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| Author(s): |
Sally Ferreira Blat
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2004-06-09 |
| Examining board members: |
Cyro Paulino da Costa;
Leila Trevizan Braz;
Hiroshi Kimati;
Keigo Minami;
Norberto da Silva
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| Advisor: | Cyro Paulino da Costa |
| Abstract | |
Powdery mildew caused by the fungus Leveillula taurica, is considered the most serious greenhouse sweet pepper disease, causing losses up to 75%. Its control by fungicide is ineffective, and the best way to control would be by genetic resistance. Powdery mildew resistance sources identified in Capsicum annuum L. have been unsatisfactory because they have partial resistance. The best resistant sources seem to be found in the species C. baccatum and C. chinense. However, the resistance inheritance has not been studied in these hot pepper species, except for C. annuum, with few published pappers. The present study aimed to screen the Capsicum ESALQ/USP collection accesses, to identify potential resistance sources in C. annuum, C. baccatum and C. chinense and elucidate the reaction inheritance to powdery mildew in sweet pepper and hot pepper. A total 156 Capsicum access were tested. Crosses among resistant and susceptible progenitors and among resistant ones were carried out. F2 and backcrosses generations were obtained. Reactions evaluations to powdery mildew were carried out during the fruit production using rating system based on score disease severity using scale varying from 1 (resistant) to 5 (highly susceptible). Estimation of segregating loci number, heritability and expected selection gains was made, to investigate the gene action and to evaluate the reaction to powdery mildew from resistant versus resistant single hybrids. Only 5% of the C. annuum accesses evaluated were considered to be resistant, in contrast with 84% and 85% obtained for C. baccatum and C. chinense, respectively. Resistance inheritance to powdery mildew in Capsicum spp. was found to be polygenic. In view of the high heritability and selection gains estimates, good selection progresses are expected. The genetic systems controlling resistance in the Capsicum annuum progenitors have different genetic mechanisms and expressions of resistance, while in C. baccatum and C. chinense showed to be the same in each ones with allelism between the sources. The sweet pepper HV-12 was the best source to use in breeding. (AU) | |