Figure 4. Constitutive expression of mj-far-1 in tomato hairy roots increases roots susceptibility to infection by the RKN M. javanica.

A. RT-PCR confirmation of mj-far-1 (upper gel) and kanR (lower gel) expression in tomato hairy roots lines far-1 E1.1, far-1 E 7.1, far-1 RNAi3.2 and far-1 RNAi11.5 compared with the respective control Vector 1.1 and WT 870. The expected size of the PCR product is 96 bp for the mj-far-1 and 81 for kanR. RT-PCR was performed on total RNA isolated from non infected transformed tomato hairy roots and WT 870 roots. B. Increased susceptibility of tomato hairy roots expressing mj-far-1 (far-1E1.1 and far-1E7.1) is accompanied by expanded galling production compared with mj-far-1 dsRNA-expressing tomato hairy root lines (far-1 RNAi3.2 and far-1 RNAi11.5) and vector control (Vector 1.1. and Vector 11.5). C. Meloidogyne susceptibility/resistance of vector transformed roots and transgenic tomato roots expressing mj-far-1, or mj-far-1 dsRNA-expressing lines, was measured as nematode developmental stages counted at 15 and 28 DAI. Roots were inoculated with 200 sterile pre-parasitic J2s and then assessed for juveniles, young females and mature females under the dissecting scope following staining with acid fuchsin dye. Note the significant (P≤0.05) increase in percentage of young females at 15DAI and increase in percentage of mature female at 28DAI in roots overexpressing mj-far-1 in comparison with vector control roots. Data are expressed as means of 25 plants from each line; the experiment was repeated three times, giving consistent results. The percentage of each developmental stage is represented by a mean ± standard error. Different letters above the bars denote a significant difference (P≤0.05, analysis of variance) between tomato roots lines analyzed by Tukey-Kramer multiple comparison tests.