Potential of Actinomycetes in Biological Control of Citrus Nematode and Some Pathogenic Fungi in in vitro condition

Citrus nematode، Tylenchulus semipenetrans has worldwide distribution and is one of the causal agents of dieback disease in citrus orchards. The infection by the nematode in association with secondary fungal pathogens affects plant growth adversely. In order to evaluate antagonistic effects of actinomycetes in control of the nematode and secondary pathogens، 30 infested soil samples were collected from rhizosphere of citrus trees in east of Guilan and west of Mazandaran provinces، Iran. As a result، 20 strains of actinomycetes were isolated using selective culture media and their effects on egg hatching and juvenile mortality of the nematode were evaluated. In another experiment، actinomycetes efficacy on plant pathogenic fungi including Fusarium oxysporum، Fusarium solani، Penicilium digitatum، Rhizoctonia solani، Pestaliopsis spp. Colletotrichum gleosporeides were also tested. The results of the first experiment revealed that eight actinomycets isolates having good antagonistic capacity، reduced egg hatching during seven days and caused juvenile mortality in four days. In the second experiment، six isolates showed the ability of control against plant pathogenic fungi. Streptomyces sp. IGM05 strain had the maximum ability in control of the plant pathogenic fungi while Streptomyces sp. IGM17 reduced egg hatching rate up to 37. 2% and juvenile mortality rate to 52. 4% and exhibited the highest potential of antagonism.