Screening and quantification of disease responses in Lens ervoides against multiple fungal pathogens

Abstract

Lens ervoides is a potential source of novel disease resistance genes against the three major lentil pathogens Ascochyta lentis, Colletotrichum lentis and Stemphylium botryosum. Experiments were conducted to evaluate 157 L. ervoides accessions for resistance to A. lentis under field and greenhouse conditions to determine whether L. ervoides has non-host resistance and revealed that A. lentis isolate AL-61 was able to complete its life cycle on all accessions. This confirmed that L. ervoides does not possess non-host resistance against the pathogen. Six out of 157 accessions were identified as highly susceptible, 34 as moderately susceptible, 38 as intermediate, 67 as moderately resistant and 12 as highly resistant. The wide range of resistance levels among L. ervoides accessions warranted further histopathological investigations into the infection process of A. lentis, as well as C. lentis and S. botryosum. Leaflet samples of selected resistant and susceptible recombinant inbred lines (RILs) of intraspecific Lens ervoides population LR-66, its parents and susceptible L. culinaris check Eston and resistant check CDC Robin were collected from 6 to 240 hours post inoculation (hpi) to determine whether resistance in L. ervoides is quantitative or qualitative. Conidial germination of A. lentis was significantly higher on susceptible RIL LR-66-570 compared to resistant RIL LR-66-629 from 6 to 24 hpi but not at 48 hpi. Pycnidia formed on all A. lentis-infected leaflets of included genotypes, further confirming that there is no non-host resistance in L. ervoides. The development of infection vesicles and primary hyphae by C. lentis were significantly higher on anthracnose-susceptible RIL LR-66-524 compared to resistant LR-66-528 at 24 and 48 hpi. Conidial germination, germ tube length and germ tube penetration by S. botryosum were not significantly different on the Stemphylium blight-resistant and susceptible RILs, but the area of dead tissue per leaflet was significantly higher in Stemphylium blight-susceptible RIL LR-66-577 compared to resistant LR-66-637 from 96 to 144 hpi. Histopathology data revealed quantitative and not qualitative differences among LR-66 RILs against the three pathogens. Ascochyta blight screening and histopathology on all three pathogens provide a foundation for further research into the molecular control of resistance in L. ervoides.