Delivery of Inoculum of Rhizophagus irregularis via Seed Coating in Combination with Pseudomonas libanensis for Cowpea Production

Ying Ma,Inês Rocha,Miroslav Vosátka,Aleš Látr,Rui Oliveira,Helena Freitas

doi:10.3390/agronomy9010033

Abstract

Cowpea (Vigna unguiculata L. Walp) is an important legume grown primarily in semi-arid area. Its production is generally inhibited by various abiotic and biotic stresses. The use of beneficial microorganisms (e.g., plant growth promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF)) can enhance agricultural production, as these microorganisms can improve soil fertility and plant tolerance to environmental stresses, thus enhancing crop yield in an eco-friendly manner. Application of PGPB and AMF in large scale agriculture needs to be improved. Thus, the use of seed coating could be an efficient mechanism for placement of inocula into soils. The aim of this study was to evaluate the effects of the AMF Rhizophagus irregularis BEG140 and the PGPB Pseudomonas libanensis TR1 alone or in combination on the biomass and physiological traits of cowpea. Four treatments were set: (i) non-inoculated control; (ii) PGPB; (iii) AMF applied via seed coating; and (iv) PGPB + AMF applied via seed coating. Cowpea plants inoculated via seed coating with R. irregularis and those inoculated with R. irregularis + P. libanensis showed root mycorrhizal colonization of 21.7% and 24.2%, respectively. PGPB P. libanensis was efficient in enhancing plant biomass and seed yield. There was no benefit of single (AMF) or dual (PGPB + AMF) inoculation on plant growth or seed yield. The application of beneficial soil microorganisms can be a viable approach for sustainable cowpea production in precision agriculture scenarios.

Highlights

Abuse of agrochemicals in agriculture to meet the needs of a growing human population can deteriorate the overall ecosystem quality and compromise the environment and public health.Sustainable agriculture has focused on developing new practices including the use of beneficial microorganisms as a safe and eco-friendly tool for fostering food production without compromising ecosystems services
Inoculation with R. irregularis via seed coating resulted in 21.7% and 24.2% root length colonized (RLC) in plants without and with PGPB, respectively (Figure 1)
No arbuscular mycorrhizal fungi (AMF) colonization was detected in the roots of non-mycorrhizal plants, indicating that there was no fungal cross-contamination among pots of different treatments

Summary

Introduction

Sustainable agriculture has focused on developing new practices including the use of beneficial microorganisms as a safe and eco-friendly tool for fostering food production without compromising ecosystems services. Beneficial microbes, such as arbuscular mycorrhizal fungi (AMF) and plant. Agronomy 2019, 9, 33 growth promoting bacteria (PGPB), representing a key functional interface between plant roots and soils, are considered as natural biofertilizers, due to their ability to exert direct and indirect beneficial effects on soil quality and structure, crop growth and quality, abiotic (e.g., drought, salt, metals and extreme temperature) and biotic (e.g., phytopathogens) stress resistance, and agricultural sustainability [1,2,3,4,5]. Root colonization by AMF is a prerequisite for the success of inoculum application, since it is a critical process in establishment of plant–microbe association [10]

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