Heterokaryosis, Genetic Diversity And A Comparison Of Parasitic Rates Of Different Isolates Of Paecilomyces Lilacinus

Plant parasitic nematodes are one of the important limiting factors in crop production throughout the world. Using chemical agents and nematicides cause many negative effect, while biocontrol can overcome these disadvantages. Paecilomyces lilacinus is one of nematophagous fungi which has been examined over the past two decades for potential use as agent for the control of plant pathogenic nematodes in agriculture. The facultative egg parasite is sometimes also able to infect larval and adult female nematodes, but it is most aggressive against eggs. Molecular tools can be effectively applied to discriminate biocontrol strains and assisted the selection of novel isolates for product development, which is also helpful to finding out the relationship between genetic variation and hosts and geographic distribution.This research include three parts. The first, heterokaryosis were tested between two monoconidial progenies from different isolates of Paecilomyces lilacunus. The second, 20 strains of Paecilomyces lilacinus from different geographic origins and other 4 species of Paecilomyces were studied by random amplified polymorphic DNA(RAPD). The third, thirteen isolates of Paecilomyces lilacinus originating from difference areas was used to assess their parasitism on eggs of Meloidogyne incognita by three treatments. The results are as follows.1. Heterokaryosis were tested between two monoconidial progenies from different isolates of Paecilomyces lilacinus. Heterokaryotic hyphae appeared as a solid line of white mycelial tufts where contact occurred between colonies of compatible isolates when they were paired on a modified peptone potato dextrose agar add medium containing 1% active carbon. A small mycelial fragment from the tufted zone was transferred to Petri dishes containing water agar and hyphal tip isolates were obtained from the resulting colonies.Thirty or more monoconidial isolates were further obtained from each hyphal tipisolate and plated on PDA in Petri dishes. The resulting cultures were compared with the two parental isolates that produced the tufted reaction. Heterokaryosis was demonstrated when different monoconidial isolates from hyphal tip cultures 459-8X 19-2, 459-7X 19-10, 459-6 X 19-1 were representative of both parental types and/or when new colony morphologies were recovered. One of 6 different combinations involving 4 different field isolates produced heterokaryons. Heterokaryons were formed at a frekuency of 12.25% between the monoconidial progeny of isolates 459 and 19.2. Tweety-one strains of Paecilomyces lilacinus from different geographic origins and other three species of Paecilomyces were studied by random amplified polymorphic DNA(RAPD). Distinct genetic diversity among 20 strains of Paecilomyces lilacinus were found. DNA fringerprinting with RAPD-PCR provides high resolution of genotype distribution. The cluster analysis showed that the genetic variations among different strains of Paecilomyces lilacinus are very distinct, intra-specific variation of P.lilacinus is larger the inter-specific variation between Paecilomyces farinosus and Paecilomyces fumosorseus. The results also indicated that genetic variations of different strians of Paecilomyces lilacinus are not related to geographic distributions.3. Thirteen isolates of Paecilomyces lilacinus originating from difference areas was used to assess their parasitism on eggs of Meloidogyne incognita by three treatments including individual eggs treated by spore suspension, individual eggs treated by fungus hypha and egg masses treated by spore suspension respectively. The results showed that egg parasitic rate differed significantly among 13 isolates and parasitic rate of the same one of all isolates differed in 3 treatments, in which parasitic rate of egg masses treated by spore suspension was more higher than that in other two treatments. In the three treatments, parasitic rate of isolate 618 among 13 isolates on egg masses of Meloidogyne incognita was the highest. Parasitic rates of different isolates are related to genoty...