First Report of Banana bract mosaic virus in Flowering Ginger in Hawaii

Piriformospora indica suppresses the symptoms produced by Banana bract mosaic virus by inhibiting its replication and manipulating chlorophyll and carotenoid biosynthesis and degradation in banana

Banana bract mosaic virus (BBrMV) infection results in characteristic reddish streaks on pseudostem and chlorotic spindle lesions on leaves leading to traveler's palm appearance and complete crop loss depending on the stage of infection in banana plants. Here, we discuss the influence of P. indica colonization (a beneficial fungal root endophyte) on BBrMV infection, specific viral component genes responsible for symptom development, chlorophyll and carotenoid biosynthesis, and degradation in BBrMV-infected banana plants. P. indica colonization significantly and substantially reduced the severity of Banana bract mosaic disease (BBrMD) in addition to increased growth, development and yield of banana plants. The percent disease incidence (PDI) of BBrMV ranges from 50 to 70 per cent in plants raised from suckers and from 58 to 92 per cent in TC plants under artificial inoculation. P. indica-colonized plants inoculated with BBrMV resulted in an enhanced plant height, root length, leaf width, and leaf length of 72, 88, 90, and 60 per cent, respectively, compared to BBrMV alone-infected banana plants along with the reduced disease severity. BBrMV infection showed a drastic decrease of chlorophyll a, chlorophyll b, and total chlorophyll contents by down-regulating chlorophyll biosynthesis (Chlorophyll synthase-CHLG) and upregulating chlorophyll degradation (Chlorophyllase-CLH1 and CLH2 and Pheophytin pheophorbide hydrolase-PPH) genes; and by up-regulating carotenoids biosynthesis (Phytoene synthases-PSY1 and PSY2) and down-regulating its degradation (Phytoene desaturase-PDS) genes compared to P. indica-colonized banana plants challenge inoculated with BBrMV. P. indica also inhibited the expression of the viral genes (P3 and HC-Pro) involved in symptom development. P. indica-colonized banana plants reduced the BBrMV symptoms severity by enhancing chlorophyll biosynthesis; and decreasing chlorophyll degradation and carotenoid biosynthesis and degradation; and inhibiting the viral genes responsible for symptom development in addition to enhanced growth and yield of banana plants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03983-y.

Occurrence of Banana bract mosaic virus on Musa ornata Roxb based hybrids in India

Musa ornata, wild species of banana is being used as a cut flower, potted plants and for landscape gardening etc., They are also being utilized in banana hybridization programmes for introgressing pest and disease tolerant traits into banana cultivars in addition to the development of inter specific ornamental banana hybrids. Symptoms of banana bract mosaic virus (BBrMV) was observed in the bracts of interspecific M. ornata based hybrid developed using another wild species i.e., Musa rubra Kurz at ICAR-National Research Centre for Banana (NRCB), Tiruchirapalli. Presence of the virus in the bracts, leaves and roots of symptomatic plants was confirmed through triple antibody sandwich enzyme linked immunosorbent assay with BBrMV monoclonal and polyclonal antibodies. BBrMV HC-Pro (1370 bp), CP (900 bp) and VPg (570 bp) genes were amplified from the infected bracts using reverse transcriptase polymerase chain reaction with BBrMV respective gene primers. The amplicons of these three genes were cloned and sequenced. Blastn analysis revealed that HC-Pro, VPg and CP gene sequences has 97.67%, 97.72% and 99.67% similarity with the respective gene sequences of BBrMV infecting banana. Phylogenetic analysis clustered the test isolate with other BBrMV isolates of banana and other hosts based on CP and HC-Pro and VPg gene sequences. The virus is transmitted through Pentalonia nigronervosa and the transmitted plants expressed symptoms under glass house conditions. To the best of our knowledge, this is the first report of BBrMV on ornamental M. ornata hybrid in India and its transmission occurs through Pentalonia nigronervosa.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13337-022-00788-6.

Cloning, expression and characterization of P1 and NIa proteases from banana bract mosaic virus (BBrMV)

Banana bract mosaic virus (BBrMV) causes the banana bract mosaic disease in banana. It belongs to the genus Potyvirus within the family Potyviridae. To the best of our knowledge apart from BBrMV coat protein gene, there are no reports on cloning, expression and characterization of any other genes from BBrMV. In this study, the BBrMV P1 and NIa protease genes were amplified from BBrMV infected banana plant cultivar Nendran and were cloned into the protein expression vector pET28b. Recombinant plasmids were transferred to BL21-CodonPlus (DE3)-RP cells and the IPTG (Isopropyl β-d-1-thiogalactopyranoside) induced BBrMV P1 and NIa proteins with molecular weights of 42 and 32 KDa respectively were purified on Ni-NTA resin column under denaturing conditions using 8 M urea. BBrMV P1 and NIa purified proteins were detected by Western blot using anti-histidine antibody. The activity of both P1 and NIa proteases in native form was analyzed through in-gel zymographic assay. The activities of both the proteases were strongly inhibited by PMSF, suggesting that both the proteases are the serine type proteases. Interestingly both the proteases showed a temperature optimum of 50 °C while the pH optimum was 8. Both proteases lost their activity when incubated at 70 °C for 1 h. This is the first report of expression, purification and characterization of BBrMV P1 and NIa proteases.

A rapid and sensitive lateral flow immunoassay (LFIA) test for the on-site detection of banana bract mosaic virus in banana plants

Banana bract mosaic virus (BBrMV) is a serious pathogen threatening the cultivation of banana and plantain worldwide. This study reports the development of a practical, rapid, sensitive, specific and user-friendly lateral flow immunoassay (LFIA) test for the on-site detection of BBrMV. The BBrMV coat protein (CP) was expressed in Escherichia coli and purified and used to immunize rabbits to produce a polyclonal antiserum (anti-BBrMVCP). The test was based on a double-antibody sandwich format. Protein-A affinity column-purified anti-BBrMVCP Immunoglobulins (IgG) (16 μg/mL), conjugated to ∼30 nm gold nanoparticles, was applied onto the conjugate pad. The anti-BBrMVCP IgG and goat anti-rabbit IgG were printed on the surface of a nitrocellulose filter membrane as the test line and control line, respectively. A positive result could be confirmed visually by the presence of a pink band that developed on the LFIA strip within 5-10 min. The detection limit of the test was 10 ng of the expressed recombinant BBrMV CP (rBBrMVCP), and a 1:20 dilution of the BBrMV-infected crude extract. This LFIA test was validated using 114 banana leaf samples randomly collected from the field and the results indicated a very high diagnostic sensitivity (99.04 %) and specificity (100 %) for the test. A Cohen's kappa coefficient of 0.861 obtained also indicated a very good agreement between the LFIA developed in this study and ELISA. This assay could be adopted by farmers, tissue culture industries and quarantine departments for surveys and surveillance. This is the first report on the development of a LFIA-based test for BBrMV detection.

Complete genome sequencing of banana bract mosaic virus isolate infecting cardamom revealed its closeness to banana infecting isolate from India

The complete genome of banana bract mosaic virus (BBrMV), a Potyvirus belonging to the family Potyviridae causing chlorotic streak disease of cardamom (Elettaria cardamomum) in India was determined for the first time from a naturally infected cardamom var. Njallani Green Gold through reverse transcription PCR using nine sets of primers designed to different overlapping regions of the genome. The complete genome has 9708 nucleotides excluding poly (A) tail and has the genome organization similar to that of BBrMV isolates infecting banana and flowering ginger (Alpinia purpurata). The virus has a single open reading frame of 9372 nucleotides that encodes for a polypeptide of 3124 amino acids which is later cleaved into ten matured proteins. The length and arrangements of different proteins in BBrMV-Cardamom was similar to other BBrMV isolates except for the P1 protein that showed a single amino acid deletion. Comparison with three available complete genome sequences revealed that, BBrMV-Cardamom isolate is more closer to BBrMV-Banana isolate from India (BBrMV-TRY) (96.7% identity) than to BBrMV-Banana isolate from Philippines and flowering ginger isolates from USA (94.5%). Analysis of polyprotein and their individual proteins also showed close identity of BBrMV-Cardamom and BBrMV-TRY. The phylogenetic analysis also suggested that BBrMV-Cardamom isolate is closely related to other BBrMV isolates.

Characterization of Canna yellow mottle virus in a New Host, Alpinia purpurata, in Hawaii

Canna yellow mottle virus (CaYMV) is an important badnavirus infecting Canna spp. worldwide. This is the first report of CaYMV in flowering ginger (Alpinia purpurata) in Hawaii, where it is associated with yellow mottling and necrosis of leaves, vein streaking, and stunted plants. We have sequenced CaYMV in A. purpurata (CaYMV-Ap) using a combination of next-generation sequencing and traditional Sanger sequencing techniques. The complete genome of CaYMV-Ap was 7,120 bp with an organization typical of other Badnavirus species. Our results indicated that CaYMV-Ap was present in the episomal form in infected flowering ginger. We determined that this virus disease is prevalent in Hawaii and could potentially have significant economic impact on the marketing of A. purpurata as cut flowers. There is a potential concern that the host range of CaYMV-Ap may expand to include other important tropical plants.

Deep sequencing of banana bract mosaic virus from flowering ginger (Alpinia purpurata) and development of an immunocapture RT-LAMP detection assay

Banana bract mosaic virus (BBrMV) has never been reported in banana plants in Hawaii. In 2010, however, it was detected in a new host, flowering ginger (Alpinia purpurata). In this study, we characterize the A. purpurata isolate and study its spread in flowering ginger in Hawaii. A laboratory study demonstrated that BBrMV could be transmitted from flowering ginger to its natural host, banana, therefore raising a serious concern about the potential risk to the rapidly growing banana industry of Hawaii. To quickly monitor this virus in the field, we developed a robust immunocapture reverse transcription loop-mediated isothermal amplification (IC-RT-LAMP) assay. Deep sequencing of the BBrMV isolate from A. purpurata revealed a single-stranded RNA virus with a genome of 9,713 nt potentially encoding a polyprotein of 3,124 aa, and another predicted protein, PIPO, in the +2 reading-frame shift. Most of the functional motifs in the Hawaiian isolate were conserved among the genomes of isolates from one found in the Philippines and India. However, the A. purpurata isolate had an amino acid deletion in the Pl protein that was most similar to the Philippine isolate. Phylogenetic analysis of an eastern Pacific subpopulation that included A. purpurata was closest in genetic distance to a Southeast Asian subpopulation, suggesting frequent gene flow and supporting the hypothesis that the A. purpurata isolate arrived in Hawaii from Southeast Asia.

Biology, etiology, and control of virus diseases of banana and plantain

Banana and plantain (Musa spp.), produced in 10.3 million ha in the tropics, are among the world's top 10 food crops. They are vegetatively propagated using suckers or tissue culture plants and grown almost as perennial plantations. These are prone to the accumulation of pests and pathogens, especially viruses which contribute to yield reduction and are also barriers to the international exchange of germplasm. The most economically important viruses of banana and plantain are Banana bunchy top virus (BBTV), a complex of banana streak viruses (BSVs) and Banana bract mosaic virus (BBrMV). BBTV is known to cause the most serious economic losses in the "Old World," contributing to a yield reduction of up to 100% and responsible for a dramatic reduction in cropping area. The BSVs exist as episomal and endogenous forms are known to be worldwide in distribution. In India and the Philippines, BBrMV is known to be economically important but recently the virus was discovered in Colombia and Costa Rica, thus signaling its spread into the "New World." Banana and plantain are also known to be susceptible to five other viruses of minor significance, such as Abaca mosaic virus, Abaca bunchy top virus, Banana mild mosaic virus, Banana virus X, and Cucumber mosaic virus. Studies over the past 100 years have contributed to important knowledge on disease biology, distribution, and spread. Research during the last 25 years have led to a better understanding of the virus-vector-host interactions, virus diversity, disease etiology, and epidemiology. In addition, new diagnostic tools were developed which were used for surveillance and the certification of planting material. Due to a lack of durable host resistance in the Musa spp., phytosanitary measures and the use of virus-free planting material are the major methods of virus control. The state of knowledge on BBTV, BBrMV, and BSVs, and other minor viruses, disease spread, and control are summarized in this review.

Population structure of Banana bract mosaic virus reveals recombination and negative selection in the helper component protease (HC-Pro) gene

Banana bract mosaic virus (BBrMV) is a serious constraint in the production of banana and plantain in India. In this study, we have cloned, sequenced and analyzed the helper component proteinase (HC-Pro) gene of 22 isolates from India and compared with previously reported BBrMV isolates. Sequence identity of BBrMV isolates encoding HC-Pro gene, were 92-100 % both at the nucleotide (nt) and amino acid level. Phylogenetic analysis based on nt sequences of non recombinant isolates showed that TN15, TN9 and TN24 formed one cluster and all the remaining isolates formed into another cluster. Different functional motifs in the central region of HC-Pro gene of BBrMV isolates were found conserved. Four potential recombinants with a total of 15 breakpoints were mostly observed at the N and a few from C terminal regions. The codon based selection analysis revealed that most of the codons were under purifying or negative selection except a codon at position 74 which was under positive selection. It is likely that recombination identified in Indian BBrMV isolates, along with strong purifying selection, enhances the speed of elimination of deleterious mutations in the HC-Pro gene. This study suggested that negative selection and recombination were important evolutionary factors driving the genetic diversification and population structure of Indian BBrMV isolates. To the best of our knowledge, this is the first report on the diversity analysis and occurrence of recombination in the HC-Pro gene of BBrMV.