Climate change conditions the selection of rust-resistant candidate wild lentil populations for in situ conservation

The Prospects of gene introgression from crop wild relatives into cultivated lentil for climate change mitigation

Crop wild relatives (CWRs), landraces and exotic germplasm are important sources of genetic variability, alien alleles, and useful crop traits that can help mitigate a plethora of abiotic and biotic stresses and crop yield reduction arising due to global climatic changes. In the pulse crop genus Lens, the cultivated varieties have a narrow genetic base due to recurrent selections, genetic bottleneck and linkage drag. The collection and characterization of wild Lens germplasm resources have offered new avenues for the genetic improvement and development of stress-tolerant, climate-resilient lentil varieties with sustainable yield gains to meet future food and nutritional requirements. Most of the lentil breeding traits such as high-yield, adaptation to abiotic stresses and resistance to diseases are quantitative and require the identification of quantitative trait loci (QTLs) for marker assisted selection and breeding. Advances in genetic diversity studies, genome mapping and advanced high-throughput sequencing technologies have helped identify many stress-responsive adaptive genes, quantitative trait loci (QTLs) and other useful crop traits in the CWRs. The recent integration of genomics technologies with plant breeding has resulted in the generation of dense genomic linkage maps, massive global genotyping, large transcriptomic datasets, single nucleotide polymorphisms (SNPs), expressed sequence tags (ESTs) that have advanced lentil genomic research substantially and allowed for the identification of QTLs for marker-assisted selection (MAS) and breeding. Assembly of lentil and its wild species genomes (~4Gbp) opens up newer possibilities for understanding genomic architecture and evolution of this important legume crop. This review highlights the recent strides in the characterization of wild genetic resources for useful alleles, development of high-density genetic maps, high-resolution QTL mapping, genome-wide studies, MAS, genomic selections, new databases and genome assemblies in traditionally bred genus Lens for future crop improvement amidst the impending global climate change.

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

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.