Response of a wild-type and modern cowpea cultivars to arbuscular mycorrhizal inoculation in sterilized and non-sterilized soil

Abstract

Cowpea is an important crop that serves as a legume and vegetable source to many smallholder farmers in sub-Saharan Africa. Soil fertility is a significant limitation to its production thus; inoculation with beneficial soil biota such as arbuscular mycorrhizal fungi (AMF) could improve its performance. However, plant-AMF interaction could vary based on crop cultivar hence affecting overall crop production. The present study aimed at determining the effect of AMF inoculation and soil sterilization on root colonization and growth of a wild-type and three modern cowpea cultivars grown by smallholder farmers in Kenya. Potted cowpea plants were inoculated with a commercial AMF inoculum comprising of Rhizophagus irregularis, Funneliformis mosseae, Glomus aggregatum and Glomus etunicatum and maintained in a greenhouse for 40 days. After harvesting, mycorrhizal colonization, nodule number and dry weight, root and shoot dry weights, nitrogen (N,) phosphorus (P) and potassium (K) content were determined. Interestingly, the modern cultivars showed significantly (p < 0.001) higher root colonization, nodulation, shoot P and N compared to the wild-type cultivar. Moreover, a strong positive correlation between AMF root colonization and shoot P (r 2 D 0.73, 0.90, p < 0.001), AMF root colonization and shoot N (r 2 D 0.78; 0.89, p < 0.001) was observed in both sterilized and non-sterilized soil, respectively. Soil sterilization affected root colonization and growth parameters with plants grown in non-sterilized soil performing better than those grown in sterilized soil. This study provides major evidence that modern cowpea cultivars are still responsive to mycorrhizal inoculation suggesting that modern breeding programs are not deleterious AMF symbiosis.

Growth and nutrition of cowpea (Vigna unguiculata) under water deficit as influenced by microbial inoculation via seed coating

“…Consequently, plants adjust belowground C allocation contributing to the formation of a shorter mycorrhizal root system (Jacobsen, Smith, & Smith, ), relying on the fungal mycelium for nutrient uptake (Smith, ). In fact, there was a significant enhancement in shoot nutrient content (Table ), particularly N and P, which has also been described in other studies with inoculated cowpea (Boby, Balakrishna, & Bagyaraj, ; Oruru et al., ; Sanginga, Lyasse, & Singh, ; Yaseen, Burni, & Hussain, ). Still, this enhancement in nutrient content was not enough to result in greater yields, fact perhaps associated with the sink of carbohydrates of the fungal mycelium that the plant could not allocate to seed development and filling.…”

“…to the formation of a shorter mycorrhizal root system (Jacobsen, Smith, & Smith, 2002), relying on the fungal mycelium for nutrient uptake (Smith, 2000). In fact, there was a significant enhancement in shoot nutrient content (Table 2), particularly N and P, which has also been described in other studies with inoculated cowpea (Boby, Balakrishna, & Bagyaraj, 2008;Oruru et al, 2018;Sanginga, Lyasse, & Singh, 2000;Yaseen, Burni, & Hussain, 2011 and establishment increases the opportunity of seedlings to achieve a positive C and nutrient balance, which is crucial, especially under stress conditions (de Albuquerque & de Carvalho, 2003). Further studies are, therefore, needed to improve this limitation on the germination of cowpea seeds coated with AM fungi.…”

“…Cowpea is considered to be highly mycotrophic (Molla & Solaiman, ) which leads to enhancement of below and above ground biomass, nutrients accumulation, protein content and grain yield under different water regimes (Kwapata & Hall, ; Oliveira et al., 2017a; Oruru, Njeru, Pasquet, & Runo, ; Rabie, Aboul‐Nasr, & Al‐Humiany, ). However, our results showed that association between AM fungi and cowpea did not result in increased plant growth or seed yield (Tables and ).…”

Abundance of the arbuscular mycorrhizal fungal taxa associated with the roots and rhizosphere soil of different durum wheat cultivars in the Canadian prairies

“…However, the evidence that plant selection reduces the ability of crop plants to respond to the AM symbiosis is rather thin (Lehmann et al 2012 and references therein). Differences in plant D r a f t susceptibility to the AM symbiosis was found in many crop plants, such as tomato (Steinkellner et al 2012), cowpea (Oruru et al 2018), and durum wheat (Singh et al 2012), but this variation did not support the hypothesis of a negative effect of plant breeding on the AM symbiosis.…”

Using microbial seed coating for improving cowpea productivity under a low‐input agricultural system

“…Previous greenhouse studies reported benefits from AM fungi and PGPR, either inoculated by the conventional method (direct application in the soil) or through seed coating in cowpea performance. Nevertheless, there is still lack of information on the effect of AM fungi and PGPR, which can represent a significant barrier to up‐scale microbial applications .…”