Nematicidal activity of Pseudomonas spp. against citrus nematode (Tylenchulus semipenetrans)

Abstract

Citrus slow decline caused by Tylenchulus Semipenetrans is a common disease deteriorating both quality and quantity of citrus fruits. The need to assess the citrus nematode population in citrus orchards is of fundamental importance in designing suitable management strategies. Population densities of nematode were assessed in different age groups and in different genera of citrus crops. Orchards reaching to the age of 20 years were most infested by T. semipenetrans as compared to new established orchards and very old orchards. Kinow genus was the most infested by nematodes as compared to sweet orange, fruiter and grapefruit. Plant parasitic nematodes are commonly managed by chemical control due to its rapid results but it is toxic to human health, causes resistance development in pathogens and exerts harmful effects on environment. So, there is a need of an alternatives to these noxious chemicals because world is shifting to organic farming. Bacterial isolates were collected from citrus rhizosphere and subjected to biochemical characterization. Nematicidal activity of isolates against citrus nematode was screened in laboratory conditions. Out of total 41 tested bacteria, 20 (48.5 % of total) displayed more than 50 % nematicidal activity against T. semipenetrans, among which 2 isolates CA26 and CA41 exhibited nematicidal activity more than 80%. Culture filtrate of tested bacteria also reduced the population of nematode. 5 strains from total tested bacteria exhibited nematicidal volatile effect on T. semipenetrans. Bacterium degrades multiple tissues of nematode body including, pharynx, intestine, cuticle, stylet, esophagus lobe and reproductive system of nematode