Resistance of local okra cultivars against Meloidogyne incognita (Kofoid & White, 1919) (Nematoda: Meloidogynidae), effects of nematode infestation on growth parameters and leaf macro- micronutrients

Okra is an important species of vegetable grown in Turkey and around the world. Root-knot nematodes cause serious yield losses in vegetables. Twenty-six cultivars okra were obtained from the Aegean Agricultural Research Institute in 2002. Resistance of this cultivars to nematode was determined and changes induced with nematode infestation on plant morphology and macro- and micronutrients in leaves measured. The experiments were conducted in completely randomized design with four replicates in climate-controlled glasshouse at Alata Horticultural Research Institute in 2019. The cultivars were tested against Meloidogyne incognita (Kofoid & White, 1919) (Nematoda: Meloidogynidae) at 25 ± 2ºC. Sixty days after inoculation, root gall indexes varied with an average of 4.56. Compared to uninoculated controls, nematode inoculated reduced plant height by 46.0%, stem thickness by 9.06%, root lengths by 39.7%, leaf widths by 15.1%, leaf lengths by 20.5% and increase root weight by 14.5%. Leaf macro- and micronutrients were determined. Compared to the control, nematode inoculation reduced leaf N, P, K and Mg concentrations by 2.31, 5.85, 5.24 and 10.3%, respectively, and increased Ca, Fe, Zn, Mn and Cu concentrations by 7.91, 17.0, 13.4, 118 and 15.6%, respectively. No studies similar to the present study have been reported, but a few studies examined plant growth parameters in okra, tomatoes and soybeans. In present study, effects of M. incognita inoculation on plant growth parameters were investigated. Compared to uninoculated control plants, root-knot nematode inoculation reduced plant height, stem thickness, root length, leaf width and leaf length but root weight was increased depending on gall formation. Kumar et al. (2012) investigated the effects of nematode inoculation on root length, shoot length, fresh and dry root weights and reported significantly effects. Root and shoot lengths were greater in control plants. Mean root length of the control and inoculated plants was reported as 40 and 32 cm, shoot length as 49 and 32 cm, root dry weights as 4.8 and 7.0 g and root fresh weights as 13.4 and 11.5 g, respectively. Odeyemi et al. (2016) reported M. incognita -induced reductions of between 13.7 and 75.6% in plant height, between 13.7 and 67.2% plant fresh weight and between 13.0 and 53.3% in fruit weight. In another study conducted on okra, Claudius-Cole (2018) reported mean number of fruits as 18.4 for control plants and 13.8 for M. incognita -inoculated plants; mean fruit weight as 167 g in control plants and 81.3 g for inoculated plants. Yield loss was reported as 51.4%. Pandey et al. (2019) reported (60 DAI) significant effects of nematode inoculation on plant length, plant diameter, root length and root diameter and reported. Plant length, plant diameter, root length and root diameter were greater in control plants in current study. Azam et al. (2011) examined M. luci infestation in tomatoes and reported decreased plant height and weights with increasing Pi density. Root-knot nematode symptoms in aboveground plant parts are reported to be stunted growth, chlorosis