J. Trop. Agric. and Fd. Sc. 37(1)(2009): 119-128

Survey and evaluation of native fungal pathogens for biocontrol of barnyard grass (Echinochloa crus-galli complex) [Bancian dan penilaian kulat patogen untuk kawalan biologi rumput sambau (Echinochloa crus-galli complex)]

S. Tosiah*, J. Kadir**, M. Sariah**, A.S. Juraimi**, N.P. Lo* and S. Soetikno***

Key words: Echinochloa, barnyard grass, Exserohilum monoceras, biocontrol agent

Abstract Echinochloa crus-galli is reported to be among the three most serious weeds of rice in many countries in Asia. In Malaysia, yield loss by E. crus-galli was about 41%. Selective chemical herbicides are primary means to control the grass. However, the extended use of the herbicides may develop negative implication to the environment and public health. Several fungal pathogens have been reported to attack barnyard grass (E. crus-galli complex) in various parts of the world. This study was to isolate, identify and evaluate the native fungi from diseased barnyard grass in paddy field, for potential as bioherbicide. From surveys carried out in 2003 to 2004 throughout the Peninsular Malaysia, several fungi species were identified to be associated with the diseases. A total of 82 isolates from 12 fungus genera have been isolated. Among the fungi were E. monoceras, E. longirostratum and Curvularia lunata. The fungus, E. monoceras, was consistently found associated with the disease, virulent, stable and has the ability to produce spores profusely in culture. These characteristics suggest that it can be used as biological control agent for the grass.

Introduction Echinochloa crus-galli complex (barnyard Echinochloa spp. is found widespread in grass) locally known as `rumput sambau' warm temperate and subtropical regions of consists of E. crus-galli var crus-galli and the world, extending into the tropics. Hill et E. cruss-galli var formosensis. The E. crus- al. (1990), stated that Echinochloa is more galli, E. orizycola and E. colona are competitive in direct-seeded rice than in annuals species, whereas the E. stagnina transplanted rice. and E. picta are perennial species. There are five important species The E. crus-galli is reported to be of Echinochloa in the rice granary in among the three most serious weeds of rice Peninsular Malaysia namely E. crus- in many countries in Asia, and is a major galli complex, E. oryzicola, E. colona, weed in a wide range of crops throughout E. stagnina and E. picta (Azmi 1998). the tropical and subtropical regions (Holm

*Strategic Resources Research Centre, MARDI Headquarters, Serdang, P.O. Box 12301, 50774 Kuala Lumpur, Malaysia **Plant Protection Department, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor Malaysia ***CAB International, MARDI Headquarters, Serdang P.O. Box 12301, 50774 Kuala Lumpur, Malaysia Authors' full names: Tosiah Sadi, Jugah Kadir, Sariah Meon, Abdul Shukor Juraimi, Lo Nyok Piang and Soetikno Sastroutomo E-mail: [email protected] ©Malaysian Agricultural Research and Development Institute 2009

119 Biocontrol of barnyard grass

et al. 1977). In Malaysia, the yield loss by M.B. Ellis, Daclylaria dimorhospora Echinochloa crus-galli is estimated about Veenbaas-Rijks., and Exserohilum oryzae 41% (Azmi 1992). Sivan have also been isolated from E. crus- Cultural and mechanical methods galli in the Philippines (Zhang et al. 1996). have been introduced to control the grass. In Korea, Colletotrichum graminocola However, selective chemical herbicides are showed strong pathogenicity in wide widely used. Although chemical herbicides range of growth stages of E. crus-galli var are the major contributory factor to highly praticola and E. crus-galli var caudata productive modern intensive agriculture, too (Yang et al. 2000). Exserohilum monoceras heavy a reliance upon them have created was also reported as potential bioherbicide certain problems. and not pathogenic on planted rice varieties These problems have arisen due to in China (Huang et al. 2001) and in Vietnam use, misuse, increasing cost, production (Khanh 2002). Kadir et al. (2003) reported contaminants, transport accidents, storage that E. longirostarum has good control on and disposal of toxic wastes. Its leads to Rottboellia cochichinensis (itch grass) and contamination of chemical herbicides on E. crus-galli in Malaysia. surface and groundwater, spray drift and The objectives of this study were to long-term impact of herbicide residues isolate, identify and evaluate native fungi in agriculture products. Other increasing from diseased Echinochloa in Malaysia rice issue caused by the continuous use of field for potential biocontrol of barnyard chemical herbicide is the development of grass. herbicide-resistant grass. Biological control was identified as one of the alternatives to Materials and methods reduce the problems and also suitable for Collection and isolation sustainable agricultural programme. Diseased leaves of Echinochloa spp. were Research in biocontrol of E. crus-galli collected from various locations of five has been intensified in Asia in the early rice granary areas throughout Peninsular 1990s. A stemborer, Emmalocera belonging Malaysia (Perlis, Kedah, Seberang Perai, to Lepidoptera; Pyralidae, discovered in Selangor and Kelantan) in 2003 and 2004. rice field in Kedah feeds only on E. crus- Various disease symptoms observed in the galli complex, E. oryzicola, E. satgnina fields were collected and placed in plastic and E. picta (Goto 1992). Mohamed and containers. Diseases collected from different Hamed (1986) reported that Sogatodes Echinochloa species were placed separately pusanus, Homoptera; Delphacidae found in and documented. Tanjung Karang, Selangor has preference to Fresh diseased parts or lesions were feed on Echinochloa compared to rice plant. cut near the edge about 1 cm2 in size Several fungal pathogens have and surface-sterilized with 10% sodium been suggested as biocontrol agents for hypochlorite solution, shaken vigorously and Echinochloa. They are Cochliobolus lunatus rinsed thrice with sterile distilled water to (Tsukamoto et al. 1997) and Exserohilum remove any debris and traces of disinfectant. monoceras [Septosphaeria monoceras] Four leaf pieces were placed onto moisten (Zhang et al. 1996; Zhang and Watson filter paper in Petri dishes and incubated at 1997). 28 ± 2 °C. All emergent fungi were isolated Besides Exserohilum monoceras daily until no new fungi were observed. (Drechslera) Leonard & Suggs, Bipolaris Isolates were initially identified to sacchari (E.J. Butler) Shoemaker, the genus level based on their conidial Curvularia geniculata, Tracy & Earle morphology (Ellis 1971, 1976; Sivanesan Boedijn, C. lunata (Wakker) Beodijn 1987). Stock cultures were maintained var aeria (Batista, Lima & Vasconcelos) in sterile tap water in bijoue bottle and

120 S. Tosiah, J. Kadir, M. Sariah, A.S. Juraimi, N.P. Lo and S. Soetikno kept at 17 ± 2 °C. Working cultures were Screening and pathogenicity testing maintained in V8 juice agar. Detached leaves methodFor the first Fungi with distinctive characteristics screening, healthy and fully developed of saprophytes were excluded from further leaves of E. crus-galli and rice plant consideration after their initial isolation. MR 219 collected from glass house were Other isolates were tested for pathogenicity cut into 3 cm long pieces, put in separated to barnyard by fulfilling Koch's postulates. container, surface-sterilized with 10% The screening was carried out in two sodium hypochlorite mixed with 2-3 drops stages: (i) detached leaves method, and wetting agent, rinsed and placed onto moist (ii) inoculation on seedling. filter paper in a Petri dish each with three pieces of E. crus-galli or rice plant leaves. Plant production Agar plug 6 mm diameter containing Seeds of E. crus-galli were collected during mycelium or spore and mycelium were the disease symptoms scouting. The seeds cut from 7-day-old cultures on V8 juice were multiplied in glass house for further agar and put on the leaf surface inversely. use. Seeds were kept in refrigerator at 4 °C. Before putting the agar plug, the leaf pieces For the rice plant, the new variety MR 219 were pricked with needles at spots where was used throughout the studies. The seeds the plug would be placed. The Petri dishes were obtained from MARDI Seberang Perai were then incubated at room temperature, gene bank. 28 ± 2 °C. The scoring was taken by visual Echinochloa crus-galli seeds were observation based on lesion development. soaked for 4 days until germinated before Further evaluation of the fungal pathogen transplanted to pots while paddy seeds was only emphasised on isolates that gave were soaked overnight before use. Five only positive reaction to E. crus-galli. pre-germinated seeds (coleoptile and radicle visible) were planted in 10 cm diameter Whole plant methodEchinochloa crus- plastic pots filled with water-saturated clay galli and rice plant at four-leaf stage were soil collected from rice field of MARDI inoculated with 20 ml spore suspension at Tanjung Karang. Seeded pots were placed about 2.5 x 106 spore/ml concentration. in green house. Green house condition was Prior to inoculation, calibration was done to 35/24 ± 5 °C day/night temperature, and a check the optimum amounts of suspension 12 hour photoperiods. that would wet the plant evenly. This was done using tap water. The initial volume of Inoculum preparation the water was measured using measuring All isolates were grown on V8 juice agar cylinder. After spraying the plants, the and incubated at 28 ± 2 °C light/dark volume of the left over was measured again. photoperiod. For the first screening, 7-day- This was carried out a few times to ensure old cultures were used. The cultures were consistency. The average of the difference cut at the actively growing mycelium using of the initial volume and the left over was 6 mm diameter cork borer. For the second considered as the optimum volume for screening, 14-day-old cultures were used to spraying the plants. ensure sporulation. To get enough spores, The spore suspensions were prepared 5-10 petri dishes were prepared for each as simple emulsion by adding 1% v/v corn isolate. The spores were collected by adding oil and 0.02% v/v commercial wetting about 10 ml water and scraping the culture agent (maxi green). The spore suspensions with spatula. The concentration of the spore were sprayed onto the plant using hand was determined using hemeocytometer. sprayer. The sprayer was held at about 30 cm away from the target plant to form an even spreading. Treatments were done in

121 Biocontrol of barnyard grass three replications. The plants were placed Identification and characterization at temperature range of 28-35 °C (glass The isolates identified and characterized house) covered with plastic bags overnight to species level were limited to those to maintain humidity. The pots were ranged confirmed pathogenic to Echinochloa. in Complete Randomized Design (CRD) Sporulating lesion on infected plants and and performed twice. Disease incidence and culture grown in PDA at 28 ± 2 °C were severity were assessed on alternate days for studied for their taxonomic characterization. 14 days. Susceptibility was based on lesions, A total of 200 spores of the isolates were necrotic or plant death. Fungal pathogen was observed. Conidia shape, colour, length, reisolated to confirm Koch's postulate. width, septum number and type, and other special character were documented. Disease assessment Disease was assessed as disease incidence Data analysis and disease severity. Disease incidence was All percentage data were arc sine- assessed based on the number of plants transformed before analysis (Gomez and infected among the total number of plants Gomez 1984). Analysis was done using inoculated and expressed as the percentage SAS 9.1 program. Means separation was of diseased plant (Horsfall and Cowling done if treatment showed significant 1978; Kranz 1988). Disease severity was difference. Results were tested for assessed on all plants of each weed within homogeneity of variance using Bartlett test a pot by visual estimation of the percentage (Gomez and Gomez 1984). of diseased (necrotic) leaves. Disease severity was assessed everyday, 2 days after Results inoculation for 14 days. Survey, collection and isolation of The effect of the fungi isolates on fungal pathogens Echinochloa was assessed based on the area Various disease symptoms have been under disease progress curve (AUDPC). observed on Echinochloa. Among the The AUDPC values were calculated using symptoms are leaf spots, leaf streaks, and formula: leaf scotch. Leaf spot is the most prominent. From the survey, leaf spot at various stages n-1 of development could be found associated AUDPC = (yi+ yi_1) (ti_1 - ti) with the grass. In natural environment, the spots are usually small and elongated 2 between the leaves veins, brown in colour with clear yellow edge. The width of spot where y, = disease severity (percentage or was usually less than 0.5 cm and the length proportion) at the ith evaluation, t, = time could be up to 1 cm, sometimes coalesced to (days, usually after planting or emergence) form a bigger spot. The disease symptoms at the ith evaluation, and n = total number could be found in most of the collection of evaluations as described by Campbell sites but the intensity was low. However in and Madden (1990). The apparent disease some places, severe infection was observed progress rates (rL) were obtained by but the situation was very rare. transforming the disease severity data using During the collection, 82 isolates a logistic model called logit as described: from 12 fungus genera have been isolated from the various disease symptoms logit = In (x/[100-x]) of Echinochloa (Table 1). Isolates of Aspergillus (4.87%), Nigrospora (12.19%), where In = natural logarithm and x = disease Mucor (2.42%), Penicillium (7.31%) and severity (percentage). Rhizoctonia (1.2%) were excluded from

122 S. Tosiah, J. Kadir, M. Sariah, A.S. Juraimi, N.P. Lo and S. Soetikno

Table 1. Fungi associated with Echinochloa spp. because the isolates were dead and could not isolated from 5 granary areas surveyed be recovered from both working culture and storage. Genus Frequency of isolation (%) Whole plant method Aspergillus sp. 4.87 Cladosporium sp. 10.9 Although there were 18 isolates identified Colletotrichum sp. 1.2 to infect Echinochloa through the detached Curvularia sp. 12.19 leaves method, only 14 isolates were used Dreschlera sp 7.31 in the whole plant inoculation method. Exserohilum spp. 23.17 Four isolates that did not sporulate were Fusarium sp. 6.09 Mucor sp. 2.42 not tested for their pathogenicity. Since the Nigrosporia sp. 12.19 trails were not conformed to the test for Penicillium sp. 7.31 homogeneity of variance using Bartlett test, Pyricularia sp. 2.42 the results were presented as individual. Rhizoctonia sp. 2.42 The calculated Area Under Disease Unidentified deuteromycetes 1.2 Mycelia sterilia 3.65 Progress Curve (AUDPC), for isolates 1125, 1100, 1080, 5, 1112b, 1065, 1076, 1105, 1103 and 1093 obtained from the further screening after their initial isolation, first trial were higher compared to isolates because they were known to be secondary 1174, 1068, 1122 and 1108 which showed pathogen and have not been reported as higher AUDPC in the second trial (Table 5). causal agent of weed disease. However, not The results showed that the isolates had all remaining isolates survived in culture. different pathogenicity and virulence in Thus, only 33 isolates were further screened infecting Echinochloa. Isolate 1125 was the and evaluated (Table 2). most virulent followed by isolates 1100 and 1180. In both trials, isolate 1125 showed Detached leaves method consistency in its virulence which translated Out of 33 isolates screened (Table 2), only as highest AUDPC (867.83 ± 39.64 unit2) in 18 isolates were pathogenic to Echinochloa, trial 1 and (762.83 ± 20.95 unit2) in trial 2 7 isolates pathogenic to both Echinochloa compared to the other isolates in both trials and rice plant, and 8 isolates not pathogenic (Figure 1). to neither Echinochloa nor rice plant All isolates showed similar symptom (Table 3). The isolates with positive reaction development although it did not appear at to rice leaves were considered as pathogenic the same time. The first disease symptom to rice. Isolates, which not infected both appeared 24-48 h after inoculation as a Echinochloa and rice plant, were considered discrete spot with necrosis or yellowing as a saprophyte fungus. edge. The entire leaves with the spots Based on their colony and conidia usually turned completely necrotic and died. morphology of fungi with positive reaction, From both trials, all tested isolates did not the fungi isolates can be grouped to four infect rice plants. species, Curvularia lunata, Exserohilum The isolates 1125, 1080, and 1100 gave longirostratum, E. monoceras and more than 50% disease severity after five Exserohilum spp. (species unidentified). days of inoculation (Figure 2). It increased The E. monoceras was the most frequently to 80% at day 7. The disease severity of isolated fungus species, and was found in all isolate 1125 increased until day 11 when it granaries surveyed (Table 4). reached 100% and all inoculated plants died. Its should be noted that no fungus However, the disease severity for isolates species isolated from E. colona were 1080 and 1100 remained unchanged from screened for pathogenicity in this study day 7 until day 14.

123 Biocontrol of barnyard grass

Table 2. Isolates tested, locations, host and their effect on Echinochloa and rice plant

No. Isolate no. Area Host Echinochloa Rice plant

1 1112b Kedah E. crus-galli var crus galli y n 2 1115 Kedah E. crus-galli var crus galli y n 3 1112a Kedah E. crus-galli var crus galli n n 4 1127 Kedah E. crus-galli var crus galli y n 5 1114 Kedah E. crus-galli var crus galli y n 6 1122 Kedah E. crus-galli var crus galli y n 7 1124 Kedah E. crus-galli var crus galli y y 8 1126 Kedah E. crus-galli var crus galli y y 9 1128 Kedah E. crus-galli var crus galli y y 10 1131 Kedah E. crus-galli var crus galli y y 11 1117 Kelantan E. crus-galli var crus galli n n 12 1118 Kelantan E. crus-galli var crus galli n n 13 1119 Kelantan E. crus-galli var crus galli n n 14 1120 Kelantan E. crus-galli var crus galli y n 15 1121 Kelantan E. crus-galli var crus galli y n 16 1123 Perlis E. crus-galli var crus galli y y 17 1129 Perlis E. crus-galli var crus galli y y 18 1080 Seberang Perai E. crus-galli varformosensis y n 19 nbm Seberang Perai E. crus-galli var crus galli y n 20 1076 Seberang Perai E. crus-galli varformosensis y n 21 1079 Seberang Perai E. crus-galli varformosensis n n 22 1081 Seberang Perai E. crus-galli varformosensis y y 23 1085 Seberang Perai E. crus-galli varformosensis n n 24 1091 Selangor E. crus-galli var crus galli n n 25 1108 Selangor E. crus-galli var crus galli y n 26 1103 Selangor E. crus-galli var crus galli y n 27 1068 Selangor E. crus-galli var crus galli y n 28 1125 Selangor E. crus-galli var crus galli y n 29 1065 Selangor E. crus-galli var crus galli y n 30 1073 Selangor E. crus-galli var crus galli n n 31 1093 Selangor E. crus-galli var crus galli y n 32 1100 Selangor E. crus-galli varformosensis y n 33 1105 Selangor E. crus-galli var crus galli y n y = positive reaction-fungi causing leaf necrosis n = negative reaction-fungi not causing necrosis

Table 3. Number of fungi isolated from Echinochloa species screened and their reaction to Echinochloa and rice plant Target weed No. of fungi No. of isolates No. of isolates No. of isolates isolates pathogenic to pathogenic to non pathogenic screened Echinochloa rice plant to both E. crus-galli var crus galli 27 15 6 6 var formosensis 6 3 1 2 E. colona 0 0 0 0 E. oryzicola 0 0 0 0 E. stagnina 0 0 0 0

Identification and characterization character. This is an advantage compared Isolates 1125, 1080 and 1100 were quite to the other two because spore production similar morphologically (Table 6). However ability is important for a fungus to be used isolate 1125 has a good conidiation as bioherbicide. The identification of isolate

124 S. Tosiah, J. Kadir, M. Sariah, A.S. Juraimi, N.P. Lo and S. Soetikno

Table 4. Frequencies of fungi species pathogenic to Echinochloa from different granaries

Granary area Curvularia E. longirostratum E. monoceras Exserohilum sp.

Kedah/Perlis (MUDA) 0 1 5 0 Kelantan (KEMUBU) 0 0 2 0 Selangor (PBLS) 2 1 3 2 Seberang Perai 0 0 4 0

Table 5. Effect of 14 fungi evaluated on Echinochloa in trial 1 and trial 2 expressed as area under disease progress curve (AUDPC) and apparent disease rate

Fungi isolates AUDPC of fungi Means Saparation Apparent disease R2 isolates on Echinochloa Group (Tukey's HSD) progress rate (rL) logit/day (unite) Trial 1 1125 867.83 ± 39.64 a 1.16 0.97 1100 799.5 ± 89.32 ab 0.80 0.98 1080 725.33 ± 42.11 be 0.68 0.99 5 601.17 ± 31.01 cd 0.57 0.97 1112b 477.83 ± 71.06 de 0.57 0.97 1065 440.67 ± 62.64 ef 0.38 0.79 1076 439.83 ± 69.1 ef 0.10 0.88 1074 425.25 ± 31.43 ef 0.72 0.93 1068 417.33 ± 39.84 of 0.47 0.95 1105 404.33 ± 27.67 of 0.39 0.86 1122 403.67 ± 36.94 of 0.48 0.93 1103 357.78 ± 25.24 ef 0.28 0.93 1108 357.33 ± 18.18 ef 0.45 0.98 1093 298.08 ± 20.10 f 0.35 0.79 Trial 2 1125 762.83 ± 20.95 a 0.66 0.95 1100 523 ± 27.97 b 0.44 0.93 1080 607.83 ± 43.47 b 0.49 0.93 5 426.17 ± 43.15 cde 0.30 0.80 1112b 393 ± 46.52 e 0.38 0.95 1065 319.33 ± 38.07 ef 0.36 0.86 1076 199.67 ± 53.75 g 0.45 0.41 1074 591 ± 53.92 b 0.35 0.94 1068 436.17 ± 56.9 cde 0.32 0.89 1105 400.75 ± 23.03 e 0.56 0.86 1122 531.67 ± 40.27 cb 0.51 0.89 1103 256.42 ± 10.81 fg 1.73 0.92 1108 412.13 ± 37.42 de 0.22 0.86 1093 204.17 ± 16.91 g 0.23 0.90 AUDPC Area under disease progress curve;rL Apparent disease progress; cv = 17.13% for trial 1 and 16.32 for trial 2; R2 is a goodness of fit; p <0.05 has been confirmed by CAB bioscience Discussion as Exserohilum monoceras (Drechsler) Of the fungi isolated from Echinochloa K.J. Leonard & Suggs. (Plate 1) and given a spp., 18 isolates of four species number 392356. namely C. lunata, E. longirostratum, and E. monoceras were pathogenic to the grass. However, E. monoceras isolate 1125 was the most pathogenic of the 14 isolates.

125 Biocontrol of barnyard grass

1000 - 900 - trial 1

I I trial 2 800 - 700 - 600 - 500 - 400 - 300 - 200 - 100 - tit* 0 If 4t

1-1 Isolate number Figure 1. Comparison of Area Under Disease Progress Curve (AUDPC) of all isolates from trial 1 and trial 2 From the survey, E. monoceras was 120 - 1125 the common pathogen attacking E. crus- 100 - 1080 galli complex in Malaysian granaries. The 1100 80 - fungus was found in all sampling locations. > In some sampling locations, the fungus 60 - caused severe leaf disease but clump in one 40 - spot. This might result from limited spore 20 - production which was always limited by the environment factors such as humidity and 0 1 2 3 4 5 6 7 8 910 11 12 13 temperature. Day after inoculation Exserohilum monoceras isolate 1125 was consistent in their virulence and Figure 2. Comparison of disease severity sporulation. Virulence is the most important development (%) caused by isolates, 1125, 1080 and 1100 on 4-leaf stage Echinochloa attribute for the selection of candidate to be developed into bioherbicide. Further work The finding was paralleled with the earlier should focus on the fungus potential as studies by Tsukatomo et al. (1996) in Japan, bioherbicide, in relation to its effectiveness Zhang and Watson (1997) in the Philippines, and safety. Huang et al. (2001) in China and Khanh (2002) in Vietnam. Acknowledgement Exserohilum monoceras is a species of This research was conducted in partial dematiaceous Hypomycetes (Ellis 1976). It fulfillment of the first author's doctoral has been associated with the Setosphaeria dissertation. The authors thank monoceras Alcorn teleomorph, which Mr S. Mahendra, Ms Zanariah Zainal is included in the family Pleoporaceae, Abidin and Ms Napsiah Abdul Rahim for the order Pleosporales, Ascomycotina their technical assistance. The project was (Sivanesan 1987; Alcorn 1988). The fungus sponsored by IRPA (01-03-03-0119 EA001). has been reported in 11 countries, namely Australia, Cuba, India, Israel, Japan, Korea, References Philippines, Russia, Turkey, United States Alcorn, J.L. (1988). The taxonomy of and Yugoslavia (Sivanesan 1987; Chung et "Helminthosporium" species. Ann. Rev. al. 1990; Gohbara and Yamaguchi 1994). Phytopathol. 26: 37-56

126 S. Tosiah, J. Kadir, M. Sariah, A.S. Juraimi, N.P. Lo and S. Soetikno

Table 6. Some morphological characters of isolates, 1125, 1080 and 1100 cultured on Potato Dextrose Agar (PDA)

Isolate character 1125 1080 1100 Colony morhoplogy Effuse hairy Effuse hairy Cottony Colony colour Brownish-black Greenish-grey Greyish-brown Hilum Present Present Present Conidia shape Straight to curve Straight to curve Straight to curve Conidia colour Olivaceous brown Olivaceous brown Brown Conidia length (pm) 67.5-180 47.5-147 90-154 Width (pm) 12.5-25 10-17.5 13.2-20 Pseudosepta (no) 3-12 3-8 6-12 Conidiation Profuse Intermediate Scanty

Plate 1. Exserohilum monoceras a) Culture morphology, b) Spore 200x

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Abstrak Echinochloa crus-galli (rumput sambau) dilaporkan antara tiga rumpai yang paling serius di kawasan padi di Asia. Di Malaysia, E. crus-galli menyebabkan kehilangan hasil padi sebanyak 41%. Racun rumpai kimia ialah kaedah utama yang digunakan untuk mengawal rumpai ini. Walau bagaimanapun, penggunaan racun kimia yang berterusan boleh membawa implikasi negatif kepada persekitaran dan kesihatan awam. Beberapa patogen kulat telah dilaporkan menyerang rumput sambau di beberapa kawasan di dunia. Kajian ini adalah untuk mengasing, mengecam dan menilai potensi patogen kulat tempatan yang dialing daripada penyakit Echinochloa yang terdapat di sawah padi di Malaysia untuk digunakan sebagai bioherbisid. Dalam bancian yang dijalankan dan 2003 sehingga 2004 di Semenanjung Malaysia, beberapa kulat telah dikenal pasti berasosiasi dengan penyakit rumpai ini. Sejumlah 82 pencilan kulat daripada 12 genus telah berjaya diasingkan. Antaranya ialah, E. monoceras, E. longirostratum, dan Curvularia lunata. Daripada pemerhatian, E. monoceras secara konsisten didapati berasosiasi dengan penyakit rumpai ini, virulen, stabil, dan boleh menghasilkan spora yang banyak di dalam kultur. Ciri-ciri ini mencadangkannya sebagai calon yang boleh digunakan untuk pengawalan rumpai ini secara biologi.

Accepted for publication on 16 December 2008

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