Identification of QTLs for resistance to anthracnose to two Colletotrichum species in pepper

Abstract

Pepper (Capsicum spp.) anthracnose caused by Colletotrichum spp. is a serious disease damaging pepper production in Asian monsoon regions. For QTL mapping analyses of anthracnose resistance, an introgression BC1F2 population was made by interspecific crosses between Capsicum annuum ‘SP26’ (susceptible recurrent parent) and Capsicum baccatum ‘PBC81’ (resistant donor). Both green and red fruits were inoculated with C. acutatum ‘KSCa-1’ and C. capsici ‘ThSCc-1’ isolates and the disease reactions were evaluated by disease incidence, true lesion diameter, and overall lesion diameter. On the whole, distribution of anthracnose resistance was skewed toward the resistant parent. It might indicate that one or two major QTLs are present. The introgression map consisting of 13 linkage groups with a total of 218 markers (197 AFLP and 21 SSR), covering a total length of 325 cM was constructed. Composite interval mapping analysis revealed four QTLs for resistance to ‘KSCa-1’ and three QTLs for ‘ThSCc-1’ isolate, respectively. Interestingly, the major QTLs (CaR12.2 and CcR9) for resistance to C. acutatum and C. capsici, respectively, were differently positioned but there were close links between the minor QTL CcR12.2 for C. capsici and major QTL CaR12.2 as well as the minor QTL CaR9 for C. acutatum and major QTL CcR9. These results will be helpful for marker-assisted selection and pyramiding two different anthracnose-resistant genes in commercial pepper breeding.