Varietal differences in physiological and biochemical responses to salinity stress in six finger millet plants

Abstract

Finger millet is one of the most important cereals that are often grown in semiarid and arid regions of East-Africa. Salinity is known to be a major impediment for the crop growth and production. This study was aimed to understand the mechanisms of physiological and biochemical responses to salinity stress of Kenyan finger millet varieties (GBK043137, GBK043128, GBK043124, GBK043122, GBK043094, GBK043050) grown across different agroecological zones under NaCl-induced salinity stress. Seeds were germinated on the sterile soil and treated using various concentrations of NaCl (100, 200 and 300 mM) for two weeks. Again, the earlyseedling stage of germinated plants was irrigated with the same salt concentrations for 60 days. Results indicated depression in germination percentage, shoot and root growth rate, leaf relative water content, chlorophyll content contents, leaf K + concentration, and leaf K + /Na + ratios increased salt levels. Contrary, proline and malonaldehyde (MDA) contents reduced sugar content and leaf total proteins. At the same time, the leaf Na + and Clamounts of all plants increased substantially with rising stress levels. Clustering analysis revealed that GBK043094 and GBK043137 were placed together and identified as salt-tolerant varieties based on their performance under salt stress. Overall, our findings indicated a significant varietal variability for most of the parameters analysed. These superior varieties identified could be potentially used as promising genetic resources in future breeding programmes development directed towards salt-tolerant finger millet hybrids. Further analysis at genomic level need to be undertaken to better understand the genetic factors that promote salinity tolerance in finger millet.

A Review of Recent Advances and Future Directions in the Management of Salinity Stress in Finger Millet

“…Proline accumulation in plants is related to water deficit and salinity stress, where it acts as an osmolyte for osmotic adjustment, stabilizes membranes and proteins, scavenges free radicals, and buffers cellular redox potential under stress conditions ( Boscaiu Neagu et al, 2012 ). An increased level of endogenous proline accumulation in plants is correlated with enhanced salt tolerance ( Sripinyowanich et al, 2013 ), and has been reported in a number of plant species such as Pisum sativum ( Ozturk et al, 2012 ), Glycine max ( Weisany et al, 2012 ), Cucumis melo ( Sarabi et al, 2017 ), Oryza sativa ( Kibria et al, 2017 ), and Eleusine coracana ( Mahadik and Kumudini, 2020 ; Mukami et al, 2020 ).…”

“…Earlier studies on the finger millet salinity tolerance primarily relied on the screening of salt-tolerant cultivars under saline conditions ( Krishnamurthy et al, 2014 ; Rahman et al, 2014 ; Mukami et al, 2020 ). Various biochemical and physiological studies have reported that salt-tolerant cultivars, when exposed to saline conditions, are not adversely affected in terms of germination, shoot length, root length, biomass, Na + and K + ratio, total soluble sugars, membrane stability, and chlorophyll content ( Rahman et al, 2014 ; Taïbi et al, 2016 ; Ishikawa and Shabala, 2019 ; Mukami et al, 2020 ). In their study, Mukami et al (2020) reported a less lower reduction of germination rate in salt-tolerant than in salt-sensitive cultivars.…”

“…Various biochemical and physiological studies have reported that salt-tolerant cultivars, when exposed to saline conditions, are not adversely affected in terms of germination, shoot length, root length, biomass, Na + and K + ratio, total soluble sugars, membrane stability, and chlorophyll content ( Rahman et al, 2014 ; Taïbi et al, 2016 ; Ishikawa and Shabala, 2019 ; Mukami et al, 2020 ). In their study, Mukami et al (2020) reported a less lower reduction of germination rate in salt-tolerant than in salt-sensitive cultivars. Salt-tolerant cultivars also displayed a lower root/shoot growth retardation and had a slightly higher growth, low Na + to K + ratio in leaves and shoots, and higher amounts of total soluble sugars in leaves compared to salt-sensitive plants ( Rahman et al, 2014 ).…”

“…Several studies suggest that chlorophyll content is a biochemical marker of salt tolerance in plants ( Taïbi et al, 2016 ; Ishikawa and Shabala, 2019 ). Salt-tolerant finger millet varieties have reported increased or unchanged chlorophyll levels under salinity conditions, whereas chlorophyll content decreased in salt-sensitive plants ( Hema et al, 2014 ; Mahadik and Kumudini, 2020 ; Mukami et al, 2020 ). Plants use compatible solute accumulation to counter-attack the adverse effects of ROS.…”

“…Seed germination and seedling establishment stages in finger millet are highly affected by salinity stress ( Hema et al, 2014 ). Many reports have shown that salinity stress substantially affects impacts seedling and root growth, levels of ion content and relative water content, photosynthetic pigments, proline content, levels of membrane peroxidation, and the amount of reducing sugars and total proteins ( Kumar and Khare, 2016 ; Sarabi et al, 2017 ; Dugasa et al, 2020 ; Mukami et al, 2020 ). Although there is limited information available on yield loss of in large-scale producing areas, pot studies have reported genotypic variability in the grain yield loss among different multiple varieties ( Krishnamurthy et al, 2014 ).…”