Grouping Bread w heat Cultivars based on Agronomic Characteristics using Multivariate Statistical Methods

In Iran, wheat is the most important agricultural product in terms of production and cultivated area, and the increase in its production has been receiving more attention day by day, and it is very important in terms of economy and food security of the people. The present study was conducted in order to investigate the relationships between different traits and to determine the most important traits affecting grain yield in bread wheat cultivars introduced in the northern climate of the country and to group them based on some morphological traits.

In this research, 20 varieties of wheat improved in the hot and humid climate of the north of the country were studied in the majority of randomized complete blocks design with three replications during three crop years of 2015-2016 at Gorgan Agricultural Research Station.

The results of combined analysis of variance showed that there was a significant difference among the studied cultivars in terms of the investigated traits. The effect of year was also significant for all traits except the number of days to anthesis, and the interaction effect of cultivar was significant for all traits except the number of tiller/m2, peduncle length and spike length, seed yield and biological yield. The highest seed yield (5.59 t ha-1) was related to Ehsan variety. Group comparison between new and old cultivars showed significant difference between the two groups in grain yield and biological yield, harvest index, 1000-seed weight, length of grain filling period and grain filling speed, number of seeds per spike, height, days to spiking and days to anthesis traits. Grain yield had the highest correlation with harvest index (r = 0.92**), seed filling speed (r=0.632**) and thousand kernel weight (r=0.595**). Three variables, length of grain filling period, number of days to maturity and spike length were entered into the regression model as the most important traits affecting grain yield, which had negative direct effects on grain yield, and the most direct effect was related to the number of days to maturity. Factor analysis identified 5 factors that explained 89.052% of the changes. Cluster analysis based on Ward method for the studied traits grouped the cultivars into four clusters. The cultivars that were in the first and second groups had higher yields, 1000 kernel weight, and seed filling speed.

According to the obtained results, among the examined traits, the harvest index had the highest correlation coefficient with grain yield, and the three traits of grain filling period, number of days to maturity, and spike length were determined as the most important traits affecting grain yield. So that the cultivars that had a shorter maturity period and the grain filling period did not interact with the stress at the end of the season, had higher grain yield. The new cultivar Ehsan, with its higher performance in three years of testing and its placement in cluster two, which had high performance, seems to be the superior variety in the climatic conditions of Gorgan.