Background 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. Results 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. Conclusion 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. Electronic supplementary material The online version of this article (10.1186/s12870-019-1774-2) contains supplementary material, which is available to authorized users.

BackgroundWild crop relatives have been potentially subjected to stresses on an evolutionary time scale prior to domestication. Among these stresses, drought is one of the main factors limiting crop productivity and its impact is likely to increase under current scenarios of global climate change. We sought to determine to what extent wild common bean (Phaseolus vulgaris) exhibited adaptation to drought stress, whether this potential adaptation is dependent on the climatic conditions of the location of origin of individual populations, and to what extent domesticated common bean reflects potential drought adaptation.MethodsAn extensive and diverse set of wild beans from across Mesoamerica, along with a set of reference Mesoamerican domesticated cultivars, were evaluated for root and shoot traits related to drought adaptation. A water deficit experiment was conducted by growing each genotype in a long transparent tube in greenhouse conditions so that root growth, in addition to shoot growth, could be monitored.ResultsPhenotypic and landscape genomic analyses, based on single-nucleotide polymorphisms, suggested that beans originating from central and north-west Mexico and Oaxaca, in the driest parts of their distribution, produced more biomass and were deeper-rooted. Nevertheless, deeper rooting was correlated with less root biomass production relative to total biomass. Compared with wild types, domesticated types showed a stronger reduction and delay in growth and development in response to drought stress. Specific genomic regions were associated with root depth, biomass productivity and drought response, some of which showed signals of selection and were previously related to productivity and drought tolerance.ConclusionsThe drought tolerance of wild beans consists in its stronger ability, compared with domesticated types, to continue growth in spite of water-limited conditions. This study is the first to relate bean response to drought to environment of origin for a diverse selection of wild beans. It provides information that needs to be corroborated in crosses between wild and domesticated beans to make it applicable to breeding programmes.

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.

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We addressed a major challenge in the in vitro clonal propagation of Corymbia citriodora, Eucalyptus urophylla and E. benthamii by using an ex vitro adventitious rooting strategy in a mini-incubator. Miniincubators were placed in four environments for rooting. A shade house with no fogging system and a greenhouse with no ventilation but with a fogging environment had the best performance in terms of rooting, root growth and survival of microcuttings. Daily recording of the temperature within each miniincubator in each environment allowed the verification of negative correlations between the maximum average temperature and the survival, adventitious rooting and root growth. The ideal maximum air temperature for the efficient production of clonal plants was 28.4°C (± 5.5°C), and the minimum was 20.3°C (± 6.2°C). E. benthamii was more sensitive to higher temperatures than C. citriodora and E. urophylla. Nevertheless, placing mini-incubators in the shade house with no fogging system resulted in a stable and uniform performance among the three species, with 100.0% survival and 81.4% rooting. Histological sections of the adventitious roots revealed connection with the stem vascular cambium. Therefore, our experimental system demonstrated the potential of mini-incubators coupled with the proper environment to optimize the adventitious rooting performance of microcuttings.

ABSTRACT: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. O USO DE HIDROGEL COMBINADO COM SUBSTRATO E FERTILIZANTE ADEQUADOS MELHORAM A QUALIDADE E CRESCIMENTO DE MUDAS DE Mimosa scabrella BENTH.RESUMO: Mimosa scabrella é uma espécie pioneira que ocorre principalmente na floresta ombrófila mista do Sul do Brasil, apresentando considerável importância econômica. Considerando as limitadas informações acerca dos substratos mais adequados para a produção de mudas da espécie, neste trabalho avaliou-se o efeito combinado do uso de hidrogel com três tipos de substratos e quatro fertilizantes no crescimento inicial e qualidade de mudas de M. scabrella. Os substratos foram preparados com proporções distintas de um substrato orgânico comercial, vermiculita (VM) e casca de pinus (PB): 1 (70% de TF, 10% de VM e 20% de PB), 2 (40% de TF e VM e 20% of PB), e 3 (70% de TF, 10% de VM e 20% de PB). Os fertilizantes consistiram de uma fórmula de liberação lenta (A), o tradicional NPK (B), um composto de superfosfato simples e de cloreto de potássio (C) e com fertilizante ausente (D). Os três compostos de substratos foram combinados com cada fertilizante na presença ou ausência de hidrogel (arranjo fatorial). O uso de hidrogel promoveu um efeito positivo no crescimento das mudas de M. scabrella, provavelmente retendo mais água e permitindo maior absorção de nutrientes. No geral, o polímero implicou em aumento no índice de qualidade de Dickson (DQI). Adicionalmente, a combinação do composto orgânico e vermiculita em proporções equilibr...

We analyzed the nucleotide variability and the expression profile of DREB genes from common bean, a crop of high economic and nutritional value throughout the world but constantly affected by abiotic stresses in cultivation areas. As DREB genes have been constantly associated with abiotic stress tolerance, we systematically categorized 54 putative PvDREB genes distributed in the common bean genome. It involved from AP2 domain location and amino acid conservation analysis (valine at the 14th position) 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, and PvDREB6B) 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. PvDREB1F and PvDREB5A showed high relative inducibilities when genotypes of common bean were submitted to stresses by drought, salt, cold, and ABA. PvDREB2A inducibility was predominantly localized to the stem under drought. PvDREB6B was 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. PvDREB6B was found as a cold- and dehydration-responsive gene, mainly in leaves. Interestingly, PvDREB6B also 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 each DREB found 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.

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