Evaluation of Yield, Yield Components and Adaptability of promising cotton genotypes in secondary planting

Introduction:

 Cotton (G.hirsutum L.) is an important cash crop in Iran, which plays a vital role in the economy of the country. The yield of cotton cultivars depends on their genotypic performance and adaptability. The most significant objectives of cotton variety improvement for dry agro systems include high yield, fair stability, better fiber quality and also special importance are given on suitability of different maturity groups for early, mid and late planting dates. A variety or genotype is considered to be the most adaptive or stable one if it has a high mean yield but a low degree of fluctuation over diverse environments (Said, 2016; Mudata et al., 2017). The association among yield related traits play a significant role toward improvement and to produce promising genotypes with high yield and quality (Nawaz et al, 2019). Low economic outcome of cotton due to low yields is one of the reasons for diminishing cotton production areas. To increase cotton economic profitability, it is necessary to first determine what critical farm management factors pose limitation to cotton production and then devise suitable plans to address these limitations. Variety selection is an example of these limitations. Cotton planting in Garmsar region begins from mid-April and continues to mid-June which lasts a span of 60 days. Evidently, the responses of cultivars to climatic conditions at each planting date are different. In spite of accomplished efforts, the majority of corn cultivation areas are still limited to Varamin and Khordad cultivars. The present research was carried out to select the best adaptable cotton variety among ten promising new genotypes for yield improvement in second planting in the dry and warm region of Garmsar.

This experiment was conducted in a RCBD experimental design with three replications under Garmsar climatic condition for three years (2014, 2015 and 2016). In this study, 10 cotton genotypes including advanced hybrids and new commercial varieties were planted in May11th, 4th and 10th in the years 2014, 2015 and 2016 respectively. The studied genotypes were: GKTB-113, Kashmar, Khorshid, SKT133, SKSH249, BC244, SKN2739, NSK847, Sahel and Varamin.

The combined analysis of three years of the study showed that the genotype BC244 produced the highest number of monopodial branches. Also, the number of nodes and plant height of this genotype was higher than the others. Genotype SKT133 was superior to others in number of sympodial branches and was placed in same statistical group as Varamin in terms of vegetative traits. Seed yield, mean of boll weight and boll number in the genotype GKTB113 were the highest among the all genotypes. Plant height and height to node ratio of this genotype was similar to Varamin and Sahel, which placed it in the same statistical group. The genotypes were classified into three groups based on Ward's method of clustering for all the investigated traits. Because of climatic and management conditions, early maturing is not the priority for some farmers in the region. Therefore, the genotype GKTB113 with producing the highest yield was found to be superior and adaptable to Garmsar conditions.

Results displayed considerable differences among hopeful cotton genotypes for the studied characters. Boll number plant-1 and boll weight were found as major yield components to have positive correlation with seed cotton yield. However, plant height was noticed negatively correlated with yield. Due to the higher yield and good vegetative characteristics of GKTB113, its introduction as a new variety will expand cotton farmer’s variety choice options. For late cropping, genotypes GKTB113, Khorshid and Kashmar are recommendable (respectively) because of their proportional earliness, seed cotton yield and yield stability.