Abstract
Genetic variation for response of flowering time to photoperiod plays an important role in adaptation to environments with different photoperiods, and as consequence is an important contributor to plant productivity and yield. To elucidate the genetic control of flowering time [days to flowering (DTF); growing degree days (GDD)] in common bean, a facultative short-day plant, a quantitative trait loci (QTL) analysis was performed in a recombinant inbred mapping population derived from a cultivated accession and a photoperiod sensitive landrace, grown in different long-day (LD) and short-day (SD) environments by using a multiple-environment QTL model approach. A total of 37 QTL across 17 chromosome regions and 36 QTL-by-QTL interactions were identified for six traits associated with time to flowering and response to photoperiod. The DTF QTL accounted for 28 and 11% on average of the phenotypic variation in the population across LD and SD environments, respectively. Of these, a genomic region on chromosome 4 harboring the major DTF QTL was associated with both flowering time in LD and photoperiod response traits, controlling more than 60% of phenotypic variance, whereas a major QTL on chromosome 9 explained up to 32% of flowering time phenotypic variation in SD. Different epistatic interactions were found in LD and SD environments, and the presence of significant QTL × environment (QE) and epistasis × environment interactions implies that flowering time control may rely on different genes and genetic pathways under inductive and non-inductive conditions. Here, we report the identification of a novel major locus controlling photoperiod sensitivity on chromosome 4, which might interact with other loci for controlling common bean flowering time and photoperiod response. Our results have also demonstrated the importance of these interactions for flowering time control in common bean, and point to the likely complexity of flowering time pathways. This knowledge will help to identify and develop opportunities for adaptation and breeding of this legume crop.
Highlights
Flowering time control involves the regulation of physiological processes that are integrated and coordinated in a complex network with other developmental processes (Weller and Ortega, 2015)
To gain a better understanding of the molecular mechanisms underlying common bean flowering time and photoperiod response, we evaluated a recombinant inbred (RI) population derived from a biparental cross between Bolita, a photoperiod-insensitive early flowering cultivar from Spain, and PHA1037, a landrace from Bolivia with a strong photoperiod response similar to wild accessions (Figure 1A)
The genetics that underlie flowering time variation, its heterogeneity in different LD and SD environments, and the associated photoperiod response was investigated here in a mapping population developed from a cross involving a cultivar and a landrace of common bean, allowing us to identify the magnitude of quantitative trait loci (QTL) effects on phenotype, and their genetic and environment interactions
Summary
Flowering time control involves the regulation of physiological processes that are integrated and coordinated in a complex network with other developmental processes (Weller and Ortega, 2015). Like wild P. vulgaris, most Andean cultivars are photoperiod sensitive, while Mesoamerican and determinate cultivars include a high proportion of day-neutral lines (White and Laing, 1989) Temperature is another environmental factor influencing flowering time control in common bean, and is known to interact with photoperiod sensitivity, which increases at higher temperatures. Overall the observed differences in photoperiod response can be broadly associated with the ecological adaptations of different races within the two genepools (Singh, 1988, 1989; Smartt, 1988) This variation is interesting from an evolutionary point of view, but presents a challenge for matching phenology to environment and planting time, and generally for improving common bean production in temperate regions. The existence of two common bean gene pools deriving from independent domestication events is an important characteristic of the species and provides additional variation and challenges for matching and developing varieties for different climatic and planting time conditions and generally for improving temperate bean production
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