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Title: TOWARDS UNDERSTANDING THE CHEMICAL TOXICITY OF RYE (SECALE CEREALE)AGAINST PLANT-PARASITIC NEMATODES

Author
item Zasada, Inga
item Meyer, Susan
item Rice, Clifford

Submitted to: American Phytopathological Society Potomac Division Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/16/2005
Publication Date: 4/22/2005
Citation: Zasada, I.A., Meyer, S.L., Rice, C. 2005. Towards understanding the chemical toxicity of rye (secale cereale)against plant-parasitic nematodes. American Phytopathological Society Potomac Division Meeting. APS publication no. P-2005-0038-PTA.

Interpretive Summary:

Technical Abstract: Cyclic hydroxamic acids are secondary metabolites found in the Poaceae and have been implicated in the allelopathy of rye (Secale cereale). The toxicity of these compounds against plant-parasitic nematodes is unknown. DIBOA (2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one) and DIMBOA (2,4-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one) and their degradation products BOA (benzoxazolin-2(3H)-one) and MBOA (6-methoxy-benzoxazolin-2(3H)-one) were screened against Meloidogyne incognita second-stage juveniles (J2) and eggs. The egg stage of M. incognita was less sensitive to the hydroxamic acids than the J2 stage; only DIBOA resulted in a 50% reduction in egg hatch, with a lethal concentration (LC50) of 74 microgram/ml compared to 21 microgram/ml for the J2 stage. When M. incognita J2 were exposed to DIBOA for 48 h and the compound was removed and replaced with water, the LC50 increased from 21.0 to 40.7 microgram/ml. MBOA was not toxic to M. incognita eggs, but was toxic to M. incognita J2, with LC50s of 44 and 20 microgram/ml before and after rinse. BOA was the least toxic hydroxamic acid tested; it did not reduce M. incognita egg hatch after one week of exposure. Knowledge of the toxicity of the chemical components of rye provides a valuable starting point for improving the utilization of this cover crop for plant-parasitic nematode suppression. This research demonstrates that rye should be incorporated into soil when the more hydroxamic acid-sensitive J2 stage is present in soil.