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Title: IMPROVED CARICA PAPAYA TOLERANCE TO THE CARMINE SPIDER MITE BY EXPRESSION OF MANDUCA SEXTA CHITINASE TRANSGENE.

Author
item MCCAFFERTY, HEATHER - HARC
item ZHU, YUN - HARC
item Moore, Paul

Submitted to: Transgenic Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2006
Publication Date: 6/20/2006
Citation: Mccafferty, H., Zhu, Y.J., Moore, P.H. 2006. Improved Carica papaya tolerance to the carmine spider mite by expression of Aanduca sexta chitinase transgene. Transgenic Research. 15:337-247.

Interpretive Summary: Each year, in spite of using costly pesticides, farmers suffer large crop losses to pests and pathogens. What is needed is increased plant resistance that might be obtained by inserting novel genes, not in the sexual germplasm pool, into the crop of interest. Papaya, an important tropical crop with inadequate natural resistance to parasitic mites, was genetically enhanced with a tobacco hornworm gene for the production of the enzyme chitinase, which is not in plants but is involved in molting of all insects. Collaborative research between scientists of the Hawaii Agriculture Research Center and ARS in Hawaii produced transformed papaya plants and evaluated their response to, and effect on, carmine spider mites, a major insect pest of a very wide range of fruit, vegetable, and ornamental plants. In field trials, the transformed papaya plants grew more vigorously and reduced the population of infecting spider mites more than did the non-transformed controls. The transformed papaya lines will be advanced in field trials for performance in fruit production and may prove beneficial to the papaya fruit industry. The same technology holds promise for a wide range of crop species.

Technical Abstract: Papaya plants producing the tobacco hornworm (Manduca sexta) chitinase protein were obtained following microprojectile bombardment of embryogenic calli derived from the hypocotyls of the cultivar Kapoho. Polymerase chain reaction (PCR) and Southern blot hybridization of reverse-transcriptase (RT)-PCR analysis were done to confirm the presence of the transgene. RT-PCR and western blot analysis showed various levels of gene expression among transgenic lines. Insect bioassays in the laboratory showed that the transgenic plants expressing the Manduca sexta chitinase inhibited multiplication of carmine spider mites (Tetranychus cinnabarinus Boisd.). Field experiments conducted to evaluate resistance of the transgenic papaya plants to mites with natural infection indicated that the Manduca sexta chitinase gene improved tolerance to carmine spider mites. Manduca sexta chitinase has potential to be used as an alternative or addition to Bt or other insecticidal genes in the control of insects that cause significant yield losses in papaya.