Characterization of the reproductive behavior of "nova" mandarin in the south coast of Uruguay

Abstract

Reproductive behavior of "Nova" mandarin in the South of Uruguay was evaluated. Trials were carried out in two experiments, localized in a  commercial orchard of Kiyú, in San José province (35º SL). Six year-old plants, grafted on Poncirus trifoliata (L.) Raf., under drip irrigation were used. The variables quantified were: flowering intensity, shoot type distribution, final fruit set and fruit set according to shoot type. Abscission timing and fruit effect on following flowering were studied . Plants flowered profusely, within a range of 90 to 344 flowers/100 nodes. A positive association between flowering intensity and leafless shoots percentage was verified. In the highest flowering levels, abscission remained high during the whole fruit set period, while in lower intensities a peak of abscission 25 days after the end of physiological drop was registered. Final fruit set was associated with shoot type, being significantly higher in leafy single flowered shoot (22%) respect to leafless multiple flowered shoots (0,4%), leafy multiple flowered shoots (1,6%) and leafless single flowered shoots (2%). The results suggest that single flowered condition has greater effect than leaf contribution on "Nova" fruit set. With flowering intensities higher than 250 flowers per 100 nodes, fruit set was very low and consequently yield was no profitable. Although fruit exerted an inhibitory effect on flowering, under low yield conditions flowering was always high (more than 200 flowers/100 nodes). This reproductive behavior place this cultivar in the pathenocarpic-unproductive group under uruguayan conditions. These results contribute to adjust management practices in order to improve "Nova" productivity.