Exploration of the yield potential of mesoamerican wild common beans from contrasting eco-geographic regions by nested recombinant inbred populations

Genetic analyzes and utilization of wild genetic variation in common bean
(Phaseolus vulgaris L.) for crop improvement have been hampered by
evaluation difficulties, identification of advantageous variation, and
linkage drag. The lack of adaptation to field conditions and the existence
of highly structured populations make association mapping of diversity
panels not optimal. Joint linkage mapping of nested populations avoids the
later constraint, while populations crossed with a common domesticated
parent allow the evaluation of wild variation within a more adapted
background. We developed three domesticated by wild backcrossed inbred
line populations (BC1S4), using three wild accessions representing the
extreme range of rainfall of the Mesoamerican wild bean distribution
crossed to the elite drought tolerant domesticated parent SEA 5. We
evaluated the populations under field conditions in three environments,
two fully irrigated trials in two seasons and a simulated terminal drought
in the second season. The goal was to test if these populations responded
differently to drought stress and to detect yield-associated genomic
regions. Our results revealed that the populations from the wild parents
of the low rainfall part of the distribution showed higher yield. We found
20 QTLs for yield in 13 unique regions on eight of the 11 chromosomes of
common bean. Five of these regions showed at least one wild allele that
increased yield over the domesticated parent. The variation explained by
these QTLs ranged from 0.6 to 5.4 % of the total variation and the
additive effects ranged from -164 to 277 kg ha-1, with evidence suggesting
allelic series for some QTLs. The average allele effects from the parent
of the wettest environment were lower through all the test environments.
Our results underscore the potential of wild variation for bean crop
improvement as well the identification of regions for efficient
marker-assisted introgression.