Abstract
Developing maize with durable resistance to maize stem borers could be enhanced by identifying genotypes with different mechanisms of resistance and pyramiding the resistances into high yielding genotypes. This study was carried out on 120 CIMMYT tropical maize inbred lines to identify the most important mechanisms of resistance that could be used to discriminate the germplasm into resistant or susceptible categories. The experiment was laid in an α-lattice design, and replicated three times during the 2011/12 seasons. Traits measured were leaf toughness, stem penetrometer resistance, trichome density, stem sugar content, leaf damage, number of stem exit holes and stem cumulative tunnel length. A selection index was computed and categorized the 120 inbred lines into 33 resistant, 29 moderately resistant, 31 moderately susceptible and 27 susceptible. The most resistant lines were those derived from the CIMMYT multiple borer-resistant populations with CKSBL10039 being most resistant and CML395 most susceptible with indices of 0.49 and 1.84, respectively. Trichome density, leaf toughness and stem sugar content in that order were the most important traits in discriminating the lines into resistance and susceptible categories. More research is needed to classify the specific types of trichomes and sugars present in both resistant and susceptible inbred lines.
Highlights
Maize is an important staple food crop for the people in Kenya where it is grown on approximately 1.7 million hectares yielding about 2.3 million tons to feed an estimated 40 million people annually (FAOSTAT, 2010)
Developing maize with durable resistance to maize stem borers could be enhanced by identifying genotypes with different mechanisms of resistance and pyramiding the resistances into high yielding genotypes
More research is needed to classify the specific types of trichomes and sugars present in both resistant and susceptible inbred lines
Summary
Maize is an important staple food crop for the people in Kenya where it is grown on approximately 1.7 million hectares yielding about 2.3 million tons to feed an estimated 40 million people annually (FAOSTAT, 2010). In Kenya, maize stem borers accounts for 13.5% annual losses, but damage depends on the maize variety and the stage of attack (De Groote, 2002). Chilo partellus Swinhoe (Lepidoptera: Crambidae), a highly invasive stem borer, has become the most important maize stem borer in Kenya since its introduction in the 1930s (Mbapila, Overholt, & Kayumbo, 2002). In a stem borer distribution study done in Kenya, about 54 % of the recovered larvae were C.partellus Swinhoe (Crambidae), 40% Busseola fusca (Fuller) (Noctuidae), 4% Sesamia calamistis Hampson (Noctuidae) and 1% Chilo orichalcociliellus (Strand) (Crambidae), the rest were minor borer species (Ong’amo et al, 2006)
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