Effects of indigenous arbuscular mycorrhizal fungi on growth of selected Carica papaya L. hybrids in Kenya

Abstract

Arbuscular Mycorrhizal Fungi (AMF) are naturally occurring root symbionts known to improve the uptake of essential nutrients by host plants due to their extra-radical hyphae. However, the effect of indigenous AMF inoculation on the growth of papaya hybrids has not been investigated. This study evaluated the effect of AMF inoculation on the growth characteristics of papaya hybrids (JKUAT and Malkia) at the vegetative stage. A greenhouse experiment consisting of three treatments—AMF inoculum, compost manure, and a combination of inoculum and compost manure—was set up in a completely random design and replicated six times. Non-treated seedlings were included as controls. Spores were isolated from rhizospheric soil samples and bulked in a potted sorghum crop for four months to obtain AMF inoculum. The treatments were applied to papaya seedlings between the second and third leaf stages. Growth parameters including plant height, leaf length, stem girth, and number of leaves were recorded every 4 weeks for a period of 20 weeks after planting (WAP). All data were subjected to one-way ANOVA at the p ≤ 0.05 level, with significant and nonsignificant means separated using Tukey's HSD test in Genstat's 15th edition. Results showed that plants treated with a combination of compost manure and AMF inoculum were significantly different (p ≤ 0.05) for all growth parameters tested, compared to compost manure alone and the control treatments. Malkia hybrids treated with a combination of compost manure and AMF inoculum (MIC) had the highest plant height of 53.2 cm at 20 WAP. JKUAT hybrids treated with AMF inoculum and composted manure and the control treatment had a root biomass of 49 and 11.80 grammes at 20 WAP, respectively. In conclusion, soil media amendment with compost manure and AMF inoculum enhanced overall papaya seedling growth, and the growth response was dependent on papaya hybrids.