ISHS Acta Horticulturae 760: XXVII International Horticultural Congress - IHC2006: II International Symposium on Plant Genetic Resources of Horticultural Crops
INHERITANCE OF RESISTANCE TO PEPPER ANTHRACNOSE CAUSED BY COLLETOTRICHUM ACUTATUM |
| Authors: | S.W. Lin, P.A. Gniffke, T.C. Wang |
| Keywords: | Capsicum annuum, backcross, susceptible, chilli pepper, recurrent parent |
| Abstract:
Anthracnose, caused by Colletotrichum acutatum, is a major disease that causes significant fruit and yield loss on pepper (Capsicum spp.) in Taiwan. High level of resistance to the pathogen in chilli pepper was identified in the C. chinense line PBC932. The resistance was transferred into C. annuum through three backcrosses into the cultivar ‘IR’. Inheritance of anthracnose resistance was evaluated in a cross between the resistance line ‘0038-9155’ (P1), a BC3F4 selection derived from an interspecific cross between PBC 932 (C. chinense) and the cultivar ‘IR’ (C. annuum PBC 535) and the susceptible line ‘9955-15’ (C. annuum) (P2). Fruit of parents, F1, F2, BC1P1F1, and BC1P2F1 generations were microinjected with isolate Coll-153 (C. acutatum) at two positions on each green and red fruit; lesion diameter was measured five days later. At the green fruit stage, seven out of ten F1 plants evaluated were resistant. Segregation ratio in the F2 generation fit a 9R:7S model, and in the BC1P2F1 generation, a1R:3S segregation suggests control by two complementary dominant genes. However, backcross to the resistant parent (BC1P1F1) failed to fit the predicted 1R:0S ratio. At the red fruit stage, seven of ten F1 plants proved susceptible. The ratio of resistant to susceptible plants in the F2 generation approximated a 7R:9S ratio, and almost all the BC1P2F1 progeny were susceptible (4R:96S plants), suggesting that the resistance may be controlled by duplicate recessive genes. However, the BC1P1F1 generation (84R:15S) did not fit the expected 1R:1S ratio. Plants with altered resistance at different fruit maturities were found far in excess of expectations based on linked inheritance. Thus, the genes conferring resistance at the immature green fruit stage appears to be distinct, and independent of those controlling resistance in mature red fruit. This study is the first report of independent genetic control of resistance to anthracnose at green and red fruit stages. | |
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