EFFECTS OF MUTAGENESIS ON DROUGHT TOLERANCE AND AGRONOMIC TRAITS OF SELECTED BREAD WHEAT (Triticum aestivum L.)

Abstract

Wheat (Triticum aestivum L) is an annual crop widely cultivated as small-grain cereal. It is among the most important cereal crops grown that contribute significantly to food security and is ranked second after maize. Abiotic stress conditions such as drought cause extensive losses in wheat production worldwide. In Kenya, arid and semiarid lands (ASALs) represent 83% of total land area, and experience crop failure due to drought stress. With very few drought tolerant varieties that have been recommended and released for commercial production, there is need to develop more drought tolerant wheat varieties. The objectives of this study were to screen for drought tolerance in some Mutant wheat lines in vitro using Polyethylene Glycol (PEG); to screen for drought tolerance at seedling stage and to morphologically characterize the Mutant wheat lines. For the in vitro test, a completely randomised design with three replicates was used in which four wheat varieties, that is, Mutant 1, Mutant 2, Chozi and Duma were placed in petri dishes on moistened filter paper. Drought stress was induced by creating different water potential of PEG that is 0, -3, -9 and -15 bars. Data was recorded on root length, shoot length and root length/shoot length ratio. For the seedling test, the seeds were sown in polythene bags in a complete randomised design and at the early stages they were screened for several parameters including emergence percentage (EP), emergence index (EI), emergence rate index (ERI), energy of emergence (EE), mean emergence time (MET), desiccation tolerance index (DTI) and percentage seedling recovery (PSR). The morphological characterization was done using a randomized complete block design where the four wheat varieties were grown and normal agronomic practices carried out. Data on plant height, spike length, number of tillers, days to 50% heading and yield was collected. Data was subjected to analysis of variance using GENSTAT 12th edition and means separated using Duncan multiple range test. Correlation was done by Pearson Correlation Coefficients. Results indicated that there was a significant difference (p≤0.05) between Mutant 1 and Mutant 2 having longer roots, shoots and a better root to shoot ratio compared to Chozi and Duma in the different PEG concentrations used. Mutant 1 and Mutant 2 had a better performance in terms of EP, EI, ERI, EE, MET, DTI and PSR compared to the other wheat varieties (Chozi and Duma) evaluated. Morphological characterizations revealed significant difference in terms of yield, Mutant 2 had the highest mean grains per spike followed by Chozi then Mutant 1. Mutant 2 and Mutant 1 had shorter days to heading compared to Chozi and Duma varieties which means they mature earlier which is a good trait for drought tolerance. Hence, the two Mutant varieties can be candidates for commercial production in ASALs regions. It is recommended that the Mutant wheat be screened for other biotic and abiotic stresses that affect wheat production in Kenya.