Seedling Resistance to Stem Rust and Molecular Marker Analysis of Resistance Genes in Wheat Cultivars of Yunnan, China

Abstract

Stem rust is one of the most potentially harmful wheat diseases, but has been effectively controlled in China since 1970s. However, the interest in breeding wheat with durable resistance to stem rust has been renewed with the emergence of Ug99 (TTKSK) virulent to the widely used resistance gene Sr31, and by which the wheat stem rust was controlled for 40 years in wheat production area worldwide. Yunnan Province, located on the Southwest border of China, is one of the main wheat growing regions, playing a pivotal role in the wheat stem rust epidemic in China. This study investigated the levels of resistance in key wheat cultivars (lines) of Yunnan Province. In addition, the existence of Sr25, Sr26, Sr28, Sr31, Sr32, and Sr38 genes in 119 wheat cultivars was assessed using specific DNA markers. The results indicated that 77 (64.7%) tested wheat varieties showed different levels of resistance to all the tested races of Puccinia graminis f. sp. tritici. Using molecular markers, we identified the resistance gene Sr31 in 43 samples; Sr38 in 10 samples; Sr28 in 12 samples, and one sample which was resistant against Ug99 (avirulent to Sr32). No Sr25 or Sr26 (effective against Ug99) was identified in any cultivars tested. Furthermore, 5 out of 119 cultivars tested carried both Sr31 and Sr38 and eight contained both Sr31 and Sr28. The results enable the development of appropriate strategies to breed varieties resistant to stem rust.

Evaluation of resistance to powdery mildew and identification of resistance genes in wheat cultivars

“…Our results showed that eighteen wheat cultivars contain Pm8, accounting for 26.1% of the tested cultivars from Yunnan. Conversely, pedigree tracking indicated that resistant stocks carrying Pm 8, such as 'Kavkaz' and 'Lovrin' lines, were widely used in wheat breeding in Yunnan Province, suggesting the origin of resistance genes in these wheat cultivars [22]. Our results were consistent with previous reports.…”

“…Resistance to stripe rust in Yunnan wheat cultivars has been studied by Li et al (2013) [23]. In our previous study, resistance to stem rust in main wheat cultivars of the region was also studied [22,24]. In recent years, the epidemic level of powdery mildew has been increasing in Yunnan [17].…”

“…Because of the disease-favorable environments, Yunnan provides initial inoculum for wheat powdery mildew, stem rust, leaf rust, and stripe rust, playing a key role in the regional spread and large-scale epidemic of the diseases in China [21,22]. Therefore, assessment of the resistance level of the main production cultivars to these diseases as well as identification of resistance genes in the cultivars can provide a theoretical basis for diseases management by rationally deploying cultivars with various resistance genes in different areas.…”

Peer Review #2 of "Identification of stem rust resistance genes in wheat cultivars in China using molecular markers (v0.1)"

“…Pedigree tracking indicated that 'Kehan 3' parents contained A. glaucum, but Sr25 is derived from T. ponticum, so the result obtained for this cultivar might not be accurate. Expectedly, none of the wheat varieties carried Sr26, as this gene is not widely used in breeding programs in China (Li et al, 2016). Results obtained here are similar to those of previous studies; for example, using marker Sr26#43, Li et al (Li et al, 2016) detected that none of the 119 wheat materials examined carried Sr26.…”

“…Manuscript to be reviewed 'Aftab LeEr', 'Kavkaz', and 'Luofulin' lines carrying Sr31 have been released in wheat growing regions in China. Although, this gene is susceptible to Ug99, it is effective against TKTTF and TTTTF and all Pgt races in China (Pretorius et al, 2000;Olivera et al, 2015;Bhattacharya 2017;Li et al, 2016). Markers Iag95 and SCSS30.2 576 , which were used to screen the gene Sr31 in the present study, revealed that 25 wheat cultivars contained Sr31, and pedigree information and low ITs supported these results.…”