Abstract
Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a globally serious disease adversely affecting wheat production. The Bgt-resistant wheat breeding line CH09W89 was derived after backcrossing a Bgt resistant wheat-Thinopyrum intermedium partial amphiploid TAI7045 with susceptible wheat cultivars. At the seedling stage, CH09W89 exhibited immunity or high resistance to Bgt pathotypes E09, E20, E21, E23, E26, Bg1, and Bg2, similar to its donor line TAI7045 and Th. intermedium. No Th. intermedium chromatin was detected based on genomic in situ hybridization of mitotic chromosomes. To determine the mode of inheritance of the Bgt resistance and the chromosomal location of the resistance gene, CH09W89 was crossed with two susceptible wheat cultivars. The results of the genetic analysis showed that the adult resistance to Bgt E09 in CH09W89 was controlled by a single recessive gene, which was tentatively designated as pmCH89. Two polymorphic SSR markers, Xwmc310 and Xwmc125, were linked to the resistance gene with genetic distances 3.1 and 2.7 cM, respectively. Using the Chinese Spring aneuploid and deletion lines, the resistance gene and its linked markers were assigned to chromosome arm 4BL in the bin 0.68–0.78. Due to its unique position on chromosome 4BL, pmCH89 appears to be a new locus for resistance to powdery mildew. These results will be of benefit for improving powdery mildew resistance in wheat breeding programs.
Highlights
Common wheat (Triticum aestivum L.) is the most widely cultivated and important staple food crop in the world, and is constantly challenged by many diseases such as powdery mildew and rusts
CH09W89, wheat-Thinopyrum intermedium partial amphiploid TAI7045, and the Th. intermedium parent Z1141 were resistant to all seven Chinese Blumeria graminis f. sp. tritici (Bgt) races tested at the seedling stage, whereas wheat parents Jinchun 5, Jin T2250, Jintai 170, and Jinmai 33 were susceptible (IT 3–4) (Table 1, Figure 1)
The markers, which span 5.8 cM in the SY95-71/CH09W89 cross, cover approximately cM in the Synthetic/Opata cross [14]. This shows that the recombination rate in the present study is about three-fold lower than in a cross involving hexaploid wheat. These results suggest that pairing and crossovers between chromosome 4B and an unidentified fragment of Th. intermedium chromosome introgressed into CH09W89 seem to be possible but at a reduced rate
Summary
Common wheat (Triticum aestivum L.) is the most widely cultivated and important staple food crop in the world, and is constantly challenged by many diseases such as powdery mildew and rusts. Tritici (Bgt), is a globally serious disease of wheat. It often occurs in regions with cool and humid climates, resulting in severe yield reductions [1,2]. In China, especially in the southwestern region, powdery mildew is the most frequently occurring disease due to moderate temperatures and rainy conditions during the wheat growing season. Powdery mildew pathogen populations are very dynamic due to the continuous appearance of new virulent pathotypes capable of overcoming widely used host resistance genes. The discovery and utilization of new powdery mildew resistance genes have become common objectives for wheat geneticists and breeders worldwide
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