Radopholus similis Reduced Banana (Musa AAA) Leaf Photosynthesis

The effect of Radopholus similis on banana (Musa AAA cv. Grande Naine) leaf photosynthesis was determined throughout four experiments that were carried out under lathhouse conditions. In vitro plants were sown in pots of 1.8 L volume containing sterilized or unsterilized soil from a commercial banana farm. In the first experiment during the three measuring times (7 am, 10 am, and 1 pm), at 45 days after inoculation, the highest photosynthesis rate was observed in the plants free of nematodes and the lowest in those plants inoculated with 500 (506 ± 18) R. similis per pot. In the evaluation at 10 am a reduction of 46% (P= 0.0307) in the photosynthesis rate was found on plants inoculated with R. similis that were grown in the sterilized banana soil. In the second experiment, after 75 days of the inoculation, from the six photosynthesis evaluation times (6-7, 8-9, and 10-11 am or 12-1, 1-2 and 2-3 pm) with exception of that at 2-3 pm, the highest photosynthesis rate was observed in the plants free of nematodes. Reductions in the photosynthesis rate with nematode inoculation varied between 12 and 36% at 6-7 am, between 13 and 57% at 8-9 am, between 32 and 57% at 10-11 am, and between 16 and 65% at 12-1 pm, and between 13 and 47% at 1-2 pm. The photosynthesis rate decreased linearly as the number of R. similis inoculated increased in the evaluations of 8-9 (P= 0.0070) and 10-11 am (P= 0.0049) or 12-1 pm (P= 0.0048) and 1-2 pm (P= 0.0255). In the third experiment, a photosynthetic light response curve was determined at 75 days after inoculation showing that the area under curve of the potential assimilation rate of the plants inoculated with 1500 (1564 ± 49) R. similis was reduced (P= 0.0153) by 70% compared to non-inoculated plants. At the last experiment, the net assimilation rate curve at 4 (P< 0.0001), 11 (P= 0.0340) and 25 (P= 0.0127) days after nematode inoculation was higher on the plants free of nematodes. So, in the four experiments, the lowest photosynthetic rate was found in the plants infected by R. similis.