Potential of Deploying Indigenous Fungi in the Management of Potato Cyst Nematodes (Globodera Spp.) on Potato in Nyandarua County, Kenya

Abstract

In Kenya, the second important food crop after maize is potato Solanum tuberosum L. whose production is severely constrained by inadequate certified seeds, pests and diseases. Among the pests, potato cyst nematodes (PCN) are the major plant parasitic nematodes. The objective of this study was to enhance potato production by developing an effective management option for PCN through adoption of indigenous fungi in Kenya. Soil samples were collected from potato growing areas in Nyandarua, Nakuru, Meru, Nyeri, Kericho, Nandi, Kiambu and Bungoma Counties between March and May 2017 for cyst extraction. The In vitro tests and greenhouse experiment were conducted at Kenyatta University and field experiments at Kwa Haraka and Engineer in Nyandarua County. Field experiments were conducted between June 2018 and February 2019 while greenhouse was conducted between December 2018 and July 2019. Completely randomized design was used for laboratory and greenhouse experiment while randomized complete block design was used for field experiment in 4 replicates. Fungi were isolated from cysts of PCN by plating them on Potato Dextrose Agar and their effect on juvenile mortality determined. Trichoderma atroviride, T. atrobrunneum, T. tomentosum 1 and 2, bionematon and control were used as treatments in greenhouse and field experiments. Treatments were applied by soil drenching at planting, 30 and 60 days after planting. Data on plant height, root length, dry root and shoot weight, potato yield and nematode population were determined in vivo. Data was analyzed using Analysis of Variance with SAS version 9.2. Means were separated using Fisher’s Least Significance Difference at P≤0.05. Eighty fungal isolates from nine genera were isolated from cysts and there was a significant (P<0.05) difference among the isolates on juvenile mortality. Juveniles treated with P. lilacinum, T. atroviride T. tomentosum 1, T. tomentosum 2 and T. atrobrunneum revealed highest mortality rates of 98-100 %. All fungal isolates significantly enhanced potato growth and yield and reduced nematode population compared to the control in the greenhouse and field. Fungal isolates reduced juvenile population by 6- 43% and 9- 39% under field conditions in Kwa Haraka and Engineer sites, respectively. In the control, an increase of 80- 104% in juvenile population was recorded. Trichoderma tomentosum 2 and T. atroviride recorded the least PCN reproduction factor of 0.4- 0.7 while the untreated control recorded the highest of 1.8-2.4 in the field. Trichoderma atroviride and T. tomentosum 2 signficantly increased yield by 200% -900% in the field and 46- 58% in the greenhouse. Trichoderma atroviride and T. tomentosum 2 were the most effective in reducing PCN populations hence should be formulated and commercialized for their management.