Safar Ali Safavi, Farzad Afshari,
Volume 1, Issue 4 (12-2012)
Abstract
Race-specific resistance of wheat to yellow rust caused by Puccinia striiformis f. sp. tritici has been reported as short-lived. Partial resistance, a kind of quantitative resistance, has been reported to be more stable. Partial resistance in terms of slow rusting parameters including final rust severity (FRS), apparent infection rate (r), relative area under disease progress curve (rAUDPC), and coefficient of infection (CI) was evaluated in a set of twenty six wheat genotypes along with susceptible control during 2010-2011 cropping year. This study was conducted in field plots at Ardabil Agricultural Research Station (Iran) under natural infection conditions with twice artificial inoculation. Artificial inoculation was carried out by yellow rust inoculum having virulence against Yr2, Yr6, Yr7, Yr9, Yr22, Yr23, Yr24, Yr25, Yr26, Yr27, YrA, and YrSU. Seedling reaction was also evaluated in greenhouse by using race 66E0A+, Yr27+. Results of mean comparison for resistance parameters showed that, lines C-89-4, C-89-17 and C-89-16 along with susceptible had the highest values of FRS, CI, r and rAUDPC, therefore were selected as moderately susceptible or susceptible lines. The lines C-89-7, C-89-8, C-89-9, C-89-10, C-89-13, C-89-14 and C-89-20 had susceptible reactions at seedling stage and low level infection at adult plant stage. Accordingly these lines with low level of different parameters supposed to be having gene/s for varying degrees of partial resistance or high temperature adult plant resistance (HTAP) that can be used for future manipulation in wheat improvement program after confirmatory studies. The remaining lines (except for C-89-2) were immune or had low level of infection. Thus, these were selected as resistant lines. In this study correlation coefficient between different parameters of slow rusting was highly significant. Based on the results, the reaction of the studied genotypes to stripe rust varied from sensitive to immune.
Volume 17, Issue 1 (1-2015)
Abstract
Basal stem rot caused by Sclerotinia sclerotiorum (Lib.) de Bary is one of the most important diseases of sunflower. Quantitative trait loci (QTL) implicated in partial resistance to two isolates of S. sclerotiorum (SSU107 and SSKH41) were investigated using F9 recombinant inbred lines (RILs) from the cross between sunflower parental lines PAC2 and RHA266. Experiments were conducted in completely randomized design with 3-6 replications under controlled conditions. The reaction of genotypes to basal stem rot disease was evaluated by measuring the percentage of necrosis area three days after inoculation. Combined analysis of experiments showed significant interactions between sunflower genotypes and S. sclerotiorum isolates suggesting that partial resistance to S. sclerotiorum should be isolate-specific in sunflower. QTLs were mapped using an updated high-density SSR and SNP linkage map. The map consisted of 210 SSRs and 11 gene-derived markers placed in 17 linkage groups (LGs). The total map length was 1,653.1 cM with a mean density of 1 marker per 7.44 cM. A total of 14 QTLs were detected for partial resistance to two isolates. The phenotypic variance explained by QTLs (R2) ranged from 0.10 to 9.85. The sign of additive gene effects showed that favorable alleles for partial resistance to isolates came from both parents. Six QTLs were common between two isolates on LGs 1, 8 and 17, whereas the others were specific for each isolate. Co-localized QTLs on LG 1 were linked to the glutathione S-transferase gene (GST). The co-localized QTLs for partial resistance to basal stem rot isolates could be good candidates for marker assisted selection (MAS).
