotic stress tolerance, we systematically categorized 54 putativePvDREBgenes distributed in the common bean genome. It involved from AP2 domain location and amino acid conservation analysis (valine at the 14^thposition) to the identification of conserved motifs within peptide sequences representing six subgroups (A-1 to A-6) of PvDREB proteins. Four genes (PvDREB1F,PvDREB2A,PvDREB5A, andPvDREB6B) were cloned and analyzed for their expression profiles under abiotic stresses and their nucleotide and amino acid diversity in genotypes of Andean and Mesoamerican origin, showing distinct patterns of expression and nucleotide variability.PvDREB1FandPvDREB5Ashowed high relative inducibilities when genotypes of common bean were submitted to stresses by drought, salt, cold, and ABA.PvDREB2Ainducibility was predominantly localized to the stem under drought.PvDREB6Bwas previously described as an A-2 (DREB2) gene, but a detailed phylogenetic analysis and its expression profile clearly indicated it belongs to group A-6.PvDREB6Bwas found as a cold- and dehydration-responsive gene, mainly in leaves. Interestingly,PvDREB6Balso showed a high nucleotide and amino acid diversity within its coding region, in comparison to the others, implicating in several nonsynonymous amino acid substitutions between Andean and Mesoamerican genotypes. The expression patterns and nucleotide diversity of eachDREBfound in this study revealed fundamental characteristics for further research aimed at understanding the molecular mechanisms associated with drought, salt, and cold tolerance in common bean, which could be performed based on association mapping and functional analyses.

Mimosa scabrella is a pioneer species that occurs mainly in the ombrophilous mixed forests of southern Brazil, assuming considerable economic relevance. As limited information is available concerning the most adequate substrates for producing seedlings of this species, we evaluated the combined effect of hydrogel with three types of substrates and four fertilizers in the initial growth and quality of seedlings of M. scabrella. The substrates were prepared with distinct proportions of a commercial organic substrate, vermiculite (VM) and pine bark (PB): 1 (70% of TF, 10% of VM and 20% of PB), 2 (40% of each TF and VM and 20% of PB), and 3 (70% of TF, 10% of VM and 20% of PB). The fertilizers consisted of a slow release formula (A), a traditional NPK (B), a compost of superphosphate and potassium chloride (C) and no fertilizer (D). The three soil mixtures were combined with each fertilizer in the presence or absence of hydrogel (factorial arrangement). The use of hydrogel promoted a positive effect on the growth of M. scabrella seedlings, probably by retaining more water and enabling increased nutrient absorption. In general, the polymer implicated in increased Dickson quality index (DQI). Additionally, the combination of organic compound and vermiculite in equilibrated proportions aid by pinus bark (substrate 2) were the best substrate. Finally, adding the fertilizers A or B resulted in the best growth performance. In conclusion, the combined effect of hydrogel, substrate mixture and fertilizers improved the quality indexes of M. scabrella seedlings.

Seeds with shiny seed coat in common bean ( Phaseolus vulgaris L.) are normally rejected by consumers due to their difficult cooking, however they can prevent insects and pathogens injuries. Seed coat shininess is known to be conditioned by the Asp gene with the dominant form and is also influenced by the J locus. The latter influences seed coat color and pattern and has been considered a precursor for proanthocyanidin only in the presence of the dominant allele. This work aimed at performing a series of morphological, biochemical and genetic analyses for screening seed coat shininess in common bean. We showed Asp and J can be easily distinguished. Colorimeter data ( L*a*b* system) can somehow provide a quantitative differentiation for seed coat shininess based on the L* variable. Palisade epidermis length and seed coat roughness profiles obtained through electronic microscopy were good indicators for Asp phenotyping. Water uptake was affected by shininess but is probably influenced by more genes, even J , or due physiological responses. A vanillin-HCl test showed to be a suitable method for tracing condensed tannins. AFLP markers partially allowed the categorization of shininess phenotypic classes. These results could be helpful regarding selection purposes and breeding. Therefore, favorable selection to Asp would lead to better resistance to pathogens and insects. J , instead, could be selected for nutritional purposes, since proanthocyanidins are important anti-oxidant and anti-carcinogenic compounds.