Laboratory Evaluation of Twenty Maize (Zea mays L.) Varieties for Resistance to the Larger Grain Borer, Ptosteptianus truncatus (Horn) {Coleoptera: BostIichidae}, in Ibadan, Oyo State, Nigeria.

OSIPITAN, A. A. AND ODEBIYI, J. A.

ABSTRACT.; Eighteen improved and two ‘local varieties ‘of maize (Zea mays L.) were evaluated for resistance to infestation by the larger grain borer, (LGB), Prostephanus truncatus (Horn);’ in the Entomology Research Laboratory of .the Department of Crop Protection and Environmental Biology, University of Ibadan, Oyo State, Nigeria at 28±1°C and 79-82% RH. -Sixty grammes of each variety were weighed into 250cm3 capacity Kilner jars and infested with 10 pairs of adult P. truncatus that were 1-5 days old. On the 40th day, all insects were collected, the maize grain dust sieved using a mesh of 0.25mm size and then ‘weighed. The’ grains were weighed and sorted into, damaged and undamaged categories and percentage damage computed, Other data recorded were the percentage grain weight loss, adult mortality and final population of adults. The study was conducted using completely randomized design and the test varieties were compared with standard using Dunnett’s t-test. The weighted average of scores generated from the five damage parameters was used to place the .varieties into one, of four rating for resistance to LGB. In addition, cluster analysis was done on the rated parameters using the centroid. hierarchical system. The results indicated that ICZBC2-B (KUI414) was highly resistant; TZBR-Ses-3C3, TZBR-Ses-IC3-Y, TZBR~Syn-YC2′ Oba Super-I and Oba Super-l l were resistant; ‘TZBR-Eld-3C2, Ama-TZBR-WC1′, TZBR-Ses-3C4-Y’ Ak- 9528-DMR-SR, Acr.91-Suwan-ISRC were moderately resistant, while others were susceptible. The mechanisms of resistance identified were antixenosis ‘and antibiosis, and the basis of resistance, were grain hardness and starch content. The resistant varieties could be used in combination with other control options in LGB-endemic areas.

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