Short communication
Relationship of leaf and fruit transpiration rates to the
incidence of spongy tissue disorder in two mango
(
Mangifera indica
L.) cultivars
K.S. Shivashankara
*, C.K. Mathai
Tree Physiology Laboratory, Division of Plant Physiology and Biochemistry, Indian Institute of Horticultural Research, Hessaraghatta Lake Post, Bangalore 560 089, India
Accepted 3 February 1999
Abstract
The relationship of leaf and fruit transpiration rates with the incidence of spongy tissue in mango cultivars Dashahari (free from spongy tissue) and Alphonso (susceptible to spongy tissue) was investigated. Leaf transpiration rates were similar in both the cultivars, however the fruit transpiration rates were significantly higher in cv. Dashahari. Artificially induced variations in fruit transpiration rates using perforated polythene covers and vaseline coating of fruits also resulted in significant changes in the incidence of spongy tissue in cv. Alphonso. The significant and negative relationship observed between the fruit transpiration rate and the spongy tissue suggests that the lower fruit transpiration rates in cv. Alphonso are a varietal specific trait, which results in slower movement of water and minerals to the fruits from soil leading to the development of spongy tissue. #1999 Elsevier Science B.V. All rights reserved.
Keywords: Mango; Spongy tissue; Leaf transpiration; Fruit transpiration; Respiration
1. Introduction
Mango cultivar Alphonso is known for its characteristic flavour, taste and colour, but is severely affected by the spongy tissue disorder (20±60%).
* Corresponding author. Present address: All India Coordinated Research Project on Betelvine, Indian Institute of Horticultural Research, Hessaraghatta Lake Post, Bangalore 560 089, India. Tel.: +91-80-8466420.
Spongy tissue was initially thought to be due to the deficiency of N, P and K. However, application of these nutrients to the soil as well as to the leaves did not reduce the incidence (Amin, 1967; Joshi and Limaye, 1984). On the contrary, their application increased the incidence of spongy tissue (Subramanyam et al., 1971; Limaye et al., 1975). Reports on the contents of Ca and P in affected and healthy tissues of a fruit were not uniform (Subramanyam et al., 1971; Gunjate et al., 1979a; Shanthakrishnamurthy, 1981; Katrodia and Sheth, 1988; Wainright and Burbage, 1989; Raymond et al., 1998). Results with pre or post harvest dips or sprays of calcium were also inconsistent (Gunjate et al., 1979b; Shanthakrishnamurthy, 1982; Katrodia and Sheth, 1988).
Contradictory results with respect to calcium sprays were mainly due to the immobility of calcium through the phloem and also to the effect of environmental factors on the disorder. High temperature during the later stages of fruit development was reported to be the main factor responsible for the development of spongy tissue (Gunjate et al., 1982; Katrodia and Sheth, 1988; Chadha, 1989). However, the occurence of spongy tissue was also noticed inside the canopy and in cooler geographical areas indicating that other environmental factors may play an important role in the development of spongy tissue. Environmental factors like relative humidity, and light were not given due importance by the earlier workers. These factors were found to have a greater influence on the growth and development of tomato and strawberry fruits (Choi et al., 1997). An increase in the incidence of spongy tissue was noticed when the fruits were harvested after a spell of heavy rains. Under dry and warm climatic conditions the incidence of spongy tissue was lower (pers. observation). High atmospheric humidity levels have been reported to be related to many fruit disorders in other crops (Bangerth, 1979; Holder and Cockshull, 1990). This was mainly due to the lower transpiration from the leaves and fruits leading to the lower transportation of mineral nutrients to the fruits (Clarkson, 1984; Menzel and Kirkby, 1987).
Therefore, in this study an attempt was made to understand the relationship between the spongy tissue disorder and the transpiration rates of leaves and fruits in a susceptible and a resistant mango cultivar during the later stages of fruit development.
2. Materials and methods
per unit area and per unit weight respectively. All the parameters were recorded during bright sunny days between 10:00 hours and 11:30 hours. Fruits were 90± 100 days old at the time of the first observation in both the cultivars.
Three more Alphonso trees were selected for altering the fruit transpiration rates. Fruits were selected for vaseline smearing and polythene covering treatments as explained above. Vaseline was smeared during the second week of April to reduce the transpiration of fruits. In another treatment, perforated polythene covers were used to cover the fruits to increase transpiration. Perforations made in the covers avoided the build up of humidity, however, the temperature rose inside the cover (data not reported) due to radiation trapping and increased the transpiration rates of fruits.
Fruits were harvested during the 1st and 2nd week of June and allowed to ripen under laboratory conditions (temperature 29±318C). Incidence of spongy tissue was recorded after slicing the fruits and expressed as per cent affected area of a fruit and also as per cent affected fruits within a treatment.
Photosynthesis and transpiration rates were analysed over varieties using completely randomised design.
3. Results
Data in Table 1 indicate that there were significant differences between the cultivars in photosynthetic rate however, the differences in leaf transpiration rates were non-significant.
Data on fruit gas exchange parameters (Table 2) showed significant differences between the cultivars in both transpiration as well as respiration rates. However, transpiration was four times higher in cv. Dashahari. Hence, fruit transpiration rate rather than the respiration rate was probably more closely associated with the spongy tissue development of fruits.
To test this hypothesis the fruit transpiration was artificially manipulated in the field in cultivar Alphonso. Two treatments namely vaseline coating and covering
Table 1
Leaf photosynthetic and transpiration rates in mango cultivars Alphonso (susceptible to spongy tissue) and Dashahari (free from spongy tissue)
Varieties Photosynthetic rates (mmol CO2mÿ2sÿ1)
Transpiration rate (mmol H2O mÿ2sÿ1)
1st week 2nd week 1st week 2nd week
Alphonso (susceptible) 7.8 8.2 3.4 3.7
Dashahari (resistant) 8.8 9.3 3.3 3.8
CV (%) 17.19 16.21 21.90 18.60
fruits by perforated polythene covers were used to decrease and increase the transpiration, respectively.
Polythene cover treatment significantly increased the transpiration rates of fruits as compared to the control (Table 3). On the other hand Vaseline coating significantly reduced the fruit transpiration. The respiration rate of fruits also showed significant differences between the treatments with the lowest rate in vaseline coated fruits. The transpiration rate was almost doubled in polythene covered fruits as compared to the control. Such fruits showed a significant reduction in the incidence of spongy tissue. Reduction in transpiration rate by vaseline coating on the other hand marginally increased the incidence of the disorder.
Correlation studies between transpiration and the incidence of spongy tissue also indicated a significant negative relationship (Table 4). This further substantiates the involvement of fruit transpiration in the occurrence of spongy tissue in mango.
Table 2
Gas exchange parameters of fruits recorded in the first and second week of May in Alphonso and Dashahari cultivars of mango in the field
Varieties Transpiration
(mmol H2O kgÿ1fw hÿ1)
Respiration
(mg CO2kgÿ1fw hÿ1)
1st week 2nd week 1st week 2nd week
Alphonso 54.3 69.3 43.6 98.8
Dashahari 212.4 229.8 67.9 51.9
CV (%) 17.82 18.71 21.92 19.04
CD (p0.05) 11.36 14.78 6.45 7.56
Table 3
Fruit gas exchange parameters in control, vaseline coated and polythene covered fruits taken during first and third week of may in mango cultivar Alphonso
Treatments Transpiration (mmol H2O kgÿ1hÿ1)
Respiration (mg CO2kgÿ1hrÿ1)
Spongy Tissue
1st week 3rd week 1st week 3rd week % of fruits % of pulp
Control 77.0 76.2 73.7 104.5 20.7 15.5 (23.19) Vaseline 57.3 36.6 42.4 82.5 24.3 16.2 (23.73) Polythene 154.6 110.2 54.5 123.2 6.9 0.9 (5.41) CV (%) 21.83 17.00 21.28 17.46 ± 31.25 CD (p0.05) 10.87 6.53 6.25 9.33 ± 3.42
4. Discussion
Since the studies on the application of major nutrients to the soil (Amin, 1967; Limaye et al., 1975; Joshi and Limaye, 1984), sprays of calcium (Subramanyam et al., 1971; Gunjate et al., 1979a; Shanthakrishnamurthy, 1981), effect of convective heat (Katrodia and Sheth, 1988) and post harvest infiltration of cal-cium (Gunjate et al., 1979b; Shanthakrishnamurthy, 1982) did not give conclusive results, even the reports on calcium concentration in the affected tissues were also not conclusive (Subramanyam et al., 1971; Gunjate et al., 1979a; Shanthakrishna-murthy, 1981; Wainright and Burbage, 1989; Raymond et al., 1998), it was felt that new lines of investigation were needed to understand this disorder.
Inconsistent results obtained by calcium sprays must be mainly due to the immobility of this mineral through the phloem. Lack of uptake, movement and distribution of calcium which is controlled by the movement of water through the transpiration stream (Choi et al., 1997) could be one of the main reasons for the incidence of spongy tissue disorder in the susceptible cultivar.
Our results show that the leaf transpiration rates did not differ significantly between the cultivars even though there was a difference in photosynthetic rates during the later stages of fruit development. This shows that the movement of calcium to the leaf may not be a problem in the susceptible cultivar. However, the movement of calcium from root or leaf to the fruit can also be controlled by the fruit transpiration. Data on fruit transpiration clearly show a difference between the cultivars. Transpiration is one of the reasons for high fruit disorders observed in other crops when grown under high humidities (Bangerth, 1979; Holder and Cockshull, 1990). This was again evident by the higher incidence of spongy tissue observed in fruits harvested after a spell of heavy rains (pers. observation). In this case high humidity associated with the rains would have reduced the transpiration rate of fruits, thereby increasing the incidence of spongy tissue in cultivar Alphonso.
Table 4
A significant reduction in spongy tissue when the fruit transpiration was increased by using perforated polythene covers as well as the slight increase in the incidence when fruit transpiration was checked, substantiates the fact that fruit transpiration is involved in the development of spongy tissue in mango. Similar results were also reported in other crops when grown under different humidities (Clarkson, 1984; Menzel and Kirkby, 1987). Therefore, in mango suitable technologies should be developed to enhance the fruit transpiration in the field to reduce the incidence of spongy tissue.
Acknowledgements
We thank Shri, S.C. Chandrashekar and V. Ramesh for the the excellent technical assistance given during the study.
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