Diversity and Community Analyses of Soil Nematodes Associated with Guava from West Bengal, India M.R. Khan, Abu Hassan, B. Ghosh, B. Das, S. Ghosh and S.K. Ray All India Coordinated Research project on Plant Parasitic nematodes Directorate of Research, Bidhan Chandra Krishi Viswavidyalaya Kalyani, West Bengal-741235 India Keywords: Population density, biomass Abstract Survey on plant and soil nematodes associated with rhizosphere of guava (Psidium guajava L.) from Baruipur, 24-Paraganas(south) and Mondouri (Haringhata) and Ghoragachha (Chakdaha), Nadia, West Bengal, India revealed the occurrence of ten genera, viz. Meloidogyne, Pratylenchus, Hoplolaimus, Rotylenchulus, Helicotylenchus, Tylenchorhynchus, Criconemoides, Xiphinema, Longidorus and Aphelenchus. Altogether thirteen species of eight plant parasitic genera identified which were Meloidogyne incognita, M. javanica, M. graminicola, Pratylenchus coffeae, P. brachyurus, Hoplolaimus indicus, Rotylenchulus reniformis, Helicotylenchus goodi, H. indicus, H. abunamai, Tylenchorhynchus mashhoodi, T. nudus and Aphelenchus avenae. The estimation of population density from rhizospheric soil indicated more number of R. reniformis (1052/200cm3 soil) and Helicotylenchus (233/200cm3 soil). Community analyses of plant and soil nematodes from the guava rhizosphere further revealed that R. reniformis ranked first in prominence followed by Helicotylenchus and Tylenchorhynchus. Among the less prominent plant parasitic species present as in guava rhizosphere, Pratylenchus, Meloidogyne, R. reniformis, Xiphinema and Longidorus were the potential pathogens to cause decline of yield either alone or in association with soil pathogens. Some ectoparasitic nematodes genera were also prominent members of soil nematode community but less important as plant pathogens. Among sapropzoic nematodes, rhabditids, dorylaimids and diplogasterids are the most prominent members of soil nematode community diversity and primarily play significant role in ecosystem processes of soil for making availability of plant nutrients. INTRODUCTION Guava (Psidium guajava L.) is an important fruit crop cultivated in approximately 7400 ha in West Bengal, India with a production of 121.3 thousand tones. Among several biotic and abiotic stresses inflicting damage to guava, plant parasitic nematodes constitute one of the major constraints for its profitable cultivation. Nematodes are of serious concern for guava planters particularly for its association with ‘guava decline’ (Avelar Mejia et al., 2001; Suarez et al., 1999) and ‘wilt disease’ problems (Hamiduzzaman et al., 1997; Khan et al., 2001; Ruchi et al., 2002). Some nematode species are highly pathogenic in nature. In West Bengal, India no systematic work on nematode problems in guava has been conducted, therefore, the present investigation, particularly survey, identification of plant parasitic nematode and analyzing nematode community to determine frequency of occurrence, density, prominence and importance value of soil and plant nematodes associated with guava rhizosphere in West Bengal was carried out and results presented in this paper. MATERIALS AND METHODS Soil (200cm3) along with root samples (10g) was collected from the rhizosphere of guava orchards at Mondouri and Ghoragachha and Baruipur areas of Nadia and south 24Parganas districts of West Bengal. Soil samples were processed by Cobb’s (1918) decanting and sieving method followed by modified Baermann’s technique (Baermann, Proc. Ist IS on Guava Eds. G. Singh et al. Acta Hort. 735, ISHS 2007
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1917). After examination of roots for galling lesion caused by nematodes, the root samples (10-20g) were cut into small pieces and placed on double-layered tissue paper supported by a wire gauge in petri plates filled with water and incubated at °C. After incubation, the nematode emerged from roots were collected from the petri plates. Nematode specimens were killed by use of hot-water-bath technique and fixed in formaldehyde 3%. The population was estimated with the help of multi-chambered counting-disc under stereoscopic binocular microscope. For identification of the species, nematode specimens were processed by Seinhorst’s (1959) glycerol-ethanol method and mounted in anhydrous glycerin on glass slide. Ecological estimates for community analysis of soil nematode were determined as per method described by Norton (1978). RESULTS AND DISCUSSION Plant parasitic nematode species were from guava rhizosphere, identified as Meloidogyne incognita, M. javanica, M. graminicola, Pratylenchus coffeae, P. brachyurus, Hoplolaimus indicus, Rotylenchulus reniformis, Helicotylenchus goodi, H. indicus, H. abunamai, Tylenchorhynchus mashhoodi, T. nudus and Aphelenchus avenae. The nematode population density /200cm3 soil along with their biomass was estimated from three different guava orchards (Table 1). Results showed clearly that the most predominant genera of plant pathogenic nematodes were Meloidogyne, Pratylenchus, Hoplolaimus, Rotylenchulus, Helicotylenchus, Tylenchorhynchus and Criconemoides. The population density of root-knot nematode, Meloidogyne incognita and M. javanica in Baruipur soil was alarmingly high (239 /200cm3 soil) as compared to other habitats. This was evident from severe root galling in younger roots of guava plants. Parasitic association M. incognita with guava (Babatola and Oyedunmade, 1992) and incidence and damage due to this nematode has been reported from Brazil (Moura et al., 1989) and from South Africa (Willers and Welgemoed, 1993). Involvement of Meloidogyne spp. and other soil borne fungi (Sauraz et al., 1999; Avelar Mejia et al., 2001) has also been reported with high incidence of guava decline. A huge population (211 to 1389 /200cm3 soil) of Rotylenchulus and Helicotylenchus was found present in all the three habitats. Willers and Grech (1986) proved the pathogenicity of Helicotylenchus dihystera on guava. Among the predatory nematodes, Mononchus was recorded in all the three habitats. Among saprozoic nematodes, rhabditids, dorylaimids and diplogasterids were abundant in number. Overall mean population density from rhizospheric soil of guava indicated a large population of R. reniformis (1052/200cm3soil) and Helicotylenchus (233/200cm3soil). Community analyses of plant and soil nematodes from the guava rhizosphere further revealed that R. reniformis ranked first in prominence value (PV) followed by Helicotylenchus, Tylenchorhynchus, Hoplolaimus and Meloidogyne spp. However, in terms of absolute biomass Hoplolaimus ranked first followed by Helicotylenchus, Longidorus, Rotylenchulus and Meloidogyne (Table 2). Nigam et al. (1995) showed that Hoplolaimus spp. even at the lowest inoculum level of 100 nematodes caused damage to guava. Hoplolaimus indicus was earlier recorded from guava rhizosphere of Sriniketan, West Bengal (Mukherjee and Dasgupta, 1979). It, the importance values (IV) of these nematodes are considered the R. reniformis remained in first position followed by Hoplolaimus, Helicotylenchus and Tylenchorhynchus (Table 2). Ansari and Ahmad (2000) also analysed the nematode community in guava rhizosphere from Aligarh, India and found that Hoplolaimus indicus had highest frequency, density and PV but not biomass. Among the less prominent plant parasitic species in guava rhizosphere, Pratylenchus, Meloidogyne, R. reniformis, Xiphinema and Longidorus were the potential pathogens to cause decline of yield either alone or in association with soil pathogens. Some ecto-parasitic nematodes genera were also found prominent members of soil nematode community but less known as plant pathogens. CONCLUSION Guava rhizosphere harboured more than thirteen species of eight nematodes genera mostly of plant parasitic, indicated occurrence of multiple nematode infestation in 484
guava. Nematode population from three guava orchards was estimated both qualitatively and quantitatively and there were differences between the orchards for density as well as for total biomass of phytophagous, predacious and saprophagous nematodes. Community analysis from guava rhizosphere revealed that the saprozoic nematodes are the prominent member in terms of abundance and total biomass in all the orchards. Potential value (PV) and importance value (IV) were calculated for community analysis of nematodes in guava rhizosphere but it did not clearly reflect the pathogenic importance of the nematode species in the community. Among the plant pathogenic genera, Pratylenchus, Meloidogyne and R. reniformis are widely known as important plant parasites which can be concern for decline of yield over the years. In addition, they indirectly aggravate soil borne pathogens particularly fungi and bacteria leading to wilt problems. The occurrence of M. graminicola in guava orchard was probably due to the weed hosts on which nematode maintained the population over the seasons. Abundance of Helicotylenchus, Tylenchorhynchus and Hoplolaimus in guava orchards are of major concern because all these nematodes are frequent root feeders causing injury to root system, which in turn make the root system prone to attack of soil pathogens. Abundant saprozoics and mononchids in guava rhizosphere are good indicators of soil health as they take part in essential processes in soil system (Neher, 2001). The results of present study indicate that the further work are understand the role of ectoparasitic nematodes, nematode-complex and nematode-wilt complex in guava rhizosphere even at regional level for profitable cultivation of guava. Literature Cited Ansari, M.A. and Ahmad, W. 2000. Community analysis of plant parasitic and predatory nematodes in Guava (Psidium guajava) orchard. Proc. 52nd Intl. Symp. on Crop Protection, Gent, Belgium, 9 May, Part II. Mededelingen Faculteit Landbouwkundige en Toegepaste Biologische Wetenschappen, Universiteit Gent. 65 : 557-562. Avelar Mejia, J.J., Teliz Ortiz, D. and Zavaleta Mejia, E. 2001. Pathogens associated to guava decline. Revista Mexicana de Fitopatologia. 19 : 223-229. Babatola, J.O. and Oyedunmade, E.E.A. 1992. Host-parasite relationships of Psidium guajava cultivars and Meloidogyne incognita. Nematol. Medit. 20 : 233-235. Baermann, G. 1917. Eine einfache Methode zur Auffindung von Ankylostomum (Nematodon) Larven in Erdproben. Geneesk. Tijdschr. Ned.- Indiё. 57 : 131-137. Cobb, N.A. 1918. Estimating the nema population of soil. Agric. Tech. Circ.. US Dept. Agric. 1: 48. Hamiduzzaman, M.M., Meah, M.B. and Ahmad, M.U. 1997. Effect of Fusarium oxysporum and nematode interaction on guava wilt. Bangladesh J. Plant Pathol. 13 : 911. Khan, R.M., Kumar, S. and Reddy, P.P 2001. Role of plant parasitic nematode(s) and fungi in guava wilt. Pest Mgt. Hort. Ecosystem. 7 : 152-16. Moura, R.M de, Moura, A.M de, Marinho de Moura, R and Marinho, de Moura, A. 1989. Root-knot on guava: a severe disease in Pernambuco State, Brazil. Nematol. Brasileira. 13 : 13-19. Mukherjee, B. and Dasgupta, M.K. 1979. Plant parasitic nematodes under different crop conditions at Sriniketan, West Bengal. Indian J. Nematol. 9 : 74-75. Neher, D.A. 2001. Role of nematodes in soil health and their use as indicators. J. Nematol. 33 : 161-168. Nigam, K., Verma, R.S., Verma, A.K. and Sinha, V. 1995. Pathogenicity of Hoplolaimus spp. Daday, 1905 to guava (Psidium guajava). Adv. Agric. Res. India. 3 : 158-160. Norton, D.C. 1978. Ecology of Plant Parasitic Nematodes, John Willey & Sons, Inc. New York. Ruchi, L., Dwivedi, B.K., Dwivedi, B.P., Shukla, D.N., Logani, R. 2002. Nematode and wilt problems of guava in and around Allahabad region. Curr. Nematol. 3 : 23-26. Seinhorst, J.W. 1959. A rapid method for the transfer of nematodes from fixative to anhydrous glycerin. Nematologica. 4 : 67-69. 485
Sharma, R.D and Loof, P.A.A. 1973. A new disease of guava trees in Bahia caused by nematodes. Cacau Atualidades. 10 : 20-21. Suarez, H.Z., Rosales L.C and Rondon, A. 1999. Synergistic effect of the fungi Macrophomina and Fusarium with the root-knot nematodes, Meloidogyne spp. on decline of guava. Nematol. Medit. 27 : 79-82. Willers, P. and Grech, N.M. 1986. Pathogenicity of the spiral nematode, Helicotylenchus dihystera to guava. Plant Dis. 70 : 352. Willers, P. and Welgemoed, C.P. 1993. Root-knot nematode damage to guavas in South Africa. Inligtingsbulletin Instituut vir Tropiese en Subtropiese Gewasse. 251: 21-23.
Tables Table 1. Status nematode population density and biomass (per 200cm3 soil) in guava rhizosphere of different orchards. Orchards Nematode species Meloidogyne Pratylenchus Hoplolaimus Rotylenchulus Tylenchorhynchus Helicotylenchus Criconemoides Xiphinema Longidorus Aphelenchus Mononchus Saprozoics
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Ghoragacha Population 83 68 79 449 128 211 21 0 0 0 42 1324
Biomass (µg) 14.77 8.91 96.38 26.49 20.10 54.23 5.59 0 0 0 54.22 226.40
Baruipur Population 239 34 80 310 62 356 0 17 0 47 16 986
Biomass (µg) 42.54 4.45 97.60 18.29 9.73 91.49 0 5.56 0 4.47 20.66 168.61
Mondouri Population 55 71 104 1389 108 203 38 66 67 27 51 1150
Biomass (µg) 9.79 9.30 126.88 81.95 16.96 52.17 10.11 21.58 206.96 2.57 65.84 196.65
Table 2. Community analyses of soil and plant nematodes from guava rhizosphere in West Bengal, India. Nematode species Meloidogyne Pratylenchus Hoplolaimus Rotylenchulus Tylenchorhynchus Helicotylenchus Criconemoides Xiphinema Longidorus Aphelenchus Mononchus Saprozoics 1 2
Absolute frequency 51.6 41.6 70 96.66 65 63.33 33.33 10 10 11.6 60 100 613.12
Relative frequency 8.42 6.78 11.42 15.77 10.6 10.33 5.43 1.63 1.63 1.89 9.78 16.31 99.99
Absolute density 90.94 65.72 99.45 1052.41 103.79 232.84 36.9 65.66 67 38.29 48.75 1143.23 3044.98
Relative density 2.98 2.16 3.27 34.56 3.41 7.65 1.21 2.16 2.2 1.26 1.6 37.54 100
1
PV
8.647 5.624 11.05 137.243 11.102 24.587 2.819 2.758 2.809 1.732 5.004 151.608 -
PV= Relative frequency√¯ relative density, IV= Relative frequency + relative density + relative biomass. J2= Second stage juvenile, J= Juvenile, Im=
Biomass (µg) 0.178(J2)2 0.131(A) 1.220(A) 0.059(Im) 0.157(A) 0.257(A) 0.266(A) 0.327(J) 3.089(A) 0.095(A) 1.291(A) 0.171(A) Immature
Absolute biomass 22.478 7.597 107.360 42.071 15.525 65.976 5.317 8.817 67.952 2.376 46.473 197.111 589.053 female,
Relative biomass 3.816 1.290 18.226 7.142 2.636 11.200 0.903 1.497 11.536 0.403 7.889 33.462 100.000 A=
1
IV
15.216 10.230 32.916 57.472 16.646 29.180 7.543 5.287 15.366 3.553 19.269 87.312 Adult
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