New sources of scald (Rhynchosporium secalis Davis) resistance for western Canadian barley
Scald, caused by Rhynchosporium secalis Davis, is an important fungal foliar disease of barley which can cause significant losses of yield and quality in western Canada. Scald can be controlled by fungicides and/or cultural methods, however, the use of genetic resistance is most desirable control strategy. The objectives of this study were to evaluate scald resistance in two New Zealand barley genotypes; to study the inheritance of that resistance and to test its novelty relative to a number of existing resistance sources available to Canadian breeding programs. New Zealand genotypes 145L2 and 4176/n, which showed scald resistance in NZ nurseries and in Alberta scald screening nurseries in 1998, were evaluated in 1999 and 2000 Alberta nurseries. To determine the genetic control of resistance, these resistant lines were each crossed with scald susceptible CDC McGwire; and resistant versus susceptible progeny ratios from F2 populations and F5 recombinant inbred lines (RILs) were tested for chi-square goodness of fit for one or two gene control. To determine the source of the resistance, ‘known’ H. vulgare parents of these NZ lines were evaluated in the Alberta scald nurseries. In addition, 145L2 was crossed with 4176/n and four local resistant lines to determine allelic relationships between ‘145L2’ resistance and the resistance in the local lines. In 1999 and 2000, both NZ lines expressed good scald resistance. Inheritance studies indicated that resistance in both NZ lines is governed by a single dominant gene. ‘145L2’ resistance is different from resistance in 4176/n and the other barley lines tested. All ‘known’ progenitors of these lines were susceptible suggesting that resistance is a result of mutation and/or introgression(s) from what is described as an ‘unknown’ parent in their pedigrees. The NZ lines provide new sources of scald resistance that can be incorporated into local breeding lines.
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