Resistance to potato leafroll luteovirus can be greatly improved by combining two independent types of heritable resistance

Abstract

Twelve potato clones were exposed to infection by aphids with potato leafroll luteovirus (PLRV) in three field trials in order to assess their resistance to infection. Up to 92% of the plants of some clones became infected, although other clones were relatively resistant to infection and one clone remained virusfree in all three trials. The resistance of the same 12 clones to PLRV multiplication was assessed in glasshouse-grown plants: plants were graft-inoculated and their daughter tubers were used to grow plants with secondary infection. High concentrations of PLRV were found in some clones (c. 1700 ng/g leaf) while in others much less virus accumulated (as little as 60 ng/g leaf). However, clones in which little virus accumulated were not necessarily those which were most resistant to infection in the field, and there was no association between the two types of resistance. Nevertheless, both types of resistance were found in some clones. The clone G8107(1), which remained virus-free in all the field exposure trials, was also the most resistant to PLRV multiplication. The combination of these two types of resistance in cultivars should help to eliminate the spread of PLRV in crops.

Mechanism of strong resistance to Potato leafroll virus infection in a clone of potato (Solanum tuberosum)

“…This raises the possibility that this resistance to infection could after all be due at least partly to the same mechanism as the resistance to accumulation, although the two types of resistance can occur separately (Solomon-Blackburn & Barker, 1993). However, only very rarely did PLRV move into other parts of aphid-inoculated G8107(1) plants: we were unable to detect PLRV in their petiole or stem tissues by ELISA, immunoprinting or return graft assay; secondary infection was detected in only two tuber progenies of 33 tested (one from a plant inoculated with 100 aphids and one from a tuber with sprouts inoculated with 25 aphids).…”

“…We therefore suggest that an important element in the very strong resistance of this clone to PLRV is resistance to virus movement within or from the leaves. Pentland Crown (Solomon-Blackburn & Barker, 1993). Mihovilovich et al (2007) also suggested that a single mechanism might account for both of these two types of resistance in S. tuberosum ssp.…”

“…The potato clone G7445(1) is intermediate in resistance/ susceptibility to PLRV infection by aphids and resistant to PLRV accumulation having only a low concentration of virus in the leaves of tuber-progeny plants of graftinoculated plants (Solomon-Blackburn & Barker, 1993). In contrast to clones susceptible to PLRV accumulation, very few cells become infected in the external phloem in stems and petioles of young plants of clone G7445(1) and clone G8107(1) described below, although movement of virus along the phloem in stems is unimpeded (Derrick & Barker, 1992, 1997.…”

Potato leafroll virus (PLRV): its transmission and control

“…Minor genes for resistance are probably derived from S. demissum and S. acaule, as well as from other natural sources (Uhrig et al 1992). A complex genetic control of resistance means that the identification of the most resistant genotypes among the progeny of crosses between resistant and susceptible parents is not straightforward (Barker and Harrison 1985;Solomon-Blackburn and Barker 1993), although the resistance ratings of cultivars can be derived from the results of field experiments (Davidson 1973).…”

Heritility of field resistance to potato leafroU virus in cultivated potato

“…Resistance to infection by aphid transfer and resistance to titre build-up after graft challenge were found to be distinct traits that were not necessarily correlated when assessed as secondary infection (e.g. indexed in foliage grown from the daughter tubers of inoculated plants) in advanced breeding clones (Solomon-Blackburn and Barker 1993). Resistance to titre build-up in the section Etuberosa was first described by Jones (1979) for S. brevidens Phil, and in somatic hybrids with cultivated potato by Austin et al (1985).…”