Abstract

Low temperature is a major environmental and evolutionary driver that limits the geographical distribution of plant speciesworldwide. The relationship between low temperature stress and the response of some different mango cultivars was monitored on some physiological and biochemical events that occur following cold exposure of mango trees leaves. These changes were studied under in vitro (controlled temperatures). However, mango trees were tested to study the changes in leaf pigments and chlorophyll fluorescence of some mango cultivars in response to exposure to low temperature. To verify this objective, 12 popular commonly mango cultivars (25 years old) which grown in private orchard in Fayoum Governorate, Egypt were selected for this study which carried out during the period from November to March of years; 2012 and 2013. The selected cultivars were: Alphonso, Baladi, Bullock's Heart, Helmand, Hindi Besennara, Mabrouka, Mestekawy, Nabeeh, Oweisi, Spates, Taimour and Zebda. Based on the obtained results, it can be stated that in cold storage trial; It was found that chlorophyll (a) level was the highest by Spates cultivar and the lowest one by the cultivar of Mabrouka at storage of 5°C and 10°C as well. Chlorophyll (b) level was the highest by the cultivar of Spates and the minimum one by Ewais cultivar at 5°C of storage while, the cultivars of Spates and Mabrouka given the highest and lowest level at 10°C of storage, respectively. Total chlorophyll values in leaves reached its maximal by the cultivar of Spates and the minimal by Mabrouka at 5°C and 10°C of storage. The obtained results explained that the level of carotenoids reached its peak at 5°C and 10°C of storage by the cultivars of Hindy Besennara and bullock’s Heart, respectively. While, the lowest one was recorded by the cultivars of Zebda and Helmand, respectively. The levels of anthocyanin in leaves were significantly differed as affected by the cultivars and storage, indicating that the cultivars of Ewais and Taimour showed the highest levels of anthocyanin and the lowest ones were recorded by the cultivars of Zebda and Alphonso at 5°C and 10°C of storage, respectively. It can be seen that the highest decline in Fv/Fm ratio were given by the cultivar of Balady while, the higher ratio was recorded by Nabeeh cultivar at 5°C of storage. At 10°C of storage, Nabeeh cultivar gave the highest ratio of Fv/Fm and the lowest one was obtained by Mestekawy one. A noticeable decline in Fv/Fm values was observed as storage period (5°C and 10°C) was progressed reaching the minimum level by day 10 of storage.

Keywords

mango, cultivars, cold tolerance, leaf pigments, chlorophyll fluorescence, geographical distribution, physiological changes, photosynthetic processes, chlorophyll fluorescence, biochemical studies, cultivar of spates, physiological and metabolic disorders, plant breeding, tropical and subtropical