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به منظور تعیین مناسب‌ترین شاخص‌های تحمل به خشکی و شناسایی اکوتیپ‌های متحمل به خشکی آویشن دنایی (Thymus daenensis subsp. daenensis)، آزمایشی در دو محیط بدون‌تنش و تنش خشکی در قالب طرح بلوک‌های کامل تصادفی با چهار تکرار در سال زراعی 97-1396 در شهرستان ابرکوه انجام شد. در این مطالعه شاخص‌های تحمل به خشکی شامل: شاخص تحمل (TOL)، شاخص حساسیت به تنش (SSI)، شاخص میانگین بهره‌وری (MP)، شاخص میانگین هندسی عملکرد (GMP)، شاخص میانگین هارمونیک (HM)، شاخص تحمل تنش (STI)، شاخص عملکرد (YI) و شاخص پایداری عملکرد (YSI) با استفاده از وزن خشک اندام هوایی اکوتیپ‌ها در شرایط بدون تنش (Yp) و تنش خشکی (Ys) محاسبه گردید. نتایج تجزیه واریانس مرکب نشان داد که بین اکوتیپ‌ها از نظر وزن خشک اندام هوایی در سطح احتمال یک درصد اختلاف معنی‌دار وجود دارد. نتایج تجزیه واریانس ساده نیز نشان داد که اختلاف معنی‌داری بین اکوتیپ‌ها از نظر Ypو Ys و شاخص‌های MP، GMP، HM، STI و YI وجود دارد. تحلیل همبستگی بین شاخص‌ها و وزن خشک اندام هوایی در شرایط بدون تنش و تنش خشکی نشان داد که شاخص‌های MP، GMP، HM، STI و YI‌ مناسب‌ترین شاخص‌ها برای انتخاب اکوتیپ‌ها هستند. نمودار چند متغیره بای‌پلات نشان داد که اکوتیپ‌های خرم‌آباد1، اراک1، خرم‌آباد2، فریدونشهر و همدان در مجاورت شاخص‌های مناسب تحمل به خشکی قرار دارند و نیز توزیع اکوتیپ‌ها در فضای بای‌پلات وجود تنوع ژنتیکی بین اکوتیپ‌ها را جهت انتخاب برای تحمل به تنش خشکی نشان داد. تجزیه خوشه‌ای نشان داد که می‌توان اکوتیپ‌های خرم‌آباد1، اراک1، خرم‌آباد2، فریدونشهر و همدان را به عنوان اکوتیپ‌های متحمل به خشکی و اکوتیپ‌های اراک2 و شازند را به عنوان اکوتیپ‌های حساس به خشکی پیشنهاد نمود.

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Introduction and Objective: Sunflower (Helianthus annuus L.) is one of the most important oil crops and due to its high content of unsaturated fatty acids and lack of cholesterol, the oil benefits from a desirable quality. Drought is the most important crop production limiting factor in the changing climate scenario and its intensity is predicted to increase in future. In this research, drought tolerance of some sunflower cultivars under non-stress and drought stress conditions was studied and SIIG method was used for integrating studied traits in order to select the best drought stress tolerant cultivars. Material and Methods: In order to evaluate the drought and susceptible cultivars using tolerance index (Ti) for studied traits and selection index of ideal genotype (SIIG), an experiment was conducted in 2022 cropping season based on randomized complete block design with three replication under non-stress and drought stress conditions separately on 10 sunflower cultivars including Azargol, All-star, Master, Hysun33, Golsa, Ghasem, Farrokh, Shams, Golshid and Barzegar in field in Abarkouh city. Grain yield, plant height, number of days to maturity, number of seeds per head and 1000 seed weight were measured in this research. Results: The results of combined analysis of variance revealed that drought stress and cultivar had significant effect on all studied traits. Cultivar effect was significant in all studied traits. Stress × cultivar interaction was significant only in grain yield. Drought stress led to a significant decrease in all studied traits. Mean comparisons showed that Farrokh, Barzegar and Shams cultivars had the highest value in the most traits and so these cultivars were suggested for cultivation under both conditions. Ghasem, Farrokh and Shams had the highest value of Ti index for grain yield, 1000 seed weight and number of seeds per head. Ghasem, Barzegar, Farrokh, Shams and Golsa had the highest value and All-star, Golshid and Hysun33 had the lowest value of SIIG, respectively. Cluster analysis, based on ward method and by using Eucilidian distance, classified studied cultivars using Ti index of traits into two groups. Azargol, Barzegar, Golsa, Shams, Master, Ghasem and Farrokh cultivars were placed in first group and these cultivars in terms of Ti index values for grain yield, 1000 seed weight and number of seeds per head were higher than second group and whole mean. Conclusion: The results of cluster analysis using Ti index of traits are similar to the results of cultivar ranking based on SIIG and it can be said that Farrokh, Ghasem, Shams, Barzegar, Azargol, Golsa and Master cultivars were drought tolerant and All-star, Hysun33 and Golshid were susceptible cultivars according to cluster analysis and SIIG values. [ABSTRACT FROM AUTHOR]

The effect of heat stress on yield, yield component and some agronomic traits of barley, was evaluated during the growing season of 2022-2023 using a randomized complete block design with three replications under normal and heat stress conditions. Eight barley cultivars including Nik, Mehr, Khatam, Reyhan, Nosrat, Fajr 30, Yoosef and Afzal were grown in Abarkouh, Yazd, central Iran. The results of combined analysis of variance revealed that cultivar effect was significant in all traits except 1000 grain weight and peduncle length. Heat stress × cultivar interaction was significant for spikes/m², grains/spike, and grain yield. Heat stress led to a significant decrease in days from sowing to physiological maturity, plant height, peduncle and spike length, spikes/m2, grains/spike, and grain yield and a significant increase in days from sowing to tillering. Grain yield under both conditions had significant negative correlation with days from sowing to tillering. Grain yield had significant positive correlation with spikes/m2 under normal condition and with spikes/m², and grains/spike under heat stress condition. Stepwise regression results showed that grains/spike and plant height could be used as criteria for increaseing grain yield under heat stress condition. Mean comparison of data for studied cultivars showed that Reyhan and Nosrat genotypes could be suggested for cultivation under both conditions. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate the relationships among some of the agronomic and physiological traits of twelve Thymus daenensis subsp. daenensis ecotypes under normal and salt (120 mM NaCl) stress conditions in a factorial experiment using randomized complete block design with three replications. Shoot dry weight under both conditions had significant positive correlation with chlorophyll a and b, potassium, relative water content, canopy area, leaf length and number of stems in plant and had significant negative correlation with sodium to potassium ratio and ion leakage. According to stepwise regression results, canopy area and carotenoid under normal condition and leaf length and number of stems in plant under salt stress condition were entered to the model. The result of path analysis showed that canopy area had the most positive direct effect on shoot dry weight under normal condition and leaf length and number of stems in plant had positive effects on shoot dry weight under salt stress condition. [ABSTRACT FROM AUTHOR]