Submitted to: Cereal Rusts and Mildews Conference European and Mediterranean Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/22/1996
Publication Date: N/A
Technical Abstract: Pathotypes of wheat stem rust pathogen (Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.) have been avirulent on hard red spring wheat (Triticum aestivum L.) cultivars, Waldron (WD), Len (LE), Coteau (CT), and Stoa (ST), and are not useful in detecting gene differences among these cultivars. A new sexual recombinant culture, 46-2, identified in progenies sfrom random selfing and crossing on barberry plants, was highly virulent o WD but varied in avirulence on the other 3 cultivars, and was used to characterize genetic variation for resistance. Rust reactions show that WD is susceptible, LE is moderately resistant, CT and ST are resistant and may have genes not in LE. ST may have a gene not in CT. To determine the inheritance of resistance (R), parental, F1, F2, and F3 seedlings of a diallel cross of the cultivars were tested for reaction to 46-2. The segregating ratios indicate that LE differed from WD by a dominant moderately resistance (MR) gene. CT has 3 genes for R not present in WD. One is an incompletely dominant gene conditioning R when homozygous, 1 is a dominant MR gene, and 1 a dominant thermosensitive gene conditioning R at low temperature and ineffective at high in part of the plant population. ST differs from WD by 3 genes that include 1 incompletely dominant gene conditioning R when homozygous and 2 dominant MR genes. Tests for allelism and chromosomal location show that the MR gene from CT is nonallelic to the MR gene from LE which is located in chromosome 2BL. Of the 2 MR genes from ST, one is allelic and one nonallelic to the MR gene from LE. The R gene from CT is allelic to the R gene from ST and is located in chromosome 2D of CT. This new culture, 46-2, permitted differentiation of resistance genes not detectable by cultures previously available.