Interspecific-derived and juvenile resistance to anthracnose in lentil

Anthracnose, caused by Colletotrichum truncatum, is a major disease of lentil (Lens culinaris Medik.) on the Canadian prairies. Resistance to the more virulent race Ct0 of the pathogen is extremely rare within the L. culinaris gene pool thus resistance is being introgressed from Lens ervoides. The overall hypothesis of this project was that resistance derived from Lens ervoides accession L-01-827A would provide uniquely low levels of resistance to Colletotrichum truncatum. Individual studies were performed to: i) test field-resistance of interspecific lines; ii) develop a cutting-method to generate replicated phenotypic data on single plants; iii) study the deterioration of resistance between the juvenile phase (JP) and adult phases (AP) in the line ‘CDC Redberry’; and iv) examine genetic control of resistance in a susceptible and partially resistant background. Field evaluations of L. culinaris x L. ervoides lines indicated resistance genes from the wild species will provide unprecedented levels of disease control and heritability of the trait was estimated to be moderate. Single plant phenotyping of resistance is unreliable, thus the feasibility of using clonal propagation of individual plants to generate replicated ratings was evaluated. Results showed consistency in segregation ratios between cutting and seedling-derived plants of the same population, thus the method was utilized for testing of genetic control of segregating populations. ‘CDC Redberry’ showed varying disease levels depending on the age of the plants with resistance acquisition in the JP that decreased as the plants proceeded through the AP. The F1, F2 and F2:3 generations of two introgression populations were tested for resistance. Resistance from L. ervoides to both races of C. truncatum appeared to be due to the same gene(s) or from the same linkage block in both populations. Models for genetic control were consistent between F2 and F2:3 generations, however were different between the populations depending on whether the interspecific line was crossed into a susceptible or partially resistant L. culinaris background. However duplicate recessive epistasis seemed to control susceptibility in the susceptible background and when JP resistance was not a factor. There were significant differences between the JP and AP on more than a third of the F2s tested supporting different resistance gene action based on growth phase. Resistance in the JP seemed to be due to dominant and recessive epistasis. It was postulated that the the populations may have had segregation distortion commonly found in interspecific populations, thus the previously described genotypes for cotyledon colour and albino plants were used to test the hypothesis of segregation distortion. Segregation of these traits were found to be similarly distorted to previously reported interspecific L. culinaris x L. ervoides populations supporting the hypothesis that continued segregation distortion was found in the introgression populations. Overall, it was found that resistance derived from L. ervoides accession L-01-827A is a highly effective source for the lentil breeding program, however the result suggest more than one backcross to L. culinaris be necessary to properly integrate the resistance genes to eventually obtain fully fertile, adapted lentil cultivars