Mapping of verticillium wilt resistance genes in cotton

Abstract Cotton quality and yield are affected by several factors during the growing season. A soil inhabiting fungus, Verticillium dahliae Kleb., can cause substantial yield loss in cotton. A molecular mapping F 2 population derived from the interspecific cross of the highly tolerant Gossypium barbadense cv. Pima S-7 and the susceptible G. hirsutum cv. Acala 44 was phenotyped for disease incidence and severity. Phenotyping of individual plant reactions to the disease was quantified using a set of growth parameters measured 3 weeks after inoculation. The F 2 phenotypic distribution of these parameters (number of healthy leaves, node number, leaf weight, stem weight, and total shoot weight) suggested that resistance is polygenic inherited. Microsatellites were used to reveal polymorphism between resistant and susceptible parents. A total of 255 simple sequence repeat (SSR) primer pairs were screened over bulks constituted by 10 resistant and 10 susceptible progeny. Sixty markers were used to analyze quantitative trait loci (QTLs). Eleven linkage groups were constructed consisting of 35 markers and spanning 531 cM with an average distance of 15.17 cM. QTL analysis was performed with MapQTL and QTL Cartographer. MapQTL indicated that 15 markers have significant linkage associations and 9 were distributed to chromosomes 10, 11, 12, and 25. Interval mapping also indicated the most likely position of markers that are significant and located on linkage groups. Three loci (CM12, STS1, 3147-2) had large effect on resistance to Verticillium wilt. Two loci were located on LG-1 and one on LG-2 and both linkage groups are located on chromosome 11.