Leaf area evolution, light interception, yield and quality of fruits in apricot trees (cv Tirynthos) trained to transverse y and vase

The aims of this study were to evaluate the effect of different training systems on the evolution of leaf area and on the amount of intercepted photosynthetic photon flux density (PPFD), and to ascertain the effect of the different amount of PPFD available within the canopy on yield and fruit quality of cultivar Tirynthos. Trials were carried out in Andriace, Italy (N 40° 20', E 16° 48') from 1993 to 1996 on mature apricot plants grafted on Mirabolano seedlings and trained to transverse Y and Vase at planting distances of 1111 p ha-1 and 400 p ha-1 respectively. Forty days after bud burst, 62% of incident PPFD was transmitted to the bottom of the canopy in plants trained to transverse Y, compared to 74% in those trained to Vase. When LAI evolution was complete, transmitted PPFD in Y was 22%, whereas in Vase it remained close to the previous values. The lower amount of radiation transmitted by transverse Y was due to its larger LAI. The different types of shoots completed their growth at different times: spurs, short fruiting shoots and long fruiting shoots from April to mid May, and watersprouts in July. Accumulated yield during the years of trials (1993–'96) was 83.1 t ha-1 in Y and 53.9 t ha-1 in Vase. Fruit size, on the other hand, was smaller in Y than in Vase. Shortly before harvest, fruits directly exposed to radiation showed a higher concentration in soluble solids (CSS) than those shaded. At harvest time the fruits on Y often had a higher CSS. The results obtained indicate that plants trained to transverse Y can better utilize solar radiation and reach higher yields per unit area, whereas plants trained to Vase produce larger fruits.