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Isolation of nematophagous fungi fromeggs and females of Meloidogyne spp.and evaluation of their biologicalcontrol potentialF.M. Aminuzzaman a , H.Y. Xie b , W.J. Duan c , B.D. Sun d & X.Z.Liu da Department of Plant Pathology, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Dhaka, Bangladeshb High-Tech Research Center, Shandong Academy of AgriculturalSciences, Jinan, People's Republic of Chinac Ningbo Entry-exit Inspection and Quarantine Bureau TechnicalCenter of People's Republic of China, Ningbo, People's Republic ofChinad State Key Laboratory of Mycology, Institute of Microbiology,Chinese Academy of Sciences, Beijing, People's Republic of ChinaAccepted author version posted online: 05 Nov 2012.

To cite this article: F.M. Aminuzzaman , H.Y. Xie , W.J. Duan , B.D. Sun & X.Z. Liu (2013)Isolation of nematophagous fungi from eggs and females of Meloidogyne spp. and evaluationof their biological control potential, Biocontrol Science and Technology, 23:2, 170-182, DOI:10.1080/09583157.2012.745484

To link to this article: http://dx.doi.org/10.1080/09583157.2012.745484

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RESEARCH ARTICLE

Isolation of nematophagous fungi from eggs and females of Meloidogynespp. and evaluation of their biological control potential

F.M. Aminuzzamana, H.Y. Xieb, W.J. Duanc, B.D. Sund and X.Z. Liud*

aDepartment of Plant Pathology, Faculty of Agriculture, Sher-e-Bangla Agricultural University,Dhaka, Bangladesh; bHigh-Tech Research Center, Shandong Academy of Agricultural Sciences,

Jinan, People’s Republic of China; cNingbo Entry-exit Inspection and Quarantine BureauTechnical Center of People’s Republic of China, Ningbo, People’s Republic of China; dState Key

Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing,People’s Republic of China

(Received 27 July 2012; returned 29 August 2012; accepted 29 October 2012)

Fungi were isolated from Meloidogyne spp. eggs and females on 102 field-collected root samples in China. Of the 235 fungi isolated (representing 18 generaand 26 species), the predominant fungi were Fusarium spp. (42.1% of the isolatescollected), Fusarium oxysporum (13.2%), Paecilomyces lilacinus (12.8%), andPochonia chlamydosporia (8.5%). The isolates were screened for their ability toparasitise Meloidogyne incognita eggs in 24-well tissue culture plates in twodifferent tests. The percentage of eggs parasitised by the fungi, the numbers ofunhatched eggs and alive and dead juveniles were counted at 4 and 7 days afterinoculation. The most promising fungi included five Paecilomyces isolates, 10Fusarium isolates, 10 Pochonia isolates and one Acremonium isolate in test 1 ortest 2. Paecilomyces lilacinus YES-2 and P. chlamydosporia HDZ-9 selected fromthe in vitro tests were formulated in alginate pellets and evaluated for M. incognitacontrol on tomato in a greenhouse by adding them into a soil with sand mixtureat rates of 0.2, 0.4, 0.8 and 1.6% (w/w). P. lilacinus pellets at the highest rate(1.6%) reduced root galling by 66.7%. P. chlamydosporia pellets at the highest ratereduced the final nematode density by 90%. The results indicate that P. lilacinusand P. chlamydosporia as pellet formulation can effectively control root-knotnematodes.

Keywords: Paecilomyces lilacinus; Pochonia chlamydosporia; Meloidogyneincognita; nematophagous fungi; screening; pellet formulation

1. Introduction

Root-knot nematodes (Meloidogyne spp.) are destructive pathogens of many

agricultural crops and cause an estimated $100 billion loss per year worldwide

(Chitwood 2003). They can reduce both crop yield and quality and can survive under

a wide range of soil moisture and temperature conditions (Sasser 1979). The

nematodes can be managed by cultural practices and chemical nematicides. However,

cultural practices alone are inadequate. For example, resistant cultivars are only

effective against specific nematode species (Roberts 1992). Chemical control also has

limitations because of environmental and human health concerns. In addition,

*Corresponding author. Email: liuxz@im.ac.cnF.M. Aminuzzaman and H.Y. Xie contributed equally to this work.

Biocontrol Science and Technology, 2013

Vol. 23, No. 2, 170�182, http://dx.doi.org/10.1080/09583157.2012.745484

# 2013 Taylor & Francis

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nematicides seldom provide long-term suppression. Therefore, there is a need to

develop alternative, environmentally friendly management strategies to control

Meloidogyne spp., and two of these alternatives are the use of biocontrol agents

and organic amendments (Noling and Becker 1994).

Biological control agents (BCAs) are generally considered safer than traditional

nematicides. Fungi have been studied the most and appear to be the most important

control agents for regulating nematode numbers in soil (Chen, Chen and Dickson

2004). Meloidogyne eggs are naturally infected by soil microorganisms, many of

which have been isolated and some of which have shown potential as BCAs when

added to soil. Sun, Gao, Shi, Li and Liu (2006) isolated 455 microorganisms from

eggs and females of Meloidogyne spp., and 21 of the isolates were able to parasitise a

high percentage of Meloidogyne eggs in pot trials in the greenhouse. The egg-

parasitic fungi Paecilomyces lilacinus and Pochonia chlamydosporia have been

extensively studied and have suppressed various plant-parasitic nematodes in

laboratory and field tests (Kerry 2001; Chen et al. 2004; Sun et al. 2006; Ganaie

and Khan 2010; Mousavi, Zare, Zamanizadeh and Fatemi 2010; Aminuzzaman and

Liu 2011; Gomes Carneiro et al. 2011). Paecilomyces lilacinus and P. chlamydosporia

have been documented to significantly reduce galling of tomato caused by

Meloidogyne javanica (Treub) in the greenhouse (Kiewnick and Sikora 2006) and

control the potato cyst nematode in commercial potato fields (Tobin, Haydock,

Hare, Woods and Crump 2008).

Although many attempts have been endeavored, there are only a few formulated

products available for biological control of nematodes (Liu and Li 2004). A

formulated product containing spores of P. lilacinus, strain 251, significantly

decreased the numbers of Meloidogyne second-stage juveniles in a greenhouse test,

and the suppression by the formulated fungus was similar to that provided by the

nematicide oxamyl (Anastasiadis, Giannakou, Prophetou-Athanasiadou and Gowen

2008). Deficiencies in formulations, however, have seriously hampered the commer-

cialisation of these fungi.

The performance of an organism, whether formulated or not, will be adversely

affected by an unfavorable environment such as low relative humidity and high UV

radiation (Faria and Wraight 2001). Granular formulations can buffer BCAs from

environmental extremes and can provide a food base for the agent (Boyette, Quimby,

Connick, Daigle and Fulgham 1991). The granules also allow controlled release of

the organism from the formulation (Weidemann 1988; Rhodes, Powell, MacQueen

and Greaves 1990; Wiwattanapatapee et al. 2004). An alginate pellet formulation

method of a nematophagous fungus has been described (Jaffee, Muldoon and

Westerdahl 1996; Jaffee and Muldoon 1997). However, the procedure is not suitable

for commercial production because it is too complex. A simpler formulation

consisting of alginate pellets containing fungal hyphae grown in liquid fermentation

has been described by Duan, Yang, Xiang and Liu (2008).

The aims of the present study were to (1) study the prevalence of fungal species

associated with Meloidogyne spp.; (2) screen egg-parasitic fungi for their ability to

reduce the hatch of Meloidogyne spp. eggs in vitro; and (3) investigate the biocontrol

potential of alginate preparations containing P. lilacinus or P. chlamydosporia in a

greenhouse pot experiment.

Biocontrol Science and Technology 171

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2. Materials and methods

2.1. Isolation of fungi from Meloidogyne spp. eggs and females

One hundred and two root samples were collected from plants infested with

Meloidogyne spp. The plants included tomato (Solanum lycopersicum L.), eggplant

(Solanum melongena), cockscomb (Celosia cristata), begonia (Begonia grandis),

balsam pear (Momordica charantia), banana (Musa acuminate), cucumber (Cucumis

sativus L.), cucurbit (Lagenaria siceraria), pepper (Piper nigrum), guava (Psidium

guajava), crotalaria (Crotalaria pallid), pumpkin (Cucurbita moschata), snapdragon

(Antirrhinum majus), loofah (Luffa aegyptiaca) and malabar spinach (Basella rubra).

Sampling locations included greenhouses, fields, farms and parks in Beijing, Fujian,

Guangdong, Guangxi, Hainan and Zhejiang, People’s Republic of China. The

samples were kept in double-layered plastic bags at 48C, and fungi were isolated

within 1 month after collection.Galled roots were washed with running tap water, and the egg masses and females

were carefully removed from the roots with a dissecting needle. Eggs were extracted

from the egg masses following the method of Hussey and Barker (1973) with some

modifications. Egg masses were treated with 1% sodium hypochlorite (NaOCl) for 1

min, and the females were treated with 0.1% NaOCl for 3 min; after treatment, eggs

and females were rinsed with sterile-distilled water. About 100 eggs were spread onto

each of Petri dish (9 cm diameter) containing potato dextrose agar (PDA), and at

least, five plates were applied for each sample. Five females were crushed by sterile

forceps and placed on each PDA plate and 10 plates were applied for each sample.

All plates were incubated at 258C and routinely examined with an inverted

microscope. The fungal hyphae growing from eggs or females were transferred to

PDA plates for isolation and identification (Domsch, Gams and Anderson 1980;

Barnett and Hunter 1998).

2.2. In vitro pathogenicity

The fungal inocula were prepared following the method described by Sun et al.

(2006). The spore suspension was adjusted to105 spores/ml for the sporulated fungi

and mycelial fragments passing through three-layered gauze were prepared for sterile

fungi. Meloidogyne incognita was maintained on tomato plants in a greenhouse for

1 month, and roots were removed from soil, washed and treated with 1% NaOCl for

1 min to release eggs from egg masses. The eggs were then washed three times withsterile-distilled water and were collected in 50-ml plastic centrifuge tubes. The eggs

were separated from debris by centrifugation in a 37.5% (w/v) sucrose solution for 5

min at 2500 rpm (Liu and Chen 2001). The collected eggs were surface disinfested by

immersing them in 0.1% NaOCl for 3 min. After the eggs were rinsed in sterile-

distilled water, they were adjusted to 300 eggs/50 ml suspension (test 1) or 50 eggs/50

ml suspension (test 2). For test 1, 50 ml of suspension containing approximately 300

eggs was pipetted into each well of a 24-well tissue culture plate containing 1 ml of a

fungal spore suspension (105 spores/ml). Control wells contained 1 ml of sterile water

without spores. The plates were sealed with Parafilm and incubated at 258C on a

shaker (150 rpm). After 4 days, all eggs were examined at 40�100�magnification

with an inverted microscope, and parasitised and non-parasitised eggs were counted,

and the percentage of eggs parasitised was calculated. Eggs with hyphae growing

172 F.M. Aminuzzaman et al.

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from them were considered parasitised (Sun et al. 2006). After three additional days

of incubation, all eggs, living juveniles and dead juveniles were counted, and egg

hatch rate, egg hatch inhibition rate and juvenile mortality were calculated (Sun et al.

2006). Corrected juvenile mortality was calculated as (juvenile mortality of

treatment �juvenile mortality of control)/(1 �juvenile mortality of control)�100%. Juveniles colonised by parasites, malformed or stiff were considered to be

killed. The same protocol was applied for test 2 except a 50-ml egg suspension

containing approximately 50 eggs was pipetted into each well.

2.3. Greenhouse pot experiment with P. lilacinus YES-2 and P. chlamydosporia HDZ-9

Soil used for the pot experiment was collected from a field as described by Zhang,

Yang, Xiang, Liu and Chen (2008). The soil was sandy loam, pH 6.7 and 1.03%

organic matter content. A mixture of air-dried field soil and sand at a ratio of 1:1

(v:v) was passed through a sieve with 3.5-mm openings.

Inoculum of M. incognita was prepared as described above. The egg density was

adjusted to 2000 eggs/ml of suspension. The susceptible tomato (Solanum

lycopersicum L.) variety Zhongshu 5 was used for the greenhouse experiment.

Tomato seeds were sterilised with 1% NaOCl for 2 min, rinsed three times with sterile

water and sown in 50-well multi-pot trays containing soil plus 50% seedling

substrate. The multi-pot trays were kept in a greenhouse and irrigated regularly.

After 4�6 weeks, the seedlings were transplanted into pots as described in the next

paragraph.

Two isolates of P. lilacinus YES-2 and P. chlamydosporia HDZ-9, previously

isolated and screened (Sun et al. 2006), were selected based on the in vitro

pathogenicity test; these isolates were deposited at the China General Microbiology

Culture Collection as CGMCC NO.2012 and CGMCC NO.310073. Alginate pellets

containing hyphae of these isolates were prepared following the method of Duan

et al. (2008). The pellets were dried and they were spherical (4�5 mm in diameter)

and weighed 23.5 mg/pellet. The number of colony-forming units (CFU)/g of pellet,

which was determined by dilution plate counts on PDA (Lee and Heo 2000), was

6.95�107 for P. lilacinus YES-2 and 1.96�108 for P. chlamydosporia HDZ-9.

Pellets of P. lilacinus and P. chlamydosporia were separately mixed into the soil

(soil:sand mixture) at 0.2, 0.4, 0.8 and 1.6% (dry weight of pellets/fresh weight of

soil�100). Each plastic pot (600 cm3) was filled with 500 cm3 of soil. One tomato

seedling free of soil was transplanted into each pot, and 5 ml of the nematode egg

suspension (10,000 eggs/pot) were added to four 2-cm-deep holes in the central area

of each. Controls included pots without nematode eggs and pellets and pots with

eggs but without pellets. Each treatment was replicated five times. The pots were

randomly arranged in a greenhouse at 25�308C. Seedlings were irrigated with tap

water daily and fertilised biweekly with a Hoagland solution.

After 8 weeks, tomato plants were cut at the soil level, and the rhizosphere soil

was washed away and carefully collected. Shoot height, shoot weight, root length and

root weight were measured. Nematode damage was determined by rating root gall

index on a 0�10 scale (Bridge and Page 1980). Egg masses on each root system were

counted using the phloxine B (0.015%, SIGMA) solution method (Holbrook, Knauft

and Dickson 1983). Nematodes from soil samples (100 cm3 per pot) and from all

Biocontrol Science and Technology 173

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root systems were extracted and then purified by centrifugation (Coolen 1979). The

greenhouse experiment was conducted twice (trials 1 and 2).

2.4. Statistical analysis

Data from the in vitro pathogenicity test and the greenhouse experiment wereanalysed and the variances were tested for homogeneity of variances and subjected to

analysis of variance (ANOVA) using the SPSS 13.0 statistical package. Mean values

of root gall index and final nematode population were compared using Student-

Newman-Keuls method at PB0.05.

3. Results

3.1. Fungi isolated from Meloidogyne spp. eggs and females

Thirty-six root samples (35.3% of the total samples collected) were encountered with

fungi. A total of 235 fungal isolates were obtained including 81 from eggs and 154from females, among which 119 isolates were isolated from 18 of the 43 samples in

Hainan and 56 isolates from 9 of the 19 samples in Fujian (Table 1). A total of 26

species belonging to 18 genera were identified, and the predominant fungi were

Fusarium spp., Fusarium oxysporum, P. lilacinus, and P. chlamydosporia; which

represented 42.1, 13.2, 12.8 and 8.5% of all isolates, respectively (Table 2). Fusarium

spp. were the most abundant isolates in Hainan, Fujian and Guangdong Province.

Table 1. Samples and number of fungi isolated from root-knot nematodes, Meloidogyne spp.

Number of isolates

Sampling sites

(Provinces and sites)

Number of

samples

collected

Number of samples

encountered with fungi

From

eggs

From

females Total

Beijing 2 2 7 � 7

Fujian 19 9

Fuzhou 7 49 56

Guangdong 27 5

Guangzhou 14 14 28

Suixi 8 8 16

Guangxi 9 1

Nanning 3 1 4

Hainan 43 18

Chengmai 3 6 9

Haikou 2 5 7

Lingao 1 4 5

Qionghai 2 11 13

Qiongzhong 3 1 4

Tunchang 2 3 5

Wenchang 27 49 76

Zhejiang 2 1

Wenzhou 2 3 5

Total number 102 36 81 154 235

174 F.M. Aminuzzaman et al.

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Table 2. Fungi isolated from Meloidogyne spp. eggs and females.

Number of isolates from different locations

Fungi Beijing Fujian Guangdong Guangxi Hainan Zhejiang Total Relative frequency (%)a

Acremonium spp. 2 2 2 � 4 � 10 4.3

Alternaria spp. � 3 � � � � 3 1.3

Aspergillus spp. � � � � 3 1 4 1.7

Aspergillus flavus � � � � 1 � 1 0.4

Aspergillus fumigatus � � � � 1 �Aspergillus nidulans � � � � 1 � 1 0.4

Botryotrichum sp. 1 � � � � � 1 0.4

Chaetomium sp. � � 1 � � � 1 0.4

Cladosporium sp. � 1 � � � � 1 0.4

Cephalosporium sp. � � 1 � � � 1 0.4

Cylindrocarpon sp. � 1 � � � � 1 0.4

Cylindrocladium sp. � � � � 1 � 1 0.4

Fusarium spp. � 37 11 3 46 2 99 42.1

Fusarium chlamydosporium � 2 � � 3 � 5 2.1

Fusarium moniliforme � � � � 1 � 1 0.4

Fusarium oxysporum � � 3 � 28 � 31 13.2

Fusarium solani � � � � 2 � 2 0.9

Mortierella spp. � � � � 4 � 4 1.7

Paecilomyces lilacinus � 5 8 � 17 � 30 12.8

Penicillium spp. � 1 � � � � 1 0.4

Penicillium janthinellum � � � � 1 � 1 0.4

Pestalotia sp. � � � � 1 � 1 0.4

Pestalitiopsis spp. � � � � 5 � 5 2.1

Pochonia chlamydosporia � � 15 1 2 2 20 8.5

Scopulariopsis brumptii � 1 � � � � 1 0.4

Trichoderma sp. � � � � 1 � 1 0.4

Sterile fungi 4 1 2 � � � 7 3.0

Total 7 54 43 4 122 5 235 100.0

�: no isolate was recovered.a(Number of isolates per species/total number of isolates)�100.

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Fusarium oxysporum was prevalent in Hainan. Isolates of P. lilacinus were prevalent

in Hainan, Guangdong and Fujian. Most of the P. chlamydosporia isolates were from

Guangdong. Seven isolates did not sporulate and were considered to be sterile fungi.

3.2. In vitro pathogenicity

In test 1, most of the 165 isolates colonised M. incognita eggs, inhibited egg hatch

and killed juveniles (Figure 1). Fifteen per cent of the isolates had no ability to

parasitise eggs whereas 12%, 12.8% and 11% of the isolates had an egg parasitismrate of 0.1�10%, 10.1�20% and 80.1�90%, respectively. Only 7.8% of the isolates had

the ability to parasitise 90% to 100% of the M. incognita eggs. High rates of egg hatch

inhibition (90�100%) were recorded for 7.9% of the isolates, and 20% of the isolates

had egg hatch inhibition rates between 80% and 90%. Of the isolates, 39.4% caused

only 0.1% to 10% corrected juvenile mortality, 18.2% caused 10% to 20% corrected

juvenile mortality and only 1.2% caused 90% to 100% corrected juvenile mortality.

Figure 1. Frequency distribution of fungal isolates under different classes of virulence. Fungal

isolates were grouped into 11 virulence classes based on their ability to parasitise eggs; inhibit

egg hatch and kill J2 of Meloidogyne spp. In test 1, 300 eggs were added into each well of a 24-

well tissue culture plate where each well contained 105 fungal spores. Four days after

inoculation, per cent eggs parasitised by the fungi was recorded. Seven days after inoculation,

egg hatch inhibition rate and juvenile mortality rate were determined by counting all eggs, live

and dead juveniles. In test 2, the fungal evaluation protocol was as test 1 except only 50 eggs

were added into each well of the same plate.

176 F.M. Aminuzzaman et al.

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In test 2, all of the isolates parasitised eggs, and most of the isolates inhibited egg

hatching and killed juveniles of M. incognita (Figure 1).In test 1, 19 isolates belonging to three genera parasitised a high percentage of M.

incognita eggs (Table 3). The isolates included two strains of P. lilacinus, eight strains

of Fusarium spp. and nine strains of P. chlamydosporia. These 19 isolates had egg

parasitism rates between 71% and 97.6%, reduced egg hatch by 23% to 91% and had

corrected juvenile mortality between 8.7% and 65%. In test 2, seven isolates

belonging to four genera parasitised high percentage of M. incognita eggs or killed

substantial juveniles (Table 4). Among these isolates, the percentage of eggs

parasitised ranged from 68.7% to 100%, egg hatch rate ranged from 2.5% to

20.6% and the corrected juvenile mortality ranged from 19.9% to 100%.

Paecilomyces lilacinus strain FZ-07-9F-2 parasitised 98% of the eggs, reduced

hatching 81% and killed 56% of the juveniles. Pochonia chlamydosporia strain WZ07-

1F-3 parasitised 96% of the eggs, reduced hatching by 68.8% and killed 47.2% of the

juveniles.

Table 3. Activity of the most promising fungal isolates in the in vitro pathogenicity experiment

(test 1).a

Fungus Isolate

Parasitism

of eggs

(%)

Egg hatch

rate

(%)

Juvenile

mortality

(%)

Corrected

juvenile

mortality

(%)

Paecilomyces

lilacinus

WC06-1F-1 88.196.1 4.190.3 15.096.5 8.7WC06-4F-2 89.399.0 2.390.4 26.9910.9 21.5

Fusarium oxysporum WC06-6F-6 82.392.5 3.392.7 24.197.9 18.5

WC06-8F-2 82.393.7 3.090.2 32.5919.9 27.5

Fusarium sp. WC06-6F-5 80.797.3 5.391.9 35.6913.9 30.8

WC06-9E-1 90.493.5 3.390.4 30.3913.8 25.1

WC06-9E-2 80.297.5 2.590.5 35.1913.9 30.3

SX06-3F-1a 77.694.1 10.091.8 59.8913.5 56.8

SX06-3F-6 80.397.5 11.992.3 50.992.2 47.3

SX06-3F-7 71.0914.7 7.991.7 67.497.5 65.0

Pochonia

chlamydosporia

SX06-3E-1 94.094.5 6.391.9 45.4912.8 41.4SX06-3E-2 93.091.0 8.090.4 63.5915.2 60.8

SX06-3E-3 94.093.6 8.192.7 54.5921.8 51.1

SX06-3E-4 94.695.0 7.791.1 35.7915.3 30.9

SX06-3E-5 91.493.8 5.292.2 32.092.2 27.0

SX06-3E-11 94.693.2 6.991.6 52.595.8 49.0

BY06-1E-9 94.392.0 15.292.7 19.392.4 13.3

BY06-5F-5 94.391.5 20.091.5 18.491.9 12.4

BY06-10E-2 97.693.2 18.491.9 18.594.0 12.5

Control � 0 26.092.7 6.992.8

LSDb 9.4 2.6 19.0

aValues are means9SD.bLSD is the least significant difference at P�0.05.

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3.3. Greenhouse pot experiment with P. lilacinus YES-2 and P. chlamydosporia HDZ-9

All the pellets containing P. chlamydosporia HDZ-9 or P. lilacinus YES-2 reduced the

nematode gall index (Table 5). Plants treated with 1.6% YES-2 reduced root galling

by 66.7%. Plants treated with HDZ-9 and YES-2 had fewer egg masses than the

negative control, and those treated with YES-2 at 1.6% had the smallest number of

egg masses. Treatments of plants with pellets of either fungus at any concentration

tested reduced the final population of nematodes. In general, nematode population

density was more consistently suppressed by the higher rates of pellet application

(0.8% and 1.6%) than by the lower rates (0.2% and 0.4%). The smallest nematode

population, which was only one-tenth of that in the negative control, occurred when

1.6% pellets of HDZ-9 were applied. The reproductive rate of M. incognita was

reduced by addition of pellets containing either one of the two fungi. The final

population per root was 23,373 for the negative control but was only 2241 with 1.6%

HDZ-9 and 2964 with 1.6% YES-2 (Table 5). Shoot weight and height and root

weight and length were unaffected by application of pellets containing YES-2 or

HDZ-9 (Table 5).

4. Discussion

Microorganisms associated with eggs and females of Meloidogyne spp. are very

diverse but some species are commonly present (Sun et al. 2006). In our study, we

obtained 235 isolates and screened these isolates as potential enemies of M. incognita

eggs. In the in vitro screening, 26 of these isolates demonstrated substantial potential

as BCAs.

Meloidogyne spp. are hosts of several fungi, and some potential fungal BCAs

have been previously screened. For example, 455 fungal isolates belonging to 24

genera and 52 isolates of Actinomycetes were obtained from 28 samples from

greenhouses and fields of north and south China (Sun et al. 2006). Viaene and Abawi

Table 4. Activity of the most promising fungal isolates in the in vitro pathogenicity experiment

(test 2).a

Fungus Isolate

Parasitism

of eggs

(%)

Egg hatch

rate

(%)

Juvenile

mortality

(%)

Corrected

juvenile

mortality

(%)

Paecilomyces lilacinus WC06-10E-13 98.792.3 10.095.3 57.998.4 55.5

FZ07-9F-2 98.092.0 4.792.3 58.3914.4 56.0

WC06-5F-1 70.0914.0 2.590.6 100.090.0 100.0

Pochonia

chlamydosporia

WZ07-1F-3 96.092.0 7.790.4 50.090.0 47.2

Fusarium oxysporum WC06-12F-1 79.393.1 4.793.1 37.5917.7 34.0

Fusarium sp. FZ07-5F-8 68.7914.2 14.097.2 27.593.5 23.4

Acremonium sp. FZ07-3EM-1 100.090.0 20.690.9 24.1911.1 19.9

Control � 0 24.790.8 5.391.4

LSDb 12.5 7.6 16.5

aValues are means9SD.bLSD is the least significant difference at P�0.05.

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Table 5. Effect of alginate pellets containing Paecilomyces lilacinus YES-2 or Pochonia chlamydosporia HDZ-9 on shoot and root fresh weight, shoot

and root length, root galling and nematode numbers on tomato in the greenhouse pot experiment.a

Shoot Root

Treatments (rate) Fresh weight (g) Height (cm) Fresh weight (g) Length (cm) Gall index (0�10) Egg masses/root Final population/rootb,c

Blank control 37.192.7 50.493.2 7.691.1 13.791.9 � � �Negative control 33.394.5 46.792.7 8.691.3 11.790.7 6.690.4 103.2925.3 23,373

HDZ-9 (0.2%) 35.293.2 43.390.7 8.692.5 13.590.8 6.091.0* 51.4915.9* 7535*

HDZ-9 (0.4%) 33.192.0 42.991.7 7.790.9 13.191.9 4.690.5* 38.2916.1* 5289*

HDZ-9 (0.8%) 33.098.6 49.395.3 8.094.1 12.593.3 3.490.5* 28.8918.7* 5765*

HDZ-9 (1.6%) 37.093.4 47.895.6 7.391.1 13.590.6 3.091.2* 16.8910.0* 2241*

YES-2 (0.2%) 35.692.8 44.293.4 9.690.8 16.391.4* 5.490.5* 47.2920.2* 12,316

YES-2 (0.4%) 34.792.6 47.892.1 7.990.8 15.491.2* 4.690.5* 41.2910.3* 10,055

YES-2 (0.8%) 35.493.5 50.093.8 7.391.0 13.692.2 3.491.4* 23.4913.6* 4269*

YES-2 (1.6%) 34.391.7 49.492.3 6.690.7 13.391.0 2.290.8* 13.699.5* 2964*

aData are the averages of one of the two trials with five replicate pots per treatment. Values are means9SD. Means followed by an asterisk are significantly different fromthe negative control (PB0.05) according to the Student-Newman-Keuls test.bFinal population of newly formed eggs and juveniles per root system.cData were transformed to homogenise variances for statistical analysis but non-transformed data are shown.

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(1998) obtained 24 fungal isolates from M. hapla egg masses and 16 isolates from

M. hapla juveniles, 15 isolates parasitised eggs and nine parasitised juveniles. In our

study, the predominant fungi were Fusarium spp., F. oxysporum, P. lilacinus and

P. chlamydosporia.

In the present study, we used an in vitro test (a 24-well tissue culture plate

technique), which was simple and provided somewhat high throughput for screening

potential BCAs. The variables evaluated included egg parasitism, egg hatch or hatch

inhibition rate and juvenile mortality, which could relate to other mechanisms like

antibiosis, competition and predation besides parasitism (Cayrol 1983; Kwork,

Plattner, Weisleder and Wicklow 1992; Zaki 1994). Nitao, Meyer and Chitwood

(1999) reported that broth extracts of Fusarium equiseti inhibited root-knot

nematode egg hatch and immobilised second-stage juveniles that did hatch. Similar

effects of culture filtrates from Verticillium leptobactrum against M. incognita were

also observed by Regaieg, Ciancio, Raouani, Grasso and Rosso (2010), confirming

that the fungi secrete nematode-antagonistic metabolites. Although the antagonistic

metabolites were not tested, we believe that they were involved in inhibition of egg

hatching and juvenile mortality in our test.

Gomes Carneiro and Cayrol (1991) reported that a P. lilacinus isolate from Peru

was effective at a density of 1�106 conidia/g soil or higher. In this study, 0.2%

P. lilacinus pellets at a density of 1.3�105 CFU/g soil significantly suppressed the

development of root-knot nematodes. High application rates of BCAs may be

necessary because much of the added inoculum can be rapidly destroyed or

inactivated. Zhang (2005) added mycelial fragments of Hirsutella rhossiliensis to

soil to control the soybean cyst nematode and found the CFU of the unformulated

mycelia decreased dramatically. A rapid decline in CFU was also typical for

P. lilacinus when it was applied at very high concentrations (Hewlett, Dickson,

Mitchell and Kannwischer-Mitchell 1988; Gomes Carneiro and Cayrol 1991). The

alginate pellet formulation might overcome the obstacles of the quick reduction of

BCA density in soil.

Acknowledgements

We thank Bruce Jaffee for correcting and editing the manuscript. We also thank those peoplewho helped us collect samples. This research was jointly supported by the TWAS-CASPostdoctoral fellowship (FR number: 3240157246 awarded to the first author), AgricultureIndustry Project (nyhyzx07-050-5), and Innovation Fund for the Post-Doctoral Program ofShandong Province (201203025).

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