Effect of selected endophytic fungi and resistant tomato cultivars on meloidogyne spp. in the Coastal Region, Kenya
Kibunja, Joyce Wambui
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Tomato production in Kenya, especially in the coastal region has remained low due to pests and diseases attack especially Meloidogyne spp. (root-knot nematodes) which is a serious threat. A study was therefore conducted in the coastal region of Kenya with the aim of sourcing for endophytic fungi (EF) which could be used alongside moderately resistant tomato cultivars to manage Meloidogyne spp. Pathogenecity test of these isolates was carried out in the screenhouse using cv. Cal J. In vitro activity of two isolates against Meloidogyne spp. second stage juveniles (J2s) was also studied. Screenhouse and field trials were carried out to determine the effect of Trichoderma spp. on growth of tomato cultivars Kilele and Cal J (local cultivars) Hawaii, Okistu, Nug, (Asian Vegetable Research and Development Centre-AVRDC) compared to untreated control under Meloidogyne spp. infestation. Tomato cultivar Cal J and Kilele were used as susceptible and resistant local check, respectively. These trials were laid out in a randomized complete block design (RCBD) replicated four times. All experiments were terminated 60 and 90 days after transplanting in the screenhouse and the field, respectively. Data on plant growth and Meloidogyne spp. infestation was recorded. Effect of Mocap®, a synthetic nematicide on Trichoderma spp. was also evaluated.Thirty nine (39) endophytic fungi were isolated from tomato roots and identified to belong to 4 genera (Trichoderma, Fusarium, Alternaria and Aspergillus spp.) using morphological characteristics. Of these, Fusarium spp. was the most prevalent endophyte (77%) among the identified fungi followed by Alternaria spp. Isolated Trichoderma spp. caused a mortality of 48% that was significantly higher from untreated control (3%). Trichoderma isolate caused more growth and higher mortality which resulted in its selection for use as a biocontrol agent against Meloidogyne spp. in tomato crops, alongside a resistant cultivar in the screenhouse and in the field. Galling index (GI), egg mass index (EMI), J2 and reproductive factor (RF) differed significantly between the cultivars. In the screenhouse and the field the shoot height and root length were not significantly different from the untreated control. However, the shoot and dry root weight of treated plants were significantly higher (p≤ 0.05) from the untreated control. One of the cultivars from AVRDC (Okistu) had the highest yield followed by cv. Kilele. Cultivar Kilele had the least GI and EMI followed by cv. Okistu in all treatments. Cultivar Cal J was highly susceptible followed by cv. Hawaii and Nug. Plants treated with Trichoderma spp. before inoculation with Meloidogyne spp. had less number of J2s and lower reproduction which was significantly lower from untreated inoculated plants. Results revealed that the non systemic nematicide had no significant inhibitory effect on Trichoderma spp. A combination of Mocap® with commercial Trichoderma harzianum led to a significant decline in number of J2s compared to the other treatments.