Investigation of the effects of some plant activators against verticillium wilt (Verticillium dahliae Kleb.) on cotton

Wilt disease (Verticillium dahliae Kleb.) causes significant yield loss in cotton production. Alternative control methods are necessary for the control of the disease. The aim of this study is to determine the effects of some plant activators (auxiGRO, Green Miracle, Maxicrop, ProAct Plus and Sojall Vitanal) against Verticillium wilt and plant growth on cotton under both in vitro and growth chamber conditions. Firstly, the effects of various concentrations of plant activators (0, 1, 5, 25, 100, 250 ve 500 ppm) on mycelial growth of V. dahliae isolates (PHCVd3-non-defoliating pathotype, PHCVd47-defoliating pathotype) in potato dextrose agar (PDA) media were investigated in vitro. The effects of plant activators on V. dahliae were determined in varieties Carmen (tolerant) and Acala SJ2 (susceptible) in two different ways as seed coating and foliar application in the growth chamber. In addition, two isolates of the non-defoliating (PHCVd3 isolate) and defoliating (PHCVd47 isolate) pathotypes of V. dahliae were used in this study. The effects of plant activators on plant growth such as plant height, plant fresh weight, root length and root fresh weight in varieties Carmen and Acala SJ2 were determined in pot experiments. In vitro experiments were carried out with three replicates, and pot experiments were with five replicates depending on a completely randomized plots design. Maxicrop, Sojall Vitanal, ProAct Plus, Green Miracle and auxiGRO plant activators inhibited mycelial growth of PHCVd3 isolate by more than 90% at 500 ppm dose. Maxicrop (Ascophyllum nodosum seaweed) also inhibited 91.00% of PHCVd47 at 500 ppm dose. The lowest disease index value against PHCVd3 isolate in the Carmen variety by seed coating of auxiGRO (GABA+%29.2 L-Glutamic acid) was determined 1.43 and 2.09 and 2.12 against PHCVd47 in Sojall Vitanal (Lactobacillus acidophilus) and ProAct Plus (harpin protein), respectively. The lowest disease index values against both isolates were found as 1.42 and 2.18 in the Carmen by foliar application of ProAct Plus, respectively. Plant activators did not show any inhibitory effect on disease severity against both isolates in Acala SJ2. AuxiGRO (22.06 cm) at plant height, ProAct Plus (7.02 g; 24.40 cm) at plant fresh weight and root length, ProAct Plus (1.45 g) and Sojall Vitanal (1.41 g) at root fresh weight gave the best results in Carmen variety. Plant activators were statistically in the same group according to plant height, plant fresh weight and root fresh weight in Acala SJ2 variety and ProAct Plus (23.56 cm) showed the highest effect on root length.