Identification of Sunflower (Helianthus annuus L.) Genotypes Tolerant to Water Stres
Abstract
The present research was carried out to determine water-stress tolerance of linoleic sunflower genotypes (P64LE119, PR63F73, P64LL62) grown under different water stress conditions [no water-stress (I100); mild water-stress (I70); strong water-stress (I35)] in the years 2015 and 2016. Variance analyses revealed significant differences between the genotypes (P<0.01). As the average of two years, the greatest yield was obtained from no water-stress x genotype interaction (I100xP64LE119) with 4094.66 kg ha-1, the lowest yield was obtained from strong water stress x genotype interaction (I35xPR63F73) with 2487.81 kg ha-1. Again as the average of two years, the greatest chlorophyll content was obtained from no water-stress x genotype interaction (I100xP64LE119) with 49.83 spad, the lowest value was obtained from strong water stress x genotype interaction (I35xPR63F73) with 34.39 spad. The greatest crop water stress index was obtained from strong water stress x genotype interaction (I35xPR63F73) with 0.53, the lowest value was obtained from no water-stress x genotype interaction (I100xP64LE119) with 0.21. The P64LE119 genotype with optimum water use efficiency and prominent with crop water stress index and chlorophyll content both in no water-stress and strong water stress treatments was identified as water stress-resistant and the genotype was considered to have reliable characteristics potentially to be used in further water stress-resistance studies.
- Introduction
Today, agronomists and plant breeders are focused on yields rather than survival of the plants. Breeding programs are mostly implemented to develop highyield cultivars. However, recent global warminginduced abiotic stressors have negatively influenced agricultural production activities and such impacts compelled the researchers to take new measures against the negative impacts of climate change and resultant global warming. Among the abiotic stressors, water stress, insufficient nutrition, salinity and high temperature are the leading ones (Kozlowski & Pallardy 1997). Recession in plant growth due to deficit moisture within the plant efficient root zone (through the soil profile of 0–90 cm) is defined as water stress. The initial symptoms of water stress realize at stomatal level and stomas close to prevent further moisture loss through transpiration (Flexas & Medrano 2002). Stomal closure reduces CO2 availability in chloroplasts and negatively influences net photosynthesis rates (Cornic 2000). Water stress is exerted on plant tissues under drought stress and this reduces photosynthesis rates significantly (Chaves 1991). Neither the soil moisture content nor the atmospheric system can accurately put forth plant inherent water status as much as crop water stress index (Reginato & Howe 1985; Gencoglan & Yazar 1999). Reginato (1983) indicated that daily crop water stress index values varied based on atmospheric demands and soil moisture contents. Water stress is experienced when the plant cover temperature was equal or greater than the air temperature (Walker & Hatfield 1979). Canopy-air temperature difference (Tc-Ta) is a significant indicator of water stress (Jackson & Reginato 1981). Choudhury & Idso (1984) carried out a water stress study on sunflower and reported significant effects of air and dew temperatures on plant cover temperature under high soil moisture conditions. Plant resistance to droughts and water stress are the primary target of plant breeders. For sunflowers, leaf canopy temperatures are the most significant parameters in measuring plant tolerance to water stress under stress conditions (Skoric 2009). Moroni et al (2012) indicated the canopy (leaf-canopy) temperature as the fastest and the most accurate means of measuring water stress and pointed out that this parameter could be used as a selection criterion in breeding studies. Crop water stress index values vary based on plant genotypes, cultivars, environmental and climate conditions (Testi et al 2008). Water stress is among the most important factors restricting plant production activities and may result in significant changes in chlorophyll content and components through hindering photosynthetic activity in plants (Mozaffari et al 1996). The parameters to be used in identification of drought or water stress should be easy, rapid, cheap and repeatable (Kaleem et al 2009; Moroni et al 2012). Oraki et al (2012) reported increased chlorophyll b levels, decreased chlorophyll a and yield levels with increasing water stress levels. Despite the studies about drought (water stress) tolerance of wheat and chickpea plants (Gunes et al 2008), the studies about plant responds to water stress in sunflower are quite limited. For sunflower, efficient selection criteria to be used in distinguishing potential status of the plants against water stress haven’t been fully elucidated, yet. That is why in present study (2015–2016), 3 different irrigation treatments (I100, I70, I35) were employed. The present study was conducted under field conditions in 2015 and 2016 to determine water stress resistance of 3 sunflower genotypes (P64LE119, PR63F73, P64LL62) grown under strong water-stress, mild water-stress and no water-stress conditions by using kernel yield, crop water stress index and chlorophyll content values.
Identification of Sunflower (Helianthus annuus L.) Genotypes Tolerant to Water Stres
Ali Beyhan UÇAK
Year 2018, Volume 24, Issue 3, 312–322
