In vitro Selection and Characterization of Drought Tolerant Somaclones of Tropical Maize (Zea mays L.)

Abstract

Somaclonal variation for drought tolerances of two Kenyan maize genotypes, KAT and PH01, were obtained from in vitro selection. Three-month-old calli derived from immature embryos were grown on N6 medium supplemented with mannitol or polyethylene glycol (PEG-6000) to find-out the appropriate concentrations of selection pressure. Calli were sequentially transferred to 3.28 and 5.28% mannitol or 18 and 20% PEG and maintained for 9 weeks. Survival percentage and regeneration capacities of selected and unselected calli were determined. It was observed that selected calli had lower survival and regeneration capacities than unselected calli. The result showed that survival percentages of maize calli grown in mannitol and PEG were 8.4 and 4.2%, respectively. Six plantlets were regenerated from mannitol-tolerant calli, while, only two plantlets were regenerated from the PEG tolerant calli. Plantlets were regenerated from selected calli at lower frequencies than those from unselected calli. To investigate the putative genetic basis of water stress tolerance, the mannitol tolerant PH01 somaclones designated MT JM1-01, MT JM2-01, MT JM3-01 and MT JM4-01 and the PEG tolerant clone, PT JM1-01, were further evaluated using RAPD. The assay with the decamers OP-07 and OPD-08 revealed that the water stress tolerant somaclones were genetically different from the controlled, unselected plants.