Abstract:

Powdery mildew, caused by Blumeria graminis D C f. sp. tritici (former Erysiphe graminis f. sp. tritici), is one of the devastating diseases of wheat (Triticum aestivum L.). So far, a total of 34 resistance genes have been formally named. However, very few of them are used in wheat production due to resistance lose and close linkage to ill agronomic traits. The new resistant germplasm N9628-2, which was derived from the backcross of Am9 (F₁ progeny of the cross between tetraploid wheat-Aegilops amphidiploid and a sensitive wheat cultivar “Shaan 160”) and Shaan 160, showed highly resistant to Guanzhong 4, the prevailing Blumeria graminis f. sp. tritici race in Shaanxi province. In the present study, we aimed to identify the resistance gene in N9628-2, and locate it on wheat chromosome. The F₁ (308 plants) and F₂ (275 plants) populations derived from crosses of N9628-2 and highly susceptible cultivars Shaan 160 and Shaanyou 225 were inoculated with powdery mildew race Guanzhong 4 at the seedling stage for resistance identification. The parents and F₂ individuals were used for gene location with 208 pairs of SSR markers including 38 pairs polymorphic marker between two parents, and the result was verified by analyzing Chinese Spring nullisomic-tetrasomic and ditelosomic lines. According to inoculation test, the resistance to powdery mildew in N9628-2 was controlled by a single dominant gene (χ² = 0.038 and 0.068 in Shaan 160 ´ N9628-2 and Shaanyou 225 ´ N9628-2, respectively; χ20.05 = 3.84). Two markers Xwmc553 and Xwmc684 on chromosome 6A generated polymorphic DNA fragments between the resistant and susceptible pools, indicating the resistance gene might be located on chromosome 6A and linked to the two markers. The resistance gene was further located on chromosome 6AS by the absence of the above polymorphic DNA fragments only in Chinese Spring 6A nullisomic-tetrasomic and 6AL ditelosomic lines. The genetic distances between the resistance gene and the two markers, calculated by Kosambi’s formula, were 10.99 (Xwmc553) and 7.43 cM (Xwmc684) respectively. Our research found that the resistance gene in N9628-2 was probably a new gene differing from the reported resistance genes PmY39, PmPS5B (Pm33), and PmPS5A.

Key words:

Triticum aestivum L., Aegilops umbelluata, Powdery mildew, Resistance gene, SSR analysis