Phenotypic evaluation and QTL analysis of yield and symbiotic nitrogen fixation in a common bean population grown with two levels of phosphorus supply

Abstract

Common bean is an important staple crop in Eastern Africa and Latin America. Low soil fertility is a major limitation to agronomic productivity. Symbiotic nitrogen fixation (SNF) is an important property of legumes, leading to high protein levels and high nutritional value. Nitrogen (N) metabolism and yield traits were evaluated in the common bean population DOR 364 × BAT 477 in field experiments under moderate and low phosphorus (P) soil conditions resembling environments found on farmers’ fields. Low P availability in soil severely limits seed yield, and trait correlations with yield reveal that high biomass as well as early maturity and efficient seed filling are important for good performance in low P stress, resembling drought resistance. Investigation of SNF and soil N uptake under low P stress showed reduced seed nitrogen levels and major variation in soil-derived N. In low P conditions, no significant reduction of %N derived from the atmosphere (%Ndfa) was observed; however, %Ndfa was correlated with yield, indicating that under stress SNF becomes an important asset. Significant genetic variation was observed for yield, yield components, and SNF ability suggesting that traits can be improved by breeding. Quantitative trait loci (QTLs) for %Ndfa and seed N concentration were discovered on chromosomes Pv07 and Pv02; independent yield QTLs were identified on the same chromosomes. Two QTL hotspots that affect several traits including yield components were found on Pv02 and Pv06; the latter represents a constitutive QTL hotspot independent from the environment. QTLs may be used for marker design and molecular breeding.