Abstract
BackgroundApple trees are often subject to severe salt stress in China as well as in the world that results in significant loss of apple production. Therefore this study was carried out to evaluate the response of apple seedlings inoculated with abuscular mycorrhizal fungi under 0, 2‰, 4‰ and 6‰ salinity stress levels and further to conclude the upper threshold of mycorrhizal salinity tolerance.ResultsThe results shows that abuscular mycorrhizal fungi significantly increased the root length colonization of mycorrhizal apple plants with exposure time period to 0, 2‰ and 4‰ salinity levels as compared to non-mycorrhizal plants, however, percent root colonization reduced as saline stress increased. Salinity levels were found to negatively correlate with leaf relative turgidity, osmotic potential irrespective of non-mycorrhizal and mycorrhizal apple plants, but the decreased mycorrhizal leaf turgidity maintained relative normal values at 2‰ and 4‰ salt concentrations. Under salt stress condition, Cl− and Na+ concentrations clearly increased and K+ contents obviously decreased in non-mycorrhizal roots in comparison to mycorrhizal plants, this caused mycorrhizal plants had a relatively higher K+/Na+ ratio in root. In contrast to zero salinity level, although ascorbate peroxidase and catalase activities in non-inoculated and inoculated leaf improved under all saline levels, the extent of which these enzymes increased was greater in mycorrhizal than in non-mycorrhizal plants. The numbers of survived tree with non-mycorrhization were 40, 20 and 0 (i.e., 66.7%, 33.3% and 0) on the days of 30, 60 and 90 under 4‰ salinity, similarly in mycorrhization under 6‰ salinity 40, 30 and 0 (i.e., 66.7%, 50% and 0) respectively.ConclusionThese results suggest that 2‰ and 4‰ salt concentrations may be the upper thresholds of salinity tolerance in non-mycorrhizal and mycorrhizal apple plants, respectively.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-014-0070-6) contains supplementary material, which is available to authorized users.
Highlights
Apple trees are often subject to severe salt stress in China as well as in the world that results in significant loss of apple production
Effect of different salinity levels on root length colonization of apple seedlings inoculated and non-inoculated with Abuscular mycorrhizal (AM) fungi In non-mycorrhizal plants root length colonization rate was always zero, mycorrhizal plants presented a trend in increase in percent root colonization at zero, low (2‰), moderate (4‰) and high (6‰) salinity levels
In mycorrhizal plants root colonization percentage continually increased with time period at zero, low and moderate salinity levels except for that root colonization rate gradually reduced with prolonged exposure to high salinity level
Summary
Apple trees are often subject to severe salt stress in China as well as in the world that results in significant loss of apple production. Plants are often stressed in three ways: (1) low water potential in the root medium leads to water deficits in plants, (2) the toxic effects of ions, mainly Na and Cl, Apple (Malus × domestica Borkh.) is one of the most valuable horticultural fruit crops in the world It produces the highest yield in China, it is not a halophyte species and sensitive to salinity, it is subject to severe salt stress in many areas (Flowers 1999; Xia et al 2005; Navarro 2003). To deal with saline soil and minimize apple loss, many strategies were proposed to counteract salt detrimental effects such as searching for new salt-tolerant apple rootstock, removing excessive salt accumulation in groundwater and desalinizing water for irrigation (Reza et al 2012; Bouksilaa et al 2013) Though successful, these approaches are costly and out of reach for developing countries. The loss of apple productivity caused by salt stress is still a major concern
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
