Screenhouse and Field Persistence of Nonpathogenic Endophytic Fusarium oxysporum in Musa Tissue Culture Plants

Two major biotic constraints to highland cooking banana (Musa spp., genome group AAA-EA) production in Uganda are the banana weevil Cosmopolites sordidus and the burrowing nematode Radopholus similis. Endophytic Fusarium oxysporum strains inoculated into tissue culture banana plantlets have shown control of the banana weevil and the nematode. We conducted screenhouse and field experiments to investigate persistence in the roots and rhizome of two endophytic Fusarium oxysporum strains, V2w2 and III4w1, inoculated into tissue-culture banana plantlets of highland cooking banana cultivars Kibuzi and Nabusa. Re-isolation of F. oxysporum showed that endophyte colonization decreased faster from the rhizomes than from the roots of inoculated plants, both in the screenhouse and in the field. Whereas rhizome colonization by F. oxysporum decreased in the screenhouse (4–16 weeks after inoculation), root colonization did not. However, in the field (17–33 weeks after inoculation), a decrease was observed in both rhizome and root colonization. The results show a better persistence in the roots than rhizomes of endophytic F. oxysporum strains V2w2 and III4w1.     

内生真菌和内生细菌接种对雷公藤生长和次生代谢产物积累的影响

为探究内生真菌与内生细菌对雷公藤(Tripterygium wilfordii)的生长和次生代谢产物积累的相互作用,用内生真菌NS33、NS6和内生细菌LG3、LY1单独或跨界联合接种雷公藤,对雷公藤的生长和雷公藤甲素、雷公藤红素合成进行了研究。结果表明,单独或混合培养的菌株具有分泌铁载体、吲哚乙酸(IAA)和溶磷能力,对种子萌发、芽伸长和根系活力有显著促进作用。接种菌株NS33、NS6、NS6-LG3和NS6-LY1均显著促进了雷公藤组培苗的生长。单独或联合接种菌株均能显著提高雷公藤组培苗雷公藤甲素和雷公藤红素的积累,其中NS33-LG3和LG3的作用最显著。菌株NS33与LG3能够协同促进IAA的分泌、小麦幼苗根系活力和雷公藤红素的积累;菌株NS6与LY1协同提高了雷公藤组培苗的高度、质量和雷公藤红素的积累。因此,内生真菌与内生细菌联合接种对雷公藤生长和次生代谢产物积累具有一定的协同效应,显示出实际应用潜力。     

Biological control of Radopholus similis in banana by combined application of the mutualistic endophyte Fusarium oxysporum strain 162, the egg pathogen Paecilomyces lilacinus strain 251 and the antagonistic bacteria Bacillus firmus

The biological control efficacy of single or multiple applications of the mutualistic endophyte Fusarium oxysporum strain 162, the egg pathogen Paecilomyces lilacinus strain 251 and the antagonistic bacteria Bacillus firmus toward Radopholus similis was investigated in pot trials with banana under glasshouse conditions. R. similis was controlled substantially in single and combined applications of F. oxysporum with P. lilacinus or B. firmus. The combination of F. oxysporum and P. lilacinus caused a 68.5% reduction in nematode density whereas the individual applications reduced the density by 27.8% and 54.8% over the controls, respectively. Combined application of F. oxysporum and B. firmus was the most effective treatment in controlling R. similis on banana (86.2%), followed by B. firmus alone (63.7%). The compatibility of the biocontrol agents, as well the capacity of F. oxysporum to colonize banana roots in the absence or presence of P. lilacinus was also investigated. P. lilacinus did not adversely affect endophytic colonization by F. oxysporum. Biological control of R. similis in banana can therefore be enhanced via combined applications of antagonists with different modes of action that target different stages in the infection process. Handling editor: Ralf-Udo Ehlers     

Identification and characterization of non-pathogenic Fusarium oxysporum capable of increasing and decreasing Fusarium wilt severity

Fusarium wilt of banana is a potentially devastating disease throughout the world. Options for control of the causal organism, Fusarium oxysporum f.sp. cubense (Foc) are limited. Suppressive soil sites have previously been identified where, despite the presence of Foc, Fusarium wilt does not develop. In order to understand some aspects of this disease suppression, endophytic Fusarium oxysporum isolates were obtained from banana roots. These isolates were genetically characterized and compared with an isolate of Fusarium oxysporum previously identified as being capable of suppressing Fusarium wilt of banana in glasshouse trials. Three additional isolates were selected for glasshouse trials to assess suppression of Fusarium wilt in two different cultivars of banana, Cavendish and Lady Finger. One isolate (BRIP 29089) was identified as a potential biocontrol organism, reducing the disease severity of Fusarium wilt in Lady Finger and Cavendish cultivars. Interestingly, one isolate (BRIP 45952) increased Fusarium wilt disease severity on Cavendish. The implications of an isolate of Fusarium oxysporum, non-pathogenic on banana, increasing disease severity and the potential role of non-pathogenic isolates of Fusarium oxysporum in disease complexes are discussed.     

Combined application of native Trichoderma isolates possessing multiple functions for the control of Fusarium wilt disease in banana cv. Grand Naine

Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc) is considered as a lethal disease of bananas worldwide. To manage the disease effectively, 20 rhizospheric and 43 endophytic Trichoderma isolates obtained from 12 different Foc resistant banana accessions were evaluated against Foc in vitro and in vivo. In vitro screening among Trichoderma isolates for their multiple functions (mycelial and spore germination inhibition, hydrogen cyanide, chitinolytic enzymes, non-volatile and volatile metabolites production) in suppressing Foc and promoting plant growth (IAA production and phosphate solubilisation) indicated that the multiple biocontrol actions were significantly higher in 6 isolates of rhizospheric Trichoderma and 10 isolates of endophytic Trichoderma compared to other isolates. The greenhouse evaluation of individual application of these rhizospheric and endophytic Trichoderma isolates against Fusarium wilt pathogen in cv. Grand Naine (AAA) indicated significant suppression of Fusarium wilt disease and increased plant growth characters as compared to Foc pathogen inoculated plants. However, none of these individual Trichoderma isolates recorded complete suppression of Fusarium wilt disease. Therefore, the greenhouse evaluation involving combination of rhizospheric Trichoderma sp. NRCB3 + endophytic Trichoderma asperellum Prr2 recorded 100% reduction of Fusarium wilt disease and increased plant growth parameters up to 250% when compared to individual isolates application and Foc alone-inoculated plants. Further, the field evaluation of this combination of Trichoderma isolates applied for three times: (1) at 15 days before planting, (2) second month after planting and (3) fourth month after planting resulting in significant reduction of Fusarium wilt disease and also increase in bunch weight as compared to untreated control plants. Therefore, these Trichoderma isolates may be used in combination for the effective suppression of Fusarium wilt disease in banana.     

Artificial inoculation of banana tissue culture plantlets with indigenous endophytes originally derived from native banana plants

Fusarium wilt disease of banana is one of the most harmful fungal diseases affecting banana production worldwide. We hypothetically proposed that the loss of indigenous endophytes in tissue culture propagation of banana might be related to increased disease severity on banana plants. In the present study, a mixture of uncultivated endophytes, which was originally derived from native healthy banana plant in plantation, was used to artificially inoculate banana tissue culture plantlets. A broad spectrum of bacterial communities was detected in the roots of artificially inoculated plantlets by 16S ribosomal RNA gene analysis, and γ-Proteobacteria was identified as the dominant group. Banana wilt pathogen Fusarium oxysporum f. sp. cubense race 4 was inoculated to the plantlets after potting to investigate disease progress. With early diagnosis of fungal pathogen infection, 54% reduction was detected in artificially inoculated plantlets compared to endophyte-free control plantlets. The re-introduction of naturally-occurring endophytes into tissue culture banana plantlets led to a 67% suppression rate of wilt disease at the fifth month after pathogen infection on plantlets in the greenhouse. In addition to disease suppression, growth of host plantlets was also promoted with the inoculation of endophytes. The artificial inoculation method provided a foundational understanding of ecological enrichment to control banana wilt disease in future.     

Effect of Endophytic Fusarium oxysporum on Host Preference of Radopholus similis to Tissue Culture Banana Plants

The burrowing nematode Radopholus similis is one of the major constraints to banana (Musa spp.) production worldwide. Resource-poor farmers can potentially manage R. similis by using naturally occurring banana endophytes, such as nonpathogenic Fusarium oxysporum, that are inoculated into tissue culture banana plantlets. At present, it is unclear at what stage in the R. similis infection process the endophytes are most effective. In this study, the effect of three endophytic F. oxysporum isolates (V5w2, Eny1.31i and Eny7.11o) on R. similis host preference of either endophyte-treated or untreated banana plants was investigated. No differences were observed between the proportion of nematodes attracted to either root segments excised from endophyte-treated or untreated plants, or in experiments using endophyte-treated and untreated tissue culture banana plantlets. These results imply that the early processes of banana plant host recognition by R. similis are not affected by endophyte infection.     

Colonisation pattern of nonpathogenic Fusarium oxysporum, a potential biological control agent, in roots and rhizomes of tissue cultured Musa plantlets

Under laboratory conditions, nonpathogenic, endophytic Fusarium oxysporum inflicts high mortality among banana weevils and nematodes. Following inoculation into banana (Musa spp.) tissue cultured plants, successful colonisation is necessary for efficient biological control of these pests. The pattern of root and rhizome colonisation by two nonpathogenic Ugandan F. oxysporum strains (V2w2 and III4w1) in cv. Nabusa (AAA‐EA) was investigated using light microscopy. Percentage of colonisation in the rhizomes (93%) was higher than in the roots (56%), but hyphal density in the roots (0.30 mm^?2) was higher than in the rhizomes (0.21 mm^?2). The root bases were better colonised (76%) than root midsections (53%) or tips (39%). Both the strains colonised the roots and the rhizomes, with numerous hyphae infecting the hypodermis but fewer infecting the cortex. Colonisation of vascular tissues was not recorded. Despite the presence of hyphae in intercellular and intracellular spaces of the roots and the rhizomes, normal cell structure was observed. Our report provides the first in situ observation and quantification of endophyte colonisation in banana. The study demonstrated the ability of F. oxysporum strains V2w2 and III4w1 to penetrate intact host tissues and recolonise the host internally upon inoculation, an important step for their suitability as biological control agents.     

Dual inoculation of Fusarium oxysporum endophytes in banana: effect on plant colonization,growth and control of the root burrowing nematode and the banana weevil

The burrowing nematode (Radopholus similis (Cobb) Thorne) and the banana weevil (Cosmopolites sordidus Germar, Coleoptera: Curculionidae) are major pests of banana (Musa spp.) in the Lake Victoria basin region of Uganda. Among biological options to control the two pests is the use of non-pathogenic Fusarium oxysporum Schltdl.: Fries endophytes of banana. We investigated the ability of endophytic F. oxysporum isolates Emb2.4o and V5w2 to control the banana weevil and the burrowing nematode, alone and in combination. Plant colonization by the endophytes was determined by inoculating their chemical-resistant mutants separately and in combination, onto banana roots. Plant growth promotion was determined by measuring plant height, girth, number of live roots and fresh root weight at harvest, and control of the nematode and weevil was determined by challenging endophyte-inoculated plants with the pests 8 weeks after endophyte inoculation. Endophytic root colonization was highest in plants inoculated with both endophytes, compared with those inoculated with only one of the endophytes. Root colonization was better for isolate V5w2 than Emb2.4o. Dually inoculated plants showed a significant increase in height, girth, fresh root weight and number of functional roots following nematode challenge. Nematode numbers in roots were reduced 12 weeks after challenge of 8-week-old endophyte-inoculated plants. Significant reductions in weevil damage were observed in the rhizome periphery, inner and outer rhizomes, compared with endophyte non-inoculated controls. We conclude that dual inoculation of bananas with endophytic isolates Emb2.4o and V5w2 increases root colonization by the endophytes, reduces nematode numbers and weevil damage, and enhances plant growth in the presence of nematode infestation.     

Identification and evaluation of two diagnostic markers linked to Fusarium wilt resistance (race 4) in banana (Musa spp.)

Fusarium wilt caused by the fungus Fusarium oxysporum f. sp. cubense race 4 (FOC4) results in vascular tissue damage and ultimately death of banana (Musa spp.) plants. Somaclonal variants of in vitro micropropagated banana can hamper success in propagation of genotypes resistant to FOC4. Early identification of FOC4 resistance in micropropagated banana plantlets is difficult, however. In this study, we identified sequence-characterized amplified region (SCAR) markers of banana associated with resistance to FOC4. Using pooled DNA from resistant or susceptible genotypes and 500 arbitrary 10-mer oligonucleotide primers, 24 random amplified polymorphic DNA (RAPD) products were identified. Two of these RAPD markers were successfully converted to SCAR markers, called ScaU1001 (GenBank accession number HQ613949) and ScaS0901 (GenBank accession number HQ613950). ScaS0901 and ScaU1001 could be amplified in FOC4-resistant banana genotypes (“Williams 8818-1” and Goldfinger), but not in five tested banana cultivars susceptible to FOC4. The two SCAR markers were then used to identify a somaclonal variant of the genotype “Williams 8818-1”, which lost resistance to FOC4. Hence, the identified SCAR markers can be applied for a rapid quality control of FOC4-resistant banana plantlets immediately after the in vitro micropropagation stage. Furthermore, ScaU1001 and ScaS0901 will facilitate marker-assisted selection of new banana cultivars resistant to FOC4.     

黄花倒水莲内生真菌生物活性评价及HNLF-44菌株鉴定

为充分开发黄花倒水莲(Polygala fallax)的内生真菌资源，获得具有抗植物病原真菌、抗氧化活性的内生真菌，该文以黄花倒水莲内生真菌为研究对象，使用平板对峙法检测内生真菌对6种植物病原真菌的抑菌活性，测定内生真菌发酵液的DPPH清除自由基能力和总还原能力，评价内生真菌的抗氧化活性，并对具有强抑菌活性和抗氧化活性的菌株进行形态和ITS鉴定。结果表明：(1)黄花倒水莲内生真菌中有2株内生真菌对香蕉专化尖孢镰刀菌、柑橘树脂病菌、叶点霉菌、香蕉具条叶斑病菌、茄病镰刀菌、三七根腐病菌具有明显的抑菌活性，抑菌率在50.3%～91.4%之间，其中HNLF-5对柑橘树脂病菌的抑菌率为73.2%,HNLF-44对香蕉专化尖孢镰刀菌抑菌率为91.4%。(2)内生真菌发酵液具有良好的抗氧化活性，DPPH清除率均在80%以上，总还原能力吸光值范围为0.279 2～0.748 8。(3)HNLF-44菌株为链格孢属真菌。该研究表明，药用植物黄花倒水莲内生真菌具有较好的生物活性，为后续从黄花倒水莲内生真菌中挖掘潜在新型抑菌活性和抗氧化活性物质奠定了基础。     

Biopriming of micropropagated banana plants at pre- or post-BBTV inoculation stage with rhizosphere and endophytic bacteria determines their ability to induce systemic resistance against BBTV in cultivar Grand Naine

ABSTRACT

Rhizospheric and endophytic bacteria isolated from the roots and corms of banana were tested to find out their efficiency in controlling against banana bunchy top virus (BBTV). Bioformulations of mixtures of endophytic Bacillus pumilus and B. subtilis isolated from banana cv. Grand Naine and rhizobacterial isolate Pseudomonas fluorescens (Pf1) were found to be effective in increasing the growth and physiological parameters such as pseudostem girth and height, number of leaves, phyllochron, and leaf area in biohardened plants under greenhouse study. The consortia of bioformulation mixture of B. pumilus, B. subtilis, and P. fluorescens I showed 61.62% disease reduction over control. The defence enzymes such as peroxidase (POX), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), and total phenol were induced to an elevated level in biohardened plants. The applications of bioformulations to plants led to delay the symptom expression for 63.75 to 70.50 days compared to control after challenge inoculation with the virus in 34–67% of plants that exhibited the symptoms till 150 DAI. However, biohardening of plants with the same combinations of bacteria three days after BBTV inoculation led to express the symptoms 29.16 to 36.71 days and there was a significant decrease in plant growth parameters. Biopriming prior to BBTV infection has attributed to the enhanced plant growth and resistance against BBTV whereas, the same treatments after virus inoculation did not induce resistance. This study has proved that the time of application of consortia of bio-inoculants determines their effect of induced resistance to BBTV in micropropagated plants.     

The Effect of Pseudomonas fluorescens and Fusarium oxysporum f.sp. cubense on Induction of Defense Enzymes and Phenolics in Banana

The effect of Pseudomonas fluorescens treatment and Fusarium oxysporum f. sp. cubense inoculation on induction of phenylalanine ammonia-lyase (PAL), peroxidase (POX), chitinase, -1,3-glucanase and accumulation of phenolics in banana (Musa sp.) was studied. When banana roots were treated with P. fluorescens strain Pf10, a two-fold increase in phenolic content in leaf tissues was recorded 3 – 6 d after treatment. Challenge inoculation with F. oxysporum, the wilt pathogen, steeply increased the phenolic content in P. fluorescens-treated banana plants. Significant increase in POX activity was detected 6 – 9 d after P. fluorescens treatment. PAL, chitinase and -1,3-glucanase activities increased significantly from 3 d after P. fluorescens treatment and reached the maximum 6 d after treatment. Challenge inoculation with F. oxysporum further increased the enzyme activities. These results suggest that the enhanced activities of defense enzymes and elevated content of phenolics may contribute to bioprotection of banana plants against F. oxysporum.     

Control of lethal browning of tissue culture plantlets of Cavendish banana cv. Formosana with ascorbic acid

Cavendish banana cv. Formosana is a high yielding commercial cultivar resistant to race 4 of Fusarium oxysporum f. sp. cubense. Mass micropropagation of this cultivar has a serious problem of high mortality due to lethal browning of plantlets. The mineral contents in leaves and corms of diseased and healthy plantlets were similar. Amendment of culture medium with anion exchange resins, cation exchange resins, polyvinylpyrrolidone or activated charcoal did not reduce the disease incidence. However, addition of ascorbic acid to the surface of culture medium not only prevented the development of lethal browning but also greatly increased the number of plantlets produced. Even at 0.005% ascorbic acid was able to reduce the disease incidence by more than 60% and caused over 8-fold increase in number of plantlets produced. When cultures raised from 12 different Formosana corms were tested, ascorbic acid was able to reduce disease incidence by an average of 83%, and increase the number of plantlets in each test. When diseased plantlets were transferred to culture medium with ascorbic acid, all of them recovered, and resumed normal growth and multiplication, while all control plantlets on culture medium without ascorbic acid died after one month.     

Improved in vitro bioassay for Musa acuminata cv. Pisang ambon kuning (AAA group) based on quantitative analysis of necrosis area and biomass changes during Foc4 infection

Abstract

Efforts in improving banana plants that are resistant to the Fusarium wilt-causing Fusarium oxysporum f.sp. cubense tropical race 4 (Foc4) are indispensable. In this study, we developed rapid, space-efficient in vitro bioassay for assessing banana plant resistance to Foc4 using 35?×?150?mm glass test tubes, followed by quantitative and objective analysis of necrosis area and biomass changes as represented by fresh weight changes. Disease resistance screening was conducted based on the necrosis area as quantified using ImageJ software and on biomass gain during in vitro bioassay. In vitro banana plantlets showed age-related resistance during the development of necrosis (p?=?.034, Kruskal–Wallis test in root and shoot system and p?=?.027, one-way ANOVA in shoot system only), in which plantlets that were infected at the youngest age (24 weeks’ post-initiation) showed the largest necrosis area (up to 46.6%). In addition, plant fresh weight gain in this group (0.233?±?0.041?g) was higher compared to the gains in older plantlets (0.079?±?0.117 and 0.009?±?0.069?g, infected at 28 and 38?weeks’ post-initiation, respectively). Overall, for consistent and reliable result, the age of banana plantlet should be taken into consideration in interpreting the result of this in vitro bioassay.     

Molecular characterisation of Fusarium oxysporum causing rot diseases in small cardamom (Elettaria cardamomum Maton)

Incidence of root rot and foliar yellowing, rhizome rot, panicle wilt and stem rot diseases of small cardamom (Elettaria cardamomum Maton) are caused by Fusarium oxysporum Schlecht., and were surveyed in the high ranges of Idukki district, Kerala during 2010–2011. The diseases were noticed in different areas to varying degrees. Root rot was found to be most severe, followed by pseudostem rot, rhizome rot and panicle wilt. The Fusarium infections were prevalent throughout the year (January–December) and varied from 1.5 to 10.6%. Even though the pathogen was isolated from different plant parts, during pathogenicity studies, all the isolates could cross-infect other plant parts too. Twenty different isolates of F. oxysporum were obtained from diseased samples, and five morphologically distinct isolates were analysed with Randomly Amplified Polymorphic DNA (RAPD) markers to study the genetic variability, if any, among them. PCR amplification of total genomic DNA with random oligonucleotide primers generated unique banding patterns, depending upon primers and isolates. Nine oligunucleotide primers were selected for the RAPD assays, which resulted in 221 bands for the five isolates of F. oxysporum. The number of bands obtained was entered into an NTSYS, and the results showed moderate genetic variability among F. oxysporum isolates causing root rot, rhizome rot, panicle wilt and pseudostem rot, collected from different locations. The dendrogram of different isolates into groups resulted in one major cluster at 0.61 similarity index comprising of four isolates (CRT 3, CRR 3, CPW 2 and CSR 1) and one isolate (CRT 5) formed in a separate cluster. Among the five isolates of F. oxysporum, CRT 5 was entirely different from the other four isolates. The isolates also differ according to the geographical area, as revealed from the genetic variability observed in different root rot isolates (CRT 3 and CRT 5). It is inferred that despite moderate variability, F. oxysporum, infecting small cardamom in Idukki district of Kerala, consists of a single clonal lineage.     

Fungicides and some biological controller agents effects on the growth of fusarium oxysporum causing paprika wilt: Wirkung von fungiziden und einigen biologischen kontrollwirkstoffen auf das wachstum des paprikawelke verursachenden fusarium oxysporum

Soil samples from both healthy and diseased paprika roots were tested to identify their mycoflora. Thirty-one species belonging to 16 genera were collected from rhizosphere and rhizoplane samples. The most frequently isolated fungi were Aspergillus flavus, A. niger, A. terreus, Fusarium oxysporum, Penicillium jensenii and Trichoderma harzianum. Fusarium oxysporum was the most common Fusarium species in the rhizoplane samples of diseased roots and identification was confirmed by RAPD-PCR technique. Trichoderma harzianum, T. pseudokoningii and Glioclaium roseum were chosen to study their biological control efficiency against Fusarium oxysporum. These fungal species reduced the percentage of seedling infection to 25, 40 and 50%, respectively. With the increasing of fungicide (Folicur and Ridomil) doses the dry weight of F. oxysporum decreased. Also, the increasing of fungicide dose lead to a slight decrease in the dry weight of T. harzianum, T. pseudokoningii and Glioclaium roseum.     

Differential bacterial endophytome in Foc-resistant banana cultivar displays enhanced antagonistic activity against Fusarium oxysporum f.sp. cubense (Foc)

Diverse endophytes with multiple functions exist in different banana cultivars. However, the diversity of cultivable bacterial endophytome that contributes to antifungal activity against Fusarium oxysporum f.sp. cubense (Foc) in resistant and susceptible banana cultivars is mostly unknown. In the present study, we isolated bacterial endophytes from resistant Yengambi KM5 (AAA) and susceptible banana cultivar Ney Poovan (AB) to determine the diversity of cultivable bacterial endophytes. Our study revealed the presence of 56 cultivable bacterial endophytes and 6 nectar-associated bacteria in YKM5 and 31 cultivable bacterial endophytes in Ney Poovan. The identified cultivable bacterial genera in YKM5 included Alcaligenes, Arthrobacter, Azotobacter, Acinetobacter, Agrobacterium, Bacillus, Brucella, Brevundimonas, Brachybacterium, Beijerinckia, Klebsiella, Leclercia, Lysinibacillus, Myroides, Ochrobactrum, Pseudomonas, Rhizobium, Stenotrophomonas, Serratia, and Verticiella. In Ney Poovan, the cultivable endophytic bacterial genera present were Agrobacterium, Bacillus, Bradyrhizobium, Enterobacter, Klebsiella, Lysinibacillus, Micrococcus, Ochrobactrum, Pseudomonas, Rhizobium, and Sphingobium. Thus, the composition and diversity of cultivable endophytic bacterial genera were higher in Foc-resistant YKM5. The antifungal efficacy of bacterial endophytes Brachybacterium paraconglomeratum YEBPT2 (65.5%), Brucella melitensis YEBPS3 (63.3%), Bacillus velezensis YEBBR6 (63.3%), and nectar-associated Bacillus albus YEBN2 (61.1%) from YKM5 showed the highest antifungal activity against Foc, compared with the antifungal activity of endophytes from the susceptible cultivar.     

Biological control ofFusarium oxysporum f.sp.cubense in banana by inoculation withPseudomonas fluorescens

Native strains ofPseudomonas fluorescens exhibitedin vitro antibiosis towards isolates of races 1 and 4 ofFusarium oxysporum f.sp.cubense, the Panama wilt pathogen of banana. The seedlings ofMusa balbisiana seedlings treated withP. fluorescens showed less severe wilting and internal discolouration due toF. oxysporum f.sp.cubense infection in greenhouse experiments. In addition to suppressing Panama wilt, bacterized seedlings ofM. balbisiana also showed better root growth and enhanced plant height.     

18份广东香蕉种质对枯萎病的抗性评价

【背景】香蕉枯萎病是世界性的香蕉毁灭性病害,尚无有效药剂防控,筛选抗病品种是目前理想的防治方法。【方法】采用组培苗伤根接种法,研究了18份香蕉种质对香蕉枯萎病菌4号生理小种的抗性水平,并根据病情指数进行抗性分级。【结果】在供试的18份香蕉种质中,2份(东莞大蕉、抗枯5号)高抗,2份(碧盛、大丰)抗病,3份(抗枯1号、粉杂、农科1号)中抗,7份(粤优抗1号、广东-741、泰国B9、大蕉、台湾8号、海贡蕉、威廉斯8818)感病,4份(巴西、广东2号、广粉1号、粉蕉)高感。【结论与意义】不同香蕉种质对香蕉枯萎病菌4号生理小种的抗病性存在较大差异,本研究初步筛选出7份抗枯萎病的香蕉种质,为香蕉枯萎病抗病育种提供了依据,为病区种植香蕉品种提供了有效参考。