Grafting onto resistant rootstocks for managing Phytophthora crown rot of peppers
Pepper (bell and hot) is a major vegetable crop grown across most states on 26082 ha (64,450 acres) and valued at $ 785 million in 2017 in the USA. Phytophthora capsici, which causes crown and root rot of peppers, is prevalent in most of these pepper producing regions. The primary means of managing Phytophthora crown rot is through fungicide applications. Many effective fungicides are currently available for conventional pepper growers. Numerous germplasm sources with resistance have also been identified and utilized in various breeding programs. Two crown rot resistant lines were developed from PI 201232 obtained from the US National Plant Germplasm system (https://npgsweb.ars-grin.gov). After screening and selections for three generations in a greenhouse, two lines with high levels of resistance were developed. The two lines were different with respect to fruit shape and size. They were also highly resistant to a South Carolina isolate of P. capsici in inoculated greenhouse and field evaluations compared to cultivars Jupiter, Paladin, and Charleston Belle. The pepper cultivar Jupiter, which is highly susceptible to P. capsici was used as the scion and grafted onto the two resistant lines. Jupiter grafted onto itself was used as the susceptible control in two trials conducted in a heavily infested field in summer and fall of 2018. The areas under disease progress curves (AUDPC) for Jupiter grafted on the two lines were significantly lower compared to Jupiter grafted onto itself. The majority of the self-grafted Jupiter plants (90%) were dead by the by end of both seasons due to crown rot. Grafting onto resistant pepper rootstocks will be an added strategy for managing P. capsici especially in organic production where highly effective fungicides are not available for management of the disease.
Kousik, C.S., Ikerd, J.L. and Hassell, R. (2021). Grafting onto resistant rootstocks for managing Phytophthora crown rot of peppers. Acta Hortic. 1302, 163-168
crown rot, Phytophthora capsici, Capsicum, rootstock