|Walker, M. Andrew|
Submitted to: Acta Horticulture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/30/2006
Publication Date: N/A
Citation: Interpretive Summary: Pierce’s disease (PD) resistant table and raisin grape varieties are needed since the spread of the disease has been increased by the Glassy-winged sharpshooter which was recently introduced into California. PD resistant grapes that are currently available have poor fruit quality. In the past, poor fruit quality was reported to be transmitted with resistance to PD. This study showed that individuals in F1 and BC1 populations have similar fruit quality independent of their PD resistance or susceptibility. This shows that progress in improving fruit quality can be made just as rapidly in developing resistant varieties as non-resistant varieties when the same parents are used.
Technical Abstract: The spread of Pierce’s disease (PD) has greatly increased with the introduction of the Glassy-winged sharpshooter into California. A collaborative breeding program to develop table and raisin grape cultivars resistant to PD was started in 2000. V. arizonica/candicans grape hybrids with PD resistance were hybridized with table and raisin grapes and the first generation screened in the greenhouse to determine resistance. The second generation was screened by molecular markers to identify resistant individuals. There was no difference between the 1st generation resistant and susceptible populations of 8909-15 x table grape for cluster weight, berry weight and seed/trace weight. The cluster weight and berry size of the best resistant individuals were twice the size of the resistant parent. Aborted seeds, similar in size to the seedless parent, were also achieved in a resistant seedling. There was also no difference between 1st generation resistant and susceptible populations of 8909-08 x table and raisin grape selections for cluster size, berry size and seed/trace size. Resistant individuals with the largest berry size averaged 1.82 g compared to 3.6 to 14.4 g for the table grape parents. Some resistant individuals had large aborted seeds but were still much larger than those found in the seedless parents. There was no difference between resistant and susceptible populations for berry size and seed/trace size in the 2nd generation that resulted from backcrossing to table and raisin grapes. The mean berry size was 0.6 g larger and the mean seed/trace size decreased from 120 g to 41g in the 2nd generation. The 2nd generation resistant individual with the largest berry averaged 4.9 g. Resistant individuals with undetectable seed traces, smaller than the seedless parents, were obtained in the second generation. This shows that fruit quality can be rapidly improved in the development of PD resistant grapes when efficient screening methods are used.