Non-Enzymatic antioxidant responses of landraces and improved drought tolerant varieties of maize (Zea mays L.) to water stress

Abstract

Maize (Zea mays L.) is a cereal crop with enormous agronomic and economic importance. However, the production of maize is severely affected by drought which limits its yield. Improvement in drought tolerant maize varieties with antioxidant capacity can have substantial impacts on maize productivity. This study determines the antioxidant contents; ascorbic acid, β-carotene, flavonoids, as well as lipid peroxidation values of three maize varieties (TZM 1422, TZM 219, and Sammaz 40) subjected to different levels of water stress at vegetative stage of growth in a screen house. There was significant increase (p<0.05) in the ascorbic acid contents and β-carotene contents of all the varieties with increase in the severity of the stress at day 15 of the experimental period. High ascorbic acid contents was measured on day 15 for the improved variety (35.94±0.02 mg/100g Fw) at 50% field capacity. At 25% field capacity of day 30, there was significant increase in the ascorbic acid content of both varieties but the improved (Sammaz 40) variety has the highest content (38.17±0.03 mg/100gFw) compared with the landraces .The landrace (TZM 219) had higher contents of β-carotene (0.86±0.01 mg/100g Fw) at 25% field capacity of day 15 of the experimental period than the improved variety with a mean of (0.65±0.02 mg/100g Fw) at day 30. There was significant increase (p<0.05) in the flavonoids contents of all the varieties with increase in the severity of the stress on day 15 of the experimental period, with landrace (TZM 1422) having the highest flavonoids contents at 25% field capacity (54.67±0.67 mg QE/g Fw) than the improved variety (44.00±1.15 mg QE/g Fw). There was significant increase (p<0.05) in the lipid peroxidation values of all the varieties except at day 15 when there was significant decrease (p>0.05) in the landrace and increase in improved variety. Landrace (TZM 219) has the lowest value of lipid peroxidation at day 30 at 25% field capacity (1.94±0.04 nmol/g Fw). This study showed that the landraces had higher contents of ascorbic acid, β-carotene, flavonoids and low value of lipid peroxidation compared to the improved variety in response to water stress, an indication of good antioxidant potentials for improvement of drought tolerance in maize cultivars.