Seed generation effect on quality of genetic information from maize (Zea mays L.) diallel cross for maize weevil (Sitophilus zeamais Motschulsky) resistance

Maize weevil (Sitophilus zeamais Motschulsky) is a common insect pest affecting stored maize (Zea mays L.) worldwide and can be controlled by breeding for host resistance. Information on combining ability and gene effects conditioning maize weevil resistance would be required to devise breeding strategies. However, there are disagreements regarding the seed generation to subject to maize weevil resistance evaluation. This study determined the seed generation effect on the quality of genetic information obtained from a maize diallel cross. Eight weevil-resistant and two susceptible maize inbred lines from eastern and southern Africa were crossed in a 10-parent diallel scheme. The resulting F-1 hybrid seed, F-2 full-sib grain from controlled pollination, and F-2 half-sib grain from open pollination were evaluated for maize weevil resistance and responses were determined using the number of F-1 weevil emergence from the seed (FWE), median development period (MDP), Dobie's index of susceptibility (DIS), and parental weevil mortality (PWM). General combining ability (GCA) and specific combining ability (SCA) effects were significant for the FWE, MDP, and DIS in all seed categories. Results revealed that reciprocal effects were predominant in F-1 hybrid seed, GCA effects were predominant in F-2 full-sib grain, while SCA effects were more important in the F-2 half-sib grain. The F-2 full-sib generation exhibited superiority in providing genetic information required for parental line selection when breeding for weevil resistance, compared to F-1 hybrid and F-2 half-sib grain. Resistant inbred lines MV170 and MV142, produced hybrids that exhibited high levels of maize weevil resistance across all the three seed categories thus, qualifying as suitable materials for breeding weevil resistant maize hybrids.

Automated summary

The maize weevil resistance evaluation was conducted on different seed generations, and the results showed that the F-2 full-sib grain was superior in providing genetic information for breeding purposes. When breeding for weevil resistant maize hybrids, hybrids produced from resistant inbred lines MV170 and MV142 exhibited high levels of maize weevil resistance across all three seed categories, making them suitable materials for breeding purposes.