Physiological Race Characterization of Phytophthora capsici Isolates from Several Host Plant Species in Brazil Using New Mexico Recombinant Inbred Lines of Capsicum annuum at Two Inoculum Levels

Abstract

<jats:p>Phytophthora blight, caused by <jats:italic>Phytophthora capsici</jats:italic>, is one of the most destructive diseases worldwide that affects <jats:italic>Capsicum</jats:italic> pepper. Attempts to provide universally resistant cultivars has been unsuccessful, which may be the result of the use of different resistance sources, pathotypes, or races of <jats:italic>P. capsici</jats:italic> isolates and screening techniques. The screening method used at Embrapa Vegetables in Brazil to detect resistance to <jats:italic>P. capsici</jats:italic> in <jats:italic>Capsicum</jats:italic> was compared with the screening method used at New Mexico State University. Both screening methods produced similar and consistent results when a range of <jats:italic>P. capsici</jats:italic> isolates were used. It was concluded that either method can successfully differentiate resistant and susceptible individuals. In addition, 20 <jats:italic>P. capsici</jats:italic> isolates from Brazil were characterized for virulence using a subset of 26 New Mexico recombinant inbred lines of pepper (<jats:italic>Capsicum annuum</jats:italic>). Within the <jats:italic>P. capsici</jats:italic> populations from Brazil, eight new physiological races for the root rot disease syndrome were identified. A total of nine isolates were pathogenic only on the susceptible control, ‘Camelot’. The ability to identify physiological races of <jats:italic>P. capsici</jats:italic> occurring in Brazil allows for a better understanding about race-specific resistance leading to improved approaches in breeding for durable resistant cultivars.</jats:p>

Virulence Phenotypes on Chili Pepper for Phytophthora capsici Isolates from Michoacán, Mexico

“…Overall, our results concur with other studies where NMRILs were successfully used as differential hosts to identify P. capsici virulence phenotypes from different parts of the world including the United States, Brazil, and Taiwan (Barchenger et al, 2018b;da Costa Ribeiro and Bosland, 2012;Jiang et al, 2015;Sy et al, 2008). Also, the NMRILs are useful to designate virulence phenotypes in P. capsici isolates from noncapsicum hosts.…”

“…The isolates CPV-270 and CPV-273 were not virulent to any host. Nonvirulent P. capsici isolates have been reported previously when using the NMRILs as differential hosts (da Costa Ribeiro and Bosland, 2012). The isolate CPV-273 was isolated from Solanum lycopersicum, and it is possible that they were not pathogenic to C. annuum due to host specificity (Cohen 2002;Michalska et al, 2016).…”

“…Not all NMRILs are needed for the identification of new virulence phenotypes, and the 10 new ones reported here are determined based on their differential reactions with six NMRILs (G, I, M, N, O, and AC; Table 3). In previous reports, 7-10 NMRILs were used to determine the virulence phenotypes of P. capsici isolates (Barchenger et al, 2018b;da Costa Ribeiro and Bosland, 2012;Jiang et al, 2015;Sy et al, 2008). Ideally, molecular markers could be used to determine virulence phenotypes and the use of a standardized set of differentials (e.g., NMRILs) is crucial to gain a reasonable estimate to support marker development (Barchenger et al, 2018b).…”

“…Recently, the term ''race'' has been replaced by the term ''virulence phenotype'' to characterize the interaction of P. capsici isolates on RILs carrying various host resistance genes (Barchenger et al, 2018b). By using the NMRILs, 12 P. capsici root rot virulence phenotypes were characterized from isolates recovered from New Mexico, 11 from isolates recovered from Brazil, and 24 from isolates recovered from Taiwan (Barchenger et al, 2018b;da Costa Ribeiro and Bosland, 2012;Jiang et al, 2015). The NMRILs have also been used to characterize foliar blight virulence phenotypes (Monroy-Barbosa and Bosland, 2010;Monroy-Barbosa and Bosland, 2011).…”

“…Characterizing the virulence phenotypes present in production zones is useful in the development of resistant lines (Glosier et al, 2008). A promising approach is the introgression of specific resistance genes that could lead to multiresistant cultivars (da Costa Ribeiro and Bosland, 2012). In Mexico, there are no reports on the presence or characterization of virulence phenotypes of isolates of P. capsici recovered from production zones.…”