Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 23, 1997
Publication Date: N/A
Interpretive Summary: Potato leafroll virus is a cause of yield decline in potato throughout the world. It is transmitted by an aphid with wide distribution. The virus is a particular problem in the warmer production zones of the northwest of the United States, because a long season provides extensive opportunity for infection. This study shows that there exists in breeding materials a high hresistance to the virus and the this resistance is highly heritable. A high heritability means that the genes that control resistance can be transmitted from the parent to the offspring in such a way that a high proportion of the progeny will have high resistance, also. In other words, the efficiency of transmission of resistance is very high. This study also provided specific information on which parents are the efficient sources of potato leafroll virus resistance. The high percentages of resistant progeny from the best parents suggest that one or two genes have a major influence on the resistance. Mapping and cloning these genes are possibilities for future work. A cloned resistance gene could be inserted into popular potato varieties. Genetic resistance is an effective way of reducing the need for expensive pesticides in the production of potato.
Technical Abstract: Potato progenies in a line x tester mating design and the clonal parents were screened for field resistance to potato leafroll virus (PLRV) to determine the heritability of this trait. Twelve advanced potato clones or varieties were crossed as pistillate parents to two pollen testers. The seedling progenies and clonal parents were exposed to aphid-transmitted potato leafroll virus for two growing seasons. Cumulative infection by potato leafroll virus was determined by post-season serological indexing of foliage grown from sprouted tubers after two years of exposure. Narrow- sense heritability was estimated from variance components from the analysis of variance as h**2 = 0.93, and by regression of mid-parent on progeny as h**2 = 0.72. Both estimates indicated high levels of usable genetic variance for PLRV resistance in advanced breeding materials. Although variation in resistance to PLRV appears to be a quantitative trait in susceptible and moderately resistant clones, performance of the most resistant parents suggests that genes with major effects may be present. These results are similar to the conclusions of other researchers who found one or two genes controlling the phenotypes of extreme resistance, resistance to infection, or suppression of virus titer.