Molecular basis of stiga hermonthica resistance resistance in some Kenyan maize cultivars

Abstract

The improvement of cereal crop production to meet the increasing demand for food by expanding population is essential. Maize is one such nutritional cereal widely distributed over the world including Kenya. It is the staple cereal diet of over 80% of Kenyan population. Small-scale farmers currently produce more than 90% of the maize grown in Kenya. However, the parasitic weed, Striga hermonthica has become a menace because it is widespread causing severe damages to major cereals like maize and sorghum. Considering the subsistence nature of farming in Kenya, the development of resistant or tolerant varieties seems to be the most promising cost-effective approach for alleviating the weed problem. This study focused on the molecular basis of Striga resistance in maize cultivars by assessing their leaf amino acid and protein composition and elution profiles of root exudates. This was done by Thin Layer Chromatography, Sodium Dodecyl Sulphate- Polyacrylamide Gel Electrophoresis and Reverse Phase-High Performance Liquid Chromatography techniques. In addition mutants lines of maize were created in the laboratory using Sodium Azide (NaN3) and their perfonnance in respect to the degree of Striga resistance screened. The presence of active chemical stimulants in the root exudate was further investigated using sensitive bioassay experiments. It was observed that the existing maize cultivars exhibited distinct protein and exudate profiles and their molecular properties varied markedly with that of the susceptible and resistant mutants. The protein subunits (Mr 66.2, 40.0 and 29.0 Kda) resolved by SDS-PAGE were found to be reproducible and similar among the resistant, tolerant and the non-stimulating varieties. The electrophoretic pattem of susceptible maize varieties revealed presence of vi ABSTRACT The improvement of cereal crop production to meet the increasing demand for food by expanding population is essential. Maize is one such nutritional cereal widely distributed over the world including Kenya. It is the staple cereal diet of over 80% of Kenyan population. Small-scale farmers currently produce more than 90% of the maize grown in Kenya. However, the parasitic weed, Striga hermonthica has become a menace because it is widespread causing severe damages to major cereals like maize and sorghum. Considering the subsistence nature of farming in Kenya, the development of resistant or tolerant varieties seems to be the most promising cost-effective approach for alleviating the weed problem. This study focused on the molecular basis of Striga resistance in maize cultivars by assessing their leaf amino acid and protein composition and elution profiles of root exudates. This was done by Thin Layer Chromatography, Sodium Dodecyl Sulphate- Polyacrylamide Gel Electrophoresis and Reverse Phase-High Performance Liquid Chromatography techniques. In addition mutants lines of maize were created in the laboratory using Sodium Azide (NaN3) and their perfonnance in respect to the degree of Striga resistance screened. The presence of active chemical stimulants in the root exudate was further investigated using sensitive bioassay experiments. It was observed that the existing maize cultivars exhibited distinct protein and exudate profiles and their molecular properties varied markedly with that of the susceptible and resistant mutants. The protein subunits (Mr 66.2, 40.0 and 29.0 Kda) resolved by SDS-PAGE were found to be reproducible and similar among the resistant, tolerant and the non-stimulating varieties. The electrophoretic pattem of susceptible maize varieties revealed presence of vi