Wheat leaf rust resistance gene Lr13 is a specific Ne2 allele for hybrid necrosis. Cloning of Lr13/Ne2m from bread wheat

Wheat gene Lr13 confers resistance to leaf rust caused by Puccinia triticina. The gene resides in the proximal region of chromosome 2BS and is pleiotropic with, or strongly linked to, the Ne2m allele, causing hybrid necrosis in crosses carrying complementary locus Ne1 alleles on chromosome 5BL. A nucleotide-binding leucine-rich repeat (NLR) immune receptor-encoding gene was isolated following Lr13 mutagenesis and resistance (R) gene enrichment and sequencing (MutRenSeq). Genetic segregation, virus induced gene silencing, comparative genomics, and analysis of 29 Lr13 mutants, which had also been shown to have lost the necrosis-inducing function of Ne2m, strongly support the identity of a single Lr13/Ne2m gene. This implicates immune system dysfunction as the cause hybrid necrosis in wheat hybrids combining the epistatic alleles at the Ne2 and Ne1 loci.

小麦基因Lr13可介导由小麦叶锈病菌（Puccinia triticina）引发的小麦叶锈病的抗性。该基因定位于2BS染色体的近端区域，且与Ne2m等位基因存在多效性或紧密连锁；在携带5BL染色体上互补位点Ne1等位基因的杂交组合中，该基因会引发杂种坏死。研究人员通过Lr13诱变、抗性（R）基因富集测序（MutRenSeq）技术，成功分离得到了编码核苷酸结合富亮氨酸重复（NLR）免疫受体的基因。通过遗传分离分析、病毒诱导基因沉默实验、比较基因组学分析，以及对29个同时被证实丧失了Ne2m坏死诱导功能的Lr13突变体的分析，有力证明了Lr13与Ne2m实为同一基因。该研究表明，在携带Ne2与Ne1位点上位性等位基因的小麦杂交种中，免疫系统功能失调是引发杂种坏死的根本原因。