Improvement of inbred lines and candidate hybrids with biological test and molecular marker assisted selection in hybrid pepper (Capsicum annuum L.) breeding

ABSTRACT IMPROVEMENT OF INBRED LINES AND CANDIDATE HYBRIDS WITH BIOLOGICAL TEST AND MOLECULAR MARKER ASSISTED SELECTION IN HYBRID PEPPER (Capsicum annuum L.) BREEDING Tomato spotted wilt virus (TSWV) has become widespread and has started to cause too much damage. The most effective method against this disease without chemical prevention is the development of resistant varieties. The Tsw single dominant gene originating from Capsicum chinense is resistance source available for commercial breeding of pepper against TSWV. In this thesis; biological (classical) and marker assisted selection-MAS (molecular test) methods are applied to develop TSWV resistant (containing Tsw gene) lines and candidate hybrids. The study was carried out in the Aşağı Kocayatak research greenhouses / compartments at Department of Vegetable and Ornamental Plants and Molecular Biology Department laboratories of Batı Akdeniz Agricultural Research Institute (BATEM) in 2012-2017. As a material; 34 commercial varieties and 33 BATEM breeding lines were used. PI152225 was used as a resistant control material and Serademre 8 was used as a susceptible control. 139 hybrid populations of variety X variety, variety X line and line X line have been formed in four different fruit types including long, charleston (banana), capia and bell. In the selected F5 stage lines, combination tests were performed and 27 candidate hybrids were developed. Resistance to TSWV were determined by applying biological and molecular marker (co-dominant CAPS marker) methods in F2, F4 and F6 stage segregation lines during line selection by Pedigri method with candidate hybrids and commercial varieties. The TSWV isolate was confirmed by DAS-ELISA method. In the developed candidate hybrids, the performance tests were performed the superior ones were determined. The study was designed and applied for the resistant varieties breeding. Biological testing of 437 genotypes and molecular testing of 346 genotypes were carried out in F2, F4, F6 stages of combination segregation lines and candidate hybrids. According to the results of the biological test; 182 resistant and 255 susceptible genotypes were determined with a resistance rate of 42%. According to molecular test results; 150 homozygous-RR, 83 heterozygous-Rr and 113 susceptible-rr genotypes were determined and the resistance rate was found to be 67%. According to the molecular results, 59 genotypes were developed in long type, 24 in charleston, 101 in capia and 49 in bell type. A total of 217 genotypes were mutually biologically and molecularly tested against to TSWV and the results were found to be harmony rate 79 %. In other words, 21% different results were obtained. 12 commercial varieties were found to be resistant heterozygous in molecular testing. As a result; homozygous-RR, heterozygous-Rr resistant and sensitive-rr lines and candidate hybrids for TSWV were developed by using both methods. TSWV resistance was found to be partially different from the molecular and classical test results. In our country, the presence of the resistance breaking isolate of TSWV has significantly affected on pepper cultivation and has become the most important problem. Especially, it is very difficult and expensive to combat a transmitter pests. At this point, there is a great need for the determination of new sources of resistance to be used in breeding studies and the development of related molecular markers. Although molecular marker-assisted selection has been successfully applied in breeding studies, it has been seen that it should be carried out together with biological tests. In the future, it will be possible to develop resistant new lines and varieties by using the new TSWV resistance resorces to be determined and the resistance breeding method applied in the thesis study. KEYWORDS: Bilogical- classical testing, Molecular marker assisted selection, Pepper (C. annuum L.), Resistance breeding, Tomato spotted wilt virus (TSWV), Tsw gene, Virus resistance,