THE LEVEL OF HETEROSIS AND THE DEGREE OF PHENOTYPIC DOMINANCE OF THE MAIN ECONOMICALLY VALUABLE CHARACTERISTICS IN F1 HYBRIDS OF THE SILKWORM (BOMBYX MORI L.)

Abstract

There were presented the results of heterosis level (hypothetical and true) and the degree of phenotypic dominance of the main economically valuable characteristics in hybrids of silkworm Bombyx Mori L. of the first generation. The crossing was conducted by full diallel scheme, including 16 variants (12 hybrids and 4 parental forms), 50 mg in triplicate replications. There were studied the types of heredity and the level of heterosis of the main economically valuable characteristics in F1 hybrids of silkworms. It was revealed that the heredity of caterpillars viability, average cocoon weight and male silkiness was mostly positive as regards to G2, G4, G6 and G7 lines, while the heredity of females was mostly depressed (negative superdominance). Determination of the effect of heterosis and the degree of phenotypic dominance made it possible to identify 7 best combinations in terms of caterpillar viability in comparison with parental forms, among them the best were hybrids G2×G6 and G6×G2 with high degree of phenotypic dominance (positive superdominance) -- 7.8 and 9.0, with hypothetical heterosis of 11.0% and 12.7% and true heterosis of 9.4% and 11.1% accordingly. The effect of heterosis (positive superdominance) was found in 8 hybrids according to cocoon weight out of 12 hybrid combinations, partial positive inheritance in 3 hybrids, and intermediate type of dominance in 1 hybrid. The hybrids G6×G4 (Ht=9.00 %, Hbt=8.30 %) and G6×G7 (Ht=1.68 %, Hbt=1.43 %), whose heredity was of the positive superdominance type, were distinguished by female silkiness with a high level of hypothetic and true heterosis (13, 92 and 6.80, accordingly), while hybrid depression was observed in 5 combinations, intermediate heredity in 3, and partial positive and negative dominance in one combination each. The 9 hybrids had positive overdominance type heredity for silkiness in males. Production of high-quality silkworm biomaterial contributes to extension of possibilities of its use in various spheres of human activity.