TEMPERATURE REQUIREMENTS FOR GROWTH OF GRASS-CLUMP DWARF WHEATS AND INHERITANCE OF TRAIT

Grass clump dwarf wheat plants (Triticum aestivum L. em Thell.) are characterized by their reduced stature, increased tiller number and frequent lack of reproductive growth. Three types of grass-clump dwarf wheat plants occur in the progeny of crosses of normal wheat cultivars. Temperature has a dramatic effect on the growth of the most severe dwarf, but its effect has not been investigated with the less severe dwarf types. On the other hand, the inheritance of the trait has been most studied with the less severe dwarf types. Crosses of several common wheat cultivars were made and the F1s were grown in controlled environmental growth cabinets under conditions of continuous 16,146-18,299 lx incandescent/fluorescent illumination and constant temperature regimes of 11, 16, 21 and 26.degree. C. In general, type 1 dwarfs grew normally at temperatures of 26.degree. C or higher, type 2 dwarfs grew normally at 21.degree. C or higher, and type 3 dwarfs grew normally at 16.degree. C or higher. At temperatures below these values, the characteristic grass-clump dwarf morphology was displayed in plants possessing a dwarfing genotype. Conventional genetic analysis of F2 populations and F3 lines showed that a 3 complementary dominant gene system adequately explained and predicted the origin of grass-clump dwarfs in inter-class wheat crosses.