Mechanisms and levels of resistance in hybrids, open pollinated varieties and landraces to Chilo partellus maize stem borers.

Reduction in maize grain losses could be enhanced through identification of existing resistant genotypes and pyramiding the resistance into elite materials. This study was carried out in two trials of 100 commercial hybrids and open pollinated varieties (OPVs), and 75 landraces to identify resistant genotypes and mechanisms of resistance to Chilo partellus maize stem borers. The trials were laid out in α-lattice designs, each replicated three times during the 2010/11 and 2012 rainy seasons. Each plant was artificially infested with five C. partellus neonates three weeks after planting. Data collected included leaf toughness, stem hardness, trichome density, stem sugar content, leaf damage, number of stem borer exit holes, tunnel length and grain yield. Data were analyzed using PROC GLM of SAS 2007 package and means separated using Fishers protected least significant difference test (LSD) at (P < 0.05). Canonical discriminant analysis was performed to discriminate the mechanisms evaluated. The most resistant genotypes were CIMMYT experimental resistant hybrid checks followed by landraces and the OPVs. Top 10 resistant commercial hybrids and OPVs were PH1, PH4, DHO1, DH04, DK8031, KDVI, KDV2, PH3253, ECA-Strigoff-VL and EEQPM-8-EA, while H629, H6212, KH 600-15A, H6213 and H6210 were the most resistant commercial hybrids. Canonical discriminant analysis identified percentage stem sugar content and trichome density as the most important resistance mechanisms for discriminating the genotypes. The resistant landraces and OPVs could be utilized in breeding for maize stem borer resistance, while the resistant commercial hybrids and OPVs could be recommended for production in the relevant ecologies in Kenya to curb maize stem borer related yield losses.