INHERITANCE OF LEAF RUST RESISTANCE IN BREAD WHEAT CULTIVARS FOR RAINFED AREAS

Abstract

Juchi F2000, Náhuatl F2000, and Tlaxcala F2000 are bread wheat varieties recently released for rainfall areas of México. Wheat leaf rust caused by Puccinia triticina E. is continuously threatening wheat production. Consequently, breeding for rust resistance has been the most effective mean for disease control. In order to determine the genetics of resistance to leaf rust in Juchi F2000, Náhuatl F2000, and Tlaxcala F2000, these were crossed with Avocet-YrA (AOC-YrA), a susceptible cultivar. One hundred and forty eight F3 families per cross, as well as the parents involved in each cross were tested against MCJ/SP rust race in the Yaqui Valley, Sonora during the fall 2001-winter 2002 growing season, under artificial inoculation using urediniospores. Families were classified as resistant, susceptible, and segregating. Based on the number of homozygous susceptible families, it was determined that Juchi F2000 and Tlaxcala F2000 carry four minor additive genes for slow leaf rust resistance. On the other hand, Náhuatl F2000 carries three minor additive genes including the possible effect of Lr16. The Lr34 gene was common in the three varieties and is well known that confers slow rusting resistance to wheat leaf rust. The number of genes is discussed according to the population size and the expected frequencies