Physiological and Morphological Changes Associated with Selection for Resistance to Stem Borer Attack in Maize (Zea mays).

Physiological and morphological changes associated with selection for resistance to stem borer attack in maize (Zea mays) Durojaiye, S.O., Olaniyan, A.B., Ajala, S. O. Corresponding author: abolaniyan@yahoo.com ABSTRACT Stem borers are among the most important insect pests of maize that causes reduction in yield ranging from 20-70% depending on its severity. Previous research with artificial infestation established clear links between stem borer incidence or damage symptoms and yield losses. This study aimed at determining the physiological changes associated with selection for resistance to stem borer attack in maize as well as understanding interrelationships among the morpho-physiological traits. Thirty eight maize entries were grown in replicated trials at two locations in Nigeria. The fields were subjected to artificial infestation with egg masses of Sesamia calamistis and Eldana saccharina raised on artificial diet in the laboratory, the non-infested fields served as control. Data were obtained on flowering dates, maturity traits, growth rate parameters, grain yield and other plant traits. Resistance was measured as levels of leaf feeding damage, dead heart, stalk breakage, cob damage and stem tunnelling. Recurrent selection significantly reduced leaf feeding damage in LNTP-W population, dead heart percentages in BRTZL, TZBREld4-W and TZBREld4-Y, tunnelling percentages in AmaTZBR-W, TZBRComp1-Y and TZLComp1-W, cob damage score in AmaTZBR-W. Significant increases in grain yield were observed as a response to recurrent selection in AmaTZBR-W, BRTZL, LNTP-YMassBR and TZBREld4-Y populations. Grain yield correlated significantly and positively with plant height, ear height, ear harvested, number of ears per plant, cob length, and number of kernels per row. Although, there were highly significant and positive correlations among leaf area index, leaf area duration, crop growth rates and total dry weights, correlations among physiological, mainly growth traits studied, resistance parameters and grain yield were generally not significant. This implies that changes observed were primarily morphological thus suggesting the need for research on additional physiological parameters.