Dynamic Diversity of NLR Genes in Triticum and Mining of Promising NLR Alleles for Disease Resistance.

Bread wheat is an essential crop with the second-highest global production after maize. Currently, wheat diseases are a serious threat to wheat production. Therefore, efficient breeding for disease resistance is extremely urgent in modern wheat. Here, we identified 2012 NLR genes from hexaploid wheat, and Ks values of paired syntenic NLRs showed a significant peak at 3.1-6.3 MYA, which exactly coincided with the first hybridization event between A and B genome lineages at ~5.5 MYA. We provided a landscape of dynamic diversity of NLRs from Triticum and Aegilops and found that NLR genes have higher diversity in wild progenitors and relatives. Further, most NLRs had opposite diversity patterns between genic and 2 Kb-promoter regions, which might respectively link sub/neofunctionalization and loss of duplicated NLR genes. Additionally, we identified an alien introgression of chromosome 4A in tetraploid emmer wheat, which was similar to that in hexaploid wheat. Transcriptome data from four experiments of wheat disease resistance helped to profile the expression pattern of NLR genes and identified promising NLRs involved in broad-spectrum disease resistance. Our study provided insights into the diversity evolution of NLR genes and identified beneficial NLRs to deploy into modern wheat in future wheat disease-resistance breeding.