Effect of some Macronutrients on the Root-knot Nematode, Meloidogyne javanica Activities in Eggplant (Solanum melongena L.)

Root-knot nematodes (Meloidogyne spp.) are among the most dangerous herbal parasites which destroy 8.8 to 14.6 percent of agricultural products annually. In vegetables, 50 to 80 percent damage caused by nematodes is normal. It is unavoidable to use safe methods for controlling root-knot nematodes. Plant parasitic nematodes can be inhibited using chemical fertilizers, which reduce the losses induced by plant parasites and increase total products. The aim of this study was to evaluate the effect of different levels of two macronutrients including nitrogen and phosphorous on the infection of M. javanica on eggplant (cv. Black Beauty) under greenhouse conditions.

In the current study, the levels of zero (N0), 50 (N1), 100 (N2), 200 (N3) mg nitrogen and zero (P0), 50 (P1), 100 (P2), 200 (P3) mg phosphorus per kg of soil were selected from nano-chelated nitrogen fertilizer and nano-chelated phosphorus fertilizer, respectively. The seeds of eggplant were planted in plastic pots containing 2 kg of culture media including equal amount of sand, farm soil and animal manure under greenhouse condition. The pots were irrigated daily and maintained at 27±4 °C with 16:8 h light: dark photoperiod. Four leaf stage seedlings were inoculated with five eggs and second stage juveniles of M. javanica per gram of soil, and 10 days after inoculation, different levels of fertilizers were added (100 ml per pot) to the pots through irrigation. Sixty days after inoculation, plant growth indices including shoot height, shoot fresh and dry weights and root fresh weight of the cultivated plants were recorded. Nematode population indices including number of galls and egg masses per root system, number of eggs in egg masses were also measured and finally the reproduction factor was calculated. The roots were gently washed with tap water and number of eggs in one gram of root were counted according to the procedure developed by Hussey and Barker (1973). One gram of root was stained with acid fuchsine according to the procedure developed by Byrd et al. (1983). The total number of eggs, galls and egg masses per plant root system was determined by multiplying with the root weight per plant. The final nematode population per pot was computed and finally, the reproductive factor (RF) of nematode was calculated by dividing the final nematode population by the initial nematode population (10000 eggs and second stage juveniles of M. javanica). Data on plant growth and nematode indices of the experiments were subjected to a factorial analysis of variance (Two-way ANOVA). Means were compared with least significant differences (LSDs) to identify significant difference at probability levels of P≤0.05 using SAS 9.1 software (Statistical Analysis System Institute Inc., USA) in a CRD (completely randomized design) with four replicates.

In nematode inoculated plants, the difference between shoot height and shoot fresh and dry weight of treated plants by phosphorus at the rate of 100 mg/kg soil and non-treated by nitrogen (N0P3) with control plants (N0P0) was significant. Similar results were observed in nematode inoculated plants treated by nitrogen and phosphorus at the rate of 50 and 100 mg/kg soil, respectively (N1P3), with nematode inoculated plants treated by nitrogen at the rate of 50 mg/kg soil and non-treated by phosphorus (N1P0), nematode inoculated plants treated by nitrogen and phosphorus at the rate of 100 and 100 mg/kg soil, respectively (N2P3), with nematode inoculated plants treated by nitrogen at the rate of 100 mg/kg soil and non-treated by phosphorus (N2P0) and also nematode inoculated plants treated by nitrogen and phosphorus at the rate of 200 and 100 mg/kg soil, respectively (N3P3), with nematode inoculated plants treated by nitrogen at the rate of 200 mg/kg soil and non-treated by phosphorus (N3P0) (P≤0.05). The results showed that using 100 mg nitrogen and 100 mg phosphorus per kg of soil from nano-chelated nitrogen fertilizer and nano-chelated phosphorus fertilizer, as the best treatment used in this experiment, decreased number of eggs, galls and egg masses per root system and reproduction factor of nematode by 53, 52, 62 and 55%, respectively. Therefore, nano-chelated nitrogen and phosphorus fertilizers, as two chelated fertilizers produced using nanotechnology, can decrease the population of M. javanica in eggplant cultivated in the greenhouse. Soil drenching of these water-soluble nano-fertilizers 10 days after infection of the eggplants by M. javanica can also reduce the population of nematode.