QTL Mapping For Slow Mildewing And Slow Stripe Rust Resistance In Common Wheat

Powdery mildew and stripe rust, caused by Blumeria graminis f. sp. tritici and Puccinia striiformis f. sp. tirtici, respectively, are the most damaging diseases in common wheat (Triticum aestivum L). Utilization of resistant cultivars is an effective way to control the disease. Identification of powdery mildew and stripe rust resistance genes is essential for breeding resistant wheat cultivars.This study included quantitative trait loci mapping for adult-plant resistance to powdery mildew and analysis of slow stripe rust resistance in common wheat.In the present study, a total of 432 molecular markers were used to map QTL for adult-plant resistance (APR) to powdery mildew in a doubled haploid (DH) population with 107 lines derived from the cross Fukuho-komugi/Oligoculm. Field trials were conducted in Beijing and Anyang during 2003-04 and 2004-05 cropping seasons, respectively. The DH lines were planted in a randomized complete block design with three replicates. Artificial inoculationwas carried out in Beijing with highly virulent isolate E20 of Blumeria graminis f. sp. tritici and the powdery mildew severity on penultimate leaf was evaluated for four times. The maximum disease severity (MDS) on penultimate leaf was investigated in Anyang under natural inoculation around May 18, 2004 and 2005. With the method of composite interval mapping (CIM), four quantitative trait loci (QTL) for APR to powdery mildew were detected on chromosomes 1AS, 2BL, 4BL, and 7DS, explaining 5.1%-26.6% of phenotypic variance. The QTL on chromosome 1AS showed high geneti fect on powdery mildew resistance, accounting for 19.5%-26.6% of phenotypic variance across two environments. The heritability of resistance to powdery mildew for maximum disease severity (MDS) in two years and two locations ranged from 0.82 to 0.93, while the heritability for AUDPC was between 0.84 and 0.91.The double haploid (DH) population with 104 lines derived from the cross Bainong64/Jingshuang16 was planted during 2005-06 cropping season in Beijing and Anyang, respectively. The experiment design was in a randomized complete block with three replictes. Artificial inoculation was carried out in Beijing with highly virulent isolate E20 of Blumeria graminis f. sp. tritici and the powdery mildew severity on penultimate leaf was evaluated for the first time 4 weeks after inoculation and then at a weekly interval, with a total of four scorings. The maximum disease severity (MDS) on penultimate leaf was investigated in Anyang under natural inoculation around May 18, 2006. The broad sense heritability of resistance to powdery mildew for maximum disease severity (MDS) in Beijing was 0.9, while that in Anyang was 0.69. The correlation coefficient was 0.79 between the AUDPC and MDS in Beijing, 0.68 between AUDPC in Beijing and MDS in Anyang, and 0.54 between MDS in Beijing and Anyang. Based on the previous mappi esults with the F_2:3 lines from the same cross, we selected 23 markers on chromosome 2B,7A and so on to genotype the DH population. The results of T-test indicated that the markers gwm282 (7A), gwm332.1 (7A) , gwm570 (6A/6B) and J116 were related to the phynotpic variance significantly, indicating the QTL for slow powdery mildew was likely to be linked with these markers.F_2:3 lines from the cross Strampelli/Huixianhong were planted in Tianshui, Gansu Province during the 2004-05 and 2005-06 cropping seasons in a randomized complete block with three replicates. Every year the stripe rust severity of the population was evaluated under natural disease pressure on May 25 for the first time, and scored for three times in total at a weekly interval. The results indicated that the broad sense heritability of the MDS in 2005 was 0.89, while that in 2006 was 0.87; the correlation coefficient between the average AUDPC and MDS of two years was 0.95.The F_2:3 and DH lines from the cross Pingyuan50/Mingxian169 were planted in the Tianshui, Gansu Province during 2005-06 cropping season. The field trial was conducted in a randomized complete block with three replicites. The stripe rust severity was evaluated under natural disease pressure from late May on, and scored for three times totally at a weekly interval. The results showed that the broad sense heritability of the MDS of the F_2:3 lines was 0.71, while that of the DH population was 0.87; the correlation coefficient was 0.87 between AUDPC and MDS in the F_2:3 lines, and 0.89 between AUDPC and MDS in the DH population.