510
publication). The isolates enhanced plant growth and macro- and micro-nutrient
uptake in maize plants. The use of multinutrient-solubilizing microorganisms is
advantageous over single-nutrient solubilizers in terms of cost and application.
4.3.2 Arbuscular Mycorrhizal Fungi (AMF)
AMF are associated with most agricultural crops, and occur over a wide range of
habitats from aquatic to desert environments. These fungi are obligate symbionts
and belong to genera such as Endogone, Glomus, Entrophospora, Gigaspora,
Acaulospora and Scutellospora. AMF have been associated with increased plant
growth and the enhanced accumulation of plant nutrients, mainly phosphorus, zinc,
copper and sulfur, through greater soil exploitation by mycorrhizal hyphae.
Maximum root colonization and sporulation occurs in soils with low phosphorus.
The beneficial effects of AMF inoculation on plant growth and yield have been
reported in stressful environments. However, the response may vary with soil type,
soil fertility and AMF culture (Nadeem et al. 2014 ). In dryland agriculture, many
researchers have reported improved plant growth and nutrient acquisition in differ-
ent crop plants due to mycorrhizal application (Table 3 ) singly or in combination
with PGPR. There is considerable demand for this product from farmers, but the
major constraint to upscaling the technology is the inability to produce clean, pure
inoculum as they are obligate symbionts.
4.4 Biocontrol Agents
The role of microbial biocontrol agents for the control of plant pests is well docu-
mented. Biocontrol agents control the growth and spread of plant pathogens through
various mechanisms including competition for space and nutrients, antibiosis
through the production of antagonistic metabolites such as hydrogen cyanide, sid-
erophores, ammonia, lytic enzymes and induced systemic resistance. Trichoderma,
Pseudomonas and Bacillus are among the important genera exploited as biocontrol
agents in agriculture. In addition, biocontrol properties of Cyanobacteria have been
recently reported. In the current scenario of deteriorating soil health and emerging
plant pests with the changing climate, the use of broad host-range biocontrol agents
as an environmentally-friendly means to control plant pathogens is highly relevant.
Leo Daniel et al. ( 2011 ) reported a significant reduction in root rot incidence and
increased yield by inoculating rainfed mungbean (Vigna mungo) with T. viride. The
positive effects of using biocontrol agents have been observed in other dryland
crops (Table 3 ) indicating their potential application in dryland agriculture.
M. Grover et al.