Fast track genetic improvement of ascochyta blight resistance and double podding in chickpea by marker-assisted backcrossing.

Ascochyta blight (AB) caused by the fungus Ascochyta rabiei Pass. Lab. is one of the major diseases of chickpea worldwide and a constraint to production in western Canada. The use of varieties with high levels of resistance is considered the most economical solution for long-term ascochyta blight management in chickpea. QTL for resistance to ascochyta blight have been identified in chickpea. The availability of molecular markers associated with QTL for ascochyta blight resistant and double podding provides an opportunity to apply marker-assisted backcrossing to introgress the traits into adapted chickpea cultivars. In the present study, molecular markers that were linked to the QTL for ascochyta blight resistance and the double podding trait, and those unlinked to the resistance were used in foreground and background selection, respectively, in backcrosses between moderately resistant donors (CDC Frontier and CDC 425-14) and the adapted varieties (CDC Xena, CDC Leader and FLIP98-135C). The strategy included two backcrosses and selection for two QTL for ascochyta blight resistance and a locus associated with double podding. The fixation of the elite genetic background was monitored with 16-22 SSR markers to accelerate restoration of the genetic background at each backcross. By the BC2F1 generation, plants with improved ascochyta blight resistance and double podding were identified. The selected plants possessed the majority of elite parental type SSR alleles on all fragments analyzed except the segment of LG 4, LG 6 and LG 8 that possessed the target QTL. The results showed that the adapted variety could be efficiently converted into a variety with improved resistance in two backcross generations.

Genetics of resistance to anthracnose and identification of AFLP and RAPD markers linked to the resistance gene in PI 320937 germplasm of lentil (Lens culinaris Medikus).

Anthracnose, caused by Colletotrichum truncatum, is a major disease problem and production constraint of lentil in North America. The research was conducted to examine the resistance to anthracnose in PI 320937 lentil and to identify molecular markers linked to the resistance gene in a recombinant inbred line (RIL) population developed from a cross of Eston lentil, the susceptible parent, and PI 320937, the resistant parent. A total of 147 F(5:6) RILs were evaluated for resistance to anthracnose in the greenhouse using isolate 95B36 of C. truncatum. Bulked segregant analysis (BSA) strategy was employed and two contrasting DNA bulks were constructed based on greenhouse inoculation of F(5)-derived F(6) RILs. DNA from the parents and bulks were screened with 700 RAPD primers and seven AFLP primer combinations. Analysis of segregation data indicated that a major dominant gene was responsible for resistance to anthracnose while variations in the resistance level among RILs could be the influences of minor genes. We designate the major gene as LCt-2. MapMaker analysis produced two flanking RAPD markers OPEO6(1250) and UBC-704(700) linked to LCt-2 locus in repulsion (6.4 cM) and in coupling (10.5 cM), respectively. Also, three AFLP markers, EMCTTACA(350) and EMCTTAGG(375) in coupling, and EMCTAAAG(175) in repulsion, were linked to the LCt-2 locus. These markers could be used to tag the LCt-2 locus and facilitate marker-assisted selection for resistance to anthracnose in segregating populations of lentil in which PI 320937 was used as the source of resistance. Also, a broader application of the linked RAPD markers was also demonstrated in Indianhead lentil, widely used as a source of resistance to anthracnose in the breeding program at the Crop Development Centre, University of Saskatchewan. Further selection within the few F(5:6) lines should be effective in pyramiding one or several of the minor genes into the working germplasm of lentil, resulting in a more durable and higher level of resistance.