Qtl Mapping For Adult-plant Resistance To Stripe Rust And Molecular Cytogenetic Characterization Of A New Leaf Rolling Triticale (x Triticosecale Wittmack) In Cimmyt Wheat Materials Chapio And Cmh83, Respectively

Wheat(Triticum spp.) was the largest area crop in the world. Stripe rust, caused by the fungus Puccinia striiformis tritici is a widespread disease of wheat that caused significant yield losses annually in many wheat-growing regions of the world. It also was one of the most important wheat diseases in China, its epidemic area can reach above 2.0×107 hm2. Breeding resistant varieties are more effective, economic and safe method to control it, particularly for cultivars with adult-plant resistance (APR). Therefore, one of the aims of this study were to genetic analysis and identify the quantitative trait loci(QTLs) for APR to stripe rust in wheat, and to assess the stability of the QTL effects detected across 4 environments. This knowledge could lead to a more efficient strategy in wheat breeding for durable resistance against stripe rust. Triticale (X Triticosecale Wittmack) is a man-made species with a short history of just over 100 years since the first attempt was made to produce an artificial hybrid. Triticale have good agronomic traits such as large head, more grains, resistance to biotic and abiotic stresses. Leaf rolling may be associated with improved grain yield in some drought situations. Identification of different kinds of rolling leaf types provides a theoretical basis and technical support for leaf shape improvement and also for crop drought tolerance.277 RILs F6 developed from Avocet-YrA/Chapio were used to genetic analysis and QTL mapping with Inclusive Composite Interval Mapping Method (IciMapping, ICIM, V3.0)according to rust severity at adult plant stage at 4 environments. At same time, Rolling leaf material CMH83 from CIMMYT was studied by phenotypic, cytological and physiological analysis. The results are as follow:1. Chapio were controlled by four pairs incomplete dominance adult-plant resistance (APR) genes against stripe rustChapio was susceptible to stripe rust race (CYR32) at seedling stage, and high resistance at adult-plant resistance(APR), all of 277 RILs F6 developed from Avocet-YrA/Chapio were susceptible to stripe rust race (CYR32), and segregated at adult plant stage. Correlation analysis showed that correlation coefficients were significant among 4 environments(P<0.001). Frequency distribution was a littler skew distribution which suggested that Chapio probably contained larger effect gene for APR. Stripe rust severity in some lines showed different value between CIMMYT and China, particularly for 22 lines which difference reached 40-78.3%. It showed that one or several genes in Chapio can identify the races between Chinese race CYR32 and Mexican race YRMV09.Genetic analysis suggested that Chapio contained 4 APR genes by Chi-squared analyses (P>0.05). Rust severity were 40-50% in Avocet-TrA x Chapio F1 and Chapio x Avocet-YrA F1. Therefore, those result suggested that there were four pairs incomplete dominance adult-plant resistance(APR) genes against stripe rust in CIMMYT variety Chapio.2. Four additive APR QTLs and one pair epistatic interactions QTL had been detected, QYr.saas-3DL should be a new QTLFour QTLs for APR against stripe rust have been detected by Inclusive Composite Interval Mapping Method on chromosomes 3BS,3DL,5BL and 7DS in 4 environments, designated QYr.saas-3BS, QYr,saas-3DL, QYr.saas-5BL and QYr.saas-7DS, respectively, explaining from 2.64 to 48.93% of the phenotypic variance. All QTLs were from Chapio. The QTL QYr.saas-3DL, different from all QTLs reported previously, was flanked by SSR markers Xgdm8 and GDM128, with a genetic distance of 10 cM, which accounted for 3.84-12.44% of phenotypic variance. The QTL QYr.caas-7DS flanked by markers csLV34 and Xgwm295, which were closely linked to QYr.caas-7DS which showed the largest effect for resistance to stripe rust and accounted for 28.18-48.93% of phenotypic variance. The QTLs QYr.saas-3BS and QYr.saas-5BL flanked by markers Xbarc147 and Xwms533, Xgwm46 and Xbarc267, with a genetic distance of 2.0 cM and 38 cM, which accounted for 7.30-17.00% and 2.64-4.76% of phenotypic variance, respectively. QYr.saas-3DL should be a new QTL, others needed to further confirm. One pair epistatic interactions QTLs (QYr.saas-3BS x QYr.saas-7DS) had been detected, which accounted for 2.59-7.79% of the phenotypic variance in 3 environments and average value. QTLs QYr.saas-3BS, QYr.saas-3DL, and QYr.saas-7DS could be used in marker-assisted selection for APR to striper rust in wheat breeding programs. 3. Leaf rolling occurs in some cereal genotypes in response to drought. In the present study, we identified a rolling leaf genotype CMH83 of hexaploid Triticale (X Triticosecale Wittmack), that exhibited reduced plant height, rolling and narrow leaves, by phenotypic, cytological and physiological analysis. Gliadin electrophoresis of seeds protein showed that CMH83 was genetically stable. The sequential Giemsa-C banding and genomic in situ hybridization showed that the CMH83 contained 12 rye chromosomes, of which two pairs of chromosomes had reduced telomeric heterochromatin bands. The test of leaf relative water content (RWC) and water loss rate (WLR) of CMH83 compared with those of wheat cultivars indicated that rapid water loss after drought stress in CMH83 could be associated with the leaf rolling phenotypes. Leaf rolling phenotype of CMH83 was a dominant trait in our preliminary inheritance studies. The triticale line CMH83 can be used to study the mechanism of triticale for drought resistances.