Comparison of Agro-meteorological Indices and Yield of Onion Cultivars in Behbahan, Southwest Iran

This research was conducted to compare agro-meteorological indices and yield of short day onion cultivars. The experiment was done in randomized complete block design including 15 cultivars (Seba, Imperateriz, Siroos, 7030, S.V. 4043, X. P. Red, Sweet Ajent, Savana Sweet, Golden I, Primavera, Texas Early White, Texas Early Grano, White Grano, Spidan and Contessa) with four replications at Behbahan Agriculture Research Station, southwest of Iran, for two years (2016-18). Seeds were sown in nursery in early October and seedlings were transplanted in early November. Bulbs were harvested when 50-80% of foliage had senesced and fallen. The differences of growing degree days and helio thermal unit were considerable among cultivars from planting to bulbing stage, however the differences of photo thermal index were not significant among cultivars at this stage. During bulbing and bulb development stage differences of growing degree days, helio thermal unit and photo thermal index were considerable among cultivars. Evaluation the correlation coefficients among yield and agro-meteorological indices during bulbing and bulb development stage suggested significant negative correlation of bulb yield with growing degree days and photo thermal indices. The highest bulb yield, thermal use efficiency and helio thermal unit use efficiency were recorded in Siroos (hybrid cultivar). As the seed price of open–pollinated cultivar is less than the prices of hybrid cultivars and the seed of open-pollinated cultivars could be produced by the growers, therefore, planting of Texas Early Grano (open-pollinated cultivar) is recommended for onion production in Khuzestan province at southwest of Iran.