INTERNATIONAL JOURNAL OF BIO-RESOURCE, ENVIRONMENT AND AGRICULTURAL SCIENCES (IJBEAS) Vol. 3(1) :453-458, 2017 www.sbear.in // ISSN 2454-3551 INCIDENCE OF CITRUS CANKER ON ACID LIME IN RED AND LATERITIC AGRO-CLIMATIC ZONE OF WEST BENGAL, INDIA Uttam Mondal, Bholanath Mondal* and Palash Mondal Department of Plant Protection, Palli-Siksha Bhavana (Institute of Agriculture), Visva-Bharati, Sriniketan *Corresponding author: [email protected] Received: December 2016 Revised accepted: January 2017 ABSTRACT Citrus canker caused by Xanthomonas axonopodis pv. citri (ex Hasse) Vauterin et al. is one of the most important diseases of acid lime [Citrus aurantifolia (Christm.) Swingle] in West Bengal. The disease was recorded from nine different blocks of three different districts under Red and Lateritic Agro-climatic Zone of the state. Lowest disease incidence (<3.0 % PDI) was recorded during November in all the districts. Highest of that was observed during August (4.70 %) followed by May (4.46%). Disease intensity was also varied district wise. All the above ground parts viz., leave, stems and fruits were infested with cankerous growth of the disease and produced characteristics symptoms. There was a sharp relation among different weather variables and disease intensity. Keywords: Acid lime, citrus canker, seasonal incidence, Xanthomonas axonopodis pv. citri INTRODUCTION Citruses are distributed worldwide and cultivated almost all the states and union territories of India. Total area under citruses is 987.6 and 846.6 thousand hacter with a production of 9637.8 and 7463.7 thousand tones of fruits in 2009-10 and 2010-11, respectively in India. The crop is suffering from several biotic (fungi, bacteria, viruses, phytoplasma and insects etc.) and abiotic stresses (nutrient deficiencies/excess). Citrus canker caused by Xanthomonas axonopodis pv. citri (ex Hasse) Vauterin et al. is one of the most important endemic diseases of citruses, and Citrus aurantiifolia (Christm.) Swingle (family: Rutaceae) is the most susceptible one (Das and Dubey, 1989). In India, citrus canker was first recorded from Punjab and subsequently from different citrus growing states (Kalita et al., 1996). Citrus leaf miner (Phyllocnistis citrella Stainton), a lepidopteran insect, has been reported to aggravate canker situation (Gottwald et al., 1997) in Australia, Brazil, India, and Yemen (Das et al., 2014; Chagas et al., 2001; Christiano et al., 2007; Cook, 1988; Sinha et al., 1972; Sohi and Sandhu, 1968). It is difficult to find out any acid lime orchard completely free from canker infection. Hence, the experiment was conducted to know the present situation of the disease in different parts of Red and Lateritic Agro-climatic Zone of West Bengal. MATERIALS AND METHODS Surveys were conducted in three different districts namely Birbhum (Nalhati, Benuria, Goyalpara, Surul, Sriniketan, Raipur), Bankura (Sonamukhi, Bebarda, Khatra) and Purulia (Hura, Manbajar-1, Bagmundi) under Red and Lateritic Agro-climatic Zone of West Bengal. A total of twelve places of nine different blocks were surveyed during 2014 to records the incidence of the disease in acid lime. As many as sixty five units of citrus orchard having five numbers of plants per unit were under the survey. The infected plants were observed minutely and the detail symptoms were recorded. Disease severity was recorded using 0-4 scale (Das et al., 2012) from randomly selected 20 leaves per plant, and per cent disease index (PDI) was calculated. The canker infected parts (leaves, stems and fruits) of acid lime were collected from the orchard and brought to the laboratory for detection and confirmation of the causal pathogen. Bacterial nature of the disease was confirmed by ooze test under microscope, through isolation and characterization (morphological and biochemical studies) in laboratory condition and also through pathogenecity test by artificial inoculation method to confirm the isolated bacteria responsible for producing identical disease symptoms on the same host. Pure culture of the bacterium was maintained in Potato Dextrose Agar (PDA) and Nutrient Agar (NA) medium. Int. J. Bio-res. Env. Agril. Sci., March 2017 RESULTS AND DISCUSSION Development of the disease The acid lime (C. aurantifolia) is popularly known as kagji lebu in Bengali. It was observed that the symptoms appeared initially as tiny, watery, translucent circular lesions on the leaves. The lesions first appeared on lower surface of the leaf and then became prominent on the upper surface. In time, these lesions became raised and surrounded by water soaked margins; later on the entire lesion was usually surrounded by faint chlorotic margin or yellow halo. The chlorotic halo became intensified after some days. Most lesions were round in shape, occasionally oval or angular. Lesion gradually converted into raised, rough, corky grayish brown structure with or without crater like appearance. In severe infection numerous small round corky raised lesions were found on the leaf. Average number of canker spots was 1.05 per cm2 area (avg. of 15 samples) of leaf. The lesion size (avg.) was around 3.65 mm x 3.48 mm in diameter. In leaf miner infected leaf, many canker lesions were formed in damaged area close to each other without yellow halo (Table 2 and 3). Table 1. District wise disease intensity of citrus canker on leaves of acid lime in West Bengal Place No. of Time of observation GPS Location unit Feb May August November Avg. PDI surveyed Avg. PDI District – Purulia Hura 5 3.57 4.10 4.61 2.70 3.75 N 23º17′27.41″ E 86º37′28.74″ Manbajar-1 6 3.45 5.00 4.52 2.24 3.80 N 23º3′26.41″ E 86º39′55.87″ Bagmundi 4 3.41 4.22 4.65 3.20 3.87 N 23º11′34.08″ E 86º3′13.45″ Sub-total (a) 15 3.48 4.44 4.59 2.71 3.81 District – Bankura Sonamukhi 6 3.00 3.95 4.75 2.80 3.63 N 23º 18′27.27″ E 87º 24′56.86″ Bibarda 5 3.25 4.45 4.86 2.67 3.81 N 23º 3′8.43″ E 87º 1′43.29″ Khatra 8 3.30 4.40 4.90 2.84 3.86 N 22º 58′50.00″ E 86º 51′12.51″ Sub-total (b) 19 3.18 4.27 4.84 2.77 3.76 District – Birbhum Nalhati 3 3.55 4.44 4.86 2.62 3.87 N 24º 17′31.54″ E 87º 50′16.02″ Binuria 8 3.64 4.89 4.87 2.83 4.06 N 23º 39′59.28″ E 87º 37′55.91″ Goyalpara 5 3.80 4.65 4.41 2.55 3.85 N 23º 42′16.79″ E 87º 40′26.30″ Surul 5 3.54 4.50 4.40 2.65 3.77 N 23º 39′55.11″ E 87º 39′20.32″ Sriniketan 5 3.30 4.62 4.63 2.60 3.79 N 23º 39′51.83″ E 87º 39′56.73″ Raipur 5 3.81 4.88 4.80 2.67 4.04 N 23º 37′52.06″ E 87º 39′24.76″ Sub-total (c) 31 3.61 4.66 4.66 2.65 3.90 - Total (a+b+c) 65 3.42 4.46 4.70 2.71 3.82 - PDI was taken from randomly selected 20 leaves/plant, there were 5 plants/unit 454 Int. J. Bio-res. Env. Agril. Sci., March 2017 Lesions were also found on mid-veins, petioles, twigs, stems, stalk-end of fruit and fruits. Cankers on the twigs were more prominent and brown to grayish brown in colour. In many cases lesions were elongated and sometime coalesced to girdle the branches. Average number of canker spots was 0.84 per cm2 area (avg. of 15 samples) of stem. The lesion size (avg.) was around 4.04 mm x 1.55 mm in diameter. Such infected branches became dead producing die back symptom at the end of the rainy season. In severe infection, girdling of the branches was common. Early defoliation was also common due to the infection on the petiole (Table 2 and 3). Symptom on the fruit was similar to that produced on leaf but only in a few cases yellow halo was recorded. Average number of canker spots was 0.98 per cm2 area (avg. of 15 samples) of fruit. The lesion size (avg.) was around 3.04 mm x 2.85 mm in diameter. Early fruit drop due to infection at the stalk-end was observed. Similar type of observations was tallied with earlier workers (Broadbent et al., 1992; Khan and Abid, 2007; Sahi et al., 2007; and Beheshti et al., 2011; Das et al., 2012). Table 2. Symptoms observed on the above ground parts of acid lime (Kagji lebu) Symptoms Yellow No. of canker Avg. Size of Cracky Crater like hallo spots / 1 sq cm the spot appearance area (avg. of (mm2) appearance 15 samples) On leaves ++++ 1.05 3.65 x 3.48 ++++ ++++ On stems - 0.84 4.04 x 1.55 - - On fruits + 0.98 3.04 x 2.85 - - Where, ++++ = Very high, +++ = High, ++ = Moderate, + = Low, - = Nil Table 3. Symptoms observed other than leaves, stems and fruits of acid lime (Kagji lebu) Symptoms Petiole stalk-end mid-veins Twig of fruit of leaf +++ +++ ++ +++ Where, +++ = High, ++ = Moderate Characterization of the causal pathogen The experiment was conducted with three isolates (XacP, XacB, XacBB) from three different districts considering fourteen most key parameters – four of them morphological and rests were bio-chemical. All the isolates (Table 4) were aerobic, Gram negative, straight rod, motile having flagella, yellow colony forming, showed negative oxidase reaction, liquefy gelatin, hydrolyse starch, showed negative arginine hydrolase activity, catalase reaction was positive (could convert hydrogen peroxide into 455 Int.