Additive gene action for resistance to Puccinia striiformis F.SP. Tritici in Triticum dicoccoides

Abstract

Triticum dicoccoides, wild emmer wheat. Puccinia striijbrmis, yellow rust, stripe rust of wheat, minor genes . SUMMARY Seven single-plant selections of wild emmer, with temperature-sensitive minor-effect genes for stripe rust resistance, were intercrossed in eight combinations . The resulting progenies were studied for a possible additive gene action .The transgressive segregation towards resistance in F 2 observed in all the combinations indicates that additive gene action for resistance indeed occurs in wild emmer. The common occurrence of this phenomenon in random combinations suggests further that several minor-effect genes are involved .Following selection of the most resistant plants in F 2 , a marked shift towards resistance was noted in F 3 , which demonstrates a positive response to selection . In some instances, additive resistance selected for (in F2) at the high temperature-profile was expressed (in F 3 ) also at the low temperature-profile . This kind of resistance, when utilized in breeding programmes, promises therefore to be effective over a range of temperatures .

Temperature-sensitive genes for resistance to Puccinia striiformis in Triticum dicoccoides

“…Various crossing programmes, to study further characteristics and combining ability of the temperature-sensitive genes in wild emmer, are in progress . One of the characteristics of minor effect genes in T. aestivum, namely additive gene action, has been investigated also in T. dicoccoides (GRAMA et al, 1984) .…”

Race-specificity of temperature-sensitive genes for resistance to Puccinia striiformis in Triticum dicoccoides

“…Therefore a number of wild emmer entries were included in the present study which in previous work had proved to possess different temperature-sensitive genes (Grama et al ., 1984) . Having had no previous 11 Entry No .…”

“…Although it is generally believed that race-specific resistance is not very durable, in this case, where we deal with genes which are both race-specific and additive in action (Grama et al ., 1984), there seems to be a better chance for stability . Parlevliet & Zadoks (1977) compared the level and durability of resistance based on race-specific minor genes with additive effects with that of resistance based on true race-non-specific minor genes with additive effects .…”

“…Comparing the characteristics of minor genes present in wild emmer with those occurring in cultivated wheat, it was found that both confer a temperature-sensitive reaction Lewellen et al ., 1967) and both, when (Grama et al ., 1984 ;Sharp et al ., 1982 ;Sharp et al ., 1970) . With regard to these minor genes in cultivated wheat, it was concluded that they are race non-specific (Sharp et al ., 1982 ;Sharp et al ., 1970 ;Stubbs, 1977) .…”

Adult-plant resistance to yellow rust in wild emmer wheat

“…In later work it was shown that numerous selections of wild emmer were highly resistant to isolates of yellow rust from many countries (Van Silfhout and Gerechter-Amitai, in preparation). In addition to this 'seedling' or overall resistance conferred by major genes, Gerechter-Amitai et al (1984) described in wild emmer also another kind of resistance conferred by temperature-sensitive 'minor-effect' genes, which are race-specific (Gerechter-Amitai and Van Silfhout, in press) and, when combined, display additive gene action (Grama et al, 1984). Gerechter-Amitai et al (1984) concluded that these genes are effective not only in the seedling stage but also in the adult-plant stage, in the field.…”