PHENOTYPIC CHARACTERIZATION OF SELECTED LOCAL MAIZE LANDRACES FOR DROUGHT TOLERANCE BASED ON FLOWERING STRESS, AND THEIR RESISTANCE TO LARGER GRAIN BORER (Prostephanus truncatus) IN KENYA

Abstract

Maize is staple food in Kenya and is grown in almost all agro-ecological zones. The average maize yield in the highlands is about 3.5 t/ha while that for the arid and semi arid (ASALs) low altitude areas is less than 1.3 t/ha. Arid and semi arid areas constitute about 82% of the total land area and supports about 20% of the country’s human population. The demand for more food culminating from the population increase and the migration of people from high potential areas to semi arid lowlands has led to maize growing in marginal areas. Kenya’s ASALs are home to the very rural poor who practice subsistence farming as a livelihood. Local landraces of maize are an important livelihood resource in these areas. The objective of the study was to characterize selected Kenyan local maize landraces for drought tolerance and resistance to larger grain borer in storage. The characterization for drought tolerance was carried out using secondary traits that exhibit high heritability for drought tolerance such as grain yield, anthesis-silking interval (ASI), tassel size, ears per plant and leaf rolling. The experiment was laid out in a lattice design (unbalanced) each with sixty-four maize genotypes. A second experiment to evaluate drought tolerance was conducted for landraces that exhibited favorable tolerance characteristics. This experiment was laid out in a split plot (RCBD) design with water levels (water stressed and unstressed, at flowering) as the main plots and germplasm as the sub plots. Irrigation was withheld one week to tasseling and resumed forty days later in water stressed plots. The wellwatered plots had continuous irrigation. The field experiments were carried out at KARIMasongaleni field station in Kibwezi district, which falls under agro-ecological zone VI. Among the characters evaluated, a low ASI (1-6 days) was associated with a high level of drought tolerance and low yield losses under moisture stress. Drought stress resulted in 17% to 81% relative grain yield losses. Germplasm GBK-032419, DT/BT/1470.DT and GBK-034659 exhibited lowest grain yield losses of 28%, 22% and 17% while KTL N 70140-4, KTL N 10162- 1 and Makueni Dry Land Composite (control) exhibited high grain yield losses of 81%, 70% and 68%, respectively. However, Katumani inbred lines DT/BT/1917.DT and DG/BT/2443.DT, though exhibiting the shortest ASI of about 1 day experienced about 50% grain yield loss under moisture stress. In general, an increase in number of ears per plant, 100-seed weight, increased plant height, high shelling %, reduced leaf rolling and low ASI were associated with yield increases under water stress. Germplasm that exhibited favorable drought tolerance characteristics were CML-492, DT/BT/1917.DT, DT/BT/1470.DT, DG/BT/2443.DT, GBK044593, GBK-032419, GBK-032423, GBK-34659, KTL N 701104 and GBK-032357. The most vii susceptible germplasm (ASI between 12-17 days) were KTL N 70133-3, KTL N 10168-1, Katumani Composite B, Makueni Dry Land Composite, KTL N 10168-2, GBK-043227, GBK034711 and GBK-027054. The germplasm that exhibited drought tolerance characteristics were further evaluated for resistance to larger grain borer (LGB) damage in storage. This experiment was done at CIMMYT field laboratory-Kiboko. Samples were laid out in complete randomized design and replicated three times. Although no absolute resistance existed, most landraces exhibited higher levels of resistance to LGB than the control variety H614. The germplasm with the highest resistance level was CML-492, while GBK-043731 had the lowest level. Germplasm CML-492, DT/BT/1971.DT, DT/BT/1470.DT, DG/BT/2443.DT, GBK-044593, GBK-032419, GBK-032423, GBK-34659 and GBK-032357 exhibited tolerance to drought and also resistance to LGB relative to control H614. Katumani Composite B, though exhibiting susceptibility to drought, had a high level of resistance to LGB than most local landraces. It was concluded that some Kenyan local landraces exhibit drought tolerance characteristics and also resistance to LGB. According to factor analysis, the phenotypic characteristics evaluated for drought tolerance accounted for 68% of the total variation.