Constraction Of Molecular Linkage Map And QTL Analysis Of Phytophthora Capsici Resistance In Pepper

Pepper is one of the most important vegetable crops in the world. As a soil borne disease happening all over the world, Phytophthora capsici L. damages pepper product more and more seriously in recent years. Resistance breeding is a effective method for Phytophthora capsici L. control in many countries. Since the 8th Five-year Plan, Phytophthora capsici L. resistance breeding has been concluded in the National Key Technologies R&D Program of China.In this thesis a F2 population including 144 individuals were used for research derived from the resistant inbred line 'perennial' and the sensitive inbred line '83-60'.Screen out the AFLP primers that have high polymorphic between parents, then analyze genotypes of the F2 population using these primers, construct a genetic linkage map of pepper, analyze QTL of Phytophthora capsici L. resistance. The results are summarized as follows:(1) 380 pairs of high polymorphic AFLP primers were sceened out from 512 pairs of primers. 28 pairs of outstanding primers were used to analyze genotypes of the F2 population. 146 AFLP polymorphic markerswere obtained. A genetic linkage map of pepper was constructed based on this F2 population by using Joinmap3.0 software. This map included 54 AFLP markers,15 RAPD markers and 1 SSR markers(RAPD, SSR markers, Hu Yongsheng, Master research thesis), distributed in 12 main linkage groups spanning lenth from 4.30 to 85.85cM, with an average interval distance is 6.12cM.(2) The artificial inoculations were performed to evaluate the Phytophthora capsici L. resistance of 'perennial', '83-60' and their F2 population. The pathogen is Phytophthora capsici L.,Changsha isolate, which was cultivated in PDA culture medium at constant 18℃for 3 days. The inoculating concentration is 10~3 spores per ml. The lesion length and shape were observed in the 10th day after inoculation. Resistance criterion ranging from 0(high resistant) to 5(susceptible) was set to identify the resistence of the indivatues.(3) QTL analyzing was performed using interval mapping (IM) with Windows QTL Cartographer (2.0). Significance thresholds were computed by 1,000-permutation tests. LOD score threshold was 2.2. Two QTLs were detected on group 4, were significant to Phytophthora capsici L.resistance that accounted for 9.5% and 16.4 % of the total phenotypic variation. One QTL is near E41M53-7 loci with 0.4cM, supporting area is 0-7.2cM; another QTL is near E41M52-6 with 7cM, supporting area is 13.6-35.6cM.Results of this research would offer available markers for molecular marker-assisted selection, accelerate the attainment of resistant varieties of pepper.