Expression and Inheritance of Resistance to Hessian Fly in Synthetic Hexaploid Wheats Derived from Triticum tauschii (Coss) Schmal.1

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Abstract
Seventeen synthetic hexaploid (SH) wheats, derived from crosses between six tetraploid Triticum species and a diverse group of diploid T. tauschii (Coss.) Schmal., were evaluated for resistance to biotype D of Hessian fly, Mayetiola destructor (Say). Resistance was identified in four of the SH wheats. Based on rections of the tetraploid × diploid crosses and the parental Triticum species to larval feeding, resistance was derived from specific lines of T. tauschii. Other lines of T. tauschii and the tetraploid Triticum species were homozygous susceptible. Resistance of the SH wheats and T. tauschii was expressed as antibiosis in that larvae died in the first instar of development.Two resistant SH wheats were crossed with susceptible common wheat (T. aestivum L. em Thell.) cultivars ‘Amigo’ and ‘Eagle’ to study the inheritance of Hessian fly resistance derived from T. tauschii. F2 populations segregated in a 3:1 ratio of resistant to susceptible plants, an indication that resistance was conditioned by a single dominant gene. Segregation ratios of F3 lines and F3 plants within segregating lines supported the single‐factor resistance hypothesis. F4 lines derived from homozygous resistant F3 lines bred true for resistance, On the basis of present knowledge of genetic relationships among wheat genes for resistance to Hessian fly, T. tauschii appears to be a new source of resistance that can be readily transferred to hexaploid wheat.