Combining ability of the response to boron deficiency in wheat

Abstract

Seven wheat lines (adapted to Thailand originated in Mexico) and their Fl hybrids from a diallel cross were grown in sand culture from November 1990 to February 1991. Plants were watered twice daily with a complete nutrient solution supplying a low level of boron at 0.2 μ M. Plant response was measured as the average number of grains set in the two basal florets (F1 + 2) of 10 central spikelets of the wheat ears.

Grain set in low boron was significantly different among parents and offspring. Both general combining ability (GCA), a measure of additive gene effects, and specific combining ability (SCA), a measure of non-additive gene effects were highly significant (p <0.01). The GCA effects were the major factor that controls this character. SCA effects were smaller, and found to be positive in six crosses between susceptible × tolerant and tolerant × tolerant lines. This indicates that it may be possible to transfer the B deficiency tolerance character to susceptible lines by a backcrossing program. The positive GCA effects of tolerant lines suggest that these lines can be useful in breeding for more tolerance in problem areas.