Reactions and field resistance of some potato varieties and hybrids to the leaf-roll virus.

Abstract

The leaf-roll reactions of a number of potato hybrids and varieties have been defined by external symptoms and the extent of phloem necrosis present in stem sections. There is no constant correlation between the leaf-roll reaction and field resistance of varieties and hybrids. The variety Bismark had the highest leaf-roll resistance of any of the types tested so it should prove a useful parent for this character. The resistance of Bismark and some hybrids is apparently dependent upon a virus-inactivating mechanism, which not only reduces field infection but prevents the transmission of leaf roll to a proportion of the tubers of infected plants. The initial selection of resistant hybrids could be made by sprout inoculating them and keeping those in which a proportion of the tuber progeny was free from leaf roll.

Resistance to phloem transport of potato leafroll virus in potato plants

“…Also, as mentioned above, we did not find resistance to phloem transport in stem sections of three other cultivars with A R. The study of fundamental features of virus transport was not an objective of this investigation. However, Hutton & Brock (1953) had previously suggested that cv. Bismark 'has a PLRV inactivating mechanism which is continually localising the virus and reducing its concentration so that even infected plants with severe symptoms produce varying percentages of progeny free of symptoms'.…”

“…Spunta leaves. As with feeding preference, the cultivar characteristic(s) responsible for different rates of colonization was independent of I R and A R. Hutton & Brock (1953) found that many progeny tubers from PLRV-infected plants of cv. Bismark were healthy.…”

“…Resistance to infection (I R) is overcome if the inoculum dose is sufficient, and this is polygenically controlled (Ross, 1958;Davidson, 1973Davidson, , 1980, whereas resistance to accumulation (AR), which decreases but does not prevent virus multiplication, may be determined by a single gene (Barker & Solomon, 1990). A third component of virus-specific resistance is recognized, decreased PLRV movement from infected foliage to tubers (McKay & Clinch, 1951;Hutton & Brock, 1953). This is independent of the non-specific 'mature plant resistance' which increases as potato plants age (Beemster, 1987).…”

Short and long distance spread of potato leafroll luteovirus: effects of host genes and transgenes conferring resistance to virus accumulation in potato.

“…For example, many virus-free progeny tubers developed from plants with a primary (current season) infection of PLRV in potato cv. Bismark (Hutton & Brock, 1953) and clone G7445(1) (Barker, 1987 b). Wilson & Jones (1992) found that the rate of systemic movement of PLRV through grafted stem sections of cv.…”

Potato virus Y (PVY) and potato virus X (PVX) resistance breeding in Kenya: applicability of conventional approaches

“…Hypersensitive resistance is type of resistance that limits spread within the plant following the initial infection (Barker, 1987). This occurs when there is a lower percentage of a virus-infected daughter tuber from an infected plant resulting from impeded virus movement (Hutton and Brock, 1953). Tolerance is when there is little or no apparent effect on the infected plant especially when infected plants are symptomless or have reduced symptom expression in the presence of disease (Cooper and Jones, 1983).…”