Authors:A. Bellatreche, S.R. Mnasri, M. Ben Naceur, and S.S.B. Gaouar
. , Ben Naceur , M.
2016 . Assessment of genetic diversity of wheat ( Triticuma estivum L.) using agro-morphological characters and microsatellitemarkers . International Journal of Biosciences 9 ( 4 ): 92 – 101
Authors:R. Singh, P. Hucl, M. Båga, and R. Chibbar
Pre-harvest sprouting (PHS) in bread wheat (Triticum aestivum L.) is one of the major abiotic constraints influencing production of high quality grain. Selection for pre-harvest sprouting (PHS) resistance in bread wheat (Triticum aestivum L.) in early generations is difficult because it is expressed as a quantitatively inherited trait and subject to environmental effects. The objectives of this study were to validate a major quantitative trait locus (QTL) for PHS resistance on chromosome 4A in bread wheat and to isolate near-isogenic lines for this QTL using marker-assisted selection. A total of 60 Canadian wheat cultivars and experimental lines were screened with three SSR markers in a QTL region for PHS resistance. The SSR markers DuPw004, barc170 and wmc650 explained 67%, 75% and 60% of total variation in germination (%), respectively, among different wheat genotypes. Marker assisted back crossing with DuPw004 reduced the population size in BC1F1 and BC2F1 generation by 41% and 59%, respectively. A survey of pedigrees of different genotypes revealed that the parental line RL4137 is a major source of increased PHS resistance in a number of western Canadian wheat cultivars. Microsatellite markers (DuPw004, barc170 and wmc650) will be useful for plant breeders to pyramid QTL from different PHS resistance sources.
Authors:F. Rafiei Boroujeni, A. Arzani, F. Afshari, and M. Torabi
The objectives of this research were to examine the inheritance of leaf rust resistance genes in the Iranian wheat cultivar ‘Marvdasht’, which is highly resistant to leaf and stripe rusts, and to identify Lr genes present in this cultivar using molecular markers. The genetic basis of resistance to the leaf rust pathogen (Puccinia triticina) in ‘Marvdasht’ was studied in F2:3 populations derived from crosses of Bolani (susceptible cultivar) × Marvdasht. Isolates 84-1 and 85-28 of P. triticina, which are the predominant isolates in Iran, were used to examine the segregation of resistance originating from ‘Marvdasht’. The results indicated that resistance in ‘Marvdasht’ to Puccinia triticina isolate 84-1 was governed by two dominant seedling resistance genes Lr1 and Lr17a. Allelism studies using an F2 population derived from a cross between ‘Falat’ (Seri 82) and Marvdasht indicated that resistance in Marvdasht was not due to the resistance gene Lr26 present in ‘Falat’. With the application of a previously developed molecular marker for Lr1, the STS marker RGA-567-5, the presence of Lr1 was verified in Marvdasht. Based on bulk segregant analysis, Lr17a was mapped to the distal end of chromosome 2AS and was closely linked to microsatellite marker Xbarc212 at a distance of 3.7 cM. In conclusion, the presence of Lr1 and Lr17a was confirmed in the cultivar Marvdasht.
In order to investigate the origin of two 4B-5R wheat-rye translocations a number of microsatellite markers were considered, (a) which were specific for the rye chromosome arm 5RL and (b) which should enable precise characterisation for the gene pool of a ‘Cornell’ wheat derivative. Seven out of eight markers revealed amplification fragments with the rye control, while the marker WMS0186 amplified only a PCR product with the appropriate chromosome arm of the wheat control. The heterogeneity of the DNA fragment patterns among five wheat-rye translocation lines confirms different wheat backgrounds of the American, Danish/UK, Hungarian, and Swedish sources of the 4B-5R translocations. The homogeneous DNA marker patterns of ‘Viking-hairy neck’ and ‘Cornell Sel. 82a1-2-4-7’ are particularly clear. The corresponding molecular markers together with the cytological data, genomic
hybridisation, the physiological investigations, and the historical review support the hypothesis of a common origin of ‘Viking-hairy neck’ and ‘Cornell Sel. 82a1-2-4-7’. The importance of the results for practical breeding and for introgression experiments is discussed.
Authors:M. Sivasamy, M. Aparna, J. Kumar, P. Jayaprakash, V. Vikas, P. John, R. Nisha, Satyaprakash, K. Sivan, and E. Punniakotti
Nearly twenty thousand wheat lines were phenotyped for the presence of leaf tip necrosis (LTN), a phenotypic trait linked to adult plant leaf rust resistance (APR) genes, viz. Lr34, Lr46 and Lr67 having pleiotropic association with multiple disease resistance genes. Thirty-six lines showed varied expression of LTN and moderate level of leaf rust severity at adult plant stage with slow rusting (disease progress at a retarded rate). Seedling resistance test (SRT) revealed susceptible and mixed infection types, a characteristic of adult plant resistance (APR) genes. Further molecular confirmation for the presence of these genes using available microsatellite markers revealed that of the 36 lines, five lines carried Lr46+ alone and five other lines carried Lr67+ alone. Seven lines carried the combination of Lr34+ and Lr67+ while six lines confirmed to carry the combination of Lr46+ and Lr67+. Remarkably three lines carried all the three APR genes, viz. Lr34+, Lr46+ and Lr67+. All these stocks can be a source of APR multiple disease resistance genes. Ten lines were not confirmed to carry any of the genes but still had LTN and SRT results showing an infection type typical of APR genes and these can be the source of identifying newer APR genes. The resistance based on minor APR genes when combined with a few additional minor genes in the background of high yielding cultivars is expected to have high level of race non-specific resistance and to be durable.