DROUGHT EFFECTS ON LEAF CANOPY TEMPERATURE AND LEAF SENESCENCE IN BARLEY

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.

Physiological Efficiency of Sugarcane Clones under Water-Limited Conditions

Highlights`Significant reductions in canopy temperature depression (CTD), chlorophyll fluorescence (Fv/Fm), SPAD index, and leaf rolling index were observed under limited irrigation during the grand growth stage of sugarcane.This study highlights the significance of CTD and Fv/Fm as useful physiological tools for selecting sugarcane clones suitable for production under water-limited conditions.Clones Co 10026, Co 13006, Co 85019, Co 62175, Co 86010, and Co 1148 performed better under limited irrigation, and these clones can reduce the amount of irrigation water required for sugarcane production, ensuring water security.Abstract. Sugarcane is one the most important commercial crops in India and globally. The annual water requirement for sugarcane ranges from about 1000 to 2900 mm, and this variation mainly depends on the agro-ecological conditions, cultivation practices, and crop cycle. In a changing climate, the delay or failure of monsoons will have a direct effect on the water available for irrigation in India. Given these constraints, sustaining sugarcane production is challenging. The ICAR-Sugarcane Breeding Institute (ICAR-SBI) in Coimbatore, India, has developed sugarcane genotypes that are resilient to drought stress. To study the role of physiological traits in identifying sugarcane varieties suitable for water-limited conditions, an experiment was conducted at ICAR-SBI with sugarcane clones in field conditions using irrigation at 100% cumulative pan evaporation (I0) and with 50% reductions in the volume and frequency of irrigation (I2). Physiological traits, including canopy temperature depression (CTD), chlorophyll fluorescence (Fv/Fm), soil plant analysis development (SPAD) index, leaf rolling index (LRI), and cane yield, were recorded for sugarcane clones grown under I0 and I2. Significant reductions of 85.9%, 15.4%, 4.9%, 44.9%, and 56.0%, respectively, in CTD, Fv/Fm, SPAD index, LRI, and cane yield were found for water-limited conditions (I2) compared to I0. Fv/Fm showed a decreasing trend in I2 compared to I0 and also showed a significant positive correlation (r = 0.43) with cane yield. CTD varied significantly between the two treatments and also showed a significant positive correlation with cane yield (r = 0.45). Both Fv/Fm and CTD are adaptive traits for water-limited conditions and are useful for screening sugarcane clones suitable for water-limited conditions. Clones Co 10026, Co 13006, Co 85019, Co 62175, and Co 86010 had superior cane yields under water-limited conditions (I2) and better physiological traits. Water deficit is one of the most critical abiotic stresses that affect sugarcane productivity. By growing clones that are water use efficient (Co 10026, Co 13006, Co 85019, Co 62175, and Co 86010), the irrigation water requirement can be reduced for sugarcane production in India. In addition, new sugarcane clones can be developed for water-limited conditions by using the identified clones in breeding programs for water use efficiency, and water security can be achieved for sugarcane grown tropical and sub-tropical areas of India. Keywords: Canopy temperature, Chlorophyll fluorescence, Global water security, Irrigation, Water productivity

Association of canopy temperature depression with yield and morphological traits of spring soft wheat under Siberian conditions

The method of infrared thermometry is widely used in the world to diagnose drought tolerance of crops. However, in Russia the measurement of Canopy temperature depression (CTD) has not yet been carried out. The aim of the study was to measure CTD and consider the possibility of using this trait to assess spring soft wheat varieties when growing in the Altai Territory (South-Western Siberia of Russia). The studies were conducted in 2017 and 2018 using 36 varieties of spring soft wheat in the vegetative stage and 14 varieties in the grain filling stage, respectively. Significant differences between the varieties for CTD values in both years of the study were established. There was no reliable correlation between CTD and most of agronomic traits of the studied genotypes. CTD also did not significantly correlate with grain yields in neither 2017 nor 2018 (r=0.31; r=-0.14, respectively). However, we found a reliable correlation of the trait with the plant height in 2018 (r=0.83). This may explain the wide distribution of tall varieties in Siberia. If drought occurs before heading, when the plants are oppressed and do not close the canopy, the use of infrared thermometry is difficult throughout the growing season, since the measurement error increases significantly. In Siberia, this method is suitable only in the conditions of mild droughts or when using the steam precursor in wheat cultivation.

Early Detection of Zymoseptoria tritici in Winter Wheat by Infrared Thermography

The use of thermography as a means of crop water status estimation is based on the assumption that a sufficient amount of soil moisture enables plants to transpire at potential rates resulting in cooler canopy than the surrounding air temperature. The same principle is applied in this study where the crop transpiration changes occur because of the fungal infection. The field experiment was conducted where 25 wheat genotypes were infected with Zymoseptoria tritici. The focus of this study was to predict the onset of the disease before the visual symptoms appeared on the plants. The results showed an early significant increase in the maximum temperature difference within the canopy from 1 to 7 days after inoculation (DAI). Biotic stress associated with increasing level of disease can be seen in the increasing average canopy temperature (ACT) and maximum temperature difference (MTD) and decreasing canopy temperature depression (CTD). However, only MTD (p ≤ 0.01) and CTD (p ≤ 0.05) parameters were significantly related to the disease level and can be used to predict the onset of fungal infection on wheat. The potential of thermography as a non-invasive high throughput phenotyping technique for early fungal disease detection in wheat was evident in this study.