Influence of Maize Grain Hardness and Phenol Content on the Resistance of Some Maize Varieties to Infestation by Larger Grain Borer, Prostephanus truncate(Horn) (Coleoptera: Bostrichidae).

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The study evaluated some maize varieties for resistance to damage by Larger Grain Borer (LGB), Prostephanus truncatus and determined their grain hardness and phenol content. One maize ear of 100g from each of the maize varieties was placed in a glass bottle with perforated lid and infested with five males and five females LGB of 1-7days old. At 90 days post-infestation, the maize ears were visually rated for damage on a scale from 0-10. Data were collected on weight of grain dust, number of adult LGB, larvae, pupae and dead LGB. Percentage grain weight loss and % grain damage were calculated. Grain hardness and phenol content of the kernels were determined and correlated with grain damage indices. The number of adult LGB, adult mortality, weight of grain dust, % grain damage and % grain weight loss of the maize varieties were significantly (P < 0.05) different from each other. The % grain weight loss (38.23) in the variety White Maya was significantly (P < 0.05) higher than those in 98/SWI-Y, DMR-LSR-Y, DMRESR-Y and SUWAN-l-SR-Y. The % grain damage (30.51) in the variety TZPB-W was significantly (P< 0.05) higher than the damage (2.85) in SUWAN-l-SR-Y. Grain hardness (1.31) was significantly (P <0.05) high in DMR-LSR- Y and significantly(P<0.05) lower (0.74) in white Maya. Phenol content (24. 17) was significantly (P< 0.05) high in SUWAN-l-SR-Yand significantly (P< 0.05) lower (0.11) in ART/98/SW5-W. The varieties TZPB-W and White Maya with visual ratings (VR) of8.50 and 9.25, respectively, were highly susceptible to the borer. Solo with VR of 7.75 was susceptible. ART/98/SW5-W and ART/98/SW 1-Y were moderately resistant with VR of5.0 each. DMR-LSR- YandART/98/SW6-W were resistant with VRof3.5 each, while DMR-ESR-Y and SUWAN-l-SR-Y were highly resistant with VR of 1.5 each. The number of adult LGB correlated positively with % weight loss, % grain damage and weight of grain dust. Phenol content of grain and grain hardness index significantly (P <0.05) correlated negatively with weight of dust, % grain damage and % weight loss. The study suggested inherent biophysical (hardness) and biochemical (phenols) components that could withstand damage by LGB among the maize varieties. Grain hardness and phenol content of the maize grains acted as suppressive variables in relation to the maize damage traits.