Changes of Simple Non- Structural Carbohydrates During Bulb Formation and Growth Analysis of Four Onion Cultivars in Behbahan

Change of simple non- structural carbohydrates (sucrose, glucose and fructose) during bulb formation were studied as well as growth analysis. A randomized complete block design containing four treatments (onion cultivars: Safid Behbahan, Dorcheh Esfahan, Kamarei Khomain and Gholi Gheseh Zanjan) and four replications was performed at Behbahan Agriculture Resarch Station. Seeds were sown in nursery in late October and seedlings transplanted in late Jaunuary. Carbohydrates accumulated in leaf bases during initiation of bulbing. The most simple non-structural carbohydrates content were found in Safid Behbahan and Gholi Gheseh Zanjan cultivats before and after bulb formation respectively. Glucose and sucrose were the maximum and minimum of increasing percent of simple non– structural carbohydrates sequentially. The grouth analysis results showed a slow grouth period (about 135 days after emergence) and a.rapid grouth after that. The yield of bulb dry weight of SafifBehbehan cultivar was higher than other cultivar at 1% level, due to the earliest date of bulbing, higher bulb growth rate (BUGR) and crop growth rate (CGR). Leaf area index increased (LAI) because of delaying in bulbing date and Dorcheh Esfahan cultivar had the maximum LAI. A high significant positive correlation (r = 69%) was found between relative growth rate (RGR) and net assimilation rate (NAR. Safid Behbahan cultivar produced the highest yield of bulb fresh weight, howevre it had no significant difference with Kamarei Khomain and Dorcheh Esfahan cultivar at 1% level. Regarding our results we recommended Safid Behbehan, Dorcheh Esfahan and Kamarei Khomain cultivars for planting at Behbahan region.