Promotion of Growth and Yield in Cucumber by Zoysiagrass Rhizosphere Fungi

Abstract

Nine fungi belonging to the Phoma sp. and one non-sporulating fungus from zoysiagrass rhizospheres were tested for their ability to promote the growth of cucumber plants (cv. Aodai kyuri, Jibai, Ochiai fushinari, and Shogoin fushinari) at 4 weeks after planting in a growth chamber. The fungal isolates were introduced individually into natural soil in barley kernels (2%, w/w). The result indicated that plant dry biomass rather than plant length was increased by all the fungal isolates and the increase was cultivar-specific. Isolates GS8-1, GS8-2 and GS8-3 which had a consistent growth-promoting effect on both the height and dry biomass of all cultivars and GU21-2, which had less of an effect on growth and yield, were further tested for their ability to promote growth of a popular cv. Jibai until 10 weeks in the greenhouse and field. All isolates significantly increased plant length and plant dry biomass at 6 and 10 weeks after planting, and the number of leaves and cucumbers produced at 10 weeks in the greenhouse. In the field, these isolates were also effective in promoting growth and increasing yield at 6 and 10 weeks. The number and fresh biomass of marketable cucumbers produced at 6 weeks was significantly high in comparison to that of untreated controls. At 10 weeks after planting, the number of marketable cucumbers was significantly increased by isolates GS8-3 and GU21-2, while the fresh biomass of marketable cucumbers was significantly increased by all four isolates. GS8-1, GS8-2 and GS8-3 were isolated from roots of cucumber (cv. Jibai) even at 10 weeks after planting in both the greenhouse and field experiments. GU21-2 was not isolated from cucumber roots. It is suggested that the increased absorption of mineral nutrient by plants following the colonization and degradation of barley kernels by fungal isolates and the association of fungal isolates with roots might lead to enhanced plant growth and increased yield. © 2005, Japanese Society of Microbial Ecology · The Japanese Society of Soil Microbiology. All rights reserved.