Potential of Host Resistance, Trichoderma Spp. And Organic Amendments in the Management of Root-knot Nematodes in Tomato

Abstract

Tomato (Solanum lycopersicum) is among the most commonly grown and utilized vegetables in Kenya. Root-knot nematode (Meloidogyne spp.) infestation results in significant loss of crop yield in susceptible tomato varieties, if not managed. This study aimed to evaluate the effect of host resistance, cattle manure and Trichoderma used singly or as a combination in managing root-knot nematodes in the Kenyan coastal region. Experiments were conducted both under field and greenhouse conditions between February and November, 2013. Ten tomato cultivars were evaluated for resistance to the nematodes. Tomato cultivars Corazon F1 and Cal J were used as checks for resistance and susceptibility, respectively. In the greenhouse experiment, each cultivar was planted in six, two-liter plastic pots with a diameter of 15 cm. Pots contained moist, steam sterilized loamy soil and a pre-plant fertilizer. One thousand eggs/juveniles of Meloidogyne spp, suspended in 10 ml of water, were introduced into each pot two weeks after transplanting. Fully decomposed cattle manure was used at the rate of 2 kg in each m2. Trichoderma harzianum strain 22 with 1 x 107 cfu/ml was incorporated during transplanting at the rate of 10 ml per plant. Destructive sampling was done two months after inoculation to assess the galling index, nematode numbers, plant height, dry shoot and root weights. Second stage Meloidogyne juveniles, galls and egg masses were not detected in pots where tomato cultivar AVTO1209 was grown. The highest galling index of 5 and egg mass of 8 gram-1 of tomato root was recorded in tomato cultivar Cal J. The highest J2 population was recorded in Cal J followed by Bridgate40 at an average population of 19, 780 and 2, 794 per 100 g of soil, respectively. Based on the reproductive index (RI), cultivars AVTO1209, AVTO1210, AVTO1211, 3080, Galilia F1 and Shanty+N were highly resistant with an index of <10%. Tomato cultivars Corazon F1 and xiv Tengeru 97 were moderately resistant with RI between 11-25% while Bridgate40 was slightly resistant with RI of 28.13 and 40.91% in the first and second experiment, respectively. Cal J was susceptible with RI of 100%. Cattle manure amended plots showed significantly higher fresh and dry weight, length of shoot and root in cultivars Shanty+N, Tengeru, Cal J and AVTO1210 compared to the control. Significantly lower egg mass index (2.33) were recorded in plots amended with cattle manure + Trichoderma while control had the highest at 9.00. Among the soil amendments, cattle manure + Trichoderma recorded significantly lower J2 population (677), while control plot had the highest population (23, 000) in susceptible cultivar Cal J. The nematode densities were significantly reduced by application of a combination of resistant cultivar, cattle manure and Trichoderma. Cultivars with lower nematode densities were more vigorous and had higher shoot and root weight and lower galling indices which resulted in higher yields. Therefore, it is important to use combination of the management strategies to reduce the populations of nematodes in the soil and maximize yields in tomato production.