Effects of entomopathogenic fungus Metarhizium anisopliae on alfalfa growth promotion and anti-aphid induction
To determine the role of entomopathogenic fungus Metarhizium anisopliae in promoting plant growth and improving plant resistance,alfalfa(Medicago sativa)was planted in soil mixed with M.anisopliae.Several growth parameters of the alfalfa plants were measured in the laboratory,along with the feeding selectivity,development,and fecundity of the aphid Therioaphis trifolii.The results showed that plant height significantly increased by 0.87 cm compared to the control group after seven days of fungal treatment.After 14 days,the number of branches was 3.88 and root length was 54.67 mm,both significantly higher than in the control group.When 14-day-old plants were exposed to aphids,the branch count and root length continued to increase,significantly exceeding the control group by the time the plants were 28 days old.Meanwhile,biomass,chlorophyll,and carotenoid content also increased to varying extents.A selective test showed that the aphid numbers on alfalfa leaves treated with the fungus decreased significantly by 28.57％compared to the control group within 24 h of testing.Feeding aphids with leaves from the fungus-treated plants delayed development of the 1st to 4th instar nymphs and shortened adult lifespan by 30.09％,resulting in a significantly reduced total lifespan com-pared to aphids in the control group.This study suggested that M.anisopliae promotes alfalfa growth and enhances its resistance to aphids through increased damage tolerance,antixenosis,and antibiosis.
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