Inheritance of Resistance to the New Race of Powdery Mildew in Watermelon

• Published in: Crop science 2013-05, Vol.53 (3), p.880-887
• Main Authors: Tetteh, Antonia Y., Wehner, Todd C., Davis, Angela R.
• Format: Article
• Language: English
• Subjects: Airborne microorganisms; Crop diseases; Environmental conditions; Genes; Genetics; Leaves; Methods; Plant introductions; Vegetables
• ISSN: 0011-183X; 1435-0653
• DOI: 10.2135/cropsci2012.07.0453

ABSTRACT Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] production in the United States has, in the past few years, incurred significant losses to races 1W and 2WU.S. powdery mildew (Podosphaera xanthii) infection. We report the mode of inheritance, gene action, and heritability of race 2WU.S. resistance in two populations derived from a cross involving the resistant genotype PI 189225 and the susceptible ‘Charleston Gray’ and PI 269677. Parents, F1, F2, BC1P1, and BC1P2 plants were inoculated and evaluated for leaf and stem resistance in two replicated greenhouse experiments. Segregation patterns revealed that only leaf resistance rating in Charleston Gray × PI 189225 fit the model for single gene inheritance. Generation mean analysis established only additive gene action for leaf resistance while for stem resistance, additive, dominance, and epistatic effects were important. Narrow‐sense heritability estimates were higher for stem (0.81) than for leaf (0.58) resistance. Lack of dominance and epistatic effects combined with high heritability indicated high probability of success in selecting for leaf resistance in early generations. Stem resistance had a higher additive effect, lower dominance, and moderate heritability, but progress toward resistance should be possible. In population PI 269677 × PI 189225, epistatic effects combined with low heritability (0.20) and presence of duplicate epistasis may result in slower progress from selection.