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Lenticels as Pomological Characteristic of Apple and Pear Fruits G. Đurić1,2, N. Mićić1,2 and B. Pašalić1

1 Genetic Resources Institute 2 Faculty of Agriculture University of Banja Luka Banja Luka Bosnia and Herzegovina Keywords: number of lenticels, aesthetic component of the fruits Abstract

The lenticels on the fruits that are permanently covered with epidermis are the organs for intercellular ventilation in the process of internal fruit tissue respiration. In this paper we analyzed morphological parameters and presence of lenticels on fruit peel in order to determine whether the lenticels on fruits can be considered as a reliable cultivar characteristic under the given ecological and production conditions. The emphasis was put on the evaluation of the presence of lenticels on fruits, bearing in mind the complexity of cold fruit storage. The research of morphological parameters and presence of lenticels on fruit peel was conducted on 10 apple cultivars and 13 pear cultivars. The average presence of the lenticels on fruits in the observed apple cultivars was 7.11 lenticels per 1 cm2. The lowest average number of lenticels per 1 cm2 of epidermis was found for the cultivar ‘Pinova’ (4.3), while the highest number was found for the cultivar ‘Granny Smith’ (12.6). The average presence of the lenticels on fruits in the observed pear cultivars was 24.15 lenticels per 1 cm2. The lowest average number of lenticels per 1 cm2 of epidermis was found for the cultivar ‘Alexander Lucas’ (11.70), while the highest number was found for the cultivar ‘Williams’ (37.50). As a cultivar characteristic it is possible to emphasize considerable variation of the number of lenticels between cultivars as well as between individual fruits of the same cultivar. The evaluation of lenticels as an aesthetic fruit component represents significant cultivar characteristic. The research shows correlations in presence and structure of lenticels with predisposition of cultivars for the duration of storage.

INTRODUCTION

Apple and pear fruits are completely covered by an epidermal layer of cells which externally exude cuticle as a permanent coating by which gas exchange of the fruit internal tissues is disabled. Gas exchange in the respiration process in these fruits is carried out through secondary tissue of lenticels which in the pomoidea fruits belong to the open type of lenticels (Clemens, 1935). During the period when determination of fruits was done solely on the basis of morphological characteristics, lenticels were used as a less important indicator in their description (Mićić, 1992). Due to methods development of genetic determination of cultivars, the morphological characteristics of the fruits are more used in the assessment of their market predisposition. However, with the introduction of new cultivars in production, especially apples (Kupferman, 2009) and technology development of the long term storage of apples and pears (ULO, DCA storage rooms), lenticels become important primarily through the emergence of newer physiological disease which is described as lenticel breakdown. Also, the water loss from apple fruits after harvest, and therefore the loss of weight of fruit, primarily depends on the number of lenticels in fruit peel and the depth of the micro-cracks in the tissue of the epidermis, but not on the thickness of the cuticle (Konarski, 2012; Maguire et al., 1999; Veraverbeke et al., 2003). This study was conducted in order to determine presence of lenticels on the fruit surface (per 1 cm2) as relative indicator of predisposition to storage conditions and to evaluate lenticels observed as a factor of aesthetic components of apple and pear fruit.

Proc. II International Symposium on Horticulture in Europe Eds.: J.-C. Mauget and S. Godet Acta Hortic. 1099, ISHS 2015

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MATERIALS AND METHODS The research was conducted on 10 apple cultivars in intensive fruit orchards: 

‘Elstar’, ‘Gala Must’, ‘Gala Schniga’, ‘Breaburn’, ‘Mairac’, ‘Granny Smith’, ‘Pink Lady’, ‘Pinova’, ‘Rubinette’ and ‘Golden Reinders’ as well as 13 pear cultivars in intensive fruit orchards: ‘Abate Fetel’, ‘Alexander Lucas’, ‘Beurré Bosc’, ‘Gellert’s Butter’, ‘Conference’, ‘Packham’s Triumph’, ‘Santa Maria’, ‘Williams’, ‘Doyenné du Comice’, ‘Beurré d’Hardenpont’, ‘Red Williams’, ‘Poire de Clion’ and ‘Kieffer’. These cultivars are stored in the  Genetic Resources Institute of University of Banja Luka. The photo documentation of the lenticels on fruits was created with the scale of 1 mm (15×15 mm), and the comparison of their appearance and presence was made by means of image analysis software (Olympus Master 2).

RESULTS AND DISCUSSION

The average presence of the lenticels on fruits in the observed apple cultivars is given in Table 1.

The average presence of the lenticels on fruits in the observed apple cultivars was 7.11 lenticels per 1 cm2 of fruit peel. The lowest number of lenticels per 1 cm2 of peel was found for ‘Pinova’ (4.3), while the highest number was found for ‘Granny Smith’ (12.6). The interval of the variation of the number of lenticels per 1 cm2 of fruit peel in the cultivars that had a coefficient of variation below 30% was 3-10 lenticels per 1 cm2, while for the cultivars that had a coefficient of variation over 30%, the interval of variation ranged from 3-23 lenticels per 1 cm2 of fruit peel.

The average presence of the lenticels on fruits in the observed pear cultivars is given in Table 2.

The average presence of the lenticels on fruits in the observed pear cultivars was 24.15 lenticels per 1 cm2 of fruit peel. A considerable variation was not only determined between cultivars but also between individual fruits of the same cultivar. The lowest average number of lenticels per 1 cm2 of peel was found for the cultivar ‘Alexander Lucas’ (11.70), while the highest number was found for ‘Williams’ (37.50). The interval of the variation of the number of lenticels per 1 cm2 of fruit peel in the cultivars that had a coefficient of variation below 30% was 7-44 lenticels per 1 cm2, while for the cultivars that had a coefficient of variation over 30%, the interval of variation ranged from 6-66 lenticels per 1 cm2 of fruit peel.

The evaluation of lenticels as an aesthetic component of fruits was done by means of observing the appearance and color of lenticels on the primary and secondary fruit color and the quality of being visible on fruits (Fig. 1). Thus, the lenticels in the following cultivars: ‘Gala Schniga’, ‘Breaburn’ and ‘Granny Smith’ make an attractive component in the fruit appearance, while the lenticels have the opposite effect in these cultivars: ‘Red Delicious’, ‘Elstar’, ‘Mairac’ and ‘Golden Reinders’. The evaluation of lenticels as an aesthetic component of pear fruits (Fig. 2) shows that the lenticels on the observed commercial pear cultivars generally have no aesthetic significance, while the lenticels on ‘Kieffer’ pear can be identified as an aesthetic component in fruit description. The question of genotype specificity in the structure of lenticels and their relatedness to intercellulars in deeper layers of apple and pear fruit flesh tissue, i.e., cytohistological changes of sub-epidermal tissues of lenticels as consequences of various storage conditions are subjects for further research.

CONCLUSIONS

The presence of the lenticels on the peels of pomoidea shows significant differences between species.  The average presence of the lenticels on fruits in the observed apple cultivars was 7.11 lenticels per 1 cm2 and  in the observed pear cultivars 24.15 lenticels per 1 cm2. Greater presence of lenticels per fruit clearly shows less storage capacity of fruits. Lenticels, as an aesthetic component of the fruits have significance on apple fruits, while their significance on pear cultivars in aesthetic terms is smaller.

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Literature Cited Clements H.F. 1935. Morphology and physiology of the pome lenticels of Pyrus malus.

Bot. Gaz. 97:101-117. Konarska, A. 2012. Differences in the fruit peel structures between two apple cultivars

during storage. Acta Sci. Pol., Hortorum Cultus 11(2):105-116. Kupferman, G., Sater, C., Walter, M. and Buchanan, N. 2009. Strategies for Minimizing

Lenticel Breakdown. Washington State University. Wenatchee, WA. Maguire K.M., Lang, A., Banks, N.H., Hall, A., Hopcroft, D. and Benneti, R. 1999.

Relationship between water vapour permeance of apples and micro-cracking of the cuticle. Postharvest Biol. Technol. 17:89-96.

Mićić, N. 1992. Specijalno voćarstvo, I dio – jabučaste i koštičave voćke. Poljoprivredni fakultet Univerziteta u Sarajevu.

Shaheen, M.A., Miles, N.W. and Kreitner, G.L. 1981. Lenticel origin on Golden Delicious apple fruits. Journal of the American Pomological Society 35(4):134-136.

Veraverbake, E.A., Verboven, P., van Oodstveldt, P. and Nicolai, B.M. 2003. Prediction of moisture loss across the cuticle of apple (Malus sylvestris subsp. Mitis (Wallr.)) during storage: part 1. Model development and determination of diffusion coefficients. Postharvest Biol. Technol. 30:75-88.

Tables Table 1. The average presence of the lenticels on fruits peel per 1 cm2 in the observed

apple cultivars.

Cultivar XSX Iv Vc

1. Elstar 6.60±0.79 3-11 37.87 2. Gala Must 7.50±0.42 6-10 18.00 3. Gala Schniga 7.90±0.75 5-13 30.00 4. Granny Smith 12.60±1.55 7-23 39.05 5. Mairac 7.60±0.43 6-10 17.63 6. Pink Lady 8.01±0.77 4-11 30.50 7. Breaburn 5.50±0.65 3-9 37.45 8. Pinova 4.30±0.36 3-7 26.74 9. Rubinette 6.60±0.70 4-10 33.63 10. Golden Reinders 4.50±0.37 3-7 26.00 The total average 7.11 3-23

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Table 2. The average presence of the lenticels on fruits peel per 1 cm2 in the observed pear cultivars.

Cultivar XSX Iv Vc

1. Abate Fetel 27.40±3.36 17-47 37.81 2. Alexander Lucas 11.70±1.08 7-18 29.31 3. Beurré Bosc 15.60±4.30 6-52 87.11 4. Gellert’s Butter 23.10±2.84 9-34 38.87 5. Conference 13.20±1.58 7-26 37.92 6. Packham’s Triumph 36.90±1.40 31-44 12.01 7. Santa Maria 22.90±1.56 14-32 21.61 8. Villiams 37.50±4.18 25-66 35.31 9. Doyenné du Comice 31.90±3.10 18-47 30.73 10. Beurré d’Hardenpont, 19.70±2.12 10-31 31.31 11. Red Williams 24.30±1.74 17-35 22.67 12. Poire de Clion 19.90±1.72 14-30 27.33 13. Kieffer pear 34.50±4.56 17-71 41.82 The total average 24.51 6-66

Figures

Fig. 1. Lenticels of studied apple cultivars.

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Fig. 2. Lenticels of studied pear cultivars.