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  • Author or Editor: Sylvia Patricia Fernández-Pavía x
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Phytophthora blight of vegetables caused by Phytophthora capsici causes significant economic losses in production of Solanaceae and Cucurbitaceae crops in Mexico. The development of universal resistant chili pepper cultivars is challenging due to the diverse virulence phenotypes produced by P. capsici. The objective of the study was to characterize the diversity of phenotypic interactions for P. capsici isolates recovered from production fields in Michoacán, Mexico, to facilitate the development of resistant cultivars. Virulence phenotypes were characterized for 12 isolates of P. capsici using 26 Capsicum annuum New Mexico Recombinant Inbred Lines (NMRILs) in greenhouse conditions. Criollo de Morelos CM-334 and California Wonder were used as resistant and susceptible controls, respectively. Seedlings at the four to eight true leaf stage were inoculated with 10,000 zoospores per seedling and disease severity was evaluated at 20 days post-inoculation. Two of the P. capsici isolates did not infect any pepper host even though the isolate was less than a year old. The 10 virulent isolates were designated in 10 virulence phenotypes. The information generated by this study is of utmost importance for efforts of producing resistant cultivars specific for Michoacán producers.

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The genus Capsicum has been distinguished by its lack of compatible rootstocks with commercial cultivars to successfully protect against Phytophthora capsici. Criollo de Morelos 334 (CM334) has been used worldwide in crosses and as a rootstock to protect against P. capsici. However, novel sources of resistance to this pathogen, such as ‘Pasilla 18M’ have not yet been explored as rootstocks. A good rootstock should be highly compatible with the scion and also maintain the quality and/or provide a benefit to the grafted cultivar. Our objectives were 1) to evaluate grafting survival using ‘Pasilla 18M’ and CM334 as rootstocks of two susceptible commercial cultivars: Sweet Pepper California Wonder (CW) and Serrano Coloso; and 2) to evaluate the efficiency of ‘Pasilla 18M’ as rootstock against P. capsici using CM334 as a resistant control. Grafting survival was analyzed over 58 days after grafting in sets of 60 plants per varietal combination. Disease severity and incidence were recorded during 24 days after inoculation with P. capsici (DAI). Incidence was also evaluated at 54 and 84 DAI. A severity scale from 0 (healthy plant) to 4 (dead plant) was applied to evaluate root rot per plant. Incidence was recorded as the percent of diseased plants (severity >0). Grafting survival of intervarietal grafts was 87% to 94%, similar to ungrafted cultivars, and exceeding autograft survival. Ungrafted and autografted Sweet Pepper and Serrano showed root rot severities 2.3 to 3.3, with 89% to 100% incidence. In contrast, intervarietal grafts remained almost free of infection (severity 0.14; incidence 0% to 4%). CM334 and ‘Pasilla 18M’ rootstocks are highly compatible with ‘Serrano Coloso’ and ‘Sweet Pepper CW’. ‘Pasilla 18M’ confers the same level of protection against P. capsici as CM334.

Open Access