Combining Ability Studies for Grain Yield and Tryptophan Content in Quality Protein Maize

Grain yield and tryptophan contents were studied in 10 QPM inbred lines and their 45 single cross hybrids at Rajendra Agricultural University, Pusa (E₁), Research Station, Madhopur (E₂) and Research Station, Manjhi (E₃) of Bihar. General combining ability (GCA) variances and Specific combining ability (SCA) variances were significant for grain yield and tryptophan content in all the three environments showing importance of additive as well as non-additive genetic variances. The values of ratio (s² GCA/s² SCA) were less than unity which indicated preponderance of non-additive genetic variance in the two traits. Different crosses exhibited differential response for SCA effects in different environments for grain yield. The SCA effect in tryptophan content was highest in P₅ x P₇ followed by P₈ x P₉ and P₆ x P₇ in all three environments which shows reproducibility of this trait.