EFFECT OF SEAWEED EXTRACT ON PEAR FRUIT QUALITY AND YIELD

Increasing market competition has forced fruit growers to produce high quality fruits. It has been reported that seaweed extract (SE) contains nutrients, aminoacids, polysaccharides, vitamins, betaines and phytohormones that affect cellular metabolism and that it has a positive impact on plant health, growth and yield. Applications of SE at different phenological phases were studied during the cultivation seasons 2008-2009 and 2009-2010 on Pyrus communis ‘William’s’ planted (1250 tree/ha) in Alto Valle de Río Negro (38°S; 67°W), Argentina. Untreated controls were compared with treatments consisting of 3 foliar sprays of 3 L/ha SE (BM^®, Göemar, basically Ascophyllum nodosum) at different stages of pear phenology: BM1 (white bud, full bloom, petals fall) and BM2 (full bloom, petals fall, fruit size 3-4 mm). Meteorological conditions were registered during the application period. In both seasons the first spray of BM1 was followed by minimum temperatures lower than the temperatures that followed the other applications. Fruit set was similar in BM2 and control, although they were higher than BM1. Early in the season (46 DAFB) fruits treated with BM2 recorded an average increase of 3% in diameter, 9% in weight and 26% in the number of cells per area of parenchymatous tissue. Fruit growth rate during the period 20-80 DAFB was similar in all cases and after this point was higher in BM2. At official commercial harvest fruits treated with BM2 registered significant (P<0.05) increase in diameter (6%), weight (20%) and seed number (40%) and also showed an improvement in the distribution of pear size classes. During 2008-2009, seasonal total yield (t/ha) was 45.9, 41.1 and 42.8 for BM2, BM1 and control respectively; being 37.6, 31.0 and 34.8 in 2009-2010. Treatments did not affect most fruit maturity indices and vegetative parameters. These results suggest that SE applied at appropriate phenological timings increases quality and productivity of pears.