INTRODUCTION Sapota (Manilkara zapota (Royen) commonly known as “chikku”, is one of the delicious tropical fruits. It was introduced into India in the 1800’s from Mexico via Sri Lanka. This climacteric fruit is well-adapted to the tropical parts of country. It is a hardy tree that can be cultivated in saline soils too. Sapota is cultivated mainly in the southern states of India, with maximum area under it in Karnataka. Apart from its use as fresh fruit, various processed products like pulp powder, fig, juice, flakes, etc., are becoming popular. Therefore demand for the fruits has increased in recent years. Two main types of sapota are found, based on fruit shape, viz., ‘round’ and ‘oval’. But, like in the other tree crops, due to occurrence of heterozygocity, there are several intermediates types. Studies on fruit variability was reported by Dinesh and Reddy (2000) Avaiyo and Singh (1991) Ponnuswamy and Irulappan (1987 and 1989). Saraswathy et al (2010) observed that number of fruits per tree and canopy-spread had positive correlation with fruit-yield per tree. Quality traits like total sugars and ascorbic acid content had negative correlation with fruit-yield. In the present study, an effort has been made to categorize the available variability into groups based on fruit characters, analyze the variability and study correlations among various fruit characteristics, which would be useful in further breeding programmes. Genetic correlation and cluster analysis in sapota (Manilkara zapota) A. Rekha, M.R. Dinesh, R. Venugopalan1 and B.N.S. Murthy Division of Fruit Crops Indian Institute of Horticultural Research Hessaraghatta Lake Post, Bangalore – 560 089, India E-mail : arekha@iihr.ernet.in ABSTRACT Sapota is classified into two main types based on fruit shape as ‘round’ and ‘oval’. However, there are several intermediates, as, it is a heterozygous tree crop. In this study, an effort was made to group available variability in sapota based on fruit characters and to analyze it. This helps in selection of parents for use in further breeding programmes. Cluster analysis revealed four definite clusters. High variability was observed for fresh-fruit weight, fruit length, fruit girth, fruit weight at ripening, pulp weight, peel weight, number of seeds and TSS. Correlation studies among fruit parameters indicated positive relationship between all the parameters studied, except TSS which had negative relationship with the rest of the fruit parameters. Selection of distantly placed cultivars in breeding programs stands to result in better progeny for further evaluation. Key words: Sapota, fruit parameters, variability, correlation, clusters MATERIAL AND METHODS Germplasm collected from various sources in Karnataka, Andhra Pradesh, Tamil Nadu and Gujarat was maintained in a field gene bank, with four trees per accession, at Indian Institute of Horticultural Research, Bangalore. Twenty accessions were selected for the study, which included an important commercial cultivar, Cricket Ball. Five mature fruits from each accession were selected after pooling the fruits from all four trees and observations were recorded in five replications, i.e., fruits were harvested five times as and when fruits matured. Observations were recorded on 25 fruits per accession on morphological characters like fresh-fruit weight, fruit length, fruit breadth (at the broadest region), ripe-fruit weight, pulp weight (after scraping the pulp from peel), peel weight, number of seeds per fruit, TSS (oBrix), seed length and seed breadth. Some morphological parameters like leaf length and leaf breadth were also included in Cluster Analysis, as, variations in leaf- size were observed. For this purpose, five fully-mature leaves from each accession were selected. The means of all 12 characters were subjected to Squared Eucledien Cluster Analysis and a dendrogram was derived using Ward’s method (1963). Variability studies were made using fruit characteristics in 17 accessions of sapota. Observations on fresh-fruit weight, fruit length, fruit breadth, ripe-fruit 1 Section of Economics and Statistics J. Hortl. Sci. Vol. 6(2):101-104, 2011 Prinect Color Editor Page is color controlled with Prinect Color Editor 4.0.70 Copyright 2008 Heidelberger Druckmaschinen AG http://www.heidelberg.com You can view actual document colors and color spaces, with the free Color Editor (Viewer), a Plug-In from the Prinect PDF Toolbox. Please request a PDF Toolbox CD from your local Heidelberg office in order to install it on your computer. Applied Color Management Settings: Output Intent (Press Profile): GrayCoated_hdm.icc RGB Image: Profile: eciRGB.icc Rendering Intent: Perceptual Black Point Compensation: no RGB Graphic: Profile: eciRGB.icc Rendering Intent: Perceptual Black Point Compensation: no CMYK Image: Profile: ISOcoated_v2_eci.icc Rendering Intent: Perceptual Black Point Compensation: no Preserve Black: no CMYK Graphic: Profile: ISOcoated_v2_eci.icc Rendering Intent: Perceptual Black Point Compensation: no Preserve Black: no Device Independent RGB/Lab Image: Rendering Intent: Perceptual Black Point Compensation: no Device Independent RGB/Lab Graphic: Rendering Intent: Perceptual Black Point Compensation: no Device Independent CMYK/Gray Image: Rendering Intent: Perceptual Black Point Compensation: no Device Independent CMYK/Gray Graphic: Rendering Intent: Perceptual Black Point Compensation: no Turn R=G=B (Tolerance 0.5%) Graphic into Gray: yes Turn C=M=Y,K=0 (Tolerance 0.1%) Graphic into Gray: no CMM for overprinting CMYK graphic: no Gray Image: Apply CMYK Profile: no Gray Graphic: Apply CMYK Profile: no Treat Calibrated RGB as Device RGB: no Treat Calibrated Gray as Device Gray: yes Remove embedded non-CMYK Profiles: no Remove embedded CMYK Profiles: yes Applied Miscellaneous Settings: Colors to knockout: yes Gray to knockout: yes Pure black to overprint: no Turn Overprint CMYK White to Knockout: yes Turn Overprinting Device Gray to K: no CMYK Overprint mode: set to OPM1 if not set Create "All" from 4x100% CMYK: no Delete "All" Colors: no Convert "All" to K: no 102 weight, pulp weight, peel weight, number of seeds per fruit and TSS (oBrix) were recorded and subjected to analysis of variation (ANOVA). Phenotypic correlation was calculated. RESULTS AND DISCUSSION Fruit variability Studies on fruit parameters involving 17 accessions showed that fresh-fruit weight at harvest ranged from 54.48g to 143.95g, with maximum in the variety CO-1 and minimum in ‘Jhumakiya’. Maximum fruit length of 7.23cm was observed in ‘CO-1’, and minimum (4.46cm) in ‘Jhumakiya’. Fruit girth was maximum in var. Bombay with 5.65cm, and minimum (4.33cm) was recorded in the variety Pilipatti. At ripening, 25% reduction in fruit weight was observed in all the accessions studied. Peel weight varied between 13.25g and 35.00g in ‘Jhumakiya’ and ‘Hybrid’, respectively. Maximum number of seeds was found in the variety Guruvayya with an average of six seeds per fruit and, the minimum of one seed per fruit was observed in var. Gavaraiah, followed by ‘CO-1’. TSS (oBrix) was maximum in Pilipatti (20.39) and minimum in Guruvayya (15.02). Coefficient of variation was maximum in peel weight (28.38%), followed by number of seeds (24.72%) and the minimum (7.23%) was observed for fruit girth, followed by 9.54% in fruit length (Table 1). Analysis of variance showed high variability for fruit characteristics among all the varieties. All the characters except fruit length and TSS exhibited variability within a variety (Table 2). Phenotypic correlation Correlation studies among the eight fruit parameters under study revealed significant positive relationship for all parameters except number of seeds/fruit and TSS, where it was found to be negative. Correlation indicated that ripe- fruit weight, fruit length, fruit breadth, pulp weight, and peel weight contributed to fresh-fruit weight. TSS showed negative correlation with all the parameters, indicating that increase in fruit weight affected quality of the fruit through TSS, as reported by Saraswathy et al (2010). Number of seeds per fruit did not show significant correlation with any character, but had significant negative correlation with fruit length. This shows that seed number can influence fruit shape (Table 3). Cluster analysis Cluster analysis clearly indicated affinity and relationship between different sapota accessions (Fig. 1). There were two main clusters, further divided into two sub- clusters i.e., a total of four sub-clusters). The first sub-cluster comprised seven varieties. The second sub-cluster included six accessions. The third sub-cluster had two accessions which were distinct. The fourth sub-cluster was composed of five accessions. All accessions within each cluster showed a close relationship. The first cluster (including sub- clusters 1 and 2) had 13 accessions comprising of small, oval fruit types. The first sub-cluster included the accessions Calcutta Round, CO-2, Vavilavalasa, Kirtibarti, Mohangooti, Table 1. Fruit parameters in 17 sapota varieties Variety Fruit Fruit Fruit Ripe fruit Pulp Peel No. of TSS weight length girth weight weight weight seeds (oBrix) (g) (cm) (cm) (g) (g) (g) 1. Cricket ball 112.70 5.16 5.13 103.67 69.99 31.20 3.35 18.75 2. Calcutta round 98.30 5.03 5.39 87.90 49.83 27.58 3.49 18.74 3. Pilipatti 64.46 5.33 4.33 58.69 37.58 17.14 2.80 20.39 4. Gavaraiah 134.62 6.60 5.62 119.34 89.21 30.78 1.52 17.99 5. Mohangooti 81.74 6.06 4.59 75.76 57.63 17.86 3.10 19.56 6. Krishna Rao 125.93 6.37 5.49 100.31 70.67 33.45 5.38 18.20 7. Jumakiya 54.48 4.46 4.38 49.42 30.70 13.25 3.66 16.49 8. Kirti barti 91.95 5.68 5.02 82.29 57.00 22.09 2.12 17.45 9. Hybrid 139.30 7.19 5.49 125.80 86.50 35.00 2.16 17.12 10. Bombay 108.99 5.17 5.65 97.56 67.97 28.18 4.19 17.69 11. Seedless 90.02 5.71 4.95 82.98 58.70 22.36 2.24 18.15 12. Dwarapudi 62.50 5.19 4.57 57.24 40.68 14.04 3.20 17.97 13. Vavilavalasa 94.82 4.94 5.47 82.72 60.33 23.15 3.35 18.31 14. CO1 143.95 7.23 5.59 131.77 92.71 41.01 1.78 16.77 15. CO2 93.76 5.19 5.57 82.49 55.42 22.33 3.70 19.01 16. Unknown 89.24 5.58 5.00 83.07 59.09 21.42 2.08 17.57 17. Guruvayya 113.05 6.04 5.39 101.69 70.36 28.89 6.23 15.02 Range 54.48 4.46 4.33 49.42 30.70 13.25 1.52 15.02 to 143.95 to 7.23 to 5.65 to 131.77 to 92.71 to 35.00 to 6.23 to 20.39 CV (%) 13.85 9.54 7.23 15.83 18.89 28.38 24.72 8.85 J. Hortl. Sci. Vol. 6(2):101-104, 2011 Rekha et al Prinect Color Editor Page is color controlled with Prinect Color Editor 4.0.70 Copyright 2008 Heidelberger Druckmaschinen AG http://www.heidelberg.com You can view actual document colors and color spaces, with the free Color Editor (Viewer), a Plug-In from the Prinect PDF Toolbox. Please request a PDF Toolbox CD from your local Heidelberg office in order to install it on your computer. Applied Color Management Settings: Output Intent (Press Profile): GrayCoated_hdm.icc RGB Image: Profile: eciRGB.icc Rendering Intent: Perceptual Black Point Compensation: no RGB Graphic: Profile: eciRGB.icc Rendering Intent: Perceptual Black Point Compensation: no CMYK Image: Profile: ISOcoated_v2_eci.icc Rendering Intent: Perceptual Black Point Compensation: no Preserve Black: no CMYK Graphic: Profile: ISOcoated_v2_eci.icc Rendering Intent: Perceptual Black Point Compensation: no Preserve Black: no Device Independent RGB/Lab Image: Rendering Intent: Perceptual Black Point Compensation: no Device Independent RGB/Lab Graphic: Rendering Intent: Perceptual Black Point Compensation: no Device Independent CMYK/Gray Image: Rendering Intent: Perceptual Black Point Compensation: no Device Independent CMYK/Gray Graphic: Rendering Intent: Perceptual Black Point Compensation: no Turn R=G=B (Tolerance 0.5%) Graphic into Gray: yes Turn C=M=Y,K=0 (Tolerance 0.1%) Graphic into Gray: no CMM for overprinting CMYK graphic: no Gray Image: Apply CMYK Profile: no Gray Graphic: Apply CMYK Profile: no Treat Calibrated RGB as Device RGB: no Treat Calibrated Gray as Device Gray: yes Remove embedded non-CMYK Profiles: no Remove embedded CMYK Profiles: yes Applied Miscellaneous Settings: Colors to knockout: yes Gray to knockout: yes Pure black to overprint: no Turn Overprint CMYK White to Knockout: yes Turn Overprinting Device Gray to K: no CMYK Overprint mode: set to OPM1 if not set Create "All" from 4x100% CMYK: no Delete "All" Colors: no Convert "All" to K: no 103 Table 2. Analysis of variance (ANOVA) of fruit characteristics df Fruit weight Fruit length Fruit girth Ripe weight Pulp weight Peel weight No. of seeds TSS Replication 4 38.22** 0.59(NS)* 5.31** 26.43** 9.47** 22.57** 3.17** 0.92(NS)* Treatments 16 18.22** 10.45** 7.75** 13.54** 10.96** 5.71** 12.44** 3.55** *NS= Non-significant ** Significant at 1% level Table 3. Phenotypic correlation among various fruit parameters of sapota 1 2 3 4 5 6 7 8 1. Fruit weight — 0.657** 0.753** 0.988** 0.899** 0.846** 0.026 - 0.191 2. Fruit length — 0.503** 0.635** 0.737** 0.385** -0.248* - 0.039 3. Fruit girth — 0.726** 0.741** 0.492** 0.117 - 0.114 4. Ripe fruit weight — 0.901** 0.850** 0.023 - 0.220* 5. Pulp weight — 0.611** - 0.130 - 0.135 6. Peel weight — 0.094 - 0.196 7. No. of seeds — - 0.263 8. TSS — * Significant at 5% level ** Significant at 1% level Fig 1. Dendrogram derived using Ward’s method for twenty varieties of sapota Variety number Scale 1-Cricket Ball, 2-Calcutta Round, 3- Pilipatti, 4- Gutti, 5- Gavaraiah, 6- Mohangooti, 7- Krishna Rao, 8- Oval, 9-Jhumakiya, 10- Kirtibarti, 11- Hybrid, 12- Bombay, 13- Pakala oval, 14- Seedless, 15-Dwarapudi, 16-Vavilavalasa, 17- CO 1, 18-CO 2, 19-Unknown, 20-Guruvayya Genetic correlations and cluster analysis in sapota J. Hortl. Sci. Vol. 6(2):101-104, 2011 Prinect Color Editor Page is color controlled with Prinect Color Editor 4.0.70 Copyright 2008 Heidelberger Druckmaschinen AG http://www.heidelberg.com You can view actual document colors and color spaces, with the free Color Editor (Viewer), a Plug-In from the Prinect PDF Toolbox. Please request a PDF Toolbox CD from your local Heidelberg office in order to install it on your computer. Applied Color Management Settings: Output Intent (Press Profile): GrayCoated_hdm.icc RGB Image: Profile: eciRGB.icc Rendering Intent: Perceptual Black Point Compensation: no RGB Graphic: Profile: eciRGB.icc Rendering Intent: Perceptual Black Point Compensation: no CMYK Image: Profile: ISOcoated_v2_eci.icc Rendering Intent: Perceptual Black Point Compensation: no Preserve Black: no CMYK Graphic: Profile: ISOcoated_v2_eci.icc Rendering Intent: Perceptual Black Point Compensation: no Preserve Black: no Device Independent RGB/Lab Image: Rendering Intent: Perceptual Black Point Compensation: no Device Independent RGB/Lab Graphic: Rendering Intent: Perceptual Black Point Compensation: no Device Independent CMYK/Gray Image: Rendering Intent: Perceptual Black Point Compensation: no Device Independent CMYK/Gray Graphic: Rendering Intent: Perceptual Black Point Compensation: no Turn R=G=B (Tolerance 0.5%) Graphic into Gray: yes Turn C=M=Y,K=0 (Tolerance 0.1%) Graphic into Gray: no CMM for overprinting CMYK graphic: no Gray Image: Apply CMYK Profile: no Gray Graphic: Apply CMYK Profile: no Treat Calibrated RGB as Device RGB: no Treat Calibrated Gray as Device Gray: yes Remove embedded non-CMYK Profiles: no Remove embedded CMYK Profiles: yes Applied Miscellaneous Settings: Colors to knockout: yes Gray to knockout: yes Pure black to overprint: no Turn Overprint CMYK White to Knockout: yes Turn Overprinting Device Gray to K: no CMYK Overprint mode: set to OPM1 if not set Create "All" from 4x100% CMYK: no Delete "All" Colors: no Convert "All" to K: no 104 Seedless, and an unknown collection from Gujarat. The second sub-cluster included varieties like Gutti, Oval, Jhumakiya, Pilipatti, Pakala oval, and Dwarapudi. Despite having round fruit-shape, the accessions Calcutta Round, CO-2 and Vavilavalasa were also grouped here in the first sub-cluster. Affinity of the varieties may be due to heterozygosity and seedling selection. The second group encompassing sub-clusters 3 and 4 had seven accessions, consisting mainly of large-fruit types. ‘Hybrid’ and ‘CO-1’, grouped in the third sub-cluster, were morphologically identical and were closely placed. Hence, the unknown hybrid collection and CO-1 seem to be identical. The fourth sub-cluster had five accessions, namely, Guruvayya, Krishna Rao, Cricket Ball, Bombay and Gavaraiah. The accessions Guruvayya, Krishna Rao and Gavaraiah showed morphological similarities too. But, inclusion of ‘Cricket Ball’ and ‘Bombay’ in this group is not justified should fruit shape be considered as a factor in clustering, as these bear round- shaped fruits. These observations reveal that affinities and grouping of varieties depend chiefly on fruit size. The study thus shows a high variability for fruit parameters like fresh-fruit weight, fruit length, fruit girth, fruit weight at ripening, pulp weight, peel weight, number of seeds and TSS, among different cultivars. Correlation studies showed relation among various fruit characteristics. Though fruit weight was directly related to all the fruit parameters studied, it affected TSS negatively. This indicated that excessive increase in fruit weight reduced quality of the fruit and, hence, selection should be preferably made for optimum fruit weight. Cluster analysis also revealed affinity among different cultivars. Selection of distantly placed cultivars in breeding programs bought to result in better progeny for further evaluation. ACKNOWLEDGMENT The authors are thankful to Director, Indian Institute of Horticultural Research, Bangalore for providing facilities to carry-out the above studies. REFERENCES Avaiyo, Y.V. and Singh, S.P. 1991. Physico-chemical study of mature sapota (Achras zapota L.) fruits of different cultivars. Orissa J. Hort., 19:83-96 Dinesh, M.R. and Reddy, B.M.C. 2000. Fruit evaluation studies in sapota (Achras zapota L.) J. Appld. Hort., 2:19-20 Ponnuswamy, V. and Irulappan, I. 1987. Evaluation of the chemical composition of fruits of different varieties and hybrids of sapota. South Ind. Hort., 35:446-47 Ponnuswamy, V. and Irulappan, I. 1989. A research note on the study of range, mean and coefficient of variability in sapota varieties (Achras zapota L.). South Ind. Hort., 37:112-114 Saraswathy, S., Parameswari, C., Parthiban, S., Selvarajan, M. and Ponnuswami, V. 2010. Evaluation of sapota genotypes for growth, yield and quality attributes. Electronic J. Pl. Breed., 1:441-446 Ward, J.H. 1963. Hierarchic grouping to optimize an objective function. J. Amer. Stat. Assoc. 58:236-239 (MS Received 20 May 2011, Revised 17 August 2011) Rekha et al J. Hortl. Sci. Vol. 6(2):101-104, 2011 Prinect Color Editor Page is color controlled with Prinect Color Editor 4.0.70 Copyright 2008 Heidelberger Druckmaschinen AG http://www.heidelberg.com You can view actual document colors and color spaces, with the free Color Editor (Viewer), a Plug-In from the Prinect PDF Toolbox. Please request a PDF Toolbox CD from your local Heidelberg office in order to install it on your computer. Applied Color Management Settings: Output Intent (Press Profile): GrayCoated_hdm.icc RGB Image: Profile: eciRGB.icc Rendering Intent: Perceptual Black Point Compensation: no RGB Graphic: Profile: eciRGB.icc Rendering Intent: Perceptual Black Point Compensation: no CMYK Image: Profile: ISOcoated_v2_eci.icc Rendering Intent: Perceptual Black Point Compensation: no Preserve Black: no CMYK Graphic: Profile: ISOcoated_v2_eci.icc Rendering Intent: Perceptual Black Point Compensation: no Preserve Black: no Device Independent RGB/Lab Image: Rendering Intent: Perceptual Black Point Compensation: no Device Independent RGB/Lab Graphic: Rendering Intent: Perceptual Black Point Compensation: no Device Independent CMYK/Gray Image: Rendering Intent: Perceptual Black Point Compensation: no Device Independent CMYK/Gray Graphic: Rendering Intent: Perceptual Black Point Compensation: no Turn R=G=B (Tolerance 0.5%) Graphic into Gray: yes Turn C=M=Y,K=0 (Tolerance 0.1%) Graphic into Gray: no CMM for overprinting CMYK graphic: no Gray Image: Apply CMYK Profile: no Gray Graphic: Apply CMYK Profile: no Treat Calibrated RGB as Device RGB: no Treat Calibrated Gray as Device Gray: yes Remove embedded non-CMYK Profiles: no Remove embedded CMYK Profiles: yes Applied Miscellaneous Settings: Colors to knockout: yes Gray to knockout: yes Pure black to overprint: no Turn Overprint CMYK White to Knockout: yes Turn Overprinting Device Gray to K: no CMYK Overprint mode: set to OPM1 if not set Create "All" from 4x100% CMYK: no Delete "All" Colors: no Convert "All" to K: no