Identification and Fine Mapping of RppM, a Southern Corn Rust Resistance Gene in Maize.

Shuai Wang,Wei Song,Yanxin Zhao,Zi Shi,Xuan Sun,Ruyang Zhang,Jiuran Zhao,Chunhui Li,Xiaqing Wang,Qian Liu,Shuaishuai Wang,Jidong Wang,Jinfeng Xing,Yuandong Wang,Yining Chen,Yunxia Zhang,Jianrong Ge,Aiguo Su

doi:10.3389/fpls.2020.01057

Shuai Wang, Wei Song + Show 16 more

Open Access

https://doi.org/10.3389/fpls.2020.01057

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Abstract

Southern corn rust (SCR) caused by Puccinia polysora Underw. is a major disease causing severe yield losses during maize production. Here, we identified and mapped the SCR resistance gene RppM from the near-isogenic line Kangxiujing2416 (Jing2416K), which harbors RppM in the genetic background of the susceptible inbred line Jing2416. In this study, the inheritance of SCR resistance was investigated in F2 and F3 populations derived from a cross between Jing2416K and Jing2416. The observed 3:1 segregation ratio of resistant to susceptible plants indicated that the SCR resistance is controlled by a single dominant gene. Using an F2 population, we performed bulked segregant analysis (BSA) sequencing and mapped RppM to a 3.69-Mb region on chromosome arm 10S. To further narrow down the region harboring RppM, we developed 13 insertion/deletion (InDel) markers based on the sequencing data. Finally, RppM was mapped to a region spanning 110-kb using susceptible individuals from a large F2 population. Two genes (Zm00001d023265 and Zm00001d023267) encoding putative CC-NBS-LRR (coiled-coiled, nucleotide-binding site, and leucine-rich repeat) proteins, a common characteristic of R genes, were located in this region (B73 RefGen_v4 reference genome). Sequencing and comparison of the two genes cloned from Jing2416K and Jing2416 revealed sequence variations in their coding regions. The relative expression levels of these two genes in Jing2416K were found to be significantly higher than those in Jing2416. Zm00001d023265 and Zm00001d023267 are thus potential RppM candidates.

Highlights

Southern corn rust (SCR), caused by the fungus Puccinia polysora Underw., can lead to poor yields and decreased nutritional quality in maize (Zea mays L.)
The objectives of the present study were to (1) evaluate the inheritance of SCR resistance in F2 and F3 populations derived from reciprocal crosses between resistant near-isogenic line Jing2416K and susceptible line Jing2416, (2) fine map the SCRresistance gene RppM using combined bulked segregant analysis (BSA) sequencing and traditional linkage analysis, and (3) predict the candidate gene of RppM using sequencing and expression data
With more than 7,000 species, rust fungi constitute the largest group of plant fungal pathogens and are difficult to control and manage because of their rapid evolution, dynamic population structure, and wide dispersal of anemochorous spores (Kangasjarvi et al, 2012; Rochi et al, 2016; Gill et al, 2018)

Summary

Introduction

Southern corn rust (SCR), caused by the fungus Puccinia polysora Underw., can lead to poor yields and decreased nutritional quality in maize (Zea mays L.). A disastrous plant disease, SCR is widely established in warm-temperate and tropical regions, such as the United States, Asia, and Africa (Liu et al, 2003; Dolezal et al, 2009; Brewbaker et al, 2011). SCR has become the major disease in maize-producing regions of the world, resulting in significant crop losses (Ali and Yan, 2012). In 1998, an outbreak and epidemic of SCR in northern China resulted in yield losses of 42% to 53% (Zhou et al, 2008). The lack of resistance in temperate germplasm is the main reason for SCR epidemics (Rodriguez-Ardon et al, 1980; Bailey, 1987; Brewbaker et al, 2011). The identification and utilization of new SCR resistance sources is essential in current maize breeding programs

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