Investigation of flowering pattern, boll retention and ripening at different densities of cotton genotypes

This research was carried out to study the flowering process and production of boll in different cultivation densities of cotton cultivars in 2017 in Varamin, Iran. In this research, five cotton cultivars including Varamin, Shirpan603, Cocker100, NO200, and SP731 in three planting densities of 5.5, 6.4, and 12.8 plants per square meter was evaluated using a factorial experiment in the form of a randomized complete block design in three replications. The number of flowers of the cultivars was counted during the period time from 1 July to 15 September (11 weeks). The results of the analysis of variance showed that the effects of plant density on flower number, number of bolls, and cottonseed were significant at 1% level and on fiber weight at 5% level. Also, with an increasing number of plants per unit area, the number of flowers, the number of bolls, boll weight, and fiber weight decreased. So, with increasing density from 5.5 to 6.4 and 12.8 plants per square meter, the average number of flowers decreased from 40.97 to 38.83 and 28.25 flowers per plant, and the average number of bolls decreased from 18.64 to 17.16 and 11.94 boll/plant. In this study, the percentage of boll retention had no significant difference in plant densities. The findings of this study showed that the peak flowering stage and boll formation occurred 11 weeks after planting by receiving about 1148 GDD. Moreover, 91% of the bolls that were made from flowers had appeared until the end of the 13th week.