EFFECT OF VERTICILLIUM WILT ON GAS-EXCHANGE OF ENTIRE EGGPLANTS

Verticillium dahliae infection may reduce growth and yield of eggplant (Solanum melongena L.) by inhibiting gas exchange per unit leaf area, and (or) by reducing leaf area. To quantify this inhibition, eggplant s were grown in a field in fumigated soil or soil naturally infested w ith V. dahliae. Photosynthesis, dark respiration, transpiration, leaf area, disease symptoms, and yield were measured. Whole plants were enc losed in clear-walled chambers to measure gas exchange for 24-h period s. Before fruit set, there were no symptoms of wilt and no difference in leaf area or in gas exchange of plants grown in infested or fumigat ed soil. After fruit set, plants grown in the Verticillium-infested so il became symptomatic and had less leaf area, smaller leaves, and less photosynthesis per plant under high irradiance than plants grown in t he fumigated soil. When whole plant gas exchange was normalized per un it leaf area there was no significant effect of disease on photosynthe sis or transpiration. Although verticillium wilt reduces photosynthesi s per unit leaf area in other species, our findings suggest that verti cillium wilt reduced gas exchange of the entire eggplant predominantly by reduced leaf area rather than by reduced photosynthetic efficiency .