Physiological Variations in Cucurbita moschata Duch. Ex. Poir Due to a Nigerian Strain of Moroccan Watermelon Virus: Lagenaria breviflora Isolate

Aim: Physiological variations in Cucurbita moschata due to infection with a Nigerian strain of Moroccan watermelon virus (MWMV): Lagenaria breviflora isolate was studied.

Study Design: Randomized block design was used.

Place and Duration of Study: Botany Department, University of Calabar, Calabar, Nigeria between March and May, 2015.

Methodology: Seeds of C. moschata were sown, on germination inoculated with the virus and analyzed for possible variations between healthy and inoculated plants.

Results: Results analysis revealed increase in all amino acids investigated. Highest significant (P=0.05) percentage variation in amino acids of inoculated and healthy were -40.0% for aspartic acid, -36.1% (histidine), -29.7% (proline), -28.8% (lysine), -23.3% (glysine), -16.6% (phenylalanine) and -12.6% (glutamic acid). Infection of C. moschata with a Nigerian Strain of MWMV: Lagenaria breviflora isolate caused significant decrease in leaf nitrogen and relative water content of inoculated plants compared to the healthy. Highest percentage decrease in leaf nitrogen was 40.7% at 2 weeks after inoculation (WAI) and lowest of 25.0% at 10 WAI. The virus caused decrease in relative water content of 29.6% at 6 WAI. Activity of oxidative stress enzymes: peroxidase (POD) and polyphenol oxidase (PPO) and enzymes of the oxidative pentose phosphate pathway: glucose-6-phosphate dehydrogenase (6PGdH) and 6-phosphogluconic acid dehydrogenase (G6PdH) were significantly (P=0.05) increased in infected C. moschata- MWMV plant. Enzymes activity was significantly higher in inoculated than in healthy plants at all stages of growth with decrease at later periods for both inoculated and healthy plants. Percentage increase in POD, PPO, G6PdH and 6PGdH activity due to infection at 8 WAI had values of -40.5%, -46.7%, -98.9% and -89.1% respectively.

Conclusion: The Nigerian strain of MWMV: Lagenaria breviflora isolate caused significant variations with increase and decrease in biochemical and physiological components of C. moschata affecting its growth and yield.