Determination of cold and freezing injury grade indexes for three tropical characteristic fruit trees

CHEN Hui; YANG Kai; LI Zheng; CHEN Fuzi; PENG Jida; LIN Jing; LI Lichun; TANG Lisheng; MA Zhiguo

doi:10.13925/j.cnki.gsxb.20170123

Abstract：[Objective]The planting benefits of wax apples,mangos and Zizyphus mauritiana are relatively large and these fruit trees had developed rapidly in recent years in Fujian,Guangxi,and Guangdong provinces.However,these areas belong to the northern edge of the tropical fruit trees planting area and coupled with the blind actions of farmers,cold and freezing injuries occur annually in varying degrees.Currently,there are no cold and freezing injury grade indexes of Zizyphus mauritiana and mangos and only preliminary studies on wax apples.In order to achieve a reasonable layout,to reduce the loss from cold and freezing injuries and to ensure the healthy and stable development of tropical fruit trees,there is an urgent need to establish cold and freezing injury grade indexes for wax apples and mangos and Zizyphus mauritiana by using a variety of different methods.[Methods] Based on the historical climate data and the investigated data of large-scale cold and freezing injuries and other experimental methods,the morphological changes of wax apples,Zizyphus mauritiana and mangos were analyzed.According to the morphological standard of cold and freezing injuries,the grade of injury samples was determined.On the basis of the cold and freezing grade (x) and the minimum temperature (Td) samples of process before 2015,the relationship between X and Td was established by means of mathematical statistics and the grade indexes of cold and freezing injuries were preliminarily determined.The grade indexes of three fruit trees were determined by validation methods of artificial climate chamber experiments and geographical transplantation experiments and actual orchard disaster samples in 2016.[Results]The relationship between the grade disaster (X) of three fruit trees and the minimum temperature (Td) of the related processes were determined by applying many functional equations,with the results showing that the fitting effect of an equation of one degree,an equation of two degrees and an equation of three degrees was very good.The cold and freezing injury grade (x=0.5,1.5,2.5,3.5) was divided into the following three equations for the fruit trees:the critical thresholds of no to light grade,light to moderate grade,moderate to severe grade and severe to most severe grade at low temperature (Td) could be concluded;the Td values from the three equations were averaged,for the convenience of the application and the values were required to take an integer of 0.5 ℃;our work in this paper determined the cold and freezing injury grades of the three tropical characteristic fruit trees with morphological indexes as follows:wax apple:Tmin＞5.5 ℃,without cold and freezing injury,normal growth;3.0 ℃ ＜Tmin≤5.5 ℃,light injury;1.0 ℃ ＜Tmin≤3.0 ℃,moderate injury;-1.5 ℃ ＜Tmin≤ 1.0 ℃,severe injury;Tmin≤-1.5 ℃,most severe injury,no recovery or death.Zizyphus mauritiana:Tmin＞ 5.0 ℃,without cold and freezing injury,normal growth;3.0 ℃＜Tmin≤5.0 ℃,light injury;0.5 ℃＜Tmin≤ 3.0℃,moderate injury;-2.5 ℃＜Tmin≤0.5 ℃,severe injury;Tmin≤-2.5 ℃,most severe injury,no recovery or death.Mango:Tmin＞2.0 ℃,without cold and freezing injury,normal growth;0.5℃＜Tmin≤2.0 ℃,light injury;-1.0 ℃＜Tmin≤0.5 ℃,moderate injury;-2.5 ℃＜Tmin≤-1.0 ℃,severe injury;Tmin≤-2.5 ℃,most severe injury,no recovery or death.The grade indexes of our research was verified by the results of the artificial climate chamber experiment:the coincidence rates were 90％,100％ and 100％,respectively,the coincidence rates of the geographical transplantation experiment were 96.3％,88.2％ and 94.1％,respectively and the validation results of a typical year were 91％,83.3％ and 90％,respectively.[Conclusion] The cold and freezing injury grade indexes of the three tropical fruits were determined with the morphological indexes,the grade index was verified by the artificial climate chamber experiment,geographical transplantation experiment and typical year's results,the accuracy rate of validation was high.The grade index could be used in practical applications.