Metarhizium flavoviride
Introduction '''''Metarhizium flavoviride''''' is a Sordariomycete in the order Hypocreales and family Clavicipitaceae. The genus ''Metarhizium'' currently consists of 45 described species and are a group of fungal isolates that are known to be virulent against Hemiptera and some Coleoptera. ''M. flavoviride'' is described as its own species, but there also exists a variety of ''M. flavoviride'', which is ''M. flavoviride'' var. ''flavoviride''. Previously described varieties of ''M. flavoviride'' have been documented, however recent random amplified polymorphic DNA (RAPD) markers have assigned these varieties as new species. The reassigned species are as follows: ''M. flavoviride'' Type E is now ''M. brasiliense''; ''M. flavoviride'' var. ''minus'' is now ''M. minus''; ''M. flavoviride'' var. ''novozealandicum'' is now ''M. novozealandicum''; and ''M. flavoviride'' var. ''pemphigi'' is now ''M. pemphigi''.All species in the ''Metarhizium'' genus are entomopathogenic, infecting a variety of hosts ranging from those in the orders Coleoptera, Hemiptera, Diptera, and Orthoptera. Hosts are often agriculturally important pests. Historically, species in the ''Metarhizium'' genus have been distinguished from each other by morphological traits such as differences in conidial shape, color, and conidiogenous cells. These taxonomic morphological differences are mostly substantiated by allozyme analyses. However, recent studies indicate that using morphological characteristics is not an accurate method to distinguish between different ''Metarhizium'' species and their respective varieties, and instead, molecular and genetic techniques should be used.''M. flavoviride'' is mainly studied for its use as a biological control to reduce pesticide resistance in plants where hosts feed on, as well as to reduce the environmental impact of using pesticides on agricultural crops.As with other ''Metarhizium'' species, there has been interest in developing isolates into mycoinsecticides: with work carried out on rice insect pests during the 1970–80s. However, such isolates appear to be more difficult to mass-produce, so there has been less commercial activity than with other ''Metarhizium'' species. In light of new molecular techniques, we now know that references to this species for control of locusts (''e.g.'' in early LUBILOSA Programme literature) should apply to ''Metarhizium acridum''.
Description ''M. flavoviride'' conidia (spores) range in color from vibrant green to light grey-green. Conidiogenous cells are 7–11 μm long and clavate, broadly ellipsoid, or ovoid. Conidia are relatively slow to develop.
Distribution and habitat ''Metarhizium'' species and ''M. flavoviride'' have been isolated from multiple soil types from all types of climates across all continents (excluding Antarctica) and have been found to infect many different arthropods. ''M. flavoviride'' has been found in a wide range of soils, particularly in agricultural habitats; they are often found in soils associated with roots of plants where host pests feed on. Some data have supported the finding that undisturbed habitats with naturally occurring vegetation are more likely to support entomopathogenic fungi such as ''M. flavoviride''. It is of interest to continue research regarding the abundance and occurrence of ''M. flavoviride'' as it concerns using entomopathogenic fungi as a form of biological control.In the Shaanxi province in China, it was found that the richness of ''Metarhizium'' species decreased with increasing elevation.
Entomopathogenicity ''M. flavoviride'' is facultatively saprophytic. ''M. flavoviride'' can be free-living in soil or in the rhizosphere of plants in the absence of a host.''M. flavoviride'' infects mainly by penetrating the host through the cuticle and colonizes through the body cavity. The fungal propagule germinates, creates an appressorium, and generates a penetration peg which produces degradative enzymes that break down the cuticle. The fungal hyphae use the epicuticular waxes and lipids for growth. ''M. flavoviride'' secretes toxic secondary metabolites that facilitate infection of the hemolymph. Death of the host is caused by physical damage and loss of normal function.
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