Effect of Extract Concentrations of the Cyanobacterium Anabaena variabilis and Application Methods on Growth and Yield of Cucumber Infected with Cucumber green mottle mosaic virus (CGMMV)

• 1Zeayd Tareq Alangood & 2Maadh A. Al-Fahad

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This study aimed to evaluate the effects of different concentrations (50%, 75%, and 100%) of  Anabaena variabilis extract and application methods (seed soaking, foliar spraying, and soil drenching) on vegetative growth and yield traits of cucumber (Cucumis sativus) plants infected with Cucumber green mottle mosaic virus (CGMMV). The experiment was conducted using a randomized complete block design (RCBD) with three replicates. The selected concentrations were designed to represent a range from moderate to high levels in order to assess the dose–response relationship of the algal extract under viral stress conditions. Growth parameters, including plant height, leaf area, fresh and dry biomass of the vegetative parts, and fruit weight per ten plants at the first and second harvests, were recorded. Results revealed that the 75% concentration consistently produced superior performance across most traits. Plant height and leaf area reached maximum averages of 70.93 cm and 98.83 cm², respectively. Fresh and dry weights of the vegetative biomass peaked at 262.22 g and 79.44 g per plant with soil drenching, while fruit weight per ten plants reached 3436 g at the first harvest and 2429 g at the second harvest when applied via seed soaking. Foliar spraying and seed soaking also showed high efficiency, whereas the lowest values were observed at 50% concentration and in the infected control. Interestingly, the intermediate concentration (75%) outperformed both lower and higher concentrations, indicating that optimal plant responses were achieved at moderate levels, while higher concentrations did not necessarily enhance performance. This suggests that excessive concentrations may not improve efficiency and could potentially limit the positive effects of the extract. The intermediate concentration of A. variabilis appeared optimal for enhancing vegetative growth and yield under viral stress, likely by improving photosynthetic efficiency, nutrient uptake, and delivery of bioactive compounds. Overall, A. variabilis extract proved an effective biostimulant for mitigating the negative impacts of CGMMV on cucumber plants. Among the treatments, 75% concentration applied through foliar spraying or seed soaking was the most efficient in promoting growth, biomass accumulation, and fruit production. These findings highlight the potential of cyanobacterial extracts as sustainable biostimulants for enhancing productivity in cucurbit crops under biotic stress conditions.

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