Resistance to Colonization by the Wheat Curl Mite in Aegilops squarrosa and its Inheritance after Transfer to Common Wheat1

Abstract

Wheat streak mosaic is a destructive disease. The agents that cause it are vectored by the wheat curl mite (Eriophyes tulipae Keifer). While no resistance to colonization by this mite has been found in common wheat (Triticum aestivum L. em. Thell.), such resistance has been found in distant relatives of wheat from the genera Agropyron and Secale. This paper investigates Aegilops squarrosa L. (a close relative of common wheat) as a potential source of resistance to mite colonization. Two accessions of Ae. squarrosa were tested in a growth cabinet for resistance to mite colonization. One accession was found to be resistant while the other was susceptible. Following transfer of this resistance to common wheat, crosses were made between resistant (AC PGR 16635) and susceptible inbred parents and their progeny. Genetic segregation in three filial generations (F1, F2, and F3) and two backcross generations (B1 F1 [F1 by susceptibles] and B2 F1 [resistant B1 F1 by susceptibles]) indicated that resistance was conditioned by a single dominant gene with normal Mendelian behavior. It is suggested that this trait be referred to as resistance to curl mite colonization, that its abbreviation be Cmc, and that this particular gene be designated Cmcl. Since the chromosomes of Ae. squarrosa are also present in common wheat, Cmcl should recombine normally without the complication of a large, attendant linkage block that exists with translocated Cmc genes derived from Secale or Agropyron.