title: Effects of Tomato Root Exudates on Meloidogyne incognita.
abstract: Plant root exudates affect root-knot nematodes egg hatch. Chemicals in root exudates can attract nematodes to the roots or result in repellence, motility inhibition or even death. However, until recently little was known about the relationship between tomato root exudates chemicals and root-knot nematodes. In this study, root exudates were extracted from three tomato rootstocks with varying levels of nematode resistance: Baliya (highly resistant, HR), RS2 (moderately resistant, MR) and L-402 (highly susceptible, T). The effects of the root exudates on Meloidogyne incognita (M. incognita) egg hatch, survival and chemotaxis of second-stage juveniles (J2) were explored. The composition of the root exudates was analysed by gas chromatography/mass spectrometry (GC/MS) prior to and following M. incognita inoculation. Four compounds in root exudates were selected for further analysis and their allopathic effect on M. incognita were investigated. Root exudates from each tomato rootstocks (HR, MR and T strains) suppressed M. incognita egg hatch and increased J2 mortality, with the highest rate being observed in the exudates from the HR plants. Exudate from HR variety also repelled M. incognita J2 while that of the susceptible plant, T, was demonstrated to be attractive. The relative amount of esters and phenol compounds in root exudates from HR and MR tomato rootstocks increased notably after inoculation. Four compounds, 2,6-Di-tert-butyl-p-cresol, L-ascorbyl 2,6-dipalmitate, dibutyl phthalate and dimethyl phthalate increased significantly after inoculation. The egg hatch of M. incognita was suppressed by each of the compound. L-ascorbyl 2,6-dipalmitate showed the most notable effect in a concentration-dependent manner. All four compounds were associated with increased J2 mortality. The greatest effect was observed with dimethyl phthalate at 2 mmol·L-1. Dibutyl phthalate was the only compound observed to repel M. incognita J2 with no effect being detected in the other compounds. Each of the four compounds were correlated with a reduction in disease index in the susceptible cultivar, T, and tomato seedlings irrigated with L-ascorbyl 2,6-dipalmitate at 2 mmol·L-1 showed the best resistance to M. incognita. Taken together, this study provided a valuable contribution to understanding the underlying mechanism of nematode resistance in tomato cultivars.
authors.affiliation: College of Horticulture, Shenyang Agricultural University, Shenyang, P. R. China.|Vegetable Research Institute, Liaoning Academy of Agricultural Sciences, Shenyang, P. R. China.
authors.forename: Guodong
authors.initials: G
authors.lastname: Yang
authors.affiliation: College of Horticulture, Shenyang Agricultural University, Shenyang, P. R. China.
authors.forename: Baoli
authors.initials: B
authors.lastname: Zhou
authors.affiliation: Vegetable Research Institute, Liaoning Academy of Agricultural Sciences, Shenyang, P. R. China.
authors.forename: Xinyu
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Vegetable Research Institute, Liaoning Academy of Agricultural Sciences, Shenyang, P. R. China.
authors.forename: Zijun
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Vegetable Research Institute, Liaoning Academy of Agricultural Sciences, Shenyang, P. R. China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Vegetable Research Institute, Liaoning Academy of Agricultural Sciences, Shenyang, P. R. China.
authors.forename: Yiming
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Vegetable Research Institute, Liaoning Academy of Agricultural Sciences, Shenyang, P. R. China.
authors.forename: Shuwen
authors.initials: S
authors.lastname: Lü
authors.affiliation: Vegetable Research Institute, Liaoning Academy of Agricultural Sciences, Shenyang, P. R. China.
authors.forename: Qingdao
authors.initials: Q
authors.lastname: Zou
authors.affiliation: Vegetable Research Institute, Liaoning Academy of Agricultural Sciences, Shenyang, P. R. China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Vegetable Research Institute, Liaoning Academy of Agricultural Sciences, Shenyang, P. R. China.
authors.forename: Long
authors.initials: L
authors.lastname: Teng
mesh_terms: D064089:Allelopathy / Q000502:physiology; D000818:Animals; D003993:Dibutyl Phthalate / Q000032:analysis / Q000494:pharmacology; D008401:Gas Chromatography-Mass Spectrometry; D018551:Solanum lycopersicum / Q000469:parasitology* / Q000502:physiology*; D010795:Phthalic Acids / Q000032:analysis / Q000494:pharmacology; D010935:Plant Diseases / Q000469:parasitology* / Q000517:prevention & control*; D053147:Plant Exudates / Q000737:chemistry / Q000502:physiology; D018517:Plant Roots / Q000469:parasitology / Q000502:physiology; D014431:Tylenchoidea / Q000187:drug effects / Q000472:pathogenicity*
chemical_list: D010795:Phthalic Acids; D053147:Plant Exudates; C024629:dimethyl phthalate; D003993:Dibutyl Phthalate