Research Article

Evaluation and Screening of Sweet Orange Cultivars for Vegetative Growth and Citrus Canker

Nadeem Khan1*, Arshad Ali Khan1, Mukhtar Ahmad2, Muhammad Nouman2 and Badshah Islam1

1Department of Agriculture, Abdul Wali Khan University, Mardan; 2Horticultural Research Institute, National Agricultural Research Centre, Islamabad, Pakistan.

Abstract | This study was conducted at National Agricultural Research Center, Islamabad. The experiment was performed on randomized complete block design (RCBD) consisting of eleven treatments (cultivars) replicated three times during 2015. The results showed that Tarocco attained maximum height (156.13 cm), followed by Mexican Lemon (146.80 cm). Similarly, maximum plant spread and leaf area were recorded in Mexican Lemon 124.07 cm and 11.35 cm2, respectively. However, Hamlin showed the highest stem girth (9.90 cm) and number of branches (66.53). The internode length was the greatest in Kinnow cultivar (2.66 cm). In case of disease incidence maximum lesion on leaves were found in Kinnow (14.2) while in Cara Cara, Salustiana and Arnold Blood, lesser lesions were found. On the basis of results and overall performance Tarocco and Hamlin performed best in all aspects while Arnold Blood and Cara Cara revealed poor growth.

Received | November 20, 2015; Accepted | May 10, 2016; Published | June 20, 2016

*Correspondence | Nadeem Khan, Abdul Wali Khan University, Mardan; Email: muhammadnadeem117@yahoo.com

Citation | Khan, N., A.A. Khan, M. Ahmad, M. Nouman and B. Islam. 2016. Evaluation and screening of sweet orange cultivars for vegetative growth and citrus canker. Sarhad Journal of Agriculture, 32(2): 121-126.

DOI | http://dx.doi.org/10.17582/journal.sja/2016/32.2.121.126

Keywords | Citrus cultivars, Plant height, Plant spread, Stem girth, Internode length, Number of branches, Leaf area, Disease incidence

Introduction

C itrus is a large group of shrubs or trees belong to the family Rutaceae. The Origin of citrus is believed to be the southern Himalaya, North East of India and China (Gmitter et al., 1990). It is extensively grown under tropical and sub-tropical climatic conditions, where the soil and climatic regimes are favourable for its growth (Shah, 2004). Due to its ornamental value, health benefits and importance in terms of fruit juice industries, citrus production increased in Pakistan and around the globe. In Pakistan it is the largest group of fruits grown over an area of 195.6 thousand hectares with an annual production of 1986.7 thousand tonnes, while Khyber Pakhtunkhwa contribute an area of 4.3 thousand hectares with total production of 33.5 thousand tonnes (Stat, 2011-12). Pakistan is ranking among the top ten producers of the world for citrus production (Nawaz et al., 2011) and sixth largest producer of Kinnow (Syed, 2009). Citrus is grown on about 170,000 hectares of land in Pakistan, constituting about 30 percent of the area under all fruit orchards (Saleem et al., 2008; Ashraf et al., 2010) Average yield of citrus in Pakistan (11 t/ha) is low as compared to the average yields of other citrus producing countries e.g. Brazil, USA and Turkey (22000, 26000 and 27000 kg/ha respectively) (Nawaz et al., 2011). Citrus is vulnerable to a number of diseases caused by different pathogen, harsh environmental condition and practices. Citrus canker was discovered in Florida in 1910 (Dopson, 1964; Loucks, 1934). It is thought to have originated in south eastern Asia or India (Civerolo, 1984). Citrus canker caused by Xanthomonas axonopodis pv. citri is one of the most important citrus diseases (Gottwald et al., 2001, 2002). It is the most devastating disease and occurs throughout the citrus growing countries of the world (Koizomi, 1985) including Pakistan. Keeping in view, the importance of citrus the present study was designed at the Fruit Program, Horticultural Research Institute in National Agricultural Research Centre Islamabad (NARC) to check the performance of different sweet orange cultivars primarily for their vegetative growth and for screening of different species resistant to citrus canker. The effective way of controlling the disease is by using resistant varieties.

Table 1: Screening of citrus cultivar against citrus canker in 2015

Cultivar | Severity rating Scale | Response | Lesion / leaf
Arnold Blood | 0 | I | 1.03 de
Cara Cara | 0 | I | 0.96 e
McMahon Valencia | 0 | I | 1.67 cde
Daisy Mandarin | 1 | R | 1.7 cde
Harvard Blood | 0 | I | 2.03 c
Ryan Navel | 1 | R | 6.6 a
Tarocco | 1 | R | 1.93 cd
Kinnow | 1 | R | 3.3 b
Salustiana | 0 | I | 1.03 de
Hamlin | 1 | R | 2.47 bc
Mexican Lemon | 1 | R | 7.07 a

Mean in the column followed by the like letters are not significantly different from each other while followed by the different letters are highly significant at P<0.05; I= Immune; R= Resistance

Materials and Methods

The study was conducted on one and half year old cultivars of sweet orange plants grown in the field area of Fruit Program, Horticultural Research Institute (HRI) in NARC Islamabad during 2015. The sweet orange cultivars included Arnold Blood, Cara Cara, McMahon Valencia, Daisy Mandarin, Hamlin, Harvard Blood, Tarocco, Kinnow LS, Ryan Navel, Salustiana and Mexican Lemon. The experiment was performed from June to September and data regarding plant growth and disease incidence i.e citrus canker was recorded. The vegetative behaviour of the experimental plants was observed by recording plants height through measuring tape from soil level to the peak branch of the plant. Stem girth was measured by a measuring tape just above the rootstock and scion joint. Leaf area was calculated by taking ten different matured leaves at four different sides of each plant. The internode length was measured through digital Vernier calliper. All the branches were counted in each varieties and the disease incidence particularly the intensity of citrus canker was checked on the basis of number of lesions on the leaves. Ten different leaves at four different sides North, South, East and West of each plant were collected from lower, middle and upper portion of the plant randomly. To measure the spread of the plant, two observations were taken from North to South and East to West at right angle with the help of measuring tape in a cross section up to the maximum outgrowth of the plant.

Statistical analysis

The data were analysed by using Randomized Complete Block Design (RCBD) with 11 treatment combination, replicated three times and the mean were further separated using Least Significant Difference (LSD) test. Statistical computer software “Statistix 8.1” was applied for computing both ANOVA and LSD (Jan et al., 2009).

Results and Discussion

Plant height

Plant height is important part of vegetative growth of citrus, if the plant has more height so there will be more number of branches and total number of leaves. The data for plant height revealed a highly significant difference ranging from 156.13 to 64.90 cm as shown in Figure 1. Maximum plant height (156.13 cm) was observed in Tarocco.

Figure 1: Effect of citrus cultivars on plant height

Level of significance= 0.05; LSD= 20.64

The results of our finding are in agreement with the early work of Khan et al. (2010) who previously reported that Torocco-N cultivar produced tallest plants, followed by Mexican Lemon (146.80 cm), Hamlin, Kinnow LS, Harvard Blood, Daisy Mandarin, McMahon Valencia, Salustiana, Ryan Navel, Cara Cara and Arnold blood. It is very much clear from the results that Tarocco and Mexican Lemon performed very well regarding plant height, while Cara Cara and Arnold Blood produced shortest plants as discussed early.

Stem girth

Vegetative growth is based on different parts in which stem girth is an important indicator for good performances of plant. The date regarding stem girth revealed a highly significant difference ranges from 9.90 to 3.98 cm as shown in Figure 2. Maximum stem girth was found in Hamlin (9.90 cm) progressively, followed by Mexican Lemon (8.63 cm), Daisy Mandarin, Harvard blood, Kinnow LS, Tarocco, McMahon Valencia, Ryan Navel, Salustiana, Arnold Blood, whereas minimum stem girth was observed in Cara Cara (3.98 cm). The stem girth is highly dependent on mineral nutrition which affected the photosynthetic rate, decreased carbohydrates production and proteins, which led to control plant growth and development (Taiz and Zeiger, 2002).

Figure 2: Effect of citrus cultivars on plant spread

Level of significance= 0.05; LSD= 15.13

Plant spread

Plant spread indicated a highly significant difference ranges from 124.07 to 54.38 cm (Figure 3). Highest plant spread was observed in Mexican Lemon (124.07 cm), progressively followed by Tarocco (106.92 cm), Hamlin, Kinnow LS, McMahon Valencia, Ryan Navel, Daisy Mandarin, Harvard Blood, Salustiana, Cara Cara, whereas minimum plant spread was observed in Arnold blood (54.38 cm). The result of our finding are in agreement with the Qureshi et al. (1993) who reported plant spread showed significant difference among citrus cultivars. Due to favourable environmental conditions and soil allowed the maximum increased in plant spread as it has been reported by Qureshi et al. (1993) ultimately showed high significant variation among different cultivar.

Figure 3: Effect of citrus cultivars on stem girth

Level of significance= 0.05; LSD= 1.5

Leaf area (cm2)

The data regarding leaf area showed a high significant difference ranges from 55.15 to 23.98 (Figure 4). The results indicated that bigger leaf area was found of Mexican Lemon (55.15 cm2), followed by Hamlin (41.57 cm2). However, the lowest leaf area was found in Ryan Navel (23.98 cm2). It was concluded from the results that Mexican lemon and Hamlin produced bigger leaf area might be due to better performance of the cultivar and compatability with the root stock (Castle et al., 1998). Similarly the better adoptability of the cultivar to take up the water and nutrients in higher quantity (Richardson et al., 2003). Leaf area is also a successful indicator for the success of crops where photosynthetic process initiated as in our study Mexican Lemon resulted in maximum plant spread so it may be allowing the larger leaf area.

Figure 4: Effect of citrus cultivars on leaf area

Level of significance= 0.05; LSD= 1.13

Number of branches

The data regarding number of the branches revealed a highly significant difference ranges from 76 to 66.5 as showen in Figure 5. The results showed that maximum number of branches were found in Kinnow (76) followed by Hamlin (66.5) and were far significant from Tarocco and Daisy mandarin. While lower numbers of branches were found in Arnold blood (13.2). The observation of this parameter showed a significant variation among different citrus cultivars. The Kinnow cultivar bitterly performed to the environmental condition of the area. Similarly the cultivar difference in the production of number of branches might also be attributed to the adaptation to different ecological conditions (Khan et al., 2014) and ultimately had better impact on the reproductive growth of citrus (Ahmed et al., 2006).

Figure 5: Effect of citrus cultivars on number of branches

Level of significance= 0.05; LSD= 11.14

Figure 6: Effect of citrus cultivars on internode length

Level of significance= 0.05; LSD= 0.47

Internode length

The data regarding internode length revealed a significant difference ranges from 2.66 to 2.2 as shown in Figure 6. Kinnow were found having maximum length (2.66 cm), followed by Tarocco (2.61 cm). However, minimum internode length was found in Ryan Navel (2.2 cm), followed by Salustiana (2.22 cm) and Harvard Blood (2.23 cm). Similarly, Khan et al. (2014) indicated that internode length showed significant difference among citrus cultivars. Internode length is strongly dependent on cell elongation that is the best indicator of plant height and might be due to environmental stress response (Guthrie, 1993) and genetic factor of the cultivar Ryan Navel and Salustiana showed shorter internodes. However, in the case of kinnow cultivar that thrive best to environmental stress, have higher internode length.

Lesion / Leaf

Disease rating scale ranges from 0-4 to know the level of resistance and susceptibility. The data regarding lesion per leaf revealed a highly significant difference ranges from 7.07 to 0.96 as shown in Figure 7. Our results indicated that higher number of lesions per leaf was found in Mexican Lemon (7.07), and Ryan Navel (6.6). However, the Cara Cara cultivar was found highly resistant and found only 0.96 lesions per leaf. Ijaz et al. (1999) also reported that Cara Cara cultivar was highly resistant to different fungal diseases. However, results were not supported by the work of Burhan et al. (2007) who reported that there was no significant variation among different citrus cultivars regarding citrus canker. Some cultivars resistant to the disease had already been reported by Leite et al. (1994) and Graham (2001).

Figure 7: Effect of citrus cultivars on number of lesion

Level of significance= 0.05; LSD= 0.91

Conclusion

Based upon the finding of our study, it is recommended that, Tarocco and Hamlin performed best regarding plant growth (plant height, plant spread, stem girth, leaf area, internode length and number of branches) and disease incidence (citrus canker). Both the varieties were found resistant against citrus canker.

Acknowledgment

The authors highly acknowledge the National Agricultural Research Centre, Islamabad for providing the facilities and scientific assistance of Mr. Mukhtar Ahmad.

Authors’ Contribution

Nadeem Khan was the main investigator of this research work. Dr. Arshad Ali Khan worked as supervisor, Mukhtar Ahmad and Muhammad Nouman worked as co-supervisor and designed the research and helped during field study in NARC, Islamabad. While, Badshah Islam as co-supervisor internal helped in the draft and statistics analysis. All the authors have contributed intellectually in research and drafting.

References

Ahmed, W., M.A. Pervez, M. Amjad, M. Khalid, C.M. Ayyub and M.A. Nawaz. 2006. Effect of stionic combinations on the growth and yield of Kinnow mandarin (Citrus reticulata Blanco). Pak. J. Bot. 38: 603–612.

Pakistan Bureau of Statistics. 2011. Agriculture Statistics Section, Islamabad, Pakistan. p. 89.

Ashraf, M.Y., A. Gul, M. Ashraf, F. Hussain and G. Ebert. 2010. Improvement in yield and quality of Kinnow (Citrus deliciosa x Citrus nobilis) by potassium fertilization. J. Plant Nutr. 33:1625-1637. http://dx.doi.org/10.1080/01904167.2010.496887

Burhan, M., N.A Chaudhary, M. Ishfaq and M. Sarwar. 2007. Incidence of citrus canker (Xanthomonas compestris pv. citri) on orange cultivars in nursery. IJBAE. 9(33):533-534.

Castle, W.S., D.P.H. Tucker, A.H. Krezdom and C.O. Youtsey. 1989. Rootstocks for Florida citrus. Univ. of Florida, Coop. Ext. Publ. SP. 41.

Chou, G.J. 1966. A new method of measuring the leaf area of citrus trees. Acta. Hort. Sci. 5:17-20.

Civerolo, E.L. 1984. Bacterial canker disease of citrus. J. Rio Grande Valley Horti. Soc. 37:127-146.

Dopson, R.N. 1964. The eradication of citrus canker. Plant Dis. Rep. 48:30-31.

Gmitter, F.G., and X. Hu. 1990. The possible role of Yunnan, China, in the origin of contemporary citrus species (Rutaceae). Econ. Bot. 44(2):267-277. http://dx.doi.org/10.1007/BF02860491

Graham, J.H. 2001. Varietal susceptibility to citrus canker: observation from southern Brazil. Citrus Ind. 82:15-17.

Gottwald, T.R., G. Hughes, J.H. Graham, X. Sun and T. Riley. 2001. The citrus canker epidemic in Florida: The scientific basis of regulatory eradication policy for an invasive species. Phytopathology. 91:30-34. http://dx.doi.org/10.1094/PHYTO.2001.91.1.30

Gottwald, T.R., X. Sun, T. Riley, J.H. Graham, F. Ferrandino and E.L. Taylor. 2002. Geo-referenced spatiotemporal analysis of the urban citrus canker epidemic in Florida. Phytopathology. 92(4): 361. http://dx.doi.org/10.1094/PHYTO.2002.92.4.361

Guthrie, W., D. Barry and B.D. Reed. 1983. Effect of plant height and the yellow-green gene in maize on leaf feeding by first-generation European corn borers (Lepidoptera: Pyralidae). J. Econ. Entomol. 76:818-820.

Horsfall, J.G and J.W. Heuberger. 1942. Measuring magnitude of defoliation disease of tomatoes. Phytopathology. 32:226-232.

Ijaz, M., M. Ishfaq, I.A Hafiz and G.A Chaudhary. 1999. Screening of citrus varieties against citrus canker (Xanthomonas Compestris pv.citri) under rainfed climate of Potohar. Int. J. Agric. Biol. 01(3):108-109.

Jan, M.T., P. Shah, P.A. Hollington, M.J. Khan and Q. Sohail. 2009. Agriculture research: Design and analysis. 1st ed. Department of Agronomy, KP Agriculture University of Peshawar, Pakistan.

Khan, A.A., M. Sajid, A. Rab, S. Alam, A. Bari. 2014. Effect of potassium sources on the growth, yield and fruit quality of tomato cultivars. Sarhad. J. Agri. 30(4):442-450.

Khan, K., A. Rehman, T. Zeb, M. Jadoon, I. Ullah and B. Shamrez. 2014. Performance evaluation of various sweet orange varieties under the Agro-climatic conditions of Haripur Hazara.Asian. J. Agric. Sci. 7(1):1-3.

Khan, M.N., M.A Nawaz, W. Ahmed, M. Afzal, A.U. Malik and B.A. Saleem. 2010. Evaluation of some exotic cultivars of sweet orange in Punjab, Pakistan. Int. J. Agri. Biol. 12:729–733.

Koizumi, M. 1985. Citrus canker: The world situation. P. 2-7. In: Citrus canker: An International perspective by L.W. Timer. Proc. Symp. Inst. Food Agri. Sci; Univ. Fla.

Leite, R.P., and S.K. Mohar. 1984. Evaluation of citrus cultivars for resistant to canker caused by Xanthomonas Compestris. Pv. Citri (Hasse) Dye in the state of Pavara, Brazil. Proc. Int. Soc. Citricult. 1:385-389.

Loucks, K.W. 1934. Citrus canker and its eradication from Florida. (Unpublished manuscript, Library). Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Gainesville, FL. P. 111.

Nawaz, M.A., M. Afzal and W. Ahmad. 2011. Obstacles in development of citrus industry of Pakistan and their possible solutions. AgriHunt. Visited on 07/10/2011.

Qureshi, M.K., M.H. Laghari, K.M. Khokhar and M. Asif Khan. 1993. Performance of mandarin (Citrus reticulata blanco) varieties at Islamabad. Pak. J. Agri. Sci. 30:4.

Richardson, A., P. Mooney, T. Dawson and M. Watson. 2003. How do rootstock affect canopy development? Hort. Research, Kerikeri Research Center New Zealand. htt://www.hortnet.co.nz/publications/science/richardson/rootc an. htm

Saleem, B.A., A.U. Malik, M.A. Pervez, A.S. Khan and M.N Khan. 2008. Spring application of growth regulators affects fruit quality of ‘Blood Red’ sweet orange. Pak. J. Bot. 40:1013-1023.

Shah, M.A., 2004. Citrus Cultivation in N.W.F.P. Proc. 1st Int. Conf. on Citriculture, p. 36-39. University of Agriculture, Faisalabad, Pakistan.

Stall, R.E., and C.P. Seymour. 1983. Canker, a threat to citrus in the gulf-coast states. Plant Dis. 67:581-585-1983.

Syed, R. 2009. Seedless Kinnow export: Pakistan to meet European countries demand. Daily Times. Published on 1507/2009.

Taiz, L. and E. Zeiger, 2002. Plant Physiology, 3rd edition. Sinauer Associates, Inc., Publishers, Sunderland, Massachusetts.