A. Tullu

Using molecular markers to pyramid genes for resistance to ascochyta blight and anthracnose in lentil (Lens culinaris Medik)

Ascochyta blight caused by the fungus Ascochyta lentis Vassilievsky and anthracnose caused by Colletotrichum truncatum [(Schwein.) Andrus & W.D. Moore] are the most destructive diseases of lentil in Canada. The diseases reduce both seed yield and seed quality. Previous studies demonstrated that two genes, ral1 and AbR1, confer resistance toA. lentis and a major gene controls the resistance to 95B36 isolate of C. truncatum. Molecular markers linked to each gene have been identified. The current study was conducted to pyramid the two genes for resistance to ascochyta blight and the gene for resistance to anthracnose into lentil breeding lines. A population (F6:7) consisting of 156 recombinant inbred lines (RILs) was developed from across between ‘CDC Robin’ and a breeding line ‘964a-46’. The RILs were screened for reaction to two isolates (A1 and 3D2) ofA. lentis and one isolate (95B36) ofC. truncatum. χ2 analysis of disease reactions demonstrated that the observed segregation ratios of resistant versus susceptible fit the two gene model for resistance to ascochyta blight and a single gene model for resistance to anthracnose. Using markers linked to ral1 (UBC 2271290), to AbR1(RB18680) and to the major gene for resistance to anthracnose (OPO61250),respectively, we confirmed that 11 RILs retained all the three resistance genes. More than 82% of the lines that had either or both RB18680 and UBC2271290markers were resistant to 3D2 isolate and had a mean disease score lower than 2.5. By contrast, 80% of the lines that had none of the RAPD markers were susceptible and had a mean disease score of 5.8. For the case of A1 isolate of A. lentis, more than 74% of the lines that carriedUBC2271290 were resistant, whereas more than 79% of the lines that do not have the marker were susceptible. The analysis of the RILs usingOPO61250 marker demonstrated that 11out of 72 resistant lines carried the marker, whereas 66 out of 84 susceptible lines had the marker present. Therefore, selecting materials with both markers for resistance to ascochyta blight and a marker for resistance to anthracnose can clearly make progress toward resistance in the population.

Breeding Annual Grain Legumes for Sustainable Agriculture: New Methods to Approach Complex Traits and Target New Cultivar Ideotypes

Although yield and total biomass produced by annual legumes remain major objectives for breeders, other issues such as environment-friendly, resource use efficiency including symbiotic performance, resilient production in the context of climate change, adaptation to sustainable cropping systems (reducing leaching, greenhouse gas emissions and pesticide residues), adaptation to diverse uses (seeds for feed, food, non-food, forage or green manure) and finally new ecological services such as pollinator protection, imply the need for definition of new ideotypes and development of innovative genotypes to enhance their commercialization. Taken as a whole, this means more complex and integrated objectives for breeders. Several illustrations will be given of breeding such complex traits for different annual legume species. Genetic diversity for root development and for the ability to establish efficient symbioses with rhizobia and mycorrhiza can contribute to better resource management (N, P, water). Shoot architectures and phenologies can contribute to yield and biotic constraint protection (parasitic weeds, diseases or insects) reducing pesticide use. Variable maturity periods and tolerance to biotic and abiotic stresses are key features for the introduction of annual legumes to low input cropping systems and for enlarging cultivated area. Adaptation to intercropping requires adapted genotypes. Improved health and nutritional value for humans are key objectives for developing new markets. Modifying product composition often requires the development of specific cultivars and sometimes the need to break negative genetic correlations with yield. A holistic approach in legume breeding is important for defining objectives with farmers, processors and consumers. The cultivar structures are likely to be more complex, combining genotypes, plant species and associated symbionts. New tools to build and evaluate them are important if legumes are to deliver their exciting potential in terms of agricultural productivity and sustainability as well as for feed and food.

Genetic and genomic resources of lentil: status, use and prospects

Extensive collections of lentil germplasm now exist in various genebanks around the world. This germplasm including wild Lens species has been used in plant introduction strategies and in efforts to widen the potential sources of increasing genetic diversity in the breeding programmes of lentil. Improved techniques are emerging to overcome hybridization barriers between species and as a result, interspecific hybrids have been successfully obtained between species. Several interspecific recombinant inbred line populations have been developed. Selected and backcrossed lentil lines are currently in advanced yield trial stages, and desirable traits such as yield, disease resistance and agronomic traits have been incorporated into cultivated lentil especially from Lens ervoides , generating a wider spectrum of variability. Secondly, further expansion of the overall pool of germplasm and examination of allelic variation at the nucleotide level will benefit lentil-breeding programmes by augmenting phenotype-based variation to further advance cultivar development. Genomic resources for lentil are limited now, but this situation is changing rapidly as the cost of genotyping has declined. As a result, two successive expressed sequence tags (EST) projects were undertaken under the NAPGEN EST project initiative ( http://www.nrc-cnrc.gc.ca/eng/programs/pbi/plant-products/napgen/.htm ) and an Agricultural Development Fund project initiative. We emphasize that creation of intraspecific and interspecific genetic populations, genetic maps, association maps, quantitative trait loci and marker-assisted selection technologies for implementation in the breeding programme will enhance deployment of genes responsible for traits of interest. The economical use of genomic technologies for use in germplasm resource management and genetic improvement is on the near horizon.

Improvement of embryo rescue technique using 4-chloroindole-3 acetic acid in combination with in vivo grafting to overcome barriers in lentil interspecific crosses

Widening the genetic base of minor grain legume crops such as lentil (Lens culinaris Medik.) is important for achieving future gains in productivity. In order to access genes from wild lentil species embryo rescue techniques are required to overcome reproductive barriers. Removing the seed coat from developing 14-day old immature hybrid seeds and culturing the interspecific zygotic embryos in medium containing auxin 4-chloroindole-3 acetic acid (4-Cl-IAA) improved successful hybrid recovery. Addition of 4-Cl-IAA to media also increased shoot proliferation when combined with a low concentration of zeatin. No significant difference in shoot elongation was observed between 4-Cl-IAA or IAA treatments. Hybrid shoots were then successfully grafted in vivo onto faba bean rootstocks. Hybrids were obtained from crosses of L. culinaris with L. tomentosus Ladiz., L. lamottei Czef., and L. odemensis Ladiz. This efficient and simple embryo rescue protocol resulted in seed production of large interspecific F2 populations from inherently weak zygotic embryos produced from wide hybridization.