Identification and Characterization of Resistance to Rust in Lentil and Its Wild Relatives

Abstract

Lentil rust is a major disease worldwide caused by Uromyces viciae-fabae. In this study, we screened a large germplasm collection of cultivated lentils (Lens culinaris ssp. culinaris) and its wild relatives, both in adult plants in the field with a local rust isolate during 2 seasons and in seedlings under controlled conditions with four fungal isolates of worldwide origin. The main results from our study were the following: (1) a significant number of accessions with resistance based on hypersensitive reaction (reduced Infection Type (IT)) were identified in cultivated lentil and in L. ervoides, L. nigricans and L.c. orientalis. The IT scores showed a clear isolate-specific response suggesting race-specificity, so each fungal isolate might be considered a different race. Resistance was identified against all isolates what might be the basis to develop a standard differential set that should be a priority for rust definition and monitoring. (2) Interestingly, although at lower frequency than in L. ervoides and L. nigricans, the hypersensitive response was also observed within cultivated lentil, with accession 1561 (L.c. culinaris) displaying resistance to the four isolates making this accession a valuable ready-to-use resource for lentil resistance breeding. Resistance to all other rust isolates was also available within L.c. culinaris in an isolate-specific manner. Accession 1308 (L. ervoides) showed resistance against all isolates tested, as well as a reduced number of accessions belonging to other wild Lens species. (3) In addition, our screenings allowed the identification of several accessions with partial resistance (reduced Disease Severity (DS) despite high IT). Adult Plant Resistance resulting in reduced severity in adult plants in the field, despite high susceptibility in seedlings, was more frequently identified in L.c. culinaris, but also in L. nigricans and L.c. orientalis.

Optimization of inoculum production of Stemphylium botryosum for large-scale resistance screening of lentils

“…As expected, disease symptoms (yellowing, wilting and death of leaves and stems) were noticed on all infected plants [ 8 ]; however, significant genotypic differences became notably evident only at the highest inoculum densities and a RH of 100%. Although under field conditions the disease mainly occurs at an advanced growth stage, the period between 10 and 15 days post-germination is considered optimal for screening for various diseases [ 29 , 30 ], facilitating the efficient use of resources and time. DR at 20 days post-inoculation offered a clear perspective on symptom severity; the most pronounced symptoms were associated with plants inoculated with 5 g L − 1 of mycelium, followed by the spore of 2 × 10 5 conidia mL − 1 .…”

Mycoviruses in the Rust Fungus Uromyces fabae

“…Our U. fabae isolate infects V. faba ; however, there is still controversy about whether the species should still be called Uromyces viciae-fabae since it is also an important pathogen in pea and lentil and can infect more than 50 other Vicia species and roughly 20 Lathyrus species [ 1 ]. There is also some evidence that this is a species complex with different species or subspecies that still have to be defined infecting different species [ 34 ]. In this context, it could be interesting to compare our U. fabae isolate with U. viciae-fabae isolates infecting pea for their virus complements.…”