Chemotaxis of <i>Meloidogyne incognita</i> in Response to Different Salts

Abstract

The chemotactic responses of Meloidogyne incognita were studied in salt gradients in an agarose gel. Forty-eight combinations of sodium, copper, cesium, manganese , barium, potassium, ferric or ammonium cations and chloride, nitrate, sulphate, hydrogen-phosphate, bicarbonate, acetic acid, thiocyanic acid and hydroxyl anions were tested at six concentrations from 0.0625 × 10 -2 to 2 × 10 -2 mol · L -1 . M. incognita was repellented to salts that included Cl - and SCN - . Other salts that comprised the same anions had different chemotactic responses, among which M. incognita was repellented to ammonium salts that included Ba(NO 3 ) 2 , NH 4 NO 3 , Mn(NO 3 ) 2 , and hydrogen-phosphate salts that included KH 2 PO 4 , K 2 HPO 4 , and bicarbonate salts that included Na ₂ CO 3 , K ₂ CO 3 , (NH 4 ) ₂ CO 3 , KHCO 3 , and hydroxyl salts that included KOH, NaOH, and organic acid that included C 2 H 4 O 2 , C3H 6 O3 and C 4 H 6 O 6 . The repellent or attraction properties of different salts having the same cations were not consistent. The order of repellence was SCN - > NO 3 - > Cl - > OH - > CO 3 2- > H 2 PO - 4 > organic acid > SO 4 2- . The chemotaxis of nematodes to KCl, Ba(NO 3 ) 2 , NH 4 NO 3 , Mn(NO 3 ) 2 , (NH 4 ) 2 CO 3 , CH 3 COOH and C 4 H 6 O 6 increased with the increasing concentration, while the concentration of other salts tested did not influence nematode chemotaxis significantly.