توصيفگر ها :
بحران كمبود آب , تحمل به خشكي , تغييرات اقليمي , تنوع ژنتيكي , كيفيت سيلاژ , ماشك علوفهاي
چكيده انگليسي :
The water scarcity crisis, driven by frequent droughts and climate change due to rising greenhouse gas concentrations, particularly carbon dioxide (CO₂), severely challenges crop production. Forage legumes like vetch, valued for nitrogen fixation, soil fertility improvement, and high-quality forage, have gained significant attention. This study investigated the effects of drought stress and elevated CO₂ on morphological, physiological, and forage traits of various vetch cultivars through three distinct experiments.
In the first study, ten vetch genotypes (V. dasycarpa Ten., V. pannonica Crantz, V. michauxii Spreng., V. sativa F. Shahr, V. villosa Roth, V. sativa Mashhad, V. sativa Ardebil, V. sativa Shahrekord, V. sativa Semirom, and V. sativa Dashtyar) were evaluated over two autumn seasons (2019–2020 and 2020–2021) at the Isfahan University of Technology’s Najafabad research farm. Three soil moisture levels were tested: normal (30% maximum allowable depletion [MAD]), moderate stress (55% MAD), and severe stress (85% MAD). Results revealed significant genotypic variation. Drought stress reduced all morphological traits. V. dasycarpa Ten. showed higher biological yield and a shorter growth period, while V. michauxii Spreng. excelled in thousand-seed weight, seeds per pod, fresh weight, biological yield, and grain yield, marking them as superior genotypes. Drought stress increased ascorbate peroxidase, catalase, and peroxidase activities, total soluble carbohydrates, leaf proline, electrolyte leakage, DPPH activity, malondialdehyde, and hydrogen peroxide, while decreasing chlorophyll a and b, carotenoid content, photosystem II quantum efficiency, leaf relative water content, and membrane stability index. In the second study, forage from all vetch genotypes was harvested at the flowering stage during the 2019–2020 and 2020–2021 seasons under the three moisture levels and ensiled in cylindrical silos for three months. Severe drought stress reduced forage quality, particularly dry matter percentage, protein, and nutritional value. Silage organic acid composition shifted, with butyric acid increasing and acetic acid decreasing under severe stress. V. michauxii Spreng. and V. pannonica Crantz outperformed others in quality traits and organic acid composition, while V. sativa genotypes were less resilient. In the third study, a factorial experiment in 2010 at the Chah Anari Farm (Isfahan University of Technology) examined six vetch genotypes under a randomized complete block design with three replications, comparing ambient (400 μmol/mol) and elevated (700 μmol/mol) CO₂ levels under drought stress. Severe drought stress caused more pronounced trait differences than moderate stress. V. michauxii Spreng. exhibited greater stress tolerance. Elevated CO₂ increased vetch yield, especially root dry weight, mitigating stress-induced reductions in relative water content and increases in hydrogen peroxide. This suggests high CO₂ levels may alleviate drought challenges, warranting further genetic and molecular research. This study offers valuable insights into drought-tolerant vetch genotypes and underscores the need for deeper investigation into the molecular mechanisms driving these adaptive responses, supporting sustainable forage production in a changing climate.
