Generation and Characterization of Transgenic Plum Lines Expressing the Gastrodia Antifungal Protein

Abstract

The Gastrodia antifungal protein (GAFP) is a monocot mannose-binding lectin isolated from the Asiatic orchid Gastrodia elata. This lectin has previously been shown to provide increased resistance in transgenic Nicotiana tabacum against taxonomically unrelated root pathogens Phytophthora nicotianae, Rhizoctonia solani, and Meloidogyne incognita, but its potential to confer disease resistance in tree species is not known. Agrobacterium tumefaciens-mediated transformation yielded three gafp-1 expressing plum lines (Prunus domestica) designated 4J, 4I, and 5D. These lines possessed one, two, and four copies of the gafp-1 gene, respectively, as demonstrated by DNA blotting. Lines 4J and 4I were not phenotypically different from the nontransformed control line, but line 5D showed significant divergence in leaf morphology and growth habit. Compared with the inoculated control line, lines 4J and 4I exhibited increased tolerance to Phytophthora root rot (PRR) caused by P. cinnamomi. When inoculated with the root-knot nematode, Meloidogyne incognita, the 4J and 4I lines showed a significantly lower degree of root galling than the inoculated control line. Nematode reproduction, as measured by the presence of egg masses and the number of eggs produced per gram fresh root, was significantly reduced in line 4J compared with the inoculated control line. The results of this study suggest that the expression of gafp-1 in the roots of a woody plant may confer some level of resistance to PRR and root-knot nematode. Long-term field trials will be necessary to confirm this hypothesis.