Analysis of Genetic Factors Influencing the Developmental Rate of Globally Important CIMMYT Wheat Cultivars
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The rate at which wheat (Triticum aestivum L.) reaches anthesis and other developmental stages depends largely on the variation of three major factors: vernalization (Vrn), photoperiod (Ppd), and earliness per se (Eps). The objectives of this study were to characterize a set of genotypes for the presence of developmental genes and their potential association to adaptability and to identify diagnostic molecular markers for the vernalization gene Vrn-D1. Fifty-one genotypes were crossed with testers containing known Vrn and Ppd genes. To determine earliness per se and its interaction with temperature, genotypes were vernalized for 8 wk and placed in a 24-h photoperiod regime at two temperatures. To validate molecular markers for Vrn-D1, the cultivars were genotyped with closely linked SSR markers Xgwm292-5D and Xgwm212-5D. Segregation analysis on F-2 populations of field-grown plants showed that Vrn-D1 was present in 66% of the cultivars, while Vrn-A1, Vrn-B1, and Vrn4 were found in 41, 39, and 8% of the lines, respectively, either solely or in combination with other Vrn genes. A low percentage of cultivars appeared to have a constitutive genetic character for early flowering (Eps), while most of the cultivars may have temperature-sensitive genes that respond to local environmental changes. Vrn-D1 was reliably detected in 76.5% of the genotypes using the 215-bp allele of microsatellite marker Xgwm292-5D, whereas Xgwm212-5D did not reveal sufficient allelic variation within the tested wheats.
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