Musa AAA Group Research Articles

Active film strips to extend the shelf life of fruits: Multibranched PLA-gallic acid as an antioxidant/oxygen scavenger in a case study of bananas (Musa AAA group)

This original research developed active polylactic acid (PLA) film strips for use inside food packaging to extend the shelf-life of bananas (Musa AAA group). Multibranched PLA functionalized with gallic acid (GA) (mPLA-GA) was prepared by ring-opening polymerization and functionalization. mPLA-GA was compounded with PLA and fabricated into PLA/mPLA-GA film strips by melt processing using different mPLA-GA contents (1, 2 and 4 wt%). The morphology, antioxidant activity, free-radical scavenging ability under a radiation sterilization dose (25 kGy), migration behavior, mechanical properties, and O2 scavenging capacity of PLA/mPLA-GA film strips were determined and compared with neat PLA and PLA/GA film strips. Bananas were vacuum-packed using commercial plastic packaging together with the PLA-based film strips and kept at room temperature for 14 days. The performance of the PLA/mPLA-GA film strips in extending the shelf-life of bananas was investigated by physical appearance, peel color difference (ΔE*ab), ripening index (RI), and firmness. Analysis of variance at the 0.05 level of significance (p ≤ 0.05) was conducted to compare mean values. PLA/mPLA-GA film strips exhibited a homogeneous matrix with improved mechanical properties and showed outstanding antioxidant as well as O2 scavenging effects by preventing the bloating of packaging, delaying fruit ripening, and extending the shelf-life of bananas. Under vacuum packaging with PLA/mPLA-GA film strips, bananas retained their green peel color and firmness after storing for 14 days. The results suggest that PLA/mPLA-GA film strips show promise as an active bioplastic for extending the shelf-life of bananas as well as other fruits and food items.

Combination of 1-MCP and modified atmosphere packaging (MAP) maintains banana fruit quality under high temperature storage by improving antioxidant system and cell wall structure

Green-ripe disorder often occurs when banana fruit (Musa AAA group) ripen at high temperature above 25 °C. In this study, the effect of modified atmosphere package (MAP) + 1-methylcyclopropene (1-MCP) treatment on the shelf-life quality of banana after high temperature storage was studied. The results showed that 300 nL L-1 1-MCP treatment combined with MAP could prevent the occurrence of green-ripe disorder in banana stored at high temperature, reduce ethylene production and respiration, then delay senescence and ripening, and reduce disease incidence and finger drop of fruit. Further analysis showed that the combined treatment decreased the content of reactive oxygen species (ROS) and enhanced the activity of defense-related enzymes and antioxidants. By inhibiting the activity of cell-degrading enzymes, the treatment increased lignin and cellulose content and maintained cell wall integrity. In addition, the treatment regulated the contents of endogenous hormones indole-3-acetic acid and abscisic acid, thus delaying the softening of fruit. This work provides a theoretical foundation for the storage and transportation of banana fruit at high temperature.

Comparative Analysis of Structural Characteristics and Expression of the CPS Gene in Williams Banana Dwarf Mutant and Its Wild-type Parent

Banana (Musa sp.) is one of the world’s most important crops, and a source of extreme economic importance in many countries around the world. However, the height of banana plant poses a significant challenge in both harvesting fruit and their tolerance to extreme weather. Gibberellin (GA) is one of the important endogenous hormones affecting plant height. Copalyl diphosphate synthase (CPS) is the first key enzyme in the GA biosynthesis pathway. In this paper, two full-length coding sequences of CPS genes were cloned from ‘William B6’ dwarf mutant banana and its wild-type parent (Musa AAA group), named CPS-A and CPS-G, respectively. The full-length complementary DNA (cDNA) sequences of CPS-G and CPS-A were both 2163 base pairs (bp), and encoded 720 amino acid residues. There were eight differences between the two speculative amino acid sequences in the alignment analysis. The molecular weights of CPS-G and CPS-A were 82,359.00 and 82,412.15 Da, respectively, and their isoelectric points were 6.17 and 6.03, respectively; there were no signal peptides and transmembrane structures. The banana CPS was mainly located in the cytoplasm by subcellular localization prediction. The results of reverse quantitative real-time polymerase chain reaction showed that CPS gene expression levels in the leaves and false stems of dwarf banana were lower than those of wild banana except for the developmental stage of the 10th leaf. Its expression level in the dwarf banana stem was significantly lower than that of the wild type at the 15th, 20th, and 25th-leaf age, respectively. The results showed that the dwarfism of the ‘Williams B6’ dwarf mutant might be related to the mutation of the CPS sequence and the difference of expression level. This study laid a foundation for further research on functional verification and the genetic regulation mechanism of the CPS gene.

The complete genome of Banana streak GF virus Yunnan isolate infecting Cavendish Musa AAA group in China.

Banana streak virus (BSV) belongs to the members of the genus Badnavirus, family Caulimoviridae. At present, BSV contains nine species in the International Committee on Taxonomy of Viruses (ICTV) classification report (2018b release). Previous study indicated that the viral particles of Banana streak virus Acuminata Yunnan (BSV-Acum) were purified from banana (Cavendish Musa AAA group) leaves in Yunnan Province, China, and its complete genome was obtained. To further determine whether this sample infecting with Banana streak GF virus (BSGFV), the polymerase chain reaction (PCR) cloning and complete genome analysis of the Banana streak GF virus Yunnan isolate (BSGFV-YN) isolate were carried out in this study. The result showed that BSGFV-YN infecting Cavendish Musa AAA group was co-infecting this sample. Its genome contains a total of 7,325 bp in length with 42% GC content. This complete genome sequence was deposited in GenBank under accession number MN296502. Sequence analysis showed that the complete genome of BSGFV-YN was 98.14% sequence similarity to BSGFV Goldfinger, while it was 49.10–57.09% to other BSV species. Two phylogenetic trees based on the complete genome and ORFIII polyprotein indicated that BSGFV-YN and other BSV species clustered into a group, while it was the highest homology with BSGFV Goldfinger. Although BSGFV-YN and BSGFV Goldfinger were highly homologous, their cultivating bananas are different. The former cultivating banana was from Cavendish Musa AAA group, while the latter cultivating banana was from Goldfinger Musa AAAB group. Compared with BSGFV Goldfinger, the genome of BSGFV-YN has an extra multiple repetitive sequences in the intergenetic region between ORFIII and ORFI, suggesting that this region might be related to host selection. In summary, a BSGFV-YN distant from BSV-Acum was identified from the same sample, and its complete genome sequence was determined and analyzed. The study extends the polymorphism of BSVs in China and provides scientific clue for the evolutionary relationship with host selection of badnaviruses.

Characteristics of few commercial and indigenous cultivars of banana grown in Assam

Characteristics of few commercial and indigenous banana cultivars of Musa AAA group, namely, Jahaji, Barjahaji, Maan Jahaji, Suti Jahaji, Grand Naine, Giant Governor, Amritsagar, Sahabkal, Red Banana and Tulshi Manohar were studied in the Instructional cum Research Farm, Department of Horticulture, Biswanath College of Agriculture, Assam Agricultural University, Biswanath Chariali during 2013–14. The experiment was laid out in randomized block design with three replications. Among the different cultivars, Red Banana recorded the highest number of functional leaves per plant. The longest fingers were produced by Grand Naine followed by Sahabkal, Barjahaji and Amritsagar, while the other cultivars produced comparatively shorter fingers. Yield and yield attributing characters were found to be significant among all the cultivars. Among the cultivars, Grand Naine recorded the highest number of hands (10.72/bunch), number of fingers (135/bunch), length of finger (20.05 cm), pulp: peel ratio (2.87), bunch weight (24.66 kg/bunch) and yield (55.91 t/ha) with the longest peduncle (52.33 cm). Though the heaviest fingers were produced by Red Banana (161.41 g/finger) but the number of hands (4/bunch), number of fingers (43.60/bunch), bunch weight (9.05 kg/bunch) and yield (20.52 t/ha) were observed to be the lowest with shortest peduncle length (29.0 cm) in Red Banana.

Effect of solid-state fermentation with Arxula adeninivorans or Hypocrea jecorina (anamorph Trichoderma reesei) on hygienic quality and in-vitro digestibility of banana peels by mono-gastric animals

This study evaluated the effectiveness of solid-state fermentation with Arxula adeninivorans or Hypocrea jecorina to improve hygienic quality and digestibility of banana peels by mono-gastric animals. Green peels of cooking bananas (Musa AAA-group) were solid-state fermented in ziploc plastic bags for 14 d either non-inoculated or inoculated with A. adeninivorans or H. jecorina. Colonies of aerobic bacteria, lactic acid bacteria, Enterobacteriaceae, yeasts and moulds were enumerated. In-vitro digestibility (total tract and pre-caecal) of dry matter (DM), organic matter (OM) and crude protein (CP) was also determined. Solid-state fermentation significantly improved (P<0.05) in-vitro total tract digestibility (9.9% for DM and 10.1% for OM), and in-vitro pre-caecal digestibility (25.0% for DM, 30.9% for OM and 74.5% for CP); however, no significant effect (P>0.05) due to inoculation was observed. Conversely, inoculation (with A. adeninivorans or H. jecorina) significantly improved (P<0.05) the hygienic quality; with lower (P<0.05) aerobic bacteria, Enterobacteriaceae and mould counts than the non-inoculated treatment. However, H. jecorina triggered a significantly superior (P<0.05) improvement in both hygienic quality and in-vitro pre-caecal digestibility than A. adeninivorans.

Proteome changes in banana fruit peel tissue in response to ethylene and high-temperature treatments.

Banana (Musa AAA group) is one of the most consumed fruits in the world due to its flavor and nutritional value. As a typical climacteric fruit, banana responds to ethylene treatment, which induces rapid changes of color, flavor (aroma and taste), sweetness and nutritional composition. It has also been reported that ripening bananas at temperatures above 24 °C inhibits chlorophyll breakdown and color formation but increases the rate of senescence. To gain fundamental knowledge about the effects of high temperature and ethylene on banana ripening, a quantitative proteomic study employing multiplex peptide stable isotope dimethyl labeling was conducted. In this study, green (immature) untreated banana fruit were subjected to treatment with 10 μL L−1 of ethylene for 24 h. After ethylene treatment, treated and untreated fruit were stored at 20 or 30 °C for 24 h. Fruit peel tissues were then sampled after 0 and 1 day of storage, and peel color and chlorophyll fluorescence were evaluated. Quantitative proteomic analysis was conducted on the fruit peels after 1 day of storage. In total, 413 common proteins were identified and quantified from two biological replicates. Among these proteins, 91 changed significantly in response to ethylene and high-temperature treatments. Cluster analysis on these 91 proteins identified 7 groups of changed proteins. Ethylene treatment and storage at 20 °C induced 40 proteins that are correlated with pathogen resistance, cell wall metabolism, ethylene biosynthesis, allergens and ribosomal proteins, and it repressed 36 proteins that are associated with fatty acid and lipid metabolism, redox–oxidative responses, and protein biosynthesis and modification. Ethylene treatment and storage at 30 °C induced 32 proteins, which were mainly similar to those in group 1 but also included 8 proteins in group 3 (identified as chitinase, cinnamyl alcohol dehydrogenase 1, cysteine synthase, villin-2, leucine-transfer RNA ligase, CP47 protein and calmodulin) and repressed 43 proteins in 4 groups (groups 4–7), of which 6 were associated with photosynthesis II oxygen-evolving protein, the photosynthesis I reaction center, sugar metabolism, the redox–oxidative system and fatty acid metabolism. Differences in the response to ethylene and holding temperature at 30 °C were also revealed and have been discussed. The identities and quantities of the proteins found were linked with quality changes. This study demonstrates that ethylene and high temperature influence banana fruit ripening and senescence at the proteomic level and reveals the mechanisms by which high temperature accelerates banana fruit ripening.

Changes in resistant starch from two banana cultivars during postharvest storage

Banana resistant starch samples were extracted and isolated from two banana cultivars (Musa AAA group, Cavendish subgroup and Musa ABB group, Pisang Awak subgroup) at seven ripening stages during postharvest storage. The structures of the resistant starch samples were analysed by light microscopy, polarising microscopy, scanning electron microscopy, X-ray diffraction, and infrared spectroscopy. Physicochemical properties (e.g., water-holding capacity, solubility, swelling power, transparency, starch–iodine absorption spectrum, and Brabender microviscoamylograph profile) were determined. The results revealed significant differences in microstructure and physicochemical characteristics among the banana resistant starch samples during different ripening stages. The results of this study provide valuable information for the potential applications of banana resistant starches.

Comparative biochemical analysis during the anaerobic digestion of lignocellulosic biomass from six morphological parts of Williams Cavendish banana (Triploid Musa AAA group) plants

We studied banana lignocellulosic biomass (BALICEBIOM) that is abandoned after fruit harvesting, and assessed its biochemical methane potential, because of its potential as an energy source. We monitored biogas production from six morphological parts (MPs) of the "Williams Cavendish" banana cultivar using a modified operating procedure (KOP) using KOH. Volatile fatty acid (VFA) production was measured using high performance liquid chromatography. The bulbs, leaf sheaths, petioles-midribs, leaf blades, rachis stems, and floral stalks gave total biogas production of 256, 205, 198, 126, 253, and 221 ml g⁻¹ dry matter, respectively, and total biomethane production of 150, 141, 127, 98, 162, and 144 ml g⁻¹, respectively. The biogas production rates and yields depended on the biochemical composition of the BALICEBIOM and the ability of anaerobic microbes to access fermentable substrates. There were no significant differences between the biogas analysis results produced using KOP and gas chromatography. Acetate was the major VFA in all the MP sample culture media. The bioconversion yields for each MP were below 50 %, showing that these substrates were not fully biodegraded after 188 days. The estimated electricity that could be produced from biogas combustion after fermenting all of the BALICEBIOM produced annually by the Cameroon Development Corporation-Del Monte plantations for 188 days is approximately 10.5 × 10⁶ kW h (which would be worth 0.80-1.58 million euros in the current market). This bioenergy could serve the requirements of about 42,000 people in the region, although CH₄ productivity could be improved.

Improved tolerance toward low temperature in banana ( Musa AAA Group Cavendish Williams)

To further understand the physiological mechanisms of cold-tolerance in banana plants, the responses of four introducing cultivars ( cv.) W811 (via long-term cold adaptation), PB, BJ10 and BJ11 to low-temperature stress (LT) were investigated. LT caused increased malondialdehyde (MDA) content, elevated contents of hydrogen peroxide (H 2O 2) and superoxide radical (O 2 −), and decreased photochemical efficiency ( F v/ F m) and net photosynthetic rate ( P n) in the leaves of four banana cultivars, but cv. W811 showed better LT tolerance than the other three cultivars. After 72 h of LT, four key antioxidative enzymes in the four cultivars showed different responses. Compared to controls, superoxide dismutase (SOD) activities in the four cultivars showed a significant decrease and W811 had the smallest amount of decrease. Catalase (CAT) activities showed a significant decrease. Peroxidase (POD) activities kept relatively higher activities and showed no significant changes (P > 0.05) in W811, BJ10 and BJ11 whereas that in PB showed a significant increase (P < 0.001). Ascorbate peroxidase (APX) activities in W811 and PB showed no significant changes (P > 0.05). Our results showed that higher cold-tolerance in cv. W811 may correlate with the long-term cold adaptation of the antioxidative enzymes such as SOD, POD and APX that alleviate oxidative stress caused by LT.

Effect of high temperature on color, chlorophyll fluorescence and volatile biosynthesis in green-ripe banana fruit

Banana (Musa AAA group) is one of the most consumed fruits in the world. It has been reported that chlorophyll breakdown and color formation in banana is inhibited by ripening temperatures above 24 °C. At this temperature thylakoid membranes are retained resulting in reduced chlorophyll degradation. In this study, green mature, untreated banana fruit were obtained from a local wholesale market and half of the fruit were subjected to ethylene treatment at 10 μL L −1 for 24 d. After ethylene treatment, both treated and untreated fruit were stored at 20 °C or 30 °C for 7 d. Fruit were sampled after 0, 1, 4 and 7 d of storage and evaluated for color, chlorophyll fluorescence, volatile production and expression of genes related to volatile biosynthesis. Storage at 30 °C reduced yellow color development in the peel, decreased chlorophyll fluorescence (Fv/Fm), but increased Fo, indicating possible heat stress of the fruit. A total of 19 volatile compounds were identified using SPME/GC/MS. Both ethylene treatment and high temperature enhanced volatile production. The increase of Fo and hexanoate and acetate esters are coincided with the stress of high temperature. Using real time PCR (qPCR), expression of genes related to volatile biosynthesis including branched-chain amino acid transaminase ( BCAT), lipoxygenase (LOX), hydroperoxide lyase ( HPL), pyruvate decarbolxylase ( PDC), alcohol dehydrogenases ( ADH, short and medium chains), and alcohol acetyl transferase ( AAT) were investigated in both peel and pulp tissues. Among the tested genes, BCAT, HPL, ADH and AAT in peel and pulp tissues increased significantly in response to ethylene and storage at 30 °C. PDC, ADH and BCAT (in pulp tissue) were induced by storage at 30 °C in ethylene-treated fruit. LOX decreased during ripening and storage at 30 °C in the peel, but increased in the pulp tissue of ethylene-treated fruit. This study demonstrates that both ethylene and high temperature influence volatile biosynthesis in banana fruit at the transcriptional level and confirms findings that high temperature causes stress in banana fruit during ripening.

Susceptibility of banana intercrops for rhizobacteria, arbuscular mycorrhizal fungi and the burrowing nematode Radopholus similis

The susceptibility of 7 non-leguminous and 7 leguminous banana intercrops (and rotation crops) for rhizobacteria, mycorrhizal fungi and the burrowing nematode Radopholus similis was investigated and compared with the host response of banana cv. Grande Naine ( Musa AAA group). In 50% of the tested combinations, the bacteria elicited nodules but these nodules were effective in fixing nitrogen only in about 11% of the tested combinations. Of the non-leguminous intercrops tested, wormseed, sweet potato cv. Tapato and cotton showed a poor mycorrhizal compatibility, based on the frequency ( F%) and intensity ( I%) of mycorrhizal colonisation. Of the leguminous intercrops tested, soybean, Grant's rattlebox, common bean, pigeon pea and sunn hemp showed a moderate mycorrhizal compatibility. Overall, F% and I% were higher in the leguminous intercrops compared with the non-leguminous intercrops. The susceptibility for R. similis differed among the intercrops tested. In the non-leguminous intercrops, marigold, sweet potato cv. Tapato, cotton and sesame were non-hosts, sweet potato cv. Inzovu, sorghum were intermediate hosts and sorgho-sudangrass was a good host. In the leguminous intercrops, hairy indigo was a non-host, Grant's rattlebox, soybean and sunn hemp were poor hosts and cowpea, common bean and pigeon pea were intermediate hosts.

Effects of cinnamon extract, chitosan coating, hot water treatment and their combinations on crown rot disease and quality of banana fruit

The antifungal activities of cinnamon extract (CE), piper extract (PE) and garlic extract (GE) were evaluated on banana crown rot fungi ( Colletotrichum musae, Fusarium spp. and Lasiodiplodia theobromae) in vitro. The assay was conducted with extracts of CE, PE and GE with concentrations of 0, 0.1, 0.5, 1.0, 5.0, 10.0 and 0.75 g L −1 of carbendazim (CBZ) on potato dextrose agar at room temperature. CE completely inhibited conidial germination and mycelial growth of all fungi at 5.0 g L −1. PE totally suppressed mycelial growth of all fungi at 5.0 g L −1 and conidial germination at 10.0 g L −1 except for Fusarium spp. GE had no significant effects but low concentrations (0.1 and 0.5 g L −1) enhanced germ tube elongation of the three fungi. The ED 50 values were higher for mycelial growth than for conidia except for Fusarium spp. Combined treatments were investigated on crown rot development in banana fruit ( Musa AAA group ‘Kluai Hom thong’). Treatments included 5.0 g L −1 CE, 1% (w/v) chitosan solution, hot water treatment (HWT, 45 °C for 20 min), CE plus chitosan, CE plus HWT and 0.75 g L −1 of CBZ, applied before and after inoculation of the fruit. Crown rot development was assessed during storage at 13 °C for 7 weeks. Disease development was least (25%) on CE treated fruit after inoculation compared to CBZ but was higher when CE was applied before inoculation. Chitosan significantly delayed ripening as in terms of peel color, firmness, soluble solids and disease severity. CE showed no negative effects on quality of fruit. CE plus HWT caused unacceptable peel browning.

Establishment of embryogenic cell suspensions and plant regeneration of the dessert banana ‘Williams’ (Musa AAA group)

Summary‘Williams’ is one of the most important dessert banana cultivars in the World. Improvement through genetic engineering depends on the development of embryogenic cell suspension (ECS) cultures. Yellow, compact meristematic globules and yellow-whiteish, friable embryogenic calli were induced from scalps (i.e., the top layer of highly proliferating meristem cultures). About 10% of induced explants gave rise to embryogenic calli. Embryogenic calli were used subsequently to establish ECS cultures. After 3 months of selection and sub-culturing, homogeneous ECS cultures with a high regeneration capacity were obtained. More than 80% of the cell culture consisted of embryogenic cell aggregates. Regenerable somatic embryos emerged about 3 weeks after the ECS was plated onto regeneration medium. Their weight increased 4.8- to 13-fold after 8 weeks of culture. The number of somatic embryos regenerated per ml settled cell volume (SCV) of embryogenic cells (i.e., somatic embryo recovery frequency) ranged between 0.92 – 2.17 105, depending on incubation and regeneration conditions. The conversion frequency from somatic embryo to plant varied between 42.5 – 55.5%, and was independent of regeneration conditions.

Relationship between browning and the activities of polyphenoloxidase and phenylalanine ammonia lyase in banana peel during low temperature storage

Kluai Khai (Musa AA Group) and Kluai Hom Thong (Musa AAA Group) bananas were stored at 6 and 10 °C. Visible chilling injury (CI) in the peel, mainly browning, occurred at both temperatures, but more so at 6 °C, and without significant differences between the cultivars. At the time of harvest, total free phenolics in the peel were three times lower in Kluai Khai than in Kluai Hom Thong fruit, the polyphenol oxidase (PPO) activity in Kluai Khai being considerably higher and phenylalanine ammonia lyase (PAL) activity much lower. As CI developed, PAL and PPO activities in the peel increased, and total free phenolics decreased. The decrease in total free phenolic compounds and the increase in PAL and PPO activities occurred more rapidly at 6 °C than at 10 °C, in both banana cultivars. Correlations between visible CI and the level of total free phenolics, and between CI and the activities of PPO and PAL, were all highly significant. The results indicate that low temperature stress induced concerted activities of PAL and PPO, which resulted in browning. Since the concentrations of free phenolic compounds and the rate of PAL and PPO activities varied considerably between the two cultivars, but browning did not, the changes in the biochemical parameters rather than their absolute levels were correlated with peel browning.

A comparison of the effects of the nematodes Radopholus similis and Pratylenchus goodeyi on growth, root health and yield of an East African highland cooking banana (Musa AAA-group)

The effects of Radopholus similis and Pratylenchus goodeyi on growth, root health and yield of the East African highland cooking banana cultivar Mbwazirume (Musa AAA-group) were compared at Mbarara, Uganda, at 1430 m above sea level. In 3-year-old mats infected only with P. goodeyi, functional root length and functional root density of suckers detached from recently-harvested plants were 40 and 45%, respectively, greater in mulched mats and 120 and 108%, respectively, greater in non-mulched/bare mats compared to mats infected with both P. goodeyi and R. similis. In mats infected with both P. goodeyi and R. similis, dead root length, dead root density and percentage necrosis of functional roots of the suckers were about 30% greater in mulched mats and about 40-50% greater in non-mulched/ bare mats compared to mats infected only with P. goodeyi. In the non-mulched/bare mats, the bunch weight of plants infected with P. goodeyi and R. similis was reduced on average by 6 kg or 30% compared with plants without R. similis, while 60% of the plants infected with both P. goodeyi and R. similis toppled, a percentage three times greater compared to plants infected only with P. goodeyi. In the mulched mats, 25% of the plants infected with both P. goodeyi and R. similis toppled, a percentage four times greater compared to plants infected only with P. goodeyi. Thus, R. similis is probably more virulent than P. goodeyi in the banana-growing areas of southwestern Uganda. However. the results also indicate that under poor management P. goodeyi alone can cause considerable damage. The presence of R. similis resulted in a reduction in the number of standing leaves. More open leaf canopies may have led to higher soil temperatures due to direct sunlight and this could have influenced the nematode population composition in favour of R. similis, resulting in turn in an increase in root damage. This cycle was most pronounced in the non-mulched/bare mats. Mulching appeared to reduce the population densities and the damaging effects of R. similis. Mulched mats had a lower soil temperature compared to non-mulched/ bare mats, which may have slowed R. similis reproduction and feeding activity and reduced root damage.

The effect of Banana streak virus on the growth and yield of dessert bananas in tropical Australia

SummaryWe have examined the effect of a strain of Banana streak virus (BSV‐Cav) on the growth and yield of dessert bananas (Musa AAA group, Cavendish subgroup cv. Williams) in north Queensland, Australia. Healthy and infected plants were compared in a replicated field experiment over plant and first ratoon crops. In both crops, symptom expression followed a similar pattern, increasing to a maximum near the estimated time of bunch initiation, then decreasing in the period prior to bunch emergence. There was no evidence of plant‐to‐plant spread of virus, but the rate of transmission through suckers was 100%. In the plant crop, the mean bunch weights of healthy and infected plants were not significantly different. However, BSV‐Cav infection resulted in an 18 day delay in harvest, causing a 6% reduction in yield per annum. In the ratoon crop, the mean bunch weight of infected plants was 7% less than that of healthy plants, and the interval between the harvest of plant and ratoon crops was delayed by 9 days, resulting in a 11% reduction in yield per annum. Also, the mean length of fruit from infected plants was 5% less than that of healthy plants, resulting in a smaller percentage of fruit in the extra large size category. We conclude that in horticulturally favourable conditions typical of the tropical Australian banana industry, the effects of BSV‐Cav infection on the growth and yield of Cavendish bananas are small.

Analysis of the distribution and structure of integrated Banana streak virus DNA in a range of Musa cultivars

Summary Banana streak virus strain OL (BSV-OL) commonly infects new Musa hybrids, and this infection is thought to arise de novo from integrated virus sequences present in the nuclear genome of the plant. Integrated DNA (Musa6+8 sequence) containing the whole genome of the virus has previously been cloned from cv. Obino l'Ewai (Musa AAB group), a parent of many of the hybrids. Using a Southern blot hybridization assay, we have examined the distribution and structure of integrated BSV-OL sequences in a range of Musa cultivars. For cv. Obino l'Ewai, almost every restriction fragment hybridizing to BSV-OL was predicted from the Musa6+8 sequence, suggesting that this is the predominant type of BSV-OL integrant in the genome. Furthermore, since only two junction fragments of Musa/BSV sequence were detected, and the Musa6+8 sequence is believed to be integrated as multiple copies in a tandem array, then the internal Musa spacer sequences must be highly conserved. Similarly sized restriction fragments were detected in four BB group cultivars, but not in six AA or AAA group cultivars, suggesting that the BSV-OL sequences are linked to the B-genome of Musa. We also provide evidence that cv. Williams (Musa AAA group) contains a distinct badnavirus integrant that is closely related to the 'dead' virus integrant previously characterized from Calcutta 4 (Musa acuminata ssp. burmannicoides). Our results suggest that the virus integrant from cv. Williams is linked to the A-genome, and the complexity of the hybridization patterns suggest multiple sites of integration and/or variation in sequence and structure of the integrants.

A Comparative Study On the Ripening and Mineral Content of Organically and Conventionally Grown Cavendish Bananas

ABSTRACT A study was undertaken to compare the postharvest properties of organically and conventionally grown bananas. The effects of ethrel treatment on the skin colour of organic and non-organic bananas (Musa AAA group Cavendish subgroup, Robusta) were determined during ripening at 22–25°C. In addition, pulp temperature, impedance (at 100 Hz, 500 Hz, 1 kHz, 10 kHz), gravimetric and volumetric pulp: peel ratios, fruit density, total soluble solids (TSS) and major (N, P, K, Ca and Mg) minerals of ripe fruit were also compared for organically and conventionally grown bananas. Organic bananas ripened faster than non-organic bananas as measured by peel colour change (reflectance, chroma and hue angle). Hedonic scale values showed that ethrel treatment promoted uniform skin change from green to yellow. Visual colour values had strong positive correlation against reflectance, chroma or hue angle, but was more closely related to hue angle. Organic and non-organic bananas had no significant difference in TSS contents. Impedance decreased with rise in frequency and pulp temperature and showed strong negative correlation against reflectance, chroma and hue angle of organic and non-organic banana at 100 Hz. Ripe nonorganic bananas had both higher gravimetric pulp: peel ratio and impedance compared with organic fruits. In all fruits, the peel had higher N, P, K, Mg and Ca than the pulp. The peel of non-organic fruits had higher N and lower P contents than organic fruits. Differences in mineral content between the pulp of organic and non-organic fruits were much less than those between the peel. This study shows that production methods of bananas has a significant influence on the postharvest behaviour of bananas and this in turn must influence their subsequent management in order to optimize quality for the consumer.

471 Defining the East African Highland Banana (I AAA) Ideotype and Breeding Objectives

The East African highland bananas are a sub-group of the Musa AAA group and are unique to the mid-altitude and highlands of Eastern Africa. In much of the area where they are grown, highland bananas are the main staple crop for both rural and urban populations. Yields of highland bananas have fallen precipitously in many areas and production deficits have been met by shifting highland banana production into new areas. Yield reductions have been attributed to a number of factors, including plant parasitic nematodes, the banana weevil (Cosmopolites sordidus), and black Sigatoka leaf streak (Mycosphaerella fijiensis). A program to breed improved highland bananas was established at the International Institute of Tropical Agriculture's Eastern and Southern Africa Regional Center (IITA-ESARC) in collaboration with the National Banana Program of Uganda in 1994. Following preliminary studies of fertility, breeding began in 1997. The breeding program has taken as its model IITA's successful plantain-breeding program. The plantain-breeding program has used an ideotype breeding approach to selection of improved plantain hybrids. The unique features, culture, and end-use of highland bananas have necessitated the definition of a new ideotype. Results of studies during the past 2 years have identified traits unique to highland bananas and a highland banana ideotype has emerged.