Inheritance of Phytophthora root rot and foliar blight resistance in pepper

The inheritance of resistance to Phytophthora capsici Leonian root tot and foliar blight was compared in two different Capsicum annuum L. var, annuum pod types. The seedling was screened for phytophthora root rot, while a gen etically identical stem cutting was screened for phytophthora foliar blight to determine if the same gene(s) confer resistance to both disease syndrom es. The susceptible parents were 'Keystone Resistant Giant #3' ('Keystone') , a bell pepper type, and 'Early Jalapeno', while 'Criollo de Morelos-334' was the resistant parent. Resistance was observed in both F-1 populations s creened for phytophthora root and foliar infection indicating dominance for resistance. Reciprocal effects were not detected. To determine if the same gene(s) conferred root rot and foliar resistance, root rot screening resul ts were matched to the corresponding foliar blight stem cutting reaction. T he segregation of resistance in the F-2 generations was dependent on the su sceptible parent. In the F-2 generation derived from 'Early Jalapeno', root rot resistance and foliar blight resistance segregated in a 9:3:3:1 (root resistant/foliar resistant : root resistant/foliar susceptible : root susce ptible/foliar resistant : root susceptible/foliar susceptible) ratio. One i ndependent, dominant gene was necessary for root rot resistance, and a diff erent independent, dominant gene was needed for foliar blight resistance. I n the F-2 generation derived from 'Keystone', root rot and foliar blight re sistance segregated in a 7:2:2:5 (root resistant/ foliar resistant : root r esistant/foliar susceptible : root susceptible/foliar resistant : root susc eptible/foliar susceptible) ratio. This segregation ratio is expected when one dominant gene is required for root resistance, and a different dominant gene is required for foliar resistance. In addition to these two genes, at least one dominant allele of a third gene must be present for expression o f root rot and foliar blight resistance.