Abstract
Drought stress is a major threat on most of the agricultural crops grown in the East Mediterranean Region in the consequence of predicted global climate change (1). Therefore, improving essential cereal crops such as barley is extremely important for this region to increase yield production due to its economic interest and adaptability to dry environments (29). This two-year experiment was carried out in Kalar technical institute, in Garmian region, Iraq during the seasons of 2016-17 and 2017-18. Canopy temperature depression (CTd) and leaf senescence traits (Onset of leaf senescence (SENonset) and End of leaf senescence (SENend)) were evaluated under irrigated and rain-fed conditions for five hybrid genotypes of barley. Canopy temperature was increased by drought by almost one degree Celsius on average for both years (P=0.002). Leaf senescence durations were also affected by water stress and advanced SENonset by around 34% (P=0.001) and SENend by around 10% (P=0.01) averaging over years. Genotypes 3//14 scored the highest canopy temperature depression and the latest onset of leaf senescence under drought for the cross year mean (P=0.05). Genotype 3//5 was also the latest to reach the end of leaf senescence averaging over years. Genotypes 3//14, 3//5 and 3//4 were generally appeared to have cooler canopy and later onset of leaf senescence than the genotypes 3//18 and 3//1 indicating the capability of these genotypes to have a better performance under water limitations comparing to other genotypes. Canopy temperature depression was positively associated with onset of leaf senescence under drought conditions averaging over years (R2=0.89; P=0.02), but not under irrigated conditions (R2=0.45; P=0.21). There was also a trend for a positive association between canopy temperature and the end of leaf senescence under drought conditions (R2=0.59; P=0.13) in 2018. These associations might be linked to genetic variations in water uptake and/or water-use efficiency.
Highlights
لذلك.)1( يمثل إجهاد الجفاف تهديًدا كبيًار على معظم المحاصيل الز ارعية التي تزرع في مناطق شرق المتوسط نتيجة للتغي ارت المناخ العالمي المتوقع تحسين محاصيل الحبوب الأساسية مثل الشعير أمر مهم للغاية بالنسبة لهذه المنطقة لزيادة إنتاج المحاصيل بسبب اهتمامها الاقتصادي بزيادة قدرة
The canopy temperature depression was calculated by the difference between actual crop canopy temperature and actual air temperature according to the equation below: Canopy Temperature Depression (CTd; °C) = Actual Air Temperature − Actual Crop Canopy Temperature Leaf senescence parameters Flag-leaf senescence was visually assessed for each sub-plot in both years from anthesis (GS61) to full senescence twice a week using a visual senescence score chart (0; fully green and 10; fully senesced)
Post-anthesis canopy temperature depression was positively correlated with onset of leaf senescence, and cooler canopies had a later onset of leaf senescence amongst genotypes averaging across years
Summary
Barley (Hordeum vulgare L.) is one of the and environmentally controlled [4, 15]. most important crops in drought prone Delaying leaf senescence can extend the environments in the world, and considered to period of grain filling and maintain CO2 be a major cereal crop mainly grown for its assimilation to increase grain yield [33]. Barley can grow in a wide range of understanding the physiological mechanisms environmental conditions based on different of drought tolerance related traits such as responses by different varieties of barley under canopy temperature and leaf senescence were various environments [10, 16]. The study region less than 1000 mm, and mostly precipitate in is known as Hyperthermic temperature regime fall and spring [7] This insufficient and [3] and semiarid climate [34] with the soil of irregular rainfall distribution during the grain Aridisols (containing saline or alkaline soils filling stage can efficiently effect on crop yield with low level of organic matter). The most effective way to genotypes of F2 tow-rowed barley (Hordeum increase grain yield under drought-prone vulgare L.) were used in these experiments conditions can be identification of drought which were named Local// Zanbaka (3//18), tolerance related traits [28].
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