Expression of endochitinase from Trichoderma harzianum in transgenic appleincreases resistance to apple scab and reduces vigor

The goal of this research was to improve scab resistance of apple by transf ormation with genes encoding chitinolytic enzymes from the biocontrol organ ism Trichoderma harzianum. The endochitinase gene, as cDNA and genomic clon es, was transferred into apple cv. Marshall McIntosh by Agrobacterium-trans formation. A total of 15 lines were identified as transgenic by NPTII enzym e-linked immunosorbent assay and polymerase chain reaction and confirmed by Southern analysis. Substantial differences in endochitinase activity were detected among different lines by enzymatic assay and western analysis. Eig ht lines propagated as grafted and own-rooted plants were inoculated with V enturia inaequalis. Six of these transgenic lines expressing endochitinase were more resistant than nontransformed cv. Marshall McIntosh. Disease seve rity compared with cv. Marshall McIntosh was reduced by 0 to 99.7% (number of lesions), 0 to 90% (percentage of leaf area infected), and 1 to 56% (con idia recovered) in the transgenic lines tested. Endochitinase also had nega tive effects on the growth of both inoculated and uninoculated plants. Ther e was a significant negative correlation between the level of endochitinase production and both the amount of disease and plant growth.