Int. J. Life. Sci. Scienti. Res., 4(3): 1805-1809, May 2018

First Report of Gummosis Disease of Major Fruits in Gilgit-Baltistan (GB) Pakistan

Aqleem Abbas^*

*Department of Plant Pathology, The University of Agriculture Peshawar Pakistan

*Address for Correspondence - Mr. Aqleem Abbas, Department of Plant Pathology, The University of Agriculture Peshawar Pakistan

ABSTRACT- Gummosis is the most severe disease on the fruit trees of Gilgit-Baltistan (GB) region of Pakistan. In summer 2016, gummosis disease was observed on apricots, cherry, peach, plum and almonds trees in orchards of Nomal and Nagar Valleys in GB region of Pakistan.  The diseased trees initially exhibited sunken lesions on the trunks, twigs, and branches of fruit trees. Later these sunken lesions become darker in color and exudation of yellowish or whitish or transparent gum through these lesions become prominent. With the age of plants, canker develops on the trunk and branches of fruit trees. Gummosis can result from infection by the plant pathogen, due to climatic changes, injuries and pest infestations. The disease can be controlled by cultural, biological and chemical methods. To my knowledge, this is the first report of gummosis disease on apricots, cherry, peach, plum, and almonds of GB.

Key words-  Gummosis, Plant disease, Gilgit-Baltistan (GB), Fruit trees, cankers

INTRODUCTION- Gilgit-Baltistan (GB) is one of the major fruits producing a region of Pakistan. The fruits are primarily produced as cash crop and notably the apricot, cherry, almonds, plum and peach. Among these fruits, apricots are widely planted in GB. Furthermore, GB is major apricot producing region in Pakistan. According to one estimate the total fruit production is about 170680 tons fruits per annum ^[1]. Regular grafting and planting seeds from the superior trees have increased the variations. However, due to varying climatic and soil conditions, the fruit trees are exposed to disorders. Heavy floods due to melting of glaciers in summer season change the soil conditions and interrupt the normal gaseous exchange between fruit trees and their environment. Moreover causes sedimentation and weaken trees. The roots, root collar, and lower stem of fruit trees are significantly affected by floods. The injuries in these parts make fruit trees susceptible to pests and diseases. Moreover, high winds in late autumn season cause severe injuries consequently fruit trees become vulnerable to severe diseases. Severe frost, snow and ice are also causing cracks in the main trunk, branches and twigs of fruits trees. These cracks become the entry point for the diseases. These diseases are continuously reducing the productive capability of fruit trees and adversely affect the fruit quality. Moreover, the introduction of high yielding varieties are continuously replaced the local varieties. Though these varieties are high yielding however in varying climatic conditions these varieties soon become exposed to diseases. The production of apricots, cherry, almonds, plum and peach has dropped largely as a result of diseases such as gummosis, cankers, crown galls, Grey mold and Shot hole disease ^[2]. Among these diseases, gummosis is one of the devastating diseases on these fruit trees. The causes of gummosis are still obscure. Gummosis is associated with the diseases, pests and also with other abiotic factors such as high winds and snow. Pruning and grafting with unsterilized tools can also cause gummosis. Some researchers consider gummosis as non-specific defensive response of trees against the diseases and other differential stresses ^[3]. Anyhow the disease has seriously affected thousands of apricots, cherry, almond, peach and plum trees in Gilgit-Baltistan (GB). The disease is characterized by deposition of gums that has oozed through the barks of main trunk, twigs, and branches and even on the fruits. With the age, cankers develop along the main trunks, branches, and twigs of fruit trees ^[4]. 

The association of gummosis disease with the fruit trees has a long history. Therefore gummosis can be considered as a perennial disease of fruit trees in GB. Local people usually consume the gum exudates as an edible food. The gums have Functional, antioxidant, antimicrobial, and medicinal properties ^[5]. In June 2016 the fruit trees are surveyed and assembled first information regarding gummosis disease. Gummosis on cultivated apricots of Nomal Valley is shown in Fig. 1, Cherry in Fig. 2 and Almonds in Fig. 3. Gummosis on apricots of Chalat Valley, District Nagar is shown in Fig.  4. Gum deposits were yellowish, transparent and irregular in shape. The diameter of the gum deposits was 4 to 5 cm around lenticels of trunk and branches. However, the diameter of the gum deposits on the twigs was 1 to 2 cm. Gummosis is continuously spreading to other fruit growing regions of GB. Not a single variety of fruit tree is found to resistant to the gummosis. Therefore timely management of this disease is very important.

 

 

 

Cherry fruit becomes prolific gum producers in particular rainy days followed by peach, apricots, almonds and plum. The diseases enter through wounds or lenticels on the branches, twigs and main trunks of fruit trees. Lenticels are breathing holes in twigs, branches and main trunk and these are entry points for the plant pathogens. Around the lenticels and injuries, small, depressed and discolored spots appear. Afterward, the area becomes dark and cracked with yellowish or whitish gummy exudation. Yellowing and drooping of leaves are common symptoms in young fruit trees. The disease has a significant economic impact in fruit trees orchards. Moreover, the disease is continuously reducing the fruit tree longevity and causing considerable losses in GB.

Causes of Gummosis

Plant Pathogens- Fungi, bacteria and viruses have all been involved in causing gummosis ^[6].  Recently Ezra et al. ^[7] consider gummosis as syndrome of deciduous fruits. The pathogenic bacteria enter through injuries or lenticels and the consequences are the formations of gums.  The inoculation of young plum and cherry trees with Pseudomonas syringae cause severe gummosis. The fungus Stereum purpureum is also known to cause gum formation in stone fruits. In May 2008, apricot trees in the commercial farms of Renai region Taiwan showed symptoms of gummosis disease. The causal agent was a fungus Botryosphaeria dothidea. Botryosphaeria obtuse and Botryosphaeria rhodina have been reported to cause gummosis symptoms in peach tree.  Previously the fungi have been reported to cause gummosis in peach trees in USA ^[8].  In 2009 gummosis diseases was observed on apricot trees of Gaotang County in Shandong province, China. Transparent, circular or irregular gums deposits were exuded from the bark lenticels on trunks and branches.  The causal agent isolated and identified was Botryosphaeria obtuse ^[9].

The fungal pathogen which is responsible for gummosis in black cherry Apiosporina morbosa ^[10].  In another study, Armillaria tabescens was isolated and identified from the orchard of almond trees of three localities in Greece. Symptoms of gummosis were found on the bark of infected almond trees ^[11]. Two fungal species i.e. Cytospora cincta and Cytospora  leucostoma commonly cause canker in black cherry. The canker caused by these fungi is on the most prevalent disease of stone fruits growing regions of the world. Gum ooze from the infection sites of Cytospora leucostoma fungus ^[12]. Phytophthora sp. cause gummosis in citrus and pistachio therefore the role of Phytophthora sp. in the gummosis of fruit trees cannot be neglected.

 In 2012, five fungal pathogens i.e. Botryosphaeria dothidea, Diplodia olivarum, D. seriata, Neofusicoccum australe, and N. parvum have been isolated and identified from symptomatic tissues of Almond trees of Mallorca Islands (Spain). These fungi are known to cause gummosis, dieback and internal necrosis of branches and trunks ^[13]. Gummosis can be managed by removing severely infected tissues. Planting seeds from the certified fruit trees. Grafting and pruning should be conducted in late winter or very early spring with sterilized tools. Chemical methods and non-chemical methods such as application of biocontrol agents should be applied to manage gummosis. Disease resistant varieties will be provided by plant breeding institutes to fruit trees growers.

Pests- Pests are also involved in causing gummosis. They hide beneath the barks of trees where they are physically protected from the harsh conditions of the environment. Beetles are common in GB and usually attack on weaken or stressed fruit trees. They create holes in barks and as a result fruit trees produce gums in response to attack of these pests. These minute holes also become entry point to plant pathogens. Borers lay egg s on the trunk and branches of fruit trees. The larvas develop from the eggs then bore into the tree which results in deposition of gum near to the injury site. The mining flies are also considered to be potential cause of gummosis in fruit trees. The larva of mining flies bore through the cambium of fruit trees and cause gummosis. Additionally, in late summer, cicadas are seen on the branches of fruit trees. They may cause the trees vulnerable to attack by other pests and diseases. These pests can be controlled by both cultural and chemical methods to prevent the plants from gummosis.

Climatic conditions- Gilgit-Baltistan (GB) is mountainous regions and trees are usually grown on ridge tops or on the tops of hills. Therefore the fruit trees grew in these exposed areas become more susceptible to damage caused by high winds snow and ice. Moreover, the application of Nitrogenous fertilizers is too much high as compared to other fertilizer suggesting gum formation. Grafting and pruning with the unhygienic tools may enhance gummosis disease of fruit trees. Gummosis in fruit trees of GB is also associated with the high rainfall in the recent years due to global climatic change.

CONCLUSIONS-The causes of Gummosis in fruit trees in Gilgit Baltistan (GB) are still unknown. There is need to isolate and identify the pathogen based on molecular markers. The area is one of the remote areas of Pakistan and there is no sophisticated plant pathology Lab where the pathogen will be isolated and identified. This is a preliminary report based on depositions of gums and cankers on the fruit trees of GB. Moreover the pathogenicity test should be conducted to verify the actual causal agent of gummosis disease. Further research is required regarding the etiology and epidemiology of the gummosis. There is no such plant breeding institute which can provide disease free nursery stock and varieties to the fruit trees growers. To manage the diseases, the fruit tree growers should select proper site for the establishment of fruit tree nurseries to prevent the injuries caused by high winds. The pests and diseases should be managed by ecofriendly bio-chemicals. In GB the temperature during winter season is very low so to prevent from cold temperature injuries irrigation should be conducted according to the need of fruit trees. Fruits trees should be trained properly to avoid injuries. Proper pruning and grafting should be done at the correct time with the sterilized equipment. No chemicals are available in GB to manage gummosis. However, the canker having gummosis can be painted with the available canker paints. The acquired knowledge will be used in the future for the implementation of the most convenient control strategies of bacterial diseases on these tree species. The awareness about the gummosis diseases of fruit trees and proper understanding of the causes of disease is crucial. Pathogenicity trials on fruit trees should be also studied in order to figure out the host range of the gummosis disease. 

ACKNOWLEDGMENTS- I would like to thank Riaz Paras designer for professional graphics for support with gummosis disease photographs from Village Nomal District Gilgit, GB Pakistan. This manuscript contains information on gummosis disease with special emphasis on the recognition of symptoms using color photographs. Riaz Paras started photography as an amateur photographer using canon camera.

CONFLICT OF INTEREST STATEMENT- The present study was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

HUMAN AND ANIMAL RIGHTS- This article does not contain any studies with human participants or animals. For this type of study, any constitutional consent is not required. No such studies have been previously conducted in this remote area of Pakistan. The present study has been conducted ethically. If any institution or any other researcher bringing up any issue regarding animals, public ethics or human rights the author of the present study would be solely responsible.

REFERENCES

1.      Ali S, Tariq M, Kashif SA. Physico-chemical characteristics of apricot (Prunus armeniaca L.) grown in Northern Areas of Pakistan. Scientia Horticulturae, 2011; 130: 386-392.

2.      Abbas A. A report of grey mold disease on grapes caused by Botrytis cinerea in Gilgit-Baltistan, Pakistan. Clinical biotechnology and microbiology, 2017; (1):117-9.

3.      Li HY, Rou-Bin C, Yong-Tan M. In vitro inhibition of Botryosphaeria dothidea and Lasiodiplodia theobromae, and chemical control of gummosis disease of Japanese apricot and peach trees in Zhejiang Province, China. Crop protection 1995; 14: 187-191.

4.      Moyo P, Damm, U, Mostert L, Halleen, F. Eutypa, Eutypella and Cryptovalsa species (Diatrypaceae) associated with Prunus species in South Africa. Plant disease, 2018.

5.      Bouaziz F, Koubaa M, Ghorbel RE, Chaabouni, SE. Recent advances in Rosaceae gum exudates: From synthesis to food and non-food applications. International Journal of biological macromolecules, 2016; 86: 535-545.

6.      Boothby D Gummosis of stone-fruit trees and their fruits. Journal of the science of food and agriculture, 1983; 34:1-7

7.      Ezra D, Michal H, Dani S. Insights into the etiology of Gummosis Syndrome of Deciduous Fruit Trees in Israel and its Impact on Tree Productivity. Plant disease,  2017; 101:         1354-1361 

8.      Beckman TG, Pusey PL, Bertrand PF. Impact of fungal gummosis on peach trees. Scientia Horticulturae, 2003; 38: 1141-1143.

9.      Liu HX, Tan WP, Sun GW, Zhao YT,  He BL, Zhu XP. First Report of Gummosis Disease of Apricot (Prunus armeniaca) Caused by Botryosphaeria obtusa in China. Plant disease, 2015; 99: 888-888. 

10.  Hepting GH. Diseases of forest and shade trees of the United States. USDA Forest Service, Agriculture Handbook No. 386, Washington, DC. 1971; 658

11.  Tsopelas P, Tjamos EC. Occurrence and pathogenicity of Armillaria tabescens on almond in Greece. EPPO Bulletin. 1997; 27: 455–461.

12.  Biggs AR, Grove GG. Leucostoma canker of stone fruits. The Plant Health Instructor, 2005;

13.  Gramaje D, Agustí-Brisach C, Pérez-Sierra A, et al. Fungal trunk pathogens associated with wood decay of almond trees on Mallorca (Spain). Persooni. Molecular Phylogeny and Evolution of Fungi. 2012; 28: 1-13.