Screening of wild and cultivated lentil germplasm for resistance to stemphylium blight

Lens culinaris Medik. ssp. culinaris is the only cultivated species in the genus Lens. Intensive selection pressure to develop new cultivars, a narrow genetic base, co-evolution of pathogens to partially resistant cultivars and other factors have accelerated susceptibility to different fungal diseases in this species. Few sources for resistance to stemphylium blight (SB) caused by Stemphylium botryosum Wallr. exist among commercial lentil cultivars. A total of 70 accessions were selected from seven species of the genus Lens to screen for SB resistance. The L. culinaris accessions were screened in four different environments, and the accessions of Lens ervoides, L. culinaris ssp. orientalis, Lens tomentosus,Lens nigricans, Lens odemensis and Lens lamottei in growth chamber or greenhouse experiments to identify resistance sources for potential use in lentil breeding. A highly aggressive isolate of SB was used as an inoculum to screen them under controlled conditions. Lentil cultivars ‘Eston’ (resistant) and ‘CDC Glamis’ (susceptible) were used as checks with consistent results in all experiments. Most of the L. culinaris accessions were susceptible to SB, whereas more than 70% of the wild lentil accessions had disease severity scores equal to or significantly lower than that of the SB-resistant check ‘Eston’. Some wild species accessions previously identified with resistance to anthracnose (Colletotrichum truncatum) and ascochyta blight (Ascochyta lentis) were also highly resistant to SB. The highest frequency of resistance to SB was found in L. lamottei followed by L. ervoides of the secondary gene pool. These sources can potentially be used to develop new commercial cultivars with multiple or single disease resistance.

Distribution of highly repeated DNA sequences in species of the genus Lens Miller

Multiple-target fluorescence in situ hybridization (FISH) was applied on mitotic chromosomes of seven Lens taxa using two highly repetitive sequences (pLc30 and pLc7) isolated from the cultivated lentil and the multigene families for the 18S–5.8S–25S (pTa71) and 5S rRNA (pTa794) from wheat simultaneously as probes. The number and location of pLc30 and pLc7 sites on chromosomes varied markedly among the species, whereas the hybridization pattern of 5S rDNA and 18S–5.8S–25S rDNA was less variable. In general, each species showed a typical FISH karyotype and few differences were observed among accessions belonging to the same species, except for the accessions of Lens odemensis. The most similar FISH karyotype to the cultivated lentil is that of Lens culinaris subsp. orientalis, whereas Lens nigricans and Lens tomentosus are the two species that showed the most divergent FISH patterns compared with all taxa for number and location of pLc30 and 18S–5.8S–25S rDNA sites.Key words: chromosome identification, comparative FISH karyotype, wild Lens species, genomic relationships.