Iranian Journal of Seed Research

Extended Abstract
Introduction: Salinity stress is one of the most important factors in decreasing crop yield. Crossing between cultivars and wild relatives is one of the methods to creating salinity tolerant plants that has led to the creation of new Tritipyrum cereals. Investigation of the effect of salinity stress at the germination stage is a reliable test in assessing salinity tolerance of many species; it reduces percentage and rate germination as well as decreases of root and shoots growth. This research aims to investigate the effects of different levels of salinity stress on germination of promising non-Iranian Tritipyrum lines and two wheat cultivars, Alvand (salinity tolerant) and Ghods (salinity sensitive).
Materials and Methods: The experiment was conducted in factorial based on the completely randomized design at the Faculty of Agriculture, Yasouj University. The first factor consisted of 13 Tritipyrum lines and two wheat cultivars and the second factor consisted of different salinity levels (240, 160, 80, 0 mM NaCl). After surface disinfection and seed culture in a petri dish, germination-related traits were measured until the 14^th day.
Results: The results showed that by increasing salinity level, germination rate and percentage, root length, shoot length, dry and fresh root weight, and shoot dry weight decreased. The highest percentage (79.79%) and rate (75.74 seed per day) of germination in stress and non-stress conditions were related to the Az/b line. The germination percentage of the Alvand tolerant cultivar (55.59%) was higher than 5 Tritipyrum lines but less than the other 7 lines, its germination rate (53.69 seed per day) was higher than 10 Tritipyrum lines. The percentage and germination rate of sensitive cultivar Ghods (40.98 and 36.87 seed per day, respectively) were lower than all Tritipyrum lines. Under salinity stress, the La/b line had the highest root length (7.77 cm) which was even longer than the root length of the Alvand tolerant cultivar (4.9 cm). The highest root dry weight (0.027 g) under stress conditions was related to the Ka/b line and the lowest root dry weight (0.013 cm) was related to the Ghods cultivar. Among germination traits, the highest and the lowest heritability were related to shoot length under stress and non-stress conditions and root fresh weight (under non-stress conditions) and root length (under stress conditions), respectively. Genetic variance of shoot length and germination percentage in non-stress conditions was higher than stress conditions and selection under non-stress conditions had a higher yield than stress conditions. Clustering of genotypes by cluster analysis divided the genotypes into four groups under normal and salinity conditions. Under salinity stress, the salt-tolerant cultivar was placed alone in the fourth cluster. The salinity-sensitive cultivar was also in the third cluster with the St/b line. The rest of the Tritipyrum lines were clustered in the first and second clusters, with (Ka/b)(Cr/b)F₆ hybrid line in the first cluster. Salt stress condition seems to have separated Qods from all Tritipyrum lines (except St/b), but under normal conditions, it did not indicate clustering accuracy of the studied genotypes.
Conclusion: The results of this study demonstrated salinity tolerance in the most simple and hybrid lines of this plant at the germination stage, among them (St/b)(Cr/b)F₃, (Ka/b)(Cr/b)F_6, and (Ka/b)(Cr/b)F₃ and La(4B/4D)×(b) and the simple lines La/b, Az/b and St/b were better than others. Therefore, these selected lines can be considered in further complementary studies.
 

Highlights:
1. The studied plant is new and needs to be examined at the germination level before introducing.
2. Simple lines with the hybrid lines of this new plant have been studied that can show the effect of crosses.
3. Grouping of lines for tolerance or susceptibility is done solely based on germination traits.

Extended Abstract
Introduction: Wheat coleoptile protects the plumule and the first leaf so they can move from the embryo to the soil surface. Coleoptile is essential for plant establishment. Cultivars with longer coleoptiles and mesocotyls are sown deeper and are more successful under drought stress conditions. However, there is not much information about their genetics. The objective of the present study was to evaluate the coleoptile and mesocotyl of Iranian, overseas and the lines developed as a part of Shahid Bahonar University breeding program, and estimate of genetic parameters of these traits.
 Materials and Methods: In this research, 30 bread wheat genotypes originated from Iran, CIMMYT, ICARDA, USA, and Australia and five lines from Shahid Bahonar University of Kerman breeding programs were sown at a 10 cm depth of soil in the research field of Shahid Bahonar University in a randomized complete block design with seven replications. Each plot consisted of three rows with two meters long and a 5 cm intra-row spacing. At harvest, the plants were gently removed from the soil, and after removing the soil from the root area, the roots were washed. In this study, coleoptile and mesocotyl length, number of seminal roots, root length, root and shoot dry weight were measured.
Results: Coleoptile and mesocotyl are important traits for increasing drought tolerance in bread wheat. In the present research, mesocotyl length varied from 5.20 for Excalibur to 2.08 for Zagros, and showed a high heritability (0.48) and response to selection (11.61%). Furthermore, this trait had a positive significant correlation with coleoptile length (r=0.53**), root weight (r=0.38*) and shoot weight (r=0.36*). Seminal and nodal root number had the highest (0.59), while root length had the lowest (0.13) narrow-sense heritability. Overall, suitable cultivars for rain-fed conditions had higher coleoptile and mesocotyl than the others. Breeding lines in Shahid Bahonar University of Kerman suitable for rain-fed conditions had longer coleoptile and mesocotyl lengths. Root and shoot dry weight had a significant positive correlation (r=0.82**).
Conclusions: In general, breeding programs to increase grain yield differ under rain-fed and irrigated conditions. In wheat breeding programs under rain-fed conditions, special attention should be paid to coleoptile and mesocotyl traits. These traits were not influenced by the plant growth habit.

Highlights:

1. Mesocotyl of the Iranian cultivars was evaluated for the first time.
2. Breeding lines developed by Shahid Bahonar University of Kerman suitable for rain-fed had appropriate coleoptiles and mesocotyls.
3. Coleoptile and mesocotyl had a significant and positive correlation.