Competition Between Tylenchorhynchus annulatus and Mesocriconema xenoplax on Grain Sorghum as Influenced by Macrophomina phaseolina

I. Wenefrida, J. S. Russin, E. C. McGawley


Greenhouse experiments were conducted to examine competition between Tylenchorhynchus annulatus and Mesocriconema xenoplax on grain sorghum roots that were colonized by the fungus Macrophomina phaseolina or free from fungus colonization. An incomplete factorial treatment design consisted of two levels of M. phaseolina (0 or 10 colony-forming units/g soil) and 12 T. annulatus:M. xenoplax ratios: 1,000:0; 750:0; 500:0; 250:0; 0:0; 0:250; 0:500; 0:750; 0:1,000; 750:250; 500:500; and 250:750. Plants were harvested after 105 days. Despite similar feeding habits, competition between these ectoparasitic nematode species was limited. Tylenchorhynchus annulatus was more susceptible to antagonism by M. xenoplax than the reverse, but susceptibility depended on initial inoculum ratio. Root colonization by M. phaseogina reduced competitive effects of T. annulatus on M. xenoplax but not the reverse. Both nematode species reduced shoot dry weight but only T. annulatus reduced root dry weight. Both plant weight parameters were reduced by M. phaseolina. Key wards: charcoal rot fungus, community ecology, competition, interaction, Macrophomina phaseolina, Mesocriconema xenoplax, nematode, ring nematode, Sorghum bicolor, stunt nematode, Tylenchorhynchus anulatus.

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