Important Foliar Disease Of Maize Biology Essay

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Southern corn leaf blight is an important foliar disease of maize. In this study, an induced systemic resistance eliciting rhizobacterium Bacillus cereus C1L was used to protect maize against SCLB. Application of B.cereus C1L in maize rhizosphere effectively protected maize from SCLB under greenhouse and field conditions. The protection effect of B. cereus C1L was similar to that of Maneb (2 kg active ingredient per hectare), a recommended fungicide. Furthermore, possible factors of B. cereus C1L to elicit ISR and to promote plant growth were investigated. The results indicate that secreted factors and rhizosphere colonisation ability of B. cereus C1L are involved in ISR elicitation. In addition to biocontrol activity, B. cereus C1L was able to promote growth of maize in field. Compared with a non-treated control, leaf length, leaf width, plant height and fresh and dry weights of B. cereus C1L-treated corn plants significantly increased. Therefore, B. cereus C1L acts as a plant growth-promoting rhizobacterium of maize.

Introduction

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Maize (Zeamays L.) is the thirdmost important cereal crop next to wheat and rice and cultivated all over the world

(Bothast & Schlicher, 2005). Southern corn leaf blight (SCLB) caused by Cochliobolus heterostrophus (Drechsler)

Drechsler [anamorph = Bipolaris maydis (Nisikado) Shoemaker; synonym = Helminthosporium maydis Nisikado] is a widespread disease throughout most of hot humid corn-growing areas of the world. Three races of this

pathogen have been identified. Race O, considered the most common race, infects all types of maize without

carrying resistance genes and regardless of the type of cytoplasm (Ullstrup, 1972). Race T is highly pathogenic

on Texas male-sterile cytoplasm (cms-T) cultivars and caused a major epidemic in 1970 and 1971 (Ullstrup,

1972). Race C has been identified in China and is highly pathogenic to the Charrua male-sterile cytoplasm cultivars (Wei et al., 1988).

Current practices for controlling plant diseases are based largely on development of resistant varieties and

application of synthetic pesticides (Emmert & Handelsman, 1999). Development of resistant varieties has been

the primary means of SCLB control. To control SCLB caused by race T, cms-T cultivars have been eliminated

from elite germ plasm cultivars (Ullstrup, 1972). In addition, one qualitative recessive gene, rhm, is considered

the main factor that confers resistance to race O and is mapped to the distal end of the short arm of chromosome

six (Zaitlin et al., 1993). Resistance conditioned by rhm is adequate during early stages of growth but is limited after silking (Thompson & Berquist, 1984). However, SCLB, predominantly caused by race O, is still a problem in sweet corn cultivation and seed production in the southern Atlantic coast area of the USA. It causes grain yield losses of 40% or more (Ullstrup, 1972). In Taiwan, C. heterostrophus race O is also an important foliar pathogen of maize (Wu & Wang, 1987; Tsai et al., 1993). Using Maneb (manganese ethylene-bis-dithiocarbamate) to control SCLB is a general way but that fungicide causes environmental pollution (P´aez-Osuna et al., 1998; Hanada et al., 2002) and human toxicity (Meco et al., 1994; Drechsel & Patel, 2008). As biocontrol is getting greater attention because of low cost and eco-friendly application (Gerhardson, 2002), the possibility to control C. heterostrophus race O by means of biocontrol should be explored.

Plant growth-promoting rhizobacteria (PGPR) are rootcolonising bacteria and can be applied to a wide range of

plants, resulting in growth promotion and disease control (van Loon et al., 1998; Kloepper et al., 2004a,b, 2007;

Compant et al., 2005; Verhagen et al., 2006). Induced systemic resistance (ISR) is an important mechanism

of biocontrol mediated by a number of PGPR strains (van Loon et al., 1998; Lugtenberg et al., 2002; Kloepper

et al., 2004b; Compant et al., 2005; Verhagen et al., 2006; Lugtenberg & Kamilova, 2009). Recently, induction of

plant resistance by application of rhizobacteria has been suggested as an alternative approach for crop disease

control, and PGPR-elicited ISR has been demonstrated in many plant species, including Arabidopsis spp., bean,

carnation, cucumber, radish, tobacco and tomato (van Loon et al., 1998; Verhagen et al., 2006). There are no

reports of PGPR-elicited ISR against SCLB in maize. In our previous study, a rhizobacterium Bacillus cereus

C1L, isolated from the rhizosphere of Formosa lily in Taiwan, was demonstrated to induce systemic resistance

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against Botrytis leaf blight in lily and to promote growth of lily potentially (Liu et al., 2008). Therefore, the objectives of this study were to evaluate the application of B. cereus C1L to induce systemic resistance, by bacterial suspension and a cell-free bacterial culture filtrate, against SCLB in greenhouse and field and to examine the plant growthpromoting activity of B. cereus C1L in maize.

Materials and methods

Microorganisms and culture media

Bacillus cereus C1L (Liu et al., 2008) was cultured in Luria-Bertani (LB) broth (1% tryptone, 0.5% yeast extract,

0.5% NaCl) at 28â-¦C with shaking overnight. Cells of B. cereus C1L were harvested by centrifugation (4000 g,

10 min, 25â-¦C) and resuspended in Milli-Q water to a final concentration of 1Ã-108 CFUmL−1 for drench application

to rhizosphere of corn plants. B. cereus C1Lrif (Liu et al., 2008), a rifampicin-resistant marker strain, was cultured

in LB broth containing 50 gmL−1 rifampicin and used for rhizosphere colonisation assay. C. heterostrophus was

cultured and maintained on Difco potato dextrose agar (BD Diagnostic Systems, Sparks, MD, USA) at 25â-¦C in the

dark.

Isolation and identification of Cochliobolus heterostrophus

race O

Cochliobolus heterostrophus race O was isolated from naturally diseased corn leaves which were collected from the experimental field of National Taiwan University, Taipei, Taiwan. C. heterostrophus was identified by morphological study and comparison of ITS1-5.8S-ITS2 sequence with BLAST program. The ribosomal DNA region ITS1-5.8SITS2 was amplified by PCR with primers ITS5 and ITS4 (White et al., 1990) and sequenced. Race of C. heterostrophus was identified by culturing on Difco malt extract agar (BD Diagnostic Systems) for 5 days at 25â-¦C under dark to evaluate formation of sclerotia (Warren et al., 1977).

Plant material

Seeds of maize cultivar Honey Jean No. 3 (Known-You Seed Co., Ltd., Kaohsiung, Taiwan) were used in this

study. For greenhouse experiments, seeds were sown in 12-cm-diameter pots (three seeds per pot) containing

potting mix (peat moss, perlite and vermiculite at a ratio of 5:2:2, 650 g potting mix per pot). Plants were grown

at 25â-¦C with 16 h/8 h light/dark cycle for 21-28 days. However, seeds were planted in soil of sand-loam-type

in the experimental field of National Taiwan University, Taipei, Taiwan, for field experiments.

Pathogen inoculation and rating techniques

For sporulation, C. heterostrophus race O was cultured on autoclaved corn leaves at 28â-¦C for 1-2 weeks (Wu &

Wang, 1987). A conidial suspension of C. heterostrophus was prepared in 0.05% Tween 20 and adjusted to

a final concentration of 5 Ã- 104 conidia mL−1 for inoculation. A spore suspension of C. heterostrophus

(5 Ã- 104 spores mL−1) was sprayed as a fine mist until running off onto both surfaces of fully expanded leaves

of corn plants. The inoculated corns were kept under moist condition at 25â-¦C for 1 day and then placed on the greenhouse bench. Disease severity was subsequently assessed and based on a 0-4 scale (i.e. 0, no symptoms; 1,

1-25%; 2, 26-50%; 3, 51-75%; 4, 75-100% leaf area covered with lesions). Disease severity was calculated as

the sumof disease severity scale multiplied by the number of diseased plants of the same category and divided by

total number of tested plants multiplied by 4.

Biocontrol assays under greenhouse conditions

Cells of overnight cultured B. cereus C1L were harvested by centrifugation (4000 g, 10 min, 25â-¦C) and resuspended in Milli-Q water to a final concentration of 1 Ã- 108 CFU mL−1. Corn plants were soil drenched with a bacterial cell suspension of B. cereus C1L (30 mL per pot) under greenhouse conditions. One to seven days after application of B. cereus C1L, a spore suspension of C. heterostrophus was inoculated on leaves and disease severity was subsequently assessed as described above 2 days after inoculation. Each treatment had 3 replicates and the test was repeated twice.

Afterwards, pots were arranged in a randomized complete block design with 30 replicates per treatment.

Corn plants were soil drenched with a bacterial cell suspension of B. cereus C1L (30 mL per pot) three times

at 5-day intervals. Fungicide Maneb (Dithane M-22, 80% wettable powder, Rohm and Haas, Philadelphia,

PA, USA) was sprayed until running off onto both surfaces of fully expanded leaves at the recommended

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dose (2 kg active ingredient per hectare) three times at 5-day intervals to serve as a positive control. One day after

the last application, a spore suspension of C. heterostrophus was inoculated and disease severity was subsequently

assessed as described above 2 days after inoculation. Each treatment had 30 replicates (3 plants per replicate) and

the test was repeated once.

Field experiments of biocontrol

Field experiments were performed in the experimental field of National Taiwan University, Taipei, Taiwan. In

the first experiment, plots (1 m2) were arranged in a randomised complete block design with 15 replicates per

treatment. Plants were grown in a sandy loam soil at 33â-¦C and 23â-¦C average day and night temperature with

71-77% relative humidity, and 11-12 h day length. Sixty days after sowing, a bacterial cell suspension of B. cereus C1L was applied as a soil drench (500 mL per plot) three times at 5-day intervals. Manebwas sprayed until running off onto both surfaces of fully expanded leaves at the recommended dose (2 kg active ingredient per hectare) three times at 5-day intervals to serve as a positive control. Three days after the last application, a spore suspension of C. heterostrophus was inoculated and disease severity was subsequently assessed 3 days after inoculation. The test was repeated once.

In the second experiment, plots (1 m2) were arranged in a randomised complete block design with 35 replicates

per treatment. Schematic diagram of the schedule to apply B. cereus C1L and Maneb is presented in Fig. 1. A bacterial cell suspension of B. cereus C1L and Maneb was applied and a spore suspension of C. heterostrophus was inoculated as described above. Disease severity was subsequently assessed 3 days after inoculation. The test was repeated once.

Assay for plant growth-promoting ability of Bacillus cereus C1L

In the first field experiment, plant height of each treatment was measured 14 days after inoculation of

C. heterostrophus. In the second field experiment, five parameters of plant growth (leaf length, leaf width,

plant height and fresh and dry weights of plants) of all treatments were measured before and after inoculation

of C. heterostrophus as indicated in Fig. 1. Localisation of possible induced systemic resistance-eliciting factors

Pots of corn plants were drenched with a bacterial cell suspension, 10-fold diluted cell-free culture filtrate and

a diluted overnight culture of B. cereus C1L (30 mL per pot) under greenhouse conditions. Cells of overnight

cultured B. cereus C1L were harvested by centrifugation (4000 g, 10min, 25â-¦C) and resuspended in Milli-Q water

to a final concentration of 1 Ã- 108 CFU mL−1. Culture supernatant of B. cereus C1L was collected and filtered

through 0.45-mfilter to obtain a cell-free culture filtrate. The cell-free culture filtrate of B. cereus C1L was diluted

10-fold with Milli-Q water. An overnight culture of B. cereus C1L was directly diluted with Milli-Q water to a

final concentration of 1 Ã- 108 CFU mL−1. One day after bacterial treatment, a spore suspension of C. heterostrophus was inoculated and disease severity was assessed as described above 2 days after inoculation. Each treatment had three replicates and the test was repeated twice.

Rhizosphere colonisation assay

Rhizosphere competence of B. cereus C1L in maize was investigated using rifampicin-resistant B. cereus C1Lrif (Liu et al., 2008) under greenhouse conditions. One to seven days after application of B. cereus C1Lrif in the rhizosphere of corn plants, root segments were taken from 0 to 1 cm below the crown (stem base) and the population size of B. cereus C1Lrif was estimated (Piyush et al., 2005; Liu et al., 2008). Three plants were assayed at each sampling date and the test was repeated once.

Statistical analysis

The data obtained were subjected to the standard analysis of variance (ANOVA) procedure. Least significant

Results

Biocontrol activity of Bacillus cereus C1L against southern corn leaf blight in greenhouse experiments

Greenhouse experiments were conducted to investigate the potential andmaintenance of B. cereus C1L-elicited ISR of maize against SCLB. As shown in Fig. 2, the disease severities were reduced 70-85% when corn plants were soil drenched with a bacterial cell suspension of B. cereus C1L 1-3 days before fungal inoculation. Four days after application of B. cereus C1L, the induced protection level decreased to 30% reduction in disease severity. However, protection of maize from SCLB by B. cereus C1L was not observed 6 days after application.

Fig. 3 shows the ability of B. cereus C1L to induce systemic resistance in maize against C. heterostrophus

under greenhouse conditions. Compared with the untreated control, maize was protected from infection

of C. heterostrophus significantly after a drench application of B. cereus C1L. In addition, the effect of B. cereus

C1L to control SCLB was slightly less than that of the recommended fungicide Maneb (Fig. 3).

Biocontrol of Cochliobolus heterostrophus in maize by Bacillus cereus C1L in field experiments Fig. 4 shows the ability of B. cereus C1L to induce systemic resistance of maize against C. heterostrophus under field conditions. In the first field experiment, maize was significantly protected from SCLB after a soil-drenching application of B. cereus C1L three times. There are no significant differences between B. cereus C1L-elicited ISR and Maneb treatment (Fig. 4).

In the second field experiment, a schedule (as present in Fig. 1) was followed to apply B. cereus C1L and

Maneb for investigation of those effects to control SCLB. Both bacterial and fungicide treatments were applied

nine times during 12 weeks. B. cereus C1L significantly protected maize from infection of C. heterostrophus (Fig. 4). The protection effect of B. cereus C1L was close to that of Maneb, although a significant difference existed between the two treatments (Fig. 4).

Growth-promoting ability of Bacillus cereus C1L in maize

In the first field experiment, height of corn plants with different treatments was measured 2 weeks after

fungal inoculation. As shown in Fig. 5, B. cereus C1L-treated maize exhibited the best growth level

among all treatments, indicating that growth of maize was significantly promoted by application of B. cereus C1L as a soil drench three times at 5-day intervals. Furthermore, the growth levels were not significantly different between Maneb-treated and untreated maize with fungal inoculation (Fig. 5).

Furthermore, detailed analysis of the growthpromoting effect of B. cereus C1L in maize was performed

in the second field experiment. Five parameters of plant growth (leaf length, leaf width, plant height and fresh

and dry weights of plants) were measured when maize were grown for 10 and 13 weeks, that is before and after

fungal inoculation (as presented in Fig. 1). Before inoculation of C. heterostrophus, the growth level of maize was

significantly enhanced by treatment of B. cereus C1L compared with the untreated control (Table 1). Not only leaf

length, leaf width and plant height of B. cereus C1L-treated maize increased 1.4-fold but also fresh and dry weights of B. cereus C1L-treated corn plants increased 2.4- and 1.9-fold, respectively. Besides, the growth levels were not significantly different between Maneb-treated and untreated maize (Table 1).

Afterwards, B. cereus C1L-treated maize still had better growth after inoculation of C. heterostrophus (Table 1).

Compared with the untreated control, the growth level of C1L-treated maize was significantly increased. Leaf

length, leaf width and plant height of B. cereus C1L-treated maize increased 1.3-fold. Fresh and dry weights of

C1L-treated corn plants also increased 3.1- and 1.9-fold, respectively. In addition, fresh and dry weights of Maneb sprayed corn plants had slight decreases, although the growth levels were not significantly different between

Maneb-treated and untreated maize (Table 2).

Secreted factors produced by Bacillus cereus C1L to elicit induced systemic resistance

Abilities of a cell suspension, a diluted culture filtrate and a diluted overnight culture of B. cereus C1L to elicit

ISR in maize were investigated. As shown in Fig. 6, all three treatments can significantly reduce disease severity

of maize caused by C. heterostrophus and there are no differences among the treatments. This result indicates

that ISR-eliciting factors of B. cereus C1L consist of secreted factors.

Colonisation as a possible trait of Bacillus cereus C1L related to eliciting induced systemic resistance and

plant growth promotion Population sizes of B. cereus C1Lrif in rhizosphere of maize were investigated as shown in Fig. 7. One to seven days after bacterial application, 0-1 cm below the crown, population sizes of B. cereus C1Lrif were maintained about 6-8 log CFU cm−1 root.

Discussion

In Taiwan, SCLB is an important foliar disease of maize and only race O of C. heterostrophus has been isolated and identified previously (Wu&Wang, 1987; Tsai et al., 1993). Race T and C of C. heterostrophus were not found in Taiwan. In this study, we isolated C. heterostrophus from field for experiments and the race was identified as race O. This result corresponded with the previous reports (Wu & Wang, 1987; Tsai et al., 1993) that only C. heterostrophus race O is the causal agent of SCLB in Taiwan.

Bacillus cereus C1L, a rhizobacterium isolated from lily rhizosphere, was able to induce systemic resistance

against Botrytis leaf blight in lily (Liu et al., 2008). In this study, B. cereus C1L was demonstrated to protect maize

from SCLB caused by C. heterostrophus race O. B. cereus C1L was able to significantly induce systemic resistance in maize against SCLB under greenhouse and field conditions (Figs 3 and 4). The results support previous reports that PGPR-elicited ISR often occurs against multiple diseases (Zehnder et al., 1997; van Loon et al., 1998). Regularly using Maneb (at 2-3 kg ha−1) once in a week is recommended to control SCLB in Taiwan. The recommended concentration ofManeb is relatively higher and more toxic to the environment (Meco et al., 1994; P´aez-Osuna et al., 1998; Hanada et al., 2002; Drechsel & Patel, 2008). B. cereus C1L elicited systemic protection against SCLB at a level similar to protection of Maneb (Figs 3 and 4), indicating that using B. cereus C1L to biocontrol SCLB is an alternative way other than chemical fungicides. Therefore, we suggest that applying

B. cereus C1L instead of Maneb to control SCLB is an effective and eco-friendly way. In addition, SCLB was

significantly suppressed by application of B. cereus C1L at 5-day intervals (close to once a week) under field

conditions (Fig. 4). We think that application of B. cereus C1L to control SCLB under field conditions is practically applicable.

Our result shows that B. cereus-elicited ISR in maize against C. heterostrophus lasted only for 4 days (Fig. 2),

whereas Botrytis elliptica-caused symptoms in Lilium formosanum were still suppressed on day 10 after bacterial

application (Liu et al., 2008). Different maintenance patterns of B. cereus-elicited ISR were exhibited in maize

and lily. PGPR-elicited ISR to reduce plant disease through manipulation of physical and biochemical properties of host plants was reviewed by van Loon et al. (1998). Although nothing is known about the physical and

biochemical responses of maize and lily to PGPR-elicited ISR, we suggest that maize and lily treated with B. cereus have similar but not identical physical and biochemical properties to cause different maintenance patterns of ISR. Moreover, different physiological conditions of maize may cause disease control to become less effective under greenhouse conditions than under field conditions. However, the growth stage of maize used for the experiments under greenhouse conditions was stage 2, the period of rapid leaf growth (Hanway, 1963). We

suggest that maize needs more energy for growth and that is the possible reason to explain that B. cereus-elicited

ISR in maize against C. heterostrophus was only effectively maintained for 4 days under greenhouse conditions

(Fig. 2). In the previous study, a positive effect of B. cereus C1L on leaf number of L. formosanum seedlings was observed (Liu et al., 2008). Herein, we investigated plant growth promoting capability of B. cereus C1L in maize. As shown in Fig. 5, Tables 1 and 2, growth of maize under field conditions was enhanced by application of B. cereus C1L before/after inoculation of the pathogen. Leaf length, leaf width, plant height and fresh and dry weights of plants of B. cereus C1L-treated corn plants had significant increases, indicating that B. cereus C1L is capable of promoting growth of maize. In addition,Maneb effectively controlled SCLB but did not promote growth of maize (Fig. 5, Tables 1 and 2). Therefore, application of B. cereus C1L in maize exhibited at least two beneficial effects, not only to control SCLB but also to promote growth of maize.

There are several mechanisms of rhizobacteria enhanced plant growth, including production of phytohormones, nitrogen fixation and antagonism of pathogens (Lugtenberg et al., 2002; Choudhary & Johri, 2009; Lugtenberg & Kamilova, 2009). PGPR might enhance plant height and productivity by synthesizing phytohormones (Burd et al., 2000). The positive effect of PGPR on growth of maize was reported and explained by nitrogen fixation, phosphate-solubilising capacity and phytohormone production (Egamberdiyeva, 2007). B. cereus strains have been reported to produce phytohormones including auxin and giberrellin (Selvadurai et al., 1991; Joo et al., 2004; Karadeniz et al., 2006; Egamberdiyeva et al., 2008; Jetiyanon et al., 2008; Ma et al., 2009). Therefore, phytohormone production of B. cereus C1L is suggested to explain the effect of this PGPR strain on growth of maize.

Plant growth-promoting rhizobacteria can colonise rhizosphere of many plant species and confer beneficial

effects, such as increasing plant growth and reducing plant susceptibility to disease (Kloepper et al., 2004a,b;

Lugtenberg & Kamilova, 2009; Yang et al., 2009). The PGPR strains of Bacillus spp. that elicit ISR typically promote plant growth (Kloepper et al., 2004b). Rhizosphere competence of B. cereus C1L was also

investigated in this study. One to seven days after bacterial application, the population sizes of B. cereus C1Lrif were about 6-8 log CFU cm−1 root in maize rhizosphere (Fig. 7). The results indicate that B. cereus C1L is a good colonist of maize rhizosphere. According to our previous study and this study, B. cereus C1L has been demonstrated to induce systemic resistance, to promote plant growth and to well colonise the rhizosphere of lily

(Liu et al., 2008) andmaize, indicating that B. cereus C1L is a PGPR. However, several PGPR have been reported to promote growth of maize (Lalande et al., 1989; Pan et al., 1999; Pal et al., 2001; Mehnaz & Lazarovits, 2006; Egamberdiyeva, 2007). Only Pal et al. (2001) reported suppression of root diseases of maize by application of PGPR and none of the PGPR has ever been reported to induce systemic resistance in maize against foliar diseases. To our knowledge, B. cereus C1L is the first reported PGPR that is able to elicit ISR in maize against a foliar disease. The population sizes of B. cereus C1Lrif were about 6-8 log CFU cm−1 root in maize rhizosphere 1-7 days after bacterial application (Fig. 7). The results suggest that establishment of B. cereus C1L in maize rhizosphere is a basic trait to promote plant growth and to elicit ISR. Recently, endophytic bacteria have received

more attention. Pleban et al. (1995) reported control of Rhizoctonia solani in cotton and Sclerotium rolfsii in bean by endophytic B. cereus strains. Thus, it is an interesting topic to investigate whether B. cereus C1L is an endophyte in maize. In our preliminary result, B. cereus C1L is suggested as an endophytic bacterium in maize by culture-based study (data not shown). Detailed studies are needed to examine the colonisation pattern of B. cereus C1L. Therefore, a green fluorescent protein or other reporter labelled B. cereus C1L will be constructed for further studies.

The qualitative recessive rhm gene has been of limited use in commercialmaize hybrids in the USA because of its

recessive inheritance and its ineffectiveness in providing effective control after anthesis. In addition, most hybrids

rely on some form of polygenic partial resistance for control of the disease. Often, SCLB is considered a late season disease of maturing maize plants, usually not developing until the postanthesis, grain-filling period

(White, 1999). According to results of the greenhouse and field experiments (Fig. 4), B. cereus C1L was able

to significantly induce systemic resistance in 4- and 12- week-old maize. Twelve-week-old maize is in the growth

stage 6 or 7, as late growth stage, of maize (Hanway, 1963). The results indicate that it is a good way to apply B. cereus C1L to control SCLB in maize from early to late growth stage.

In the studies of ISR elicitors produced by Bacillus spp., lipopeptides, volatile compounds and bacteriocin

of Bacillus spp. involved in biocontrol have been demonstrated (Ryu et al., 2004; Ongena et al., 2005, 2007;

Choudhary & Johri, 2009; Lee et al., 2009). Moreover, Romeiro et al. (2005) reported that B. cereus could release

macromolecules to trigger systemic disease resistance in tomato; thus, indicating that determinants responsible for

ISR are an intriguing subject of investigation in biocontrol strains of B. cereus. Our previous report implicated that

B. cereus C1L excreted factors that conferred activation of disease suppression in lily (Liu et al., 2008). In addition to lily, secreted factors of B. cereus C1L capable of triggering ISR in maize were also indicated in this study (Fig. 6).

Although several B. cereus strains were isolated and demonstrated to induce systemic resistance or to promote plant growth (Halverson & Handelsman, 1991; Joo et al., 2004; Silva et al., 2004; Jetiyanon et al., 2008), those strains were not reported to exhibit both abilities. To our knowledge, B. cereus C1L is the first reported

rhizobacteriumthat is able to significantly induce systemic resistance in maize against a foliar disease and to significantly promote growth of maize.