Abstract
The effect of phosphate fertilization on arbuscular mycorhizal symbiosis and grain yields of soybean cultivars was investigated on P deficient soil. A two-year field study (2017-2018) consisting of two soybean cultivars (TGx 1448-2E and TGx 1440-1E) and three phosphate rates [0, 20 and 40 kg P2O5 ha-1) was laid out in a randomized complete block design with three replications. The results showed that P fertilization significantly (p < 0.001) reduced AMF root colonization of both cultivars in the two cropping years. The arbuscular, vesicular, internal hyphae and total colonization in the root cortex of the soybean cultivars were significantly (p < 0.001) reduced with high P (40 kg) application. However, moderate P (20 kg) promote AMF symbiosis in roots of ‘TG x 1448-2E‘. Dry mass (root and shoot), P uptake and grain yield of the soybean cultivars were significantly (p < 0.001) increased with increasing P ferilization. There was a strong linear relationships between root colonization and total dry matter mass (r = 0.81), P uptake (r = 0.81) and grain yield (r = 0.85). Thus, it could be concluded that moderate P fertilizer application is needed to promote mycorrhizal symbiosis in soybean and sustainable crop production in humid tropical soil.
Highlights
Arbuscular mycorrhizal fungi (AMF) belonging to the phylum Glomeromycota form symbiotic relationships with roots of most terrestrial plants, inculding most agricultural crops (Smith and Read, 2008)
This study hypothesized that: 1) phosphate fertilization would influence the development of AMF symbiosis in roots of the soybean cultivars, 2) AMF symbiosis in soybean would be regulated by varietal difference between the soyean cultivars, and 3) assuming the soybean cultivars differ in terms of dry matter accumulation and P uptake, root colonization of the cultivars will be different
The difference observed in root colonization between the two cultivars can be explained by the nutrients demand, P and carbon supplied from the cultivars, allowing both symbiont partners to adjust the symbiosis (Kiers et al, 2011)
Summary
Arbuscular mycorrhizal fungi (AMF) belonging to the phylum Glomeromycota form symbiotic relationships with roots of most terrestrial plants, inculding most agricultural crops (Smith and Read, 2008). The mediated improvement in nutrients uptake by AMF helps to increased growth and development of plants, and confer resistance to abiotic and biotic stress (Smith and Read, 2008; Gianinazzi et al, 2010). Root colonization of oil-seed crops including soybean by native AMF taxa has been reported earlier (Adeyemi et al, 2019). In Nigeria, little attention has been paid to development of AMF symbiosis of native taxa under different phospahte fertilization (Sakariyawo et al, 2016; Adeyemi et al, 2017, 2019, 2020). The objective of the present was to investigate how phosphate fertilization regulates arbuscular mycorhizal symbiosis, dry matter accumulation, P uptake as well as grain yield of soybean cultivars on P deficient soil in a humid tropical soil of southwest Nigeria. This study hypothesized that: 1) phosphate fertilization would influence the development of AMF symbiosis in roots of the soybean cultivars, 2) AMF symbiosis in soybean would be regulated by varietal difference between the soyean cultivars, and 3) assuming the soybean cultivars differ in terms of dry matter accumulation and P uptake, root colonization of the cultivars will be different
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