Transfer of the high-temperature adult-plant stripe rust resistance gene Yr62 in four Chinese wheat cultivars

Wheat stripe rust is one of the diseases that seriously affect wheat production worldwide. Breeding resistant cultivars is an effective way to control this disease. The wheat stripe rust resistance gene Yr62 has high-temperature adult-plant resistance (HTAP). In this study, PI 660,060, a single Yr62 gene line, was crossed with four Chinese wheat cultivars, LunXuan987 (LX987), Bainongaikang58 (AK58), ZhengMai9023 (ZM9023), and HanMai6172 (H6172). F1 seeds of four cross combinations were planted and self-crossed to develop the advance generations in the field. The seeds of each cross were mixed harvested and about 2400 to 3000 seeds were sown in each generation for F1 to F4 to maintain the maximum possible genotypes. Forty-five lines were selected and evaluated for resistance to stripe rust and agronomic traits, including plant height, number of grains per spike, and tiller number, in F5 and F6. Then, 33 lines with good agronomic traits and high disease resistance were developed to F9 generation. SSR markers Xgwm251 and Xgwm192 flank linked with the Yr62 were used to detect the presence of Yr62 in these 33 F9 lines. Of these, 22 lines were confirmed with the resistance gene Yr62. Finally, nine lines with good agronomic traits and disease resistance were successfully selected. The selected wheat lines in this study provide material support for the future breeding of wheat for stripe rust resistance.


Introduction
Stripe (yellow) rust of wheat, caused by Puccinia striiformis f. sp.tritici (Pst), is one of the most important wheat diseases in the world and Pst can signi cantly reduce the yield and quality of wheat (Roelfs 1985;Tao 2018).By 2050, global wheat production will need to increase by 60% to feed 9.6 billion people of the world, given the challenges posed by diminishing land and water resources and changing climate conditions (Savadi 2018).The yield losses caused by stripe rust vary from 10-70%, depending on the prevailing weather conditions, cultivars, and disease development (Chen 2005b).Pst is suitable for living at low temperature.Some areas in northwest Sichuan, China have high altitude and low temperature, and wheat is vertically planted at different altitudes, which leads to the successful completion of oversummering, overwintering, and the annual life cycle of stripe rust.Such an environment is not only conducive to the generation of new races of stripe rust but also provides su cient conditions for naturally infected by Pst of wheat grown in Sichuan (Chen 2005a;Li 1997;Liu 2002;Xiang 2013).The most effective, economical, and environmentally friendly way to control wheat stripe rust is to plant resistant cultivars (Line 1995;Parlevliet 1985).Wheat stripe rust resistance can be divided into all-stage resistance (ASR) and adult-plant resistance (APR).APR genes often confer incomplete resistance and have historically been more durable than race-speci c genes.Therefore, one of the promising approaches to solving the problem of the yield loss of disease resistance is using APR genes, which is effective in the adult plant stage and is considered to have a broader range of resistance and longer durability (Brown 2015;Lowe 2011;Niks 2015).The most important type of APR in wheat is High-temperature adult-plant (HTAP) resistance.HTAP resistance is non-race speci c and persistent (Chen 2005b; Chen 2013; Line 2002), and its resistance will increase as the temperature increases and the plant matures.Therefore, breeding HTAP cultivar is one of the most promising methods to control wheat stripe rust.Conventional breeding, however, is a time-consuming and labor-intensive process that can take 7 to 20 years.Markassisted selection (MAS) is a combination of modern molecular biology and conventional breeding, which select breeding wheat lines at the DNA level by employing molecular markers, to achieve e cient improvement of comprehensive traits such as crop yield, quality, and disease resistance (Collard 2005).
At present, MAS breeding is the most effective and rapid method to select excellent plants containing target genes.Since 2000, simple sequence repeats (SSR) markers have gradually become widely used (Akbari et al. 2006).Yr76 was identi ed with anking SSR makers WMC11 and WMC532 by an F 2 mapping population of Tyee and Avocet Susceptible (AvS) crosses (Xiang 2016).Three SSR markers, Xics13, Xics43, and Xics76, were highly polymorphic among the different wheat cultivars used for validation, which were added to the genetic linkage map of Pm4b (Wu 2018).Christiansen et al. reported a QTL in the population of a cross between Deben and Wasmo on chromosome 6BL linked to SSR markers Xwmc397 and Xwmc105b (Christiansen 2006).QYr.cimmyt-6BL was mapped to 6BL with SSR markers Xgwm58 and Xgwm626 in Pavon76 (William 2006).Four stem rust resistance genes (Sr33, Sr36, Sr-Cad, and Sr43) and three stripe rust resistance genes (Yr5, Yr18, and Yr26) were simultaneously in ltrated into Plateau448 by marker-assisted backcrossing hybridization combined with phenotypic selection, which improved the resistance to stem rust (Ug99) and stripe rust (Liu 2020).
The resistance gene Yr62 was derived from Portuguese spring wheat cultivar PI 192252, which was closely linked to two SSR molecular markers Xgwm251 and Xgwm192, and it maintained good resistance in the resistance evaluation experiment in the Washington area of the United States (Lu 2014).PI 660060 (Yr62) involved in this study is a single-gene line derived from a resistant line of AvS/PI 192252 hybrid F 4 -103, which has maintained good resistance in the eld.At present, there are few studies on the utilization of HTAP resistance genes in China.
The purposes of this study are to 1) rst screen the phenotypes of the progeny of the breeding population, and then use marker selection to transform Yr62 into four excellent Chinese wheat cultivars, 2) screen new wheat germplasm with excellent agronomic traits and strong resistance to stripe rust, and 3) speed up the molecular design breeding of wheat resistance to stripe rust.It provides a scienti c basis for further research on the utilization and breeding of resistance genes.LX987 is a winter wheat variety bred by the Chinese Academy of Agricultural Sciences through recurrent selection breeding of dwarf and sterile wheat and pedigree method.It has excellent quality and disease resistance and has been widely planted in the Huang Huai wheat region (Wang 2010;Yang 2006).AK58 is a semi-winter wheat cultivar bred from Zhoumai11//Wenmai6/Zhengzhou8960 by the Wheat Center of Henan University of Science and Technology.It has the characteristics of high yield, lodging resistance, disease resistance, and stable yield (Wang 2012a).ZM9023, a weak spring cultivar developed from the cross of Shan213//Xiaoyan6/Xinong65 by the Wheat Research Institute of Henan Academy of Agricultural Sciences, has high salt tolerance, superior gluten quality, and Fusarium head blight resistance (QFhb.7D)(Gao 2011; Zhang 2021); it was extensively planted in Henan and other provinces.H6172 is a semi-winter wheat developed from the cross of 4032/Zhongyin1 by the Hebei Handan Academy of Agricultural Sciences.It has excellent characteristics such as strong adaptability, drought resistance, and immunity to stem rust (Sun 2004).These four cultivars have high yields, except for H6172, which has slow stripe rust, the other three cultivars have strong resistance to stripe rust when they were released.But with the emergs of a new race of stripe rust, CYR34, their resistance to stripe rust is gradually lost (Liu 2017).However, due to their special agronomic properties, they can continue to be used as recipient parents.Spring wheat germplasm PI 192252 showed a high level of HTAP resistance to stripe rust in germplasm evaluation over 8 years in the State of Washington.In Yangling city (Shaanxi province), Tianshui city (Gansu province) and Mianyang (MY) city (Sichuan province), China, PI 660060 also maintains a high level of resistance to stripe rust (IT 2-3, DS 2%-30%) more than 5 years (Zhou 2015).PI 660060, has same resistance to stripe rust and relatively better agronomic traits compared to PI 192252 (Wang 2012b) and we used it as the donor parent of Yr62 in crosses with four Chinese cultivars.

Construction breeding populations and screening of recombinant inbred lines
PI 660060 was crossed with LX987, AK58, ZM9023, and H6172, of which PI 660060 was the donor parent and four superior cultivars were the recipient parents.The harvested F 1 seeds were sown in the eld and selfed to the F 4 generation, and then lines with Plant height (PH, cm) < 100, Number of grains per spike (SGN) ≥ 40, Tiller number (TN) ≥ 4, and IT<6, were selected from the plants of the four combinations of the F 4 generation.The F 5 -F 6 seeds of these selected lines were sown in the eld.Before the F 5 generation, we used a mixed harvest method for each combination to retain all possible genotypes.The F 2 -F 4 seeds of each hybrid combination were sown in 30 rows, with a row length of 200 cm and a spacing of 25 cm.About 80-100 seeds were sown in each row.Then lines were selected again from the four crosses of F 6 generation lines according to the agronomic character standard of 80<PH<90, SGN ≥ 40, TN ≥ 4, Thousand Grain weight (TGW, g) ≥ 40, and the standard of resistance to stripe rust between IT 0-5.After several generations of evaluation, nally, we obtained selected F 9 lines with stable and excellent resistance to stripe rust, moderate plant height, high number of tillers and spikelets, and high yield in the 2021-2022 crop season (Figure 1).

Disease resistance and agronomic trait evaluation in the eld
In the growing seasons of 2018-2022, the parental PI 660060 was compared with LX987, AK58, ZM9023, H6172, and selected lines of their four crosses were identi ed for stripe rust resistance and agronomic trait evaluation in the experimental site in MY, Sichuan (31°33′N, 104°55′E, 485 m above sea level).Each line was sown in 3 rows in each sowing season, the row length was 1 m, the row spacing was 25 cm, and about 30 seeds were sown in each row.To increase the eld inoculum for stripe rust, a column of Mingxian169 (MX169) was planted vertically in the experimental eld and adjacent to the experimental row.
Stripe rust on each row was evaluated from heading (Z50) to grain filling (Z80) (Zadoks 1974).Under the condition that the severity of stripe rust in the susceptible wheat variety MX169 was 80-100%, the infection type and disease severity of 5 parents and their selected lines were tested twice respectively.Infection type (IT) was recorded following the 0-9 scale (Line 1995), with 0 considered immune, 1 to 3 highly resistant, 4 to 6 moderately resistant, and 7 to 9 susceptible.Disease severity (DS) was recorded as 0, 5,10,15,20,25,30,35,40,45,50,55,60,65,70,75,80,85,90,95, or 100 for the percentage of leaf area infected by Pst.The survey results are averaged.Agronomic traits were selected according to the following criteria: Plant height (PH, cm): the height from the tiller node to the top of the tassel (excluding awn), taking the average height of 10-20 plants.Spike length (SL): length from the base of the ear to the top of the ear (excluding awn).Number of grains per spike (SGN): the total number of grains on the spike of wheat.Thousand Grain weight (TGW, g): Take the dry and winnow thoroughly grains as the standard.After mixing the samples, randomly take 1000 grains and weigh them with a 1/100 electronic balance.Tiller number (TN): the number of branches near the ground that can normally bear fruit by heading.All screened lines were named with the abbreviation of Southwest University of Science and Technology, SWUST.

Genotyping wheat lines by markers
Using two SSR markers, Xgwm192 and Xgwm251, which are ank linked to Yr62, the linkage distances are 2.0 cM and 3.3 cM, respectively, to genotype the parents of the four combinations and selected lines, and select lines with the same bands as donor parent PI 660060 that have successfully transferred the Yr62.(The primer sequences are shown in Table 1)

DNA extraction and PCR
In 2022, fresh leaves of F 9 lines and 5 parents were collected in the MY experimental eld, and DNA was extracted by the modi ed cetyltrimethylammonium bromide (CTAB) method (Cuc 2008).
The polymerase chain reaction (PCR) system is as follows: the total volume of the system is 10 μl, which contains 1 μl of 10× PCR buffer, 0.2 μl of Taq enzyme, 0.8 μl of dNTP, 4 μl of dd H 2 O, forward and reverse primers in a volume of 1 μl each, and 2 μl of DNA sample, the sequences of the two pairs of primers used in the molecular marker test and the reaction procedures are shown in Table1.Linked-tagged PCR ampli cation products were separated using 6% polyacrylamide gel electrophoresis (PAGE).

Initial selection for stripe rust resistance and Yr62 molecular marker detection
The four main Chinese cultivars and PI 660060 were hybridized, self-crossed, and screened according to method showed in Figure 1.Because the Sichuan basin is a hotspot for wheat stripe rust in China, it occurs in all of the trial elds in MY.The F 4 plants were screened according to the agronomic characters and stripe rust resistance described as PH<100, SGN ≥ 40, TN ≥ 4, and IT<6, and 45 F 4 plants were obtained.Then 45 F 5 seeds were sown in the eld to complete self-cross.According to the agronomic traits and stripe rust resistance criteria described as 80<PH<90, SGN ≥ 40, TN ≥ 4, TGW ≥ 40, and IT between 0-5.Thirty-three F 7 generation lines were screened again.The F 8 generation seeds were sown in the eld so that they could self-cross to the F 9 generation, and nally, Thirty-three F 9 generation lines with excellent agronomic traits and stable disease resistance were obtained.
The 33 F 9 lines were then tested with Xgwm192 and Xgwm251, result showed that 22 lines (67%) contained Yr62, and 11 lines did not show the presence of Yr62.Among 22 lines contained Yr62 gene, two lines from LX987/PI 660060, two lines from AK58/PI 660060, ve lines from ZM9023/PI 660060, and thirteen lines from H6172/PI 660060 (Table 2).

Evaluation of disease resistance
According to the eld disease resistance identi cation, the recipient parents LX987, AK58, ZM9023, and H6172 showed intermediate resistance to susceptible to stripe rust at the adult stage in the eld, and the four-year average IT was 4, 7, 5 and 6, respectively.DS was 20%, 55%, 50%, and 35%, respectively.The resistance donor PI 660060 (Yr62) showed high resistance (IT 1, DS 10) at the adult stage in the eld.The disease resistance of the progeny with the Yr62 gene was shown in Figure 3.It can be seen from Table 5 and Figure 2 that 33 higher generation lines of the four crosses have shown resistance to stripe rust to varying degrees.The IT of 33 higher generation lines (Table 5, Figure 2) was mainly distributed in 1-6, and no susceptible and immune lines were found.The DS is mainly distributed in 5-50%, and the DS of progeny lines is less than 40%.Among the four lines of LX987/PI 660060 hybrid combination, SWUST-413 was highly resistant (IT 0, 4, 3, 7, DS 0, 25,8,35) and SWUST-407, SWUST-408, and SWUST-409 were intermediately resistant.The disease resistance of the three lines of AK58/PI 660060 was higher than The correlation analysis of disease resistance phenotypes of each family in different years showed that the correlation between IT and DS of each family in 2019 and 2020 was extremely signi cant (P<0.001), and the correlation coe cients were r=0.78 and r=0.84, respectively.There is no signi cant difference in IT and DS correlation between 2019 and 2021, 2020 and 2021, and 2021 and 2022 (r=0.11-0.36,Table 4).The broad-sense heritability of IT and DS is 0.67 and 0.75 respectively.An ANOVA of IT and DS revealed significant differences (P < 0.01) in four environments, but not signi cant in line×environment interactions.This shows that each family is greatly affected by the environment due to the great change of races every year.(Table 3).

Evaluation of agronomic traits
In the crop seasons 2021-2022, the mean plant heights of the 5 parents, Yr62, LX987, AK58, ZM9023, and H6172, were 88, 84, 77, 86, and 88 cm, respectively (Table 4, Figure 4).Among the progeny lines, the PH values were mainly in the range of 80-120 cm.The mean SGN values of the 5 parents were 20, 49, 39, 55, and 57.Among the 33 lines, 32 lines had SGN values ≥ 45.The average tiller values of the ve parents were 9, 6, 5, 5, and 5, respectively.All 33 lines had TN values ≥ 5.The mean SL value of the 5 parents were 11, 13, 12, 12, and 14.And the SL value of all progeny lines is between 12 and 16.The average TGW of the ve parents were 16, 47, 46, 44, and 50g, respectively.The average TGW values of the four combinations were mainly between 40g and 55g.(Figure 4, Table 4).By comparing the TGW and SGN of the progeny lines with or without Yr62, the mean value of TGW of more than half of the 33 lines was within the range of recipient parents (47g-50g), and similarly, the mean value of SGN of more than half of the 33 lines was within the range of recipient parents (45-60 grains) (Figure 5).

Evaluation of wheat stripe rust
Wheat stripe rust is a major fungal disease that seriously threatens the safety of wheat production.It has a wide distribution, strong epidemic, and serious harm, therefore is an important factor restricting stable and high wheat yield (Gou 2010).In the process of long-term prevention and control of stripe rust, Chinese, as well as international scienti c research workers, have summarized that using resistant cultivars is the most economic, effective, and environmentally friendly measure to prevent and control the disease.However, due to the frequent occurrence of virulence variation in Puccinia striiformis f. sp.tritici (Pst) populations, the occurrences of new physiological races of Pst usually led to the resistant major varieties of becoming susceptible, which caused the loss of utilization value.Moreover, due to the special geographical location of Sichuan, China, it is also known as the "oversummering variable area" of wheat stripe rust or the source of new races of stripe rust (Kang 2015).Therefore, breeding durable disease resistant cultivars is the most direct, economical, and effective method.
In this study, PI 660060 containing Yr62 showed excellent disease resistance at the adult stage (IT 1, DS 10).Lu et al. at Pullman and Mt Vernon two experimental sites with different physiological species identi ed the resistance of PI 192252 (Yr62) to stripe rust in the eld and the resistance to high temperatures in the greenhouse at the adult stage.The results showed that PI 192252 had typical HATP resistance (Lu 2014).The four main cultivars LX987, H6172, AK58, and ZM9023 selected in this study showed middle resistance at the eld mature stage (IT 4-7, DS 20%-55%).Similarly, Xue used CYR32 and CYR33 to identify the resistance of 74 wheat cultivars at adult stage for two consecutive years.Among them, research shows that under the infection of two races, the IT of LX987, H6172, AK58, and ZM9023 are respectively 8, 8, 5, 7, and 7, 7, 7 and 8 in the seeding stage.Under the infection of mixed races in the adult stage, H6172 shows middle resistance to middle susceptibility, LX987 shows susceptibility, AK58 shows resistance to middle susceptibility, and ZM9023 shows susceptible (Xue 2014).Combined with this study, IT and DS were shown that infected plants of the same rust race from the same cultivar can vary in different environments (Rasheed 2018).In this experiment, the IT and DS of four recipient parents in 2019 and 2022 are different, for example, the IT and DS of AK58 in 2019 and 2020 are 8, 3, and 65%, 30% respectively.The IT and DS of H6172 in 2020 and 2021 are 7, 3, and 50%, 10% respectively.The other two main cultivars LX987 and ZM9023 maintained middle resistance level in 2019-2022.This shows that the new epidemic races are different in different years, and the composition of epidemic races is different in different regions, resulting in different disease severity.It is reported that ZM9023 contains APR genes Yr29 and Yr30 (Li 2020).Therefore, in the progeny lines of the hybrid combination ZM9023/PI 660060, SWUST-427 has not detected the Yr62 gene, but it still maintains a high level of resistance to stripe rust.The lines without Yr62 gene in the remaining three crosses also maintained similar resistance with recipient parents to strip rust, possibly because AK58 contained the Yr9 gene, and LX987, and H6172 contained unknown resistance genes (Ma 2021).The progeny lines that successfully introduced the Yr62 gene maintained stable resistance to stripe rust in the eld (IT 1-4, DS 5%-40%) (Table 5).

Molecular marker evaluation
In the past few decades, desirable traits in wheat have often been obtained through crosses in traditional improvement programs, without the knowledge of the use of heritable molecular mechanisms (Dreisigacker 2016).This lengthy process preserves desirable traits in wheat, protects it from various disease stresses, and improves wheat yield and quality (Rasheed 2018).As a complementary tool to traditional breeding, MAS accelerated the process of wheat breeding.It can be used to select early target traits, especially when the shape is under complex genetic mechanisms or di cult to study.It can provide breeders with new ways to select traits and devote limited resources and energy to more promising crosses and progeny (Facundo 2017).The molecular maker has been developed mainly including AFLP, RAPD, SCAR, RGAP, SSR, STS, and SNP.However, SSR is the most widely used molecular marker in the last ve years.For example, Yr59 was successfully introgressed into Jimai22 Chuanmai42, Zhengmai9023, and Xinmai26 by marker-assisted backcross selection and screened for 16 lines with agronomic traits similar or superior to their parents and higher resistance to stripe rust (Zhang 2022).The molecular markers in this study were derived from SSR markers Xgwm192 and Xgwm251 discovered by Lu et al (Lu 2014).They were closely linked to Yr62 with genetic distances of 3.3 cM and 2.0 cM, respectively.The polymorphism of these markers was 100% in 140 wheat cultivars in the United States.In this study, after Yr62 was introduced into four major cultivars in China, the descendant lines containing Yr62 still maintained stable disease resistance.Several lines detected without Yr62 in the four cross combinations still have a high level of resistance to stripe rust.The rst possible reason is that the genetic distance between the SSR marker used in this study and Yr62 is more than 1.0 cM, leading to recombination between genes, so it is not detected (Gupta et al. 1999).The second possible reason is that the recipient parent contains unknown disease resistance genes, so the eld phenotype of the lines without Yr62 maintains a similar resistance to stripe rust to the recipient parent.The third reason may be that the cross population used in this study is different from the mapping population of Yr62, so there is different recombination between molecular markers and genes, resulting in few lines without the Yr62 gene was detected by molecular markers.To sum up, the number of lines with Yr62 detected by molecular markers is less than the actual number.Due to the above possibility, Yr62 was not detected in some progeny lines, so it is necessary to develop makers close to Yr62 for maker-assisted selection breeding.

Evaluation of availability of disease resistant germplasm resources
PI 660060 (AvS/PI 192252 F 4 -103), which was previously developed from AvS/PI 192252, was registered as a single gene reference line of Yr62 (Wang 2012b).Yr62 was susceptible to both low-temperature and high-temperature seedling greenhouse tests (IT 8), while it showed high resistance (IT 1-2) from the elongating stage in eld tests abroad (Lu 2014).In China, Yr62 is susceptible to CYR32, CYR33, and PST-V26 at the seedling stage (IT 8), and highly resistant to CYR32, CYR33, and PST-V26 from elongating stage (IT 2-3, DS 2%-30%) at Yangling, Shanxi and Tianshui, Gansu eld test sites (Zhou 2015).In this study, Yr62 showed high resistance to stripe rust (IT 1, 1, 1, 0, DS 10, 15, 10, 0) at the adult plant stage from 2018 to 2022.In 2022, the IT of Yr62 was 0, which may be because the race virulence in 2022 is not very strong, so the phenotype of Yr62 is immune.All these prove that Yr62 has a high level of durable HTAP resistance to stripe rust.Therefore, Yr62 was selected to be introduced into Chinese main cultivars in this study to provide excellent resistant germplasm resources for China.
In wheat stripe rust epidemic years, cultivars with different resistance levels were often associated with yield losses, ranging from 10% to 70%, and affected wheat quality (Chen 2005a;Syed 2007).Therefore, one of the main concerns of breeders in practical production is to improve the availability of the origin of resistance while considering the yield, quality, and combining ability of disease resistance (Deng 2017;Figueroa 2018;Nelson 2018).In this study, nine lines were selected based on disease resistance and agronomic traits between the donor parent and recipient parent.In the breeding process, SWUST-441 (IT 1, DS 5) and SWUST-447 (IT 1, DS 5) were found to have the same good resistance compare to donor resistant parent PI 660060, however the plant height for both lines were over 105 cm; SWUST-442 (IT 2, DS 10) and SWUST-421 (IT 3, DS 30) had good disease resistance to stripe rust, but the TGW was less than the selected lines.But SWUST-441, SWUST-447, SWUST-442 and SWUST-421 were not selected due to these drawbacks.The nal selected nine wheat lines were not only highly resistant to wheat stripe rust but also superior to the donor resistant parent PI 660060 in important agronomic traits such as PH, SL, TN, and SGN.These selected lines could be applied in further practical production.Heritability constructs of breed traits provide a reference index for breeders in population construction and progeny trait selection.In this study, the PH, SN, TGW, and SL of the line with the H6172 background were higher than those of the other crosses, while the TN of the line with the ZM9023 background was higher than that of the other crosses.
In this study, recipient parents LX987, AK58, ZM9023, and H6172 were used as materials, which were all released cultivars with good agronomic characteristics and yield potential.Through the evaluation of the resistance, agronomic traits, and yield of the Recombinant Inbred Lines (RIL) lines of the four crosses, the results showed that the resistance gene Yr62 has been successfully transfer into the different genetic backgrounds, and the grain growth and development status were better than the recipient parents.Nevertheless, the present study showed that line Yr62 can be used as a useful stripe rust resistance germplasm resource for developing wheat cultivars with durable resistance.

Conclusion
In this study, the resistance gene Yr62 of wheat stripe rust resistance gene PI 660060 was transfer into the main domestic wheat cultivars, such as LX987, AK58, ZM9023, and H6172, by combining conventional breeding and molecular marker identi cation.Through molecular marker detection and agronomic traits evaluation, progeny lines with the high level of stripe rust resistance and excellent agronomic traits were selected from the four crosses, which can be used to cultivate multi-gene polymerized cultivars and have important application value and research value.The practice shows the advantages of this method, saving a lot of human and material resources, and nally achieving the purpose of selecting excellent new wheat cultivars.1000-grain weight and grains per spike distribution in 4 hybrid progeny lines."Yr62 + " represents the presence ofYr62; "Yr62 -" represents the absence of Yr62; p-value was generated by the t-test; "ns" represents p > 0.05, no significant differences, "*" represents p < 0.05, significant differences.

2. 1
Plant materials PI 660060, a single-gene line containing Yr62, is derived from a disease resistant line of Avocet S/PI 192252 hybrid F 4 .It has been reported that PI 660060 contains Yr62, is a HTAP resistance gene to stripe rust (Lu 2014).Chinese elite cultivars LX987 [approved by the National Crop Variety Approval Committee (NCVAC) in 2003], AK58 (from Henan Province and approved by the NCVAC in 2005), ZM9023 (from Henan Province and approved by the NCVAC in 2003), H6172 (from Hebei province and approved by the NCVAC in 2003) were the recipient parents in this study.

Figures Figure 1
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Figure 2 Field
Figure 2

Table 1
Declarations Province, China (No. 22GJHZ0288), PhD Foundation of Southwest University of Science and Technology (No. 19zx7116, 18zx7159, 16zx7162), and Longshan Academic Talent Research Support Program of SWUST (No. 17LZX5).Sequence and ampli cation information for SSR markers linked to Yr62.

Table 2
Statistical analysis of molecular marker detection results of four combinations.

Table 3
Results of ANOVA of infection type and disease severity of 33 recombinant inbred lines in 2019-2022.H 2 indicates the estimated heritability in the broad sense based on the mean across replications and environments (or heritability per mean).
a σ2g was estimated for genotypic (line) variances.b

Table 4
Correlation analysis of resistance phenotypes data of all wheat lines in four years (2019 -2022).

Table 5
Evaluation of resistance to stripe rust, agronomic traits, and molecular marker detection of the selected wheat lines that the values are the average of the 2019-2022 seasons.
a: finally selected nine lines with excellent agronomic traits and high-level resistance to stripe rust.