Vahabi S, Charehgani H, Abdollahi M, Rezaei R (2021) Response of eight melon cultivars to Meloidogyne javanica. Plant Pathology Science 10(2):65-73.       Doi: 10.2982/PPS.10.2.65.

 Introduction: The Root-knot nematodes (Meloidogyne spp.) are one of the most damaging plant pathogens with a wide host range and cause major losses to agricultural crops. The use of resistant cultivars is considered a safe, economical, and effective method to control these nematodes. Materials and Methods: In the present study, eight melon cultivars namely Ahlam, 105, Tracey, Ronak, Deltagrin, Mac, Holar, and Veno were evaluated for their response to M. javanica. The seeds were planted in 2 kg pots and maintained under natural conditions in Khormuj city, Bushehr province. Seedlings at the four-leaf stage were inoculated with 5000 eggs and second-stage juveniles. The factorial experiment was conducted in a completely randomized design with five replicates. Sixty days after nematode inoculation, the plants were harvested and the plant growth and nematode population indices were evaluated. Results: The results showed that the nematode reproduction factor was significantly lower in Ronak, Deltagrin, and Veno than in the other cultivars. No significant difference was observed in shoot fresh weight of nematode inoculated and non-inoculated plants of Ronak cultivar. Conclusion: Ronak, Delta-green and Veno cultivars are less susceptible to M. javanica.

DL-β-amino-n-butyric acid (BABA) induces resistance in plants against root-knot nematodes (Meloidogyne spp.) by activating natural defense mechanisms. This study evaluated the effect of BABA on the resistance of okra (Abelmoschus esculentus cv. Clemson Spineless) to M. javanica under greenhouse conditions. Seeds were sown in 1 kg plastic pots and maintained at 27 ± 3℃ under a 16:8 hours of light-dark cycle and with daily irrigation. At the four-leaf stage, seedlings were foliar-sprayed with BABA at concentrations of 0 (control), 0.5, 1, and 2 mM. After 24 hours, plants were inoculated with M. javanica at initial population densities of 0 (control), 1, 2, 4, and 8 second-stage juveniles (J2s). Sixty days post-inoculation, plant growth and nematode reproduction indices were assessed. Results showed that higher BABA concentrations significantly improved plants growth and reduced nematodes populations. Plants treated with 2 mM of BABA and inoculated with 8, 4, 2 and 1 J2s showed increases in shoot length by 43.9%, 45.1%, 32.5%, and 32.2%, respectively; shoot fresh weight by 37%, 38.2%, 69%, and 61.5%; and shoot dry weight by 23.5%, 24.5%, 37.4% and 39.7% compared to untreated control. Meanwhile, the nematode reproduction factor decreased by 25.1%, 25.9%, 14.1% and 38.4%, respectively. This study demonstrated that BABA application improves okra growth against M. javanica. Although BABA had no significant effect on the reproduction factor at the highest nematode population level, all concentrations improved plant growth, even under severe nematode pressure. Foliar application of 2 mM BABA effectively enhances okra resistance to M. javanica under greenhouse conditions.