Stability of General and Specific Combining Ability Effects for Grain Yield in Elite Iranian Maize Inbred Lines

Abstract

Diallel analyses provide estimates of general combining ability (GCA) and specific combining ability (SCA) effects to facilitate efficient utilization of maize (Zea mays L.) inbred lines in breeding programs. Multi-environment trials are commonly conducted to evaluate GCA, SCA, and the stability of grain yield (GY) for single-crosses across environments (E). In these studies the significant GCA × E and SCA × E interactions are usually not examined, yet they indicate that the rankings of the parental inbred lines for GCA and SCA change across environments. The major objective of this study was to quantify stability of GCA and SCA effects of nine maize inbred lines developed in Iran using a 9 × 9 diallel mating design. The 36 single- cross hybrids were evaluated for GY, kernel rows per ear (KR), and kernels per row (KN) at three locations across two years (six environments), using a randomized complete-block design with four replicates. Rank sum and rank variance were used to measure the stability of GCA and SCA for GY across environments, and the Quade's test was used to separate the rank sums. The main effect of E, hybrid, and hybrid × E was significant. Significant GCA and SCA effects were found for the traits, with GCA being more important than SCA for KR, but vice versa for GY and KN. Significant GCA × E and SCA × E were observed for the traits, indicating changes in ranking of GCA and SCA across environments. Inbred lines KE75039 and K1263/2-1 had significant positive GCA for GY. The highest SCA for GY resulted from KE75039 × K2331 cross (15.07 Mg ha−1). Ranking of GCA and SCA for GY across environments exhibited different patterns for the parental inbred lines. Inbreds KE75039 and K1263/2-1 exhibited high stability for GCA across environments for GY, and they contributed only 9% and 7% to GCA × E interaction, respectively. Cross combination KE75039 × K2331 had the highest stability for SCA across the environments, followed by K2331 × K1263/2-1 and K1263/1 × OH43/1-43 crosses. The three other notable cross combinations with relatively stable SCA each had inbred line K1263/1 in common. Combining ability and stability analyses suggest that maize breeding programs in Iran could improve GY by using inbred lines KE75039, K1263/1, and K1263/2-1. It is suggested that new adapted germplasm be introduced to broaden the genetic base of maize germplasm available in Iran.