Resistant Banana Cultivars Research Articles

Proteomic analysis of Fusarium oxysporum f. sp. cubense tropical race 4-inoculated response to Fusarium wilts in the banana root cells.

BackgroundFusarium wilt of banana is one of the most destructive diseases in the world. This disease has caused heavy losses in major banana production areas. Except for molecular breeding methods based on plant defense mechanisms, effective methods to control the disease are still lacking. Dynamic changes in defense mechanisms between susceptible, moderately resistant, and highly resistant banana and Fusarium oxysporum f. sp. cubense tropical race 4 (Foc4) at the protein level remain unknown. This research reports the proteomic profile of three banana cultivars in response to Foc4 and transcriptional levels correlated with their sequences for the design of disease control strategies by molecular breeding.ResultsThirty-eight differentially expressed proteins were identified to function in cell metabolism. Most of these proteins were positively regulated after Foc4 inoculation. These differentially regulated proteins were found to have important functions in banana defense response. Functional categories implicated that these proteins were associated with pathogenesis-related (PR) response; isoflavonoid, flavonoid, and anthocyanin syntheses; cell wall strengthening; cell polarization; reactive oxygen species production and scavenging; jasmonic acid-, abscisic acid-, and auxin-mediated signaling conduction; molecular chaperones; energy; and primary metabolism. By comparing the protein profiles of resistant and susceptible banana cultivars, many proteins showed obvious distinction in their defense mechanism functions. PR proteins in susceptible ‘Brazil’ were mainly involved in defense. The proteins related to PR response, cell wall strengthening and antifungal compound synthesis in moderately resistant ‘Nongke No.1’ were mainly involved in defense. The proteins related to PR response, cell wall strengthening, and antifungal compound synthesis in highly resistant ‘Yueyoukang I’ were mainly involved in defense. 12 differentially regulated genes were selected to validate through quantitative real time PCR method. Quantitative RT-PCR analyses of these selected genes corroborate with their respective protein abundance after pathogen infection.ConclusionsThis report is the first to use proteomic profiling to study the molecular mechanism of banana roots infected with Foc4. The differentially regulated proteins involved in different defense pathways are likely associated with different resistant levels of the three banana cultivars.

Polymorphism at selected defence gene analogs (DGAs) of Musa accessions in Mauritius

One of the major diseases affecting banana is Sigatoka or leaf spot disease that comprises three species, Mycosphaerella fijiensis , Mycosphaerella musicola and Mycosphaerella eumusae . Plants have a large number of defence related genes which trigger a cascade of defense responses that halt the spread of pathogens. Knowledge of the diversity present in genes related to the defense against Sigatoka disease will be useful in developing disease resistant banana cultivars. The defence genes of all sterile commercial banana cultivars (AAA genomes) are considered to have arisen from a similar gene pool belonging to the Musa acuminata complex. The objectives of this study were, (i) to assess the disease response of twelve banana cultivars to M. eumusae, (ii) to assess the level of polymorphisms in selected genes associated with defence against Sigatoka in banana, and (iii) ascertain if this polymorphism was related to levels of resistance to M. eumusae . Defence genes reported to act in response to M. fijiensis were selected and related to the response of M. eumusae . The genetic diversity of selected defence gene analogs (DGA) was assessed using degenerate primers designed from conserved motifs in the aligned amino acid sequences from known resistance genes. Highly polymorphic amplicon profiles for DGAs were selected for comparison. Cluster analysis was used to differentiate to some extent, cultivars considered as resistant/susceptible to M. eumusae . Specific amplicons from the profiles of phenylalanine ammonia-lyase (PAL), iron superoxide dismutase (FeSOD) and ascorbate peroxidase (APX) were unique to a group of resistant cultivars and could act as markers for resistance to M. eumusae . Keywords: Banana, defence gene analogs, polymorphism

Transgenic banana expressing Pflp gene confers enhanced resistance to Xanthomonas wilt disease

Banana Xanthomonas wilt (BXW), caused by Xanthomonas campestris pv. musacearum, is one of the most important diseases of banana (Musa sp.) and currently considered as the biggest threat to banana production in Great Lakes region of East and Central Africa. The pathogen is highly contagious and its spread has endangered the livelihood of millions of farmers who rely on banana for food and income. The development of disease resistant banana cultivars remains a high priority since farmers are reluctant to employ labor-intensive disease control measures and there is no host plant resistance among banana cultivars. In this study, we demonstrate that BXW can be efficiently controlled using transgenic technology. Transgenic bananas expressing the plant ferredoxin-like protein (Pflp) gene under the regulation of the constitutive CaMV35S promoter were generated using embryogenic cell suspensions of banana. These transgenic lines were characterized by molecular analysis. After challenge with X. campestris pv. musacearum transgenic lines showed high resistance. About 67% of transgenic lines evaluated were completely resistant to BXW. These transgenic lines did not show any disease symptoms after artificial inoculation of in vitro plants under laboratory conditions as well as potted plants in the screen-house, whereas non-transgenic control plants showed severe symptoms resulting in complete wilting. This study confirms that expression of the Pflp gene in banana results in enhanced resistance to BXW. This transgenic technology can provide a timely solution to the BXW pandemic.

CONTROL OF BANANA XANTHOMONAS WILT DISEASE USING GENETIC ENGINEERING

The banana Xanthomonas wilt (BXW) disease, caused by the bacterium Xanthomouas campestris pv. musacearum (XCM), endangers the livelihoods of millions of farmers in the Great Lakes region of East and Central Africa. The disease was first identified in Uganda in 2001 and has since then also been reported in Eastern Democratic Republic of Congo, Rwanda, Kenya and Tanzania. The pathogen kills plants quickly and spreads rapidly over a large area making the disease one of the most dreaded in banana (Musa spp.). The development of disease resistant banana cultivars remains a high priority, since farmers are reluctant to employ labor-intensive disease control measures. Prospects of developing cultivars with resistance to BXW through conventional breeding are limited, as no source of germplasm exhibiting resistance against XCM has been identified. Transgenic technologies for banana may provide a timely and cost-effective alternative solution to the BXW pandemic. The ferredoxin-like amphipathic protein (pflp) and hypersensitive response assisting protein (hrap), isolated from sweet pepper (Capsicum annuum) are novel proteins that can intensify the harpinPSS-mediated hypersensitive response. The International Institute of Tropical Agriculture (IITA) has negotiated royalty-free license from Academia Sinica, Taiwan, patent holder, through the African Agricultural Technology Foundation (AATF) for access to the technology for bacterial wilt resistance. The partners, IITA, the National Agriculture Research Organization (NARO) in Uganda and AATF, have signed a tripartite agreement for development of BXW-resistant transgenic bananas. Hundreds of transgenic lines of banana cultivars have been generated, which are screened for disease resistance under laboratory conditions. Most promising lines will be evaluated for efficacy against XCM in fields.

Banana: cultivars, biotechnological approaches and genetic transformation

SummaryGenetic modification of banana has been considered as a path towards increasing the value of this crop according to health and nutrition in developing countries. Banana as a crop is one of the most important and widely consumed fruits as a weaning food by children and as a starchy staple for all other consumers. As well as providing a low cost and easily produced source of energy, bananas are also rich in certain minerals and in vitamins A, C and B6. Growing urbanisation in many developing countries upgraded the crop importance as a source of revenue, occasionally providing the main source of income for rural communities. Genetically modified organism bananas have been advocated as carrier for vaccines and as a source of carotenoids that can counteract debilitating vitamin A deficiency. The rather high vulnerability of banana to pests and diseases triggered biotechnological applications in an attempt to produce new, more resistant banana cultivars. However, the potential biosafety of genetically modified banana and its applications should be taken into account prior to its extensive usage. The current survey summarises the most important biotechnological techniques (in vitro culture, DNA fingerprinting, somatic emrbyogenesis, DNA flow cytometry, etc.) and applications (micropropagation, in vitro selection, somaclonal variation, protoplast fusion, haploid production, etc.) in banana and emphasises on genetic transformation in conjunction with the expressed gene and modified trait aiming at a further improvement of this crop.

Effect of Juglone on Active Oxygen Species and Antioxidant Enzymes in Susceptible and Partially Resistant Banana Cultivars to Black Leaf Streak Disease

The black leaf streak disease (BLSD), caused by Mycosphaerella fijiensis, is the most destructive disease of bananas and plantains around the world. Breeding for resistance is the most promising strategy to fight this disease especially in small farmer plantations. Mycosphaerella fijiensis produces many phytotoxins such as juglone, which can be used, jointly with field and inoculations under controlled conditions, for screening banana cultivars for BLSD-resistance. This non-host specific phytotoxin has been shown to act on chloroplasts and disturbs the proton electrochemical gradient across the plasmalemma membrane. Moreover, an involvement of the oxidative burst during the interaction has been suggested. The present study was carried out using two cultivars that differed for either their juglone-responses or their resistance to BLSD (cv. Grande Naine susceptible to BLSD and juglone and cv. Fougamou partially resistant to BLSD and highly tolerant to juglone). The production of active oxygen species (AOS) and the enhancement of the enzymatic and/or non-enzymatic AOS-scavenging systems were investigated after treatment of the two cultivars with juglone. The time-course of AOS-production and AOS-scavenging was shown to be the key difference between these two tested cultivars after treatment with juglone. Thus, an early release of AOS (O2− radical and H2O2) and a quick stimulation of a preferment anti-oxidant system (superoxide dismutases, catalases, and peroxidases) was observed for cv. Fougamou as compared to cv. Grande Naine for which a late and weak generation of AOS accompanied by a late stimulation of the anti-oxidant systems were detected.

Identification of discriminant factors after treatment of resistant and susceptible banana leaves with Fusarium oxysporum f. sp. cubense culture filtrates

AbstractAmong the most important crops in developing countries are banana and plantain. However, the production is threatened by increasingly virulent forms of Fusarium wilt, and therefore, intensive breeding programmes are being carried out worldwide. As conventional field studies of banana resistance to this disease are time‐consuming and destructive, an easy‐to‐do procedure was previously developed to differentiate field‐grown resistant and susceptible banana cultivars at leaf level. Such a procedure involved the in vitro treatment of fungal culture filtrates on to field‐grown adult leaves and the measurement of lesion areas 48 h later. The present report includes measurements of other indicators such as biochemical compounds. The cultivar ‘Gross Michel’ (susceptible) and cv. ‘FHIA‐01’ (resistant) leaves were treated with Fusarium oxysporum f. sp. cubense race 1 culture filtrates. Evaluations were performed 48 h after leaf treatment. Compared with culture medium‐treated leaves (control treatment), fungal metabolites produced leaf lesions, decreased freephenolic contents and increased protein levels in both cultivars. In ‘FHIA‐01’, the culture filtrate increased contents of cell wall‐linked phenolics and the pool of aldehydes (except malondialdehyde). Fungal metabolites did not cause variations in peroxidase activity, chlorophyll pigment contents or malondialdehyde level in any cultivar. The use of Fisher's linear discriminant analysis to differentiate resistant and susceptible banana cultivars in breeding programmes is also a novel aspect of this report. Such an estimation was performed from a data matrix that included the effects of the fungal metabolites (leaf lesion area and levels of free and cell wall‐linked phenolics, aldehydes, except malondialdehyde, and proteins) on banana leaves of seven cultivars (four susceptible and three resistant).

Phenylphenalenonic phytoanticipins. New acenaphtylene and dimeric phenylphenalenones from the resistant Musa selected hybrid SH-3481

Abstract A new acenaphtylene derivative and two new dimeric phenylphenalenones has been isolated from healthy rhizomes of Musa selected hybrid resistant cultivar SH-3481. The structures of the new substances were elucidated using spectroscopy data. The chemical shift for all the hydrogen and carbon atoms in the substances were unambiguously established by mono and bi-dimensional, homo and heteronuclear NMR experiments. Seven previously reported phenylphenalenone type phytoalexins were also now isolated as constitutive natural antibiotics and so as phytoanticipins from this resistant banana cultivar, suggesting that this type of phytoalexins play an important role as part of the resistance mechanisms to fungal diseases in this important alimentary resource botany family.

1,8-Cineole: An attractant for the banana weevil, Cosmopolites sordidus

1,8-Cineole was identified as one of the electrophysiologically active components of the volatiles from banana cultivars susceptible to the banana weevil. It was also shown to be an attractant for the banana weevil Comopolites sordidus in laboratory behavioural bioassays. The resistant cultivar did not contain 1,8-cineole. β-Phellandrene, which exhibited electrophysiological activity, but did not show any attraction to the banana weevil, was found only in the resistant banana cultivar.

Characteristics of the surface of banana peel in cultivars susceptible and resistant to maturity bronzing

Maturity bronzing, a disorder of banana fruit in the humid tropics, is characterised by a preharvest discoloration of the peel. Lesions in the peel of the commercial banana cultivar Williams occur on the surface of the fruit peel primarily in the wet season and their formation involves (i) separation of epidermal cells and (ii) intercellular cracking. During rapid growth the epidermis and the cuticle appear to be insufficiently elastic to accommodate the expansion of internal tissues. The resulting fracture patterns indicate that maturity bronzing is stress induced. Development of the epidermis of the fruit peel was studied by scanning electron microscopy in susceptible and resistant banana cultivars. Observations were compared with those found for the commercial cultivar Williams. At bunch emergence, susceptible cultivars had ridged epidermal cells but the epidermal cells of resistant cultivars had papillate outgrowths.

The ultrastructure of tylose formation in resistant banana following inoculation with Fusarium oxysporum f.sp. cubense

In a resistant banana cultivar tylose initials appeared within vessel lumina of roots two days after inoculation with race 1 of Fusarium oxysporum f.sp. cubense. The tyloses were formed as extensions of contact (paratracheal) parenchyma cells. By 8 days after inoculation the tyloses had enlarged to such an extent that the vessel lumina were completely occluded and walls of adjacent tyloses adhered to form a tissue that completely blocked the vessel interior. Cytological changes that occurred during their development suggest that the growth of tyloses resulted from processes common to normal cell enlargement. The formation of a “protective layer” that occurred in some contact parenchyma cells was not associated with subsequent tylose formation, but may represent a variation of the same basic process.