EFFECT OF MASS VISUAL RECURRENT SELECTION FOR YIELD ON THE ADULT PLANT RESISTANCE TO YELLOW RUST AND LEAF RUST IN WHEAT

Abstract

The development of wheat varieties should consider, besides high yield capacity, other important traits such as the genetic resistance to diseases. The objective of this study was to evaluate in bread wheat (Triticum aestivum L.) the resistance of adult plant to yellow rust (Puccinia striiformis f. sp tritici Wensted.) and to leaf rust (Puccinia recondita Rob. Ex. Desm. f. sp. tritici). This was done on F₅ families developed from seven cycles of recurrent selection for grain yield, under natural incidence of these diseases. Four experiments were established in the Experimental Station El Bajio, located in Celaya, Gto. Mexico, with two planting dates in the period Autumn-Winter 1998-99 to evaluate resistance at yellow rust and two planting dates in the period Spring-Summer 1999 to evaluate resistance to leaf rust. The cultivar Moroco was inoculated for yellow rust with the race that attacks gene Yr9, and for leaf rust with the race MCJ/SP. The results obtained indicate that when recurrent selection for grain yield is practiced there is not genetic advance for some non selected traits, such as the resistance to yellow rust and leaf rust. Therefore, it is suggested to artificially inoculate these diseases when breeding with the objective to develop wheat commercial varieties.