Study On The Resistance Of Several Malus Species

Using Malus robusta ?Malus prunifolia?Malus zumi?Malus micromalus ?Malus sieboldii and Malus prunifolia var.Ringo grown in pots as the test materials shoot growth,leaf pigments and properties,photosynthesis,physiological and biochemical characteristics were studied combined with field observation to understand drought,salt and cold tolerances of the tested plants and to provide a theoretical reference for rootstock selection of ‘Bramley's Seedling' apple.Results obtained showed that under drought stress,Pn,Tr and Gs,shoot growth,relative growth rate,leaf area and thickness and root activity of 5 M.spp.,that can be uesd as apple rootstock,showed a trend to decrease while Ci,stomatal density and MDA content had a trend to increase,with the smallest change ranges for M.robusta and the biggest one for M.sieboldii.The soluble sugar and protein contents,SOD activity,stomatal opening and the ratio of palisade to spongy tissues varied in the distinctive species.According to membership function analysis and morphological expression of the tested plants the drought resistance of five tested species could be ranked as M.robusta >M.micromalus > M.prunifolia >M.zumi >M.sieboldii.With the increase of salt concentration,salt injury rate and its index,stomatal density,soluble sugar and MDA contents of 5 tested species increased but Pn,root activity,leaf area,total shoot and relative growth rates,leaf thickness and stomatal opening degree decreased instead,with the smallest change ranges for M.robusta and the biggest one for M.sieboldii.SOD activities of M.prunifolia and M.zumi had a trend to decline at the beginning and then to rise during the salt stress was enhanced but that of M.micromalus and M.sieboldii had a reversed trend to rise firstly and then to decline,with no significant variation for M.Robusta in SOD activity.According to the membership function analysis and the plant morphological expression observed in the field the salt resistance of five tested species could be evaluated as follows M.robusta >M.micromalus >M.prunifolia>M.zumi >M.sieboldii.Electrolyte leakage of all tested species increased obviously when treated temperatures were lowered,with the largest increasing range and regression coefficient of-7.78 for M.sieboldii,the smallest one and that of-2.86 for M.robusta.M.sieboldii suffered the most seriously damage based on morphological characters ofbranch sections after cold treatments and M.robusta had the most lightly damage in all.Critical lethal temperatures of M.sieboldii,M.micromalus,M.zumi,M.prunifolia var ringo,M.prunifolia,and M.robusta were-25.4?,-28.5?,-33.2?,-34.5?,-43.5? and-50.4? respectively.A conclusion could be drown from the indexes quoted above that cold resistance of the six tested species can be ranked as M.robusta >M.prunifolia >M.prunifolia var ringo >M.zumi >M.micromalus >M.sieboldii.Based on comprehensive analysis of drought,salt and cold tolerances of all the tested species and the plants growth observation in the field the resistance of the tested M.spp.to adverse environment was evaluated as follows: M.robusta >M.micromalus >M.prunifolia var ringo >M.prunifolia >M.zumi >M.sieboldii.