ISHS Acta Horticulturae 528: VII International Symposium on Grapevine Genetics and Breeding
BREEDING VITIS RUPESTRIS X MUSCADINIA ROTUNDIFOLIA ROOTSTOCKS TO CONTROL XIPHINEMA INDEX AND FANLEAF DEGENERATION |
| Authors: | M.A. Walker, Y. Jin |
| Keywords: | RAPD, AFLP, pseudotestcross linkage map |
| Abstract:
Fanleaf degeneration, caused by grapevine fanleaf virus (GFLV) and vectored by the dagger nematode, Xiphenema index, remains one of the world's most serious grape diseases. Muscadinia rotundifolia has very strong resistance to X. index feeding and has been reported to resist GFLV. Vitis rupestris x M. rotundifolia seedlings were produced at the University of California, Davis and 200 F1 individuals were screened for X. index resistance. Seventy of them were found to be resistant and two seedling populations (8909 and 8913) were used for DNA marker screening and inheritance testing. One of 70 RAPD primers (OPA-12) was found to be linked with resistance. The OPA-12 product was cloned and sequenced to develop a more sensitive SCAR (sequence characterized amplified region) primer. About 30 of these resistant seedling selections are now in seven trials to evaluate field performance and resistance to fanleaf degeneration. Cytogenetic investigation of these F1 hybrids revealed 38 chromosomes, although abnormal segregation ratios for X. index resistance were obtained. These V. rupestris x M. rotundifolia hybrids are unexpectedly fertile and we produced F2 generations of resistant x susceptible, resistant x resistant, backcrosses to both parents and a selfed resistant seedling to investigate the inheritance of resistance. More than 2,000 hybrid individuals have been tested for X. index resistance and normal Mendelian segregation ratios were obtained. The results, except those for the selfed group, suggest that resistance is controlled by a single dominant gene. Construction of genetic linkage maps is a fundamental process in the detection of gene(s) controlling trait expression. One of the F2 seedling groups (resistant x susceptible) with 350 individuals was used for genetic linkage analysis. AFLP (amplified fragment length polymorphism) technology was used to search for markers in a 116 randomly selected seedlings from the group of 350 seedlings. Over 500 segregating AFLP markers generated 19 linkage groups for both parents. This map will form framework for introgression of many important resistance traits from Muscadinia into Vitis. | |
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