Genetic expression of brevis-2 mutant in comparison with its normal counterpart

In diallel crossing of 5 bv2 inbreds (B1S6) and their normal counterparts, 10 bv2 hybrids and their normal counterparts were released. Results from their comparison and studies of other bv2 hybrids give some results useful for utilization of the bv2 gene in breeding programs.

Plant height of bv2 hybrids, 140-150 cm, corresponds to the optimal level of this trait for a short-stem modified plant type. In comparison with their normal counterparts the plant height was reduced by 30-50%. The growth curve showed that most expressive growth reduction was manifested between tasseling and flowering period. Contrary to normal hybrids the vegetative growth of bv2 hybrids ceased at the beginning of flowering. It seems to be favorable for ear shoot growth and development. The vegetation period of bv2 hybrids was shorter by about 8 days on average and grain moisture at harvest time 2-6% lower (3.5% average). The date of flowering of normal and bv2 hybrids was identical.

In 1979 the grain productivity of bv2 hybrids was equal to normal hybrids, and in 1980 normal hybrids significantly outyielded the bv2 counterparts (16% in average). In only a few cases, the bv2 hybrids yielded better. 1000-kernel weight of bv2 hybrids decreased by about 28%. Stalk breakage was not present in bv2 hybrids from the diallel cross.

Combining ability analysis showed that both general (GCA) and specific (SCA) combining abilities were important in conditioning of observed characters (grain yield and its components, plant height). From the GCA standpoint bv2 inbreds should be considered as totally new inbreds. The results supported use of bv2 mutant for modification of plant height.

A. Piovarci

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