EFFECT OF AMMONIUM-NITRATE AND TIME OF HARVEST ON MASS-PRODUCTION OF PASTEURIA-PENETRANS

Pasteuria penetrans, a biological control agent for root-knot nematode s, has great potential for development as a bionematicide. Previous st udies have shown that high nitrogen levels affect the development of r oot-knot nematodes. The objectives of this study were to determine the effects of various levels of ammonium nitrate and of han;est time on development of P. penetrans. Five levels of ammonium nitrate (0.0, 0.2 , 0.4, 0.8, 1.6 g/pot) and five different harvest times (37, 44, 51, 5 8, 65 days after inoculation) were tested separately with six replicat es each for both experiments. Ammonium nitrate adversely affected the development of both M. arenaria race 1 and P. penetrans. A quadratic r elationship was established between the number of females per root sys tem and the nitrogen levels, Number of endospores per root system and number of endospores per female were negatively correlated with the ni trogen levels and decreased 1.1 million and 0.013 million, respectivel y, per 0.1 g ammonia nitrate increment. Numbers of endospores per fema le were correlated with the time of harvest. Endospores per female inc reased 0.031 million per 100 degree days increment based on a developm ental threshold of 17 degrees C. These results will be useful for the cultivation of P. penetrans.