Effects of Arbuscular Mycorrhizal Fungi and Trichoderma spp. on Nutrient Uptake and Water Stress Tolerance in Vigna unguiculata (L.) Walp. (Cowpea)
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Date
2024-07
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Kenyatta University
Abstract
In a bid to explore alternatives that mitigate effects of low water and nutrient supply for crops, the influence of arbuscular mycorrhizal fungi and Trichoderma spp. on cowpea growth and nutrient uptake at different soil water levels under greenhouse conditions was undertaken. Cowpea is an essential food crop for both humans and livestock. It’s a source of income in marginal areas and also adds nutritive value to the soil by fixing nitrogen. The experiment was arranged on a completely randomized design (CRD) with the three water levels treatment, of 90 % (no stress), 60 % (mild stress), and 30 % (severe stress) of field capacity (FC). Two cowpea varieties including KVU 27-1 and Katumani 80 (K80) that are commonly grown by farmers were used in each water level. Each water level was subjected to seven fungal inoculation treatments: I- Funneliformis mosseae (BEG 12), II- Rhizophagus irregularis (BEG 44), III- Trichoderma harzianum (Har), IV- Trichoderma asperellum (Asp), V- BEG 12 + BEG 44 (BB), VI- Har + Asp (HarS), VII- Har + BEG 12 + BEG 44 (HBB), and VIII- which was un-inoculated as control (C). Each experimental unit was replicated four times resulting in 192 pots. The variables measured included, plant height, chlorophyll content, Shoot Dry Weight, Root Dry Weight, Root Length, Leaf Area, Stem Diameter, Relative Water Content, Specific Leaf Area and root mycorrhizal colonization. The shoot tissue analysis was also done to determine the nitrogen (N), phosphorous (P) and potassium (K) contents. All data were subjected to a two-way ANOVA in R software version 4.2.1 to test levels of significance due to treatments and their interactions. Means that were significant at p ≤ 0.05 were separated using Bonferroni test. Results showed that all the growth parameters and the shoot nutrient content were statistically significant at (p ≤ 0.05) with soil water level treatment in both varieties. Water stress had a negative influence on growth and the shoot nutrient content. The fungal inoculants were significant on stem diameter (p = 0.006), relative water content (p = ˂0.001) and p = 0.002 for KVU 27-1 and K80 respectively) and Specific Leaf Area (p = 0.049) for KVU 27-1. The widest stem diameter was 0.4 cm in KVU 27-1 under Har and HarS fungal treatments. The highest Relative Water Content was 94 % in KVU 27-1 with the inoculation of HBB while the highest SLA was 657 g/cm2 in K80 with HarS inoculation. In addition, the interaction between water levels and fungal inoculations were observed in Stem Diameter, Relative Water Content and Specific Leaf Area. The combined inoculation of HarS and HBB had the greatest influence on the shoot nutrient levels for both cowpea varieties. The highest N and P shoot content were 3.7 % (in KVU 27-1) and 0.12 % (in K80) inoculated with HBB and HarS respectively. The highest K content was 2.7 % in both varieties inoculated with HarS. Mycorrhizal colonization increased with increase in soil water level with the highest root colonization percentage of 37.8 % at 90 % FC. From the study, the co-inoculation of HarS and HBB was the most appropriate to enhance growth and nutrient uptake in the cowpea varieties. Therefore, these two treatments are recommended to be incorporated on agricultural soils to enhance plant growth.
Description
A Thesis submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science (Plant Physiology and Biochemistry) in the School of Pure and Applied Sciences of Kenyatta University, July 2024.
Supervisor
Adelaide Mutune
Ezekiel Mugendi Njeru