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- Author or Editor: Rafael González-Torres x
A total of 110 melon accessions with different geographical origins (18 countries) were screened for resistance to Fusarium oxysporum f.sp. melonis race 1.2 (pathotypes 1.2Y and 1.2W) using two artificial inoculation procedures. Twelve accessions showed some resistance to one or both strains. Three Japanese accessions, Shiro Uri Okayama (var. conomon), Kogane Nashi Makuwa, and C-211 (var. makuwa), and a Portuguese accession, BG-5384 (var. cantalupensis), showed the highest levels of resistance to both strains. The remaining eight accessions (all var. inodorus) had some level of partial resistance to 1.2W only. To our knowledge, this is the first time a high level of resistance to F. oxysporum f.sp. melonis race 1.2 has been identified in melon accessions of Western origin. The morphological traits of the 12 accessions that showed partial resistance were characterized to assess their suitability as resistance sources in melon breeding programs. Because most of the Western commercial cultivars belong to the cantalupensis, reticulatus, or inodorus botanical varieties, the resistant accessions from these varieties seem to be the most useful sources of resistance in breeding programs for developing melon cultivars of these types resistant to fusarium wilt race 1.2. The Portuguese accession BG-5384 had a high level of resistance within the Western types, and its morphological characteristics were fairly similar to some of the Western commercial cultivars.
In total, 139 Cucumis melo accessions were evaluated for resistance to races 0, 1, and 2 of Fusarium oxysporum fsp. melonis and 127 accessions were evaluated for resistance to races 1 and 2 of Sphaerotheca fuliginea. In addition, seven C. melo wild relatives were also tested. Artificial inoculations were performed and plants were scored for presence or absence of symptoms. The screening revealed that sources of natural resistance to these fungi are limited. However, several sources of resistance were found in C. melo accessions. Thus, the accession `CUM-334' from Tajikistan has shown resistance to the three races of F. oxysporum fsp. melonis, behaving similarly to the melon inbred line `MR1'. Two accessions of C. melo var. conomon, `CUM-190' and `Shiroubi Okayama', from Japan, were resistant to races 0 and 1 and twelve accessions were resistant to races 0 and 2. Intra-specific variability for resistance to powdery mildew in C. melo was found to be poor. Nevertheless, six Spanish cultivars and the accessions `TGR-1551', `CUM-313', and `CUM-129' were resistant to races 1 and 2 of S. fuliginea.
Seven pepper (Capsicum chinense Jacq.) populations from the Yucatán Peninsula, México, that were selected from a field screening for viral diseases were tested for pepper huasteco geminivirus (PHV) resistance. Two populations (UX-SMH-1 and UX-SMH-24) displayed <50% of infection with PHV. Four plants did not show viral symptoms 3 months postinoculation using biolistic and grafting methods. When leaf tissue from these individuals was analyzed for PHV using quantitative PCR, it supported PHV replication, thus, the ineffective PHV infection in these symptomless individuals may be a result of restricted viral movement.