Evaluate The Effect Of Arbuscular Mycorrhizal Fungi And Rhizobacteria Inoculation On Performance Of Potato (Solanum Tuberosum)

Abstract

Production of potatoes in Kenya is threatened by diseases, lack of quality potato seeds and low soil fertility. The objective of the current study was to evaluate the contribution of arbuscular mycorrhizal fungi and phosphate solubilizing rhizobacteria inoculants on production of selected Irish potato cultivars Three greenhouse experiments were established and a follow-up laboratory study conducted. A pot experiment was established using three potato varieties using soil-coco peat based media inoculated with Pseudomonas spp and three strains of arbuscular mycorrhizal fungi (AMF). Bacterial wilt experiment was conducted using two potato cultivars inoculated with three strains of AMF and rhizobacteria, while a second experiment was inoculated with three rhizobacteria isolates in single, duo and triple inoculation, three organic amendments and unfertilized control while potato variety Asante grown under asceptic aeroponic conditions was inoculated with three AMF strains to assess their efficacy. The experiments were laid out in complete randomized block design. Performance was based on tuber number, weights, mineral contents, percent mycorrhizal colonization and disease severity. From the AMF and Pseudomonas experiment, the large sized (>5g) tubers was triple in G. mosseae, G. etunicatum and G. intradices + Pseudomonas while G. intradices and G. mosseae had the highest number of small sized (<2.5g) tubers compared to unfertilized control. G. intradices + Pseudomonas in Tigoni had 1.5 times P content than fertilized control. As for root colonization, Tigoni inoculated with Glomus etunicatum and Pseudomonas had the highest percentage (29%), while no mycorrhizal colonization was observed in all the three uninoculated varieties. Control of Bacterial wilt with AMF and rhizobacteria inoculants was successful in duo inoculates of G. intradice and Pseudomonas, G. etunicatum and Bacillus in clone 387164.4 and G. intradice and Bacillus for both

cultivars with 0% disease severity and tested negative for latent infection. The disease was more pronounced in Tigoni than in clone 387164.4. G. etunicatum+Bacillus had 40% more tuber weight than uninoculated and fertilized control. However, there was no variety treatment interaction on tuber number and mineral tuber content. The results from rhizobacteria experiment in control of bacterial wilt indicated disease suppression in all rhizobacteria inoculated treatment and poultry manure mainly in triple inoculation of Pseudomonas + Bacillus + Azoctobacter that also had the highest tuber weight and tested negative for latent infection in clone 387164.4. There was no effect of the microbial inoculants and organic amendments on tuber grades and on tuber phosphorus content. Glomus intradices had the highest percentage of root colonization of 63% compared to 43% in G. etunicatum while control was uncolonized in aeroponics experiment. G. intradices gave a 22% increase in tuber weight above the control. G. intradices, G. mosseae, G. etunicatum and control had 93, 84, 82 and 73 tubers per plant respectively Importance of AMF and rhizobacteria as biocontrols and biofertilizers especially when used in combination was demonstrated where, rhizobacteria enhanced nutrient uptake especially P through solubilzation and mineralization while mycorrhizal hypae increased the surface area for nutrient absorption thereby improving plant growth and yield. These beneficial microorganisms are therefore critical for sustainable agriculture as they may reduce the use of fertilizers, pesticides and other chemicals. There is, however, need to test these microorganisms in the field to determine their efficiency and effectiveness.