Molecular mapping of a novel lesion mimic gene (lm4) associated with enhanced resistance to stripe rust in bread wheat.

Background: Lesion mimics (LMs) are disease-like symptoms that occur randomly on plant green leaves in the absence of pathogens. A previous study showed that LMs are related to enhanced resistance to a broad spectrum of diverse pathogen races and programmed cell death (PCD). Stripe rust is a globally epidemic fungal disease that can substantially reduce the quality and yield of crops. The development of resistant cultivars is an economical and environmentally friendly way to enhance the adaptability and yield stability of crops instead of the use of fungicide applications.

Results: In this study, a novel LM gene affording Pst resistance was identified and mapped with molecular markers developed for marker-assisted selection (MAS)-based wheat breeding. In this study, a novel LM gene named lm4, which is closely linked (8.06 cM) to SSR markers Xgwm210 and Xgwm455, was identified by using a Yanzhan 1/Neixiang 188 RIL population. The genetic distance of lm4 was then narrowed such that it was flanked by SSR markers with 0.51 cM and 0.77 cM intervals. Two SSR markers, lm4_01_cib and lm4_02_cib, were developed based on the content in the Chinese Spring genome database and wheat 660 K SNP results; these markers can be used to conduct MAS of LMs in wheat. The results also showed that lm4 significantly improved the resistance of stripe rust in wheat.

Conclusions: Therefore, lm4 is associated with stripe rust resistance, which may provide theoretical support for future crop disease-resistance breeding and for understanding the plant apoptosis mechanism.