Mycorrhizal Fungi Associated with Aspilia pluriseta And Phosphorus Availability on Sorghum Growth
Muchoka, James Peter
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Global reserves of phosphorus (P) are continually getting depleted and this poses an enormous challenge to food production. Phosphorus is one of the major limiting nutrients for plant productivity. Use of plant-mycorrhizal fungi in relation to replenishing phosphate is one of the biological techniques being considered. In this study, the association of Aspilia pluriseta Schweif. with mycorrhizal fungi and their role in promoting growth and enhancing P availability to gadam sorghum (Sorghum bicolor L.) was investigated. The main objective of this study was to determine effects of mycorrhiza in the rhizosphere of Aspilia pluriseta on growth and phosphorus availability to sorghum crop. The samples were taken from Tunyai and Gakurungu in Tharaka Nithi County and Kanyuambora in Embu County, Kenya. Soil samples were taken at depths 0-20cm, 21-40cm and 41-60cm. This was followed by greenhouse experiments at the University of Embu. The experiments involved use of potted plants with four treatments; Aspilia pluriseta vegetation covered soils; soil textural types; soil depth and mycorrhiza fungi inoculated gadam sorghum seeds. The treatment combinations were carried out in a series of two experiments on a completely randomized block design on a factorial model replicated thrice. Data obtained was subjected to ANOVA using SAS Edition 9.2 and differences between treatment means examined using Least Significant Difference (LSD) at p≤0.05. Illumina sequencing method was used on the Internal Transcribed Spacer (ITS) region on the total soil community DNA to capture the genetic fungal community within the rhizosphere. Analysis of Operational Taxonomic Units (OTUs) was done using QIIME 1.8.0 and taxonomic classification done using BLASTn on SILVA 119 database. Programming software, R was used for hierarchical clustering. The study shows that sorghum perfomed better where its seeds were inoculated with mycorrhiza-soils previously inhabited with Aspilia pluriseta vegetation. Spore counts varied significantly among silty clay, silt loam and sandy loam soils. The spore morphotypes was significantly higher at p≤0.05 for soils inhabited by Aspilia pluriseta compared to those not habited. Three hundred and seventy-three (373) OTUs were found at 3% genetic distance. Thirty-five fungal taxa were recorded in the rhizosphere of Aspilia pluriseta. The soil had five main phyla; Glomeromycota (90.7%), Basidiomycota (3.7%), Ascomycota (3.4%), Chytridiomycota (1.5%), and unspecified phylum fungi (0.7%). The genera Glomus was the most prevalent in all soil depths. The association of Aspilia pluriseta and mycorrhiza gave sorghum yield of 15.2 g per 1000 grains compared to yield of 13.1 g per 1000 grains in soils that did not have Aspilia pluriseta mycorrhiza association. This was a yield increase of 16%. Differences between gadam sorghum yields in Aspilia pluriseta soils and gadam sorghum seeds inoculated with mycrorihza spores was significant at p≤0.05 This study therefore, recommends use of Aspilia pluriseta in improving sorghum yield.