Amino acids and carbohydrates secreted by Meloidogyne incognita.

There is clear evidence that plantparasitic nematodes secrete numerous orgallic substances (4, 5). As a part of our studies of root exudates in Meloidogyne incognita-infected and uninfected tomato plants (8), a quali tat ive and quanti tat ive identification was made of the amino acids and carbohydrates secreted by larvae of M. ineognita. Second-stage larvae of M. incognita (Kofoid and White) Chitwood, collected from galled roots of gnotobiotic cultures of Lycopersicon esculentum Mill. 'Tecumseh, ' were surface-sterilized. Flasks, each containing 106 larvae in 300 ml sterile deionized water, were incubated in a shaker at 25 C for 48 h under monoxenic conditions. Water in which larvae had been incubated was passed through three layers of filter paper in a sterile sintered-glass filter to remove the larvae. Sterility was tested by plating 1 ml of incubation solution on PDA medium (8). Incubat ion solutions were further passed through a sterile Millipore (Bedford, Mass) filter (0.45 and 0.22 #m), concentrated in a rotary evaporator at 45 C, adjusted to p H 7, and passed ~equential ly through a column (1 × 4 cm) of Dowex 50 resin H + form and a column (1 × 4 cm) of Dowex 1 resin in formate form at a flow rate of 1 ml per 2 rain. (8). T h e effluent from the Dowex 1 column contained the neutral fraction (carbohydrates). T h e cationic fraction (amino acids) was obtained by eluting a Dowex 50 column with 2N NH4OH. Both fractions were evaporated to dryness at 45 C. T h e cationic fraction was redissolved in citrate buffer, pH 2.2, and placed in an amino acid analyzer (Beckman, model 120C) for qualitative and quanti ta t ive analysis of amino acids. The neutral fraction was redissolved in 38% isopropanol for two-dimensional