The Degeneration Of Metarhizium Anisopliae Presenting In Passage

The effect of Metarhizium anisopliae on biological control becomes more andmore evident. So we must research the degeneration of M. anisopliae for its extensiveuse. This paper aims to research the degeneration of 4 strains of M. anisopliaepresenting in passage. The results are as follows.(1) Rejuvenate and passage of four strains of M. anisopliae. After rejuvenationin ivio of host the spore yields much more and the growth rate become slower. Theresults also show that the spore yields of strains becomes fewer along with thepassage. There are some strains have no spore yield which suggested that the strainshave degenerated.(2) Measure the growth rate and spore yield. The growth rate and spore yield ofthe test strains have significantly difference on the anaphase of growth. The growthrate of strains becomes faster along with passage. At the same time the strain Mbpresents mycelium hypertrophy. The growth rate of the first generation is3.87±0.2465mm/d. Comparing with other generations the growth rate of the ninthgeneration represents significantly different is 4.8433±0.0408 mm/d. The spore yieldbecomes fewer and fewer along with passage. Spore yield of the strain 985 is5.06×10⁹/cm² in the first generation, and is 2.49×10⁹/cm² in the ninth.(3) Measure the virulence. The virulence of experimental strains is analyzed bythe time-dose-mortality model. All the passage strains can kill experimental insects.The LT₅₀ of the 15th generation of the strain 985 is 11.85d, which means its lowestvirulence. The significantly difference the 12th generation. So when using M.anisopliae, the strains after many generations should avoid.(4) Compare the isozyme of the different strains. The esterase isozyme ofdifferent subcultures showed same type of zymogram, but its activity decreasesobviously from generation to generation. Distinct genetic diversity among differentpassage generations, the figure of clustering analysis shows that the generationordering by passage. The genetic distance between the first generation and othersbecome longer from generation to generation. In all, more generation means moreaberrance in M. anisopliae. (5) RAPD analysis of DNA diversity. The genetic distances between 18thgeneration and the others are largest, while there similarities are engendered. Itsuggested that genetic variation has happened on the level on DNA.