Association analysis of some morphological traits of durum wheat (Triticum turgidum var. Durum Desf) in rainfed and supplementary irrigation conditions using SSR molecular marker

Durum wheat is one of the most important crops in the world. Various environmental stresses such as drought stress can affect grain yield. Drought stress is one of the most important and common causes of wheat yield decline in most parts of the world. A large part of Iran's wheat cultivated lands is located in a Mediterranean climate. In these areas, the main part of rainfall is in winter and early spring, and from mid-spring, along with reduced rainfall and ambient humidity, the air temperature also rises sharply. Drought tolerance is a slightly complex trait controlled by many genes, and it is one of the most challenging traits to study and describe. Nevertheless, existing studies on drought have shown that the drought resistance mechanism of plants is morphological, physiological, and molecular, and strategies have been developed to deal with drought stress such as mass screening, modification, marker selection, and the use of exogenous hormones. Therefore, it is necessary to find a way to grow plants with limited water in areas deprived of water.

The study was conducted to identify molecular markers associated with the studied traits using SSR markers in rain-fed and supplementary irrigation conditions. The seeds of 150 genotypes of durum wheat, including two germplasm of durum wheat of ICARDA and germplasm of durum wheat of Iran, originated from the Seed and Plant Research Improvement Institute of Karaj, were planted in two cropping years 2018-2019 and 2019-2020. The experiment was performed in an augmented design with four controls in 6 blocks in the Farm of the Agricultural and Natural Resources Campus of Razi University of Kermanshah in supplementary irrigation and rainfed sites. The traits of plant height, peduncle length, weight of main stem, spike length, number node, weight spike, number grain per spike, weight grain per spike, thousand kernel weight were selected randomly and measured in 10 plants.

Based on the results, the GWM513 marker in the supplementary irrigation environment and the marker of GWM448-1 in the rain-fed environment showed the highest correlation with the number of seeds per spike (35% and 30%, respectively). GWM153 and GWM408 markers are suggested due to the high explanation coefficient (18-35%) and the most significant relationship with yield traits as the most suitable markers to improve most of the traits related to yield in rain-fed conditions.

In the supplementary irrigation environment, a total of 24 significant markers were identified with the studied traits; among them, the number of seeds per spike had the highest amount of changes explained (30%) by the associated marker. In the rain-fed environment, a total of 21 significant associations of markers with the studied traits were identified among them; the number of seeds per spike had the highest coefficient explained (35%) by the associated marker. In the supplementary irrigation environment, 17 SSR markers significantly related to the studied traits, five markers, and in the rain-fed environment, out of 13 markers related to traits in this environment four markers participated in more than one feature.