|HEILIG, J - Michigan State University|
|WRIGHT, E - Michigan State University|
|KELLY, J - Michigan State University|
|BEAVER, J - University Of Puerto Rico|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2016
Publication Date: 12/8/2016
Citation: Heilig, J.A., Wright, E.M., Kelly, J.D., Beaver, J.S., Song, Q. 2016. QTL analysis of symbiotic nitrogen fixation in a black bean RIL population. Crop Science. 57:1-12.
Interpretive Summary: Legumes, with the help of soil bacteria called rhizobia, fix 20–22 million tons of nitrogen from the atmosphere each year. Nitrogen fixation efficiency, however, is different among legume crops. For example, 75% of the total nitrogen in faba bean plants was derived through fixation, but only 39% of the total nitrogen in common bean plants was derived this way. The percentage of nitrogen fixed by dry beans is also variable among cultivars of dry beans. Furthermore, cultivars with high nitrogen fixation rates may not necessarily produce high seed yields. Thus, the objective of this study was to investigate the traits related to nitrogen fixation in black beans and to identify genomic regions associated with nitrogen fixation and the improvement of seed yield. We identified 19 genomic regions associated with the traits enhancing nitrogen fixation, and three were associated with known nitrogen fixation traits. In addition, candidate genes involved in sensing nitrogen fixation bacteria were observed in those genomic regions. The DNA regions discovered in this study may serve as good targets for improving nitrogen fixation in common bean by the breeders in public and private sectors.
Technical Abstract: Dry bean (Phaseolus vulgaris L) acquires nitrogen (N) from the atmosphere through symbiotic nitrogen fixation (SNF) but it has a low efficiency to fix nitrogen. The objective of this study is to map the genes controlling nitrogen fixation in common bean. A mapping population consisting of 122 recombinant inbred lines derived from the cross of black beans ‘Puebla 152’ X ‘Zorro’ was grown in the field in East Lansing, MI, Isabela, Puerto Rico and in the greenhouse under N free conditions, and was evaluated for yield, nodule development, biomass growth, agronomic traits, and N fixation rate. In addition, the population was also genotyped with single-nucleotide polymorphism (SNP) markers developed through the BeanCAP project. We constructed a genetic linkage map containing 430 SNPs and spanning 972 cM. A total of 19 quantitative trait loci (QTL) associated with SNF traits were identified on all 11 chromosomes except chromosome Pv02, clusters of the QTL were discovered on Pv01, Pv06, and Pv08. Many of the QTL associated with traits, suchas percentage of N derived from atmosphere, N harvest index, and percentage of N in biomass, were also associated with candidate genes expressed in the nodules and roots. Majority of QTL alleles associated with genes expressed in the root or nodule were derived from Puebla 152, however, QTL associated with genes enhancing expression in stems and pods were associated with Zorro. The identified QTL could be potentially used for the improvement of SNF characteristics in adapted commercial dry bean genotypes in the temperate zones.