Grouping promising durum wheat lines for frost resistance using some morphophysiological traits

Wheat is one of the most important crops and an essential source of calories and protein in the world. Food security depends on agricultural production to supply the growing world population with certain nutrients. Plants are often exposed to stressful conditions. Stress can occur within minutes, days, or even months. Temperature is the most important environmental variable that affects the growth, development, and final productivity of agricultural grain products. Cold or freezing temperatures cause a lot of damage to agriculture, especially in cereal crops in subtropical and temperate regions. Most of the world's wheat fields are often under low-temperature stress. The ability of plants to tolerate cold without damaging their growth cycle is called cold tolerance. Crop plants, including wheat, tend to overcome cold stress through cold adaptation. In winter cereals, low-temperature stress in the vegetative stage causes chlorosis and wilting of leaves and eventually leads to necrosis and growth inhibition. Wheat needs an ideal temperature range for growth and ideal performance, and any deviation from it affects the natural growth process. In general, winter cereals like wheat have two varieties, sensitive to cold and resistant to cold. Numerous studies show that the intraspecies genetic diversity of wheat has not yet been fully exploited. The purpose of this study is to investigate the diversity of durum wheat lines under conditions of freezing stress, identify cold-resistant lines in durum wheat based on some morphophysiological traits, and determine the relationship between durum wheat traits and cold tolerance.

Freezing and laboratory experiments were carried out in the greenhouse and plant breeding laboratory of Mohaghegh Ardabili University in 2019 on 45 durum wheat genotypes as a factorial experiment in the form of a randomized complete block design with three replications. In this experiment, four control temperature treatments (without freezing), -8, -10 and -12 degrees Celsius were investigated. LT50 of several applied temperatures (-8, -10, and -12), and by analyzing Probit was calculated for each genotype. The mean comparison was done with the LSD method at the five percent probability level. Lines grouping was done by Ward's clustering method using the square measure of Euclidean distance.

The highest amount of LT50 trait was observed in genotype number 44, and the lowest amount was observed in genotype number 36. LT50, survival percentage, height, fresh weight of shoots, dry weight of shoots, saturated weight of shoots, number of leaves, relative water content, and electrolyte leakage were investigated. The correlation was calculated separately in stress levels. Lines with high height in terms of LT50 trait were also included in the group of resistant lines. Multivariate variance analysis based on unbalanced one-way variance analysis was used to determine the most favorable groups. The lines were placed in four groups in the control conditions, the stress of -8, and -12°C, and in five groups in the -10°C stresses. The traits of shoot weight, number of leaves, relative leaf water content and electrical conductivity had an important role in the average of the groups. Decomposition into factors was done in separate stress levels. Four factors were selected in control levels, and -8°C stress, and three factors were selected in the -10°C, and -12°C stress levels.

In general, lines 35, 40, and 44 were recognized as lines with higher averages in all clusters, and lines 4, 5, 6, and 20 were placed in groups with lower averages. The traits of shoot weight, number of leaves, relative leaf water content, and electrical conductivity had an important role in the average of the groups. According to the final results of the study, lines 17, 24, 27, 35, 38, and 40 were recognized as resistant lines. Lines 3, 12, 18, 20, and 44 were found to be sensitive.