Development of a Double‐inoculation Method to Assess Resistance to Anthracnose in Trispecies Capsicum Hybrid

Abstract Chilli anthracnose is caused by a complex of Colletotrichum species. Breeding for resistance to anthracnose has been focused on introgressing resistance from Capsicum chinense and C. baccatum into commercial C. annuum cultivars. Trispecies hybrids of C. annuum cv. Bangchang, C. chinense PBC932 and C. baccatum PBC80 were successfully produced. Assessments for resistance in F 1 progeny to Colletotrichum capsici isolate 158ci ( Cc 158ci) and C. acutatum isolate MJ5 ( Ca MJ5) were carried out by inoculating fruit using a laboratory microinjection method. Due to the poor fruit set of the F 1 hybrid, a double‐inoculation method was developed to inoculate the same chilli fruit with two isolates of two Colletotrichum species. The positions (apex, centre, end) at which the fruit were inoculated with either isolate did not affect disease development. At 7 days after inoculation, Cc 158ci produced larger lesions on chilli fruit than Ca MJ5; and lesions from single inoculation were larger than those from double inoculation. The double‐inoculation technique was applied to the trispecies F 1 hybrid to select individual F 1 plants that contained resistance to both Colletotrichum species. Of the nine F 1 plants that produced fruits for inoculation, all were resistant to Cc 158ci at both mature green and ripe fruit stages. Two plants were also resistant to Ca MJ5 at both fruit maturity stages, and one plant was resistant at the ripe fruit stage but susceptible at the green fruit stage.