Inheritance of Anthracnose (Colletotrichum acutatum) Resistance in Capsicum Using Interspecific Hybridization

Reliable genetic resources resistant to anthracnose, caused by Colletotrichum acutatum, in Capsicum have only been found in certain Capsicum species, e.g., Capsicum baccatum and C. chinense. Interspecific hybridization using embryo rescue was used to introgress anthracnose resistance from C. baccatum var. PBC81 into C. annuum var. Matikas. Because the interspecific hybrids were completely pollen-sterile, an interspecific BC₁F₁ as the first segregating population was raised through intensive backcrosses in which Matikas was used as the male parent. Among the hundreds of BC₁F₁ progeny, 88 plants setting many fruits were used to study inheritance of anthracnose resistance. The segregation of resistance to susceptibility in the BC₁F₁ population did not fit expected Mendelian ratios such as 1:1 or 3:1, and the frequency distribution of progenies varied continuously from resistant to susceptible. To estimate broad sense heritability of resistance, we used a real method of selection differential (i) and genetic gain (ΔG). According to the equation h²= ΔG/i, heritability was estimated as about 0.61. This result suggests that resistance of C. baccatum var. PBC81 can be controlled quantitatively, although we do not know yet how many genes are associated with the resistance.