Assessment of germination and carnivorous activities of a nematode-trapping fungus Arthrobotrys dactyloides in fungistatic and fungicidal soil environment

• Arthrobotrys dactyloides was investigated for carnivorous activities in fungistatic and fungicidal soil.
• A. dactyloides was found a poor saprobe but an efficient nematode trapper in soils.
• Conidia bearing traps failed to grow in soil without capturing of nematodes.
• A. dactyloides found highly carnivorous to Meloidogyne spp. in vitro.
• Many fungicides found inhibitory to carnivorism of A. dactyloides in soil.

Carnivorism is the ability of nematode-trapping fungi to trap and digest the nematodes by sophisticated devices called traps. Delivery of nematode-trapping fungi in soil for bio-control of pest nematodes often fails or gives inconsistent results. Possible reasons for failure could be the effect of soil fungistasis on germination of nematode-trapping fungi in soil environment, use of avirulent species and sensitivity of these fungi to fungicidal residues in soil. Exploitation of nematode-trapping fungi for nematode control demands that it be compatible with fungicides applied in soil or crops and proliferate in soil. This investigation represents is one of the first to evaluate the effect of fungicides on the nematode-trapping fungus Arthrobotrys dactyloides. A. dactyloides showed in vitro carnivorous potential against Meloidogyne incognita, Meloidogyne javanica, Meloidogyne graminicola, Helicotylenchus dihystera and Heterodera cajani. Conidia of A. dactyloides exposed to agricultural soils showed poor germination but formed conidial traps, which captured and killed the soil nematodes. Conidial traps, which trapped the nematodes, grew well in all soils after killing and nutrient absorption from nematode body. Soil amended with 20 mg ai kg−1 of carbendazim and thiram, 30 mg ai kg−1 of mancozeb, 50 mg ai kg−1 of captan, and 100 mg ai kg−1 of carboxin completely checked the conidial trap formation and nematode capturing. 30, 50 and 100 mg ai kg−1 of metalaxyl adversely affected the conidial trap formation and nematode capturing in soil. Propiconazole inhibited 15.2% conidial trap formation up to 50 mg ai kg−1 but caused 93.3% inhibition of conidial traps formation and complete inhibition of nematode capturing at 100 mg ai kg−1. Sulphur, triademefon, and tricyclazole showed least toxic effect on conidial trap formation and nematode capturing activities of A. dactyloides in soil up to 100 mg ai kg−1.

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