Goss's wilt (Leaf Freckles and Wilt) is a vascular and foliar disease incited by the bacterial pathogen Corynebacterium (Clavibacter) michiganense ssp. nebraskense. We previously reported use of crosses between M14 (resistant) translocation stocks and inbred A632 (susceptible) to locate a gene for resistance on the long arm of chromosome 7 (MGCNL 59:57, 1985). Similar field tests conducted in 1985 indicate that genes for resistance are also located on the short arm of chromosome 4 and the long arm of chromosome 8 (Table 1). These findings are consistent with a quantitative mode of inheritance for resistance to this disease.
Environment appears to influence expression of this disease. The genetic stocks involving translocation T4-9e demonstrated a significant difference in 1985 but did not in 1984. T8-9(6673) was not in 1984 tests. The effect of environment was also demonstrated in greenhouse tests. Genetic stocks involving translocations T4-9e, T7-9a and T8-9(6673), all of which demonstrated differences in the field, were greenhouse tested in fall 1985. Only stocks involving translocation T4-9e demonstrated a significant difference.
Preliminary results from greenhouse studies conducted with A632 (susceptible) translocation stocks crossed with Mo20W (resistant) are supportive of a quantitative mode of inheritance for susceptibility to this disease. These stocks will be field tested before chromosomal locations of genes effecting susceptibility are reported. Of interest is the potential location of a gene on the short arm of chromosome 4 that causes a susceptible reaction. Many sweet corn and popcorn cultivars have demonstrated susceptibility to this disease. The sugary-1 locus and the gametophyte factor locus, Ga, are both found on the short arm of chromosome 4. It may be worthwhile to evaluate for a possible relationship between selection for sugary-1 in sweet corn or selection for gametophyte factor in popcorn and the level of susceptibility to Goss's wilt.
Torbert R. Rocheford, Charles O. Gardner and Anne
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