Kemai 1609, a molecular designed wheat variety with stripe rust and leaf rust resistance

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Wheat (Triticum aestivum L.), a globally important food crop, is challenged by numerous diseases during its growth, resulting in significant reduction in yield and quality. Stripe rust, caused by the fungus Puccinia striiformis f. sp. tritici, is one of the most destructive wheat diseases in China (Zhao and Kang 2023). It primarily affects the northwest and southwest wheat-growing regions, prompting its classification as a top class of crop disease by the Ministry of Agriculture and Rural Affairs of China due to its severe impact (https://www.moa.gov.cn/govpublic/ZZYGLS/202303/t20230314_6422981.htm). Leaf rust, caused by the fungus Puccinia triticina Erikss. (Pt), occurs predominantly in the North China Plain, the middle and lower reaches of the Yangtze River, the southwest, and the northeast of China. Although effective control measures have reduced its prevalence in recent decades, leaf rust continues to pose a threat, especially in key wheat-growing areas such as the Huang-Huai River Valley regions of China (Zhang et al. 2020).

The management of wheat stripe rust and leaf rust primarily relies on the use of resistant varieties and chemical treatments. While chemical control can be effective, it is labor-intensive, increases production costs, and contributes to environmental pollution. Breeding resistant varieties remains the most cost-effective, efficient, and eco-friendly approach. However, the ongoing mutation and evolution of pathogens often render single resistance genes ineffective. To overcome this challenge, incorporation of multiple resistance genes from diverse disease-resistant germplasms enhances both the level and durability of resistance. This strategy is critical for developing wheat varieties with durable, broad-spectrum resistance (Liu et al. 2024).

To expand the genetic resources for resistance to stripe rust and leaf rust, it is an ongoing task to explore resistance genes in cultivated varieties, landraces, wild relatives, and distant species. Currently, numerous resistance genes against stripe rust and leaf rust have been officially designated, along with many provisionally named genes and allelic loci (Gupta et al. 2022; Sharma et al. 2024). This extensive collection of resistance genes provides essential resources for molecular breeding, enabling the pyramiding of multiple resistance genes and the development of wheat varieties resistant to both stripe rust and leaf rust.

Wheat resistance genes for stripe/leaf rust are classified into two main types based on their resistance characteristics: seedling/all-stage resistance (ASR) and adult plant resistance (APR). ASR is largely qualitative resistance usually controlled by a single major gene, effective at all the developmental stages. APR is often non-race specific and partial resistance at the adult stage controlled by multiple minor-effect genes. The multi-resistance locus Yr30/Lr27/Sr2/Pm70, located on the short arm of chromosome 3B, confers APR and has been widely utilized in wheat breeding programs due to its effectiveness against multiple pathogens. (Singh et al. 2000). Another ASR gene, YrZH84, has been mapped to chromosome arm 7BS of the Chinese wheat parental line Zhou 8425B (Li et al. 2006). In contrast, YrZH22, another APR gene associated with resistance to stripe rust, is located on chromosome arm 4BL of the wheat variety Zhoumai 22 (Wang et al. 2017). For leaf rust resistance, the high-temperature adult-plant resistance gene Lr13/LrZH22, found on chromosome 2BS, is one of the most widely distributed genes in wheat (Bansal et al. 2008; Yan et al. 2021). Numerous Chinese wheat varieties carry the Yr30/Lr27/Sr2/Pm70 locus, and some of these varieties, due to their superior agronomic traits, serving as main cultivars. They are frequently used as foundational lines for the pyramiding of additional resistance genes to develop durable, multi-resistant varieties. By integrating foundational resistance to stripe rust, leaf rust, stem rust, and powdery mildew conferred by Yr30/Lr27/Sr2/Pm70 with genes such as YrZH22, YrZH84, and Lr13, it is possible to achieve moderate to high levels of adult-plant resistance to stripe rust and leaf rust. This process involves gene pyramiding, field resistance evaluations, and the use of molecular marker-assisted selection (MAS) strategies. The development of high-yield, multi-resistant wheat varieties provide a more effective solution to the challenges posed by stripe rust and leaf rust in Chinese wheat production (Liu et al. 2024).

To develop a wheat variety resistant to both stripe rust and leaf rust, we selected three parental varieties: Xuke 1 (XK1), Bainong AK58 (AK58), and Yanzhan 4110 (YZ4110) to make crosses (Fig. S1). XK1, developed by Henansheng Xuke Seed Co., Ltd. in Henan, is a winter wheat variety known for its high yield and resistance to stripe rust and leaf rust, and it harbors genes YrZH22 and Lr13. AK58, developed by Henan Science and Technology College in Xinxiang, Henan, is a winter wheat variety known for its high yield and disease resistance, and it carries YrZH84. YZ4110, a wheat variety developed by the Henan Yuxi Crop Variety Exhibition Center in Luoyang, Henan, is characterized by high yield, early maturity, and resistance to leaf rust, and it carries Yr30/Lr27/Sr2/Pm70 and Lr13 (Figs. S2, 3; Table S1).

In May 2005, a cross was made using XK1 as the female parent and AK58 as the male parent at the Yuanyang experimental station of the Henan Academy of Agricultural Sciences in Xinxiang, Henan. The harvested F₁ progeny was sown in October 2005. In May 2006, the F₁ progeny, serving as the female parent, was crossed with YZ4110 as the male parent (Fig. S1). The resulting progeny was planted in autumn 2006 in the experimental station of Henansheng Xuke Seed Co., Ltd., in Xuchang, Henan Province.

Phenotypic selection for resistance to stripe rust and leaf rust was conducted start following artificial inoculation from the F₈ generation. Resistant individuals were selected in the field and then subjected to molecular marker analysis to confirm the presence of target resistance genes. In F₃ to F₈ generations, the lines were genotyped and selected for resistance to stripe rust and leaf rust, as well as for agronomic and yield traits (Fig. S1). In the 2013–2014 cropping season, six F₈ lines were grown in a non-replicated comparison trial in Xuchang, with one plot for each line. The top three high-yielding lines were selected for further testing. During the 2014–2015 cropping season, these lines underwent yield comparison trials and resistance evaluations with three replicated plots each in Zhengzhou and Xuchang. Using MAS and field resistance evaluations, we pyramided the resistance genes Yr30/Lr27/Sr2/Pm70, YrZH22, YrZH84, and Lr13 into a single line (Fig. S3). After several years of selection, this process resulted in the high-yielding line Kemai 1609 (KM1609), which exhibits resistance to both stripe rust and leaf rust (Fig. 1, Fig. S2) in the field condition.

Fig. 1.

KM1609 approved as a new wheat variety. a Whole plant of KM1609. b Stripe rust resistance performance in Chengdu, 2017. SCV, Susceptible control variety (Nongda399). c Leaf rust resistance performance in Xuchang, 2018. Susceptible control variety (Zhoumai 18). d Field performance in Zhengzhou, 2022. e Approval certificate by Henan Provincial Crop Variety Certification Committee. f Approval certificate by National Crop Variety Certification Committee, Ministry of Agriculture and Rural Development, China

Between 2016 and 2020, a four-year evaluation of KM1609 for resistance to stripe rust was conducted at Modern Agricultural High-Tech Demonstration Park of Sichuan Academy of Agricultural Sciences in Chengdu, Sichuan. The average severity of stripe rust over this period was 16.25%, with an infection type score of 2.25, reaching a resistant level (Table S2). Concurrently, KM1609 underwent a four-year evaluation for resistance to leaf rust at Breeding and Propagation Base of Henansheng Xuke Seed Co., Ltd., in Henan province. The average severity of leaf rust was recorded at 23.75%, with an infection type score of 3.25, reaching a moderately resistant level (Table S2).

KM1609 was involved in the Henan Provincial regional trials for high-fertilizer irrigation winter wheat varieties, organized by the Henan Provincial Seed Management Station, during the 2017–2018 and 2018–2019 cropping seasons. Due to its promising performance in these trials (Table S3), KM1609 was officially approved by the Henan Crop Variety Approval Committee as a new variety in 2021 (Fig. 1e). KM1609 was also included in the national regional trials for the Yellow-Huai River South irrigation group of winter wheat varieties, organized by the Wheat Research Institute of the Henan Academy of Agricultural Sciences, during the 2020–2021 and 2021–2022 cropping seasons. The variety again demonstrated excellent performance in these trials (Tables S4 and S5) and was officially approved by the National Crop Variety Approval Committee as a new national variety in 2024 (Fig. 1f).

KM1609 yielded 6.81–9.31 t/ha in the 15 test sites and two years in the Henan provincial winter wheat yield trials. This represents yield increase 7.6–8.4% compared to the control variety Zhoumai 18. The whole growth duration 217.2 to 231.7 days. Other key agronomic traits included effective ears 5.48–6.10 million/ha, grain number per ear 31.2–33.4, thousand-grain weight 46.6–52.2 g, and plant height 78.6– 82.3 cm. In the quality analysis of mixed samples from the two-year regional trial (Zhengzhou), KM1609 exhibited a protein content (dry basis) of 15.1%–15.4%, bulk density of 742–782 g/L, wet gluten content of 30.8%–32.6%, and water absorption of 56.2–66.3 mL/100 g. The dough had a stability time of 3.7–8.3 min, an extensibility area of 59–93 cm², and maximum resistance to extension ranging from 233–440 EU. KM1609 showed moderate resistance to stripe rust (HR–MR), moderate susceptibility to leaf rust, powdery mildew, and sharp eyespot (MS–MS), and high susceptibility to Fusarium head blight (HS-HS) over the two years of field trials.

In the national winter wheat yield trials, KM1609 achieved an average yield of 8.4–9.6 t/ha in 23 test sites, demonstrating a yield increase of 3.48–5.57% compared to the control Zhoumai 18. The whole growth duration 224.3–232.3 days. Agronomic traits included an ear count of 5.8 million per ha, a grain number per ear of 32.5–34.4, a thousand-grain weight of 51.3–52.4 g, and plant height ranging from 84.3–89.6 cm. In the quality analysis of mixed samples from the two-year national trial (Zhengzhou), KM1609 exhibited a protein content (dry basis) ranging from 13.6%–15.5%, bulk density of 782–822 g/L, wet gluten content of 32.4%–34.8%, and water absorption of 60.0–62.0 mL/100 g. The dough had a stability time ranging from 3.0–8.3 min. Based on these quality parameters, KM1609 is classified as a medium-gluten wheat. KM1609 was moderately resistant to stripe rust (MR-SR) and moderately susceptible to leaf rust (HS-MS), but highly susceptible to powdery mildew (HS-HS), Fusarium head blight (HS-HS), and sharp eyespot (HS-MS) over the two years of field trials. Kemai 1609 shows moderate resistance under local conditions in Henan, its leaf rust resistance provided by Lr13 may be less effective under higher or more virulent disease pressure.

KM1609 is a winter-type variety with spindle-shaped ears, white glumes, white grain, and hard grain texture. Based on its characteristics, it is recommended for cultivation in Henan Province (excluding Xinyang), northern Anhui, northern Jiangsu, and the Guanzhong area of Shaanxi. KM1609 represents a successful case of molecular design breeding through pyramiding multiple resistance genes. This demonstrates the utility of marker-assisted selection for enhancing durable disease resistance in wheat, offering a practical model for future precision breeding efforts.

Supplementary Information

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Author contributions

Yongxing Chen, Tingjie Cao, Xiuhua Zhu and Qiuhong Wu completed the field work of the breeding. Zhiyong Liu, Tingjie Cao and Xicheng Wang designed and conducted the breeding experiments. Lingli Dong, Huaizhi Zhang, Hongkui Fu, Ping Lu, Miaomiao Li, Guanghao Guo, Keyu Zhu, Gaojie Wang and Chengguo Yuan conducted disease resistance identification and molecular marker detection experiments. Yongxing Chen and Qiuhong Wu wrote the manuscript. Zhiyong Liu and Hongjie Li revised the manuscript.

Funding

This work was financially supported by the National Key Research and Development Program of China (2023YFD1200402), Strategic Priority Research Program of the Chinese Academy of Sciences (XDA24010305) and Key Research and Development Program of Hebei Province (22326305D).

Data availability

All data generated or used during the study are available from the corresponding authors by request.

Declarations

Competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.