Genetic mapping of basal root gravitropism and phosphorus acquisition efficiency in common bean.

LIAO H., X. YAN, G. RUBIO, S. BEEBE, M.H. BLAIR AND J P. LYNCH

FUNCTIONAL PLANT BIOLOGY (formerly AUSTRALIAN J PLANT PHYSIOLOGY)

Año: 2004 vol. 31 p. 959 - 970

1445-4408

Root gravitropism determines the relative distribution of plant roots in different soil layers, and may therefore influence the acquisition of shallow soil resources such as phosphorus. Growth pouch and field studies were conducted to evaluate root gravitropism of common bean in response to phosphorus deficiency and to detect quantitative trait loci (QTLs) associated with this trait. A deep-rooted genotype, DOR364, was crossed to a shallow-rooted genotype, G19833, to obtain 87 F10 recombinant inbred lines (RILs). Root gravitropic traits were measured as the growth angle of basal roots and the length of basal roots near the soil surface. Large genetic variability was found in the parents and RILs, with basal root growth angles ranging from –18.73o to 56.69o and shallow basal root length ranging from 0.42 to 2.63 m/plant. The parents and six RILs contrasting for root gravitropism were further evaluated in the field, where root shallowness was significantly correlated with plant growth and phosphorus uptake. Based on a constructed map with 318 RFLP/AFLP/RAPD/SCAR/SSR markers, four QTLs conferring basal root angle were detected on linkage groups 2, 3 and 4, and nine QTLs conferring shallow basal root length were detected on linkage groups 2, 3, 6, 8, 9 and 11. At least 5 of the above loci were associated with the QTLs for phosphorus acquisition efficiency in a field study, including some that explained as much as 10% of variability. Our results suggest that root gravitropic traits are closely associated with phosphorus acquisition efficiency, and that QTLs for these traits may facilitate selection and breeding for higher phosphorus efficiency in common bean and other crops.