RESUMEN
Mango malformation disease (MMD) is one of the most devastating diseases causing severe economic losses to this crop worldwide. MMD has not been reported in Sri Lanka although the disease was reported in neighboring India over a century ago. Abnormal, thick, and fleshy mango panicles (40%) and proliferating stunted shoots (<1%) showing characteristic malformation symptoms were observed in Peradeniya-Kandy area (7°17'4.15" N, 80°38'14.08" E). Malformed inflorescences and vegetative shoots were collected during January to March and September to November, in 2008 through 2012. Pieces of malformed tissues were surface sterilized in 1% sodium hypochlorite and transferred to potato dextrose agar (PDA). The plates were incubated at 26 ± 2°C for 7 days. Monoconidial cultures of 41 isolates that resembled Fusarium spp. were obtained. Colonies showed white sparse aerial mycelium and magenta-dark purple pigmentation on the underside. Growth rate of the isolates averaged 3.67 mm/day in the dark at 25°C on PDA. To stimulate conidia development, Fusarium isolates were transferred to carnation leaf agar (CLA). Sympodially branched conidiophores bearing mono- and polyphialides with 2 to 3 conidiogenus openings originated erect and prostrate on aerial mycelium. Oval to allontoid, abundant microconidia were produced in false heads on mono- and polyphialides. Dimensions of aseptate conidia were 2.5 to 12.5 (6.47) × 1.25 to 3.8 (2.29) µm. Macroconidia were long and slender, 3 to 5 celled and 27.5 to 47.5 (38.59) × 2.5 to 5 (2.94) µm. Chlamydospores were absent. These characters are consistent for F. mangiferae. DNA was extracted from 30 monoconidial Fusarium isolates (1) and amplified with species-specific PCR primers 1-3F/R (forward: 5'-TGCAGATAATGAGGGTCTGC-3'; reverse: 5'-GGAACATTGGGCAAAACTAC-3') (3). Eight isolates from malformed inflorescences (I6, I13, I15, and I16) and malformed vegetative tissues (V1, V2, V3, and V4), were identified as F. mangiferae based on a 608-bp species-specific amplified DNA fragment. Pathogenicity of F. mangiferae isolates, I15 and V2, was tested on 1-year-old seedlings cv. Willard planted in 10-liter plastic pots. Conidia suspensions (107 conidia/ml of 0.1% water agar) were obtained from 10-day-old monoconidial cultures. Each isolate was inoculated onto 15 apical buds by placing drops (20 µl) of conidia (2). Both F. mangiferae isolates, I15 and V2, on artificial inoculation produced typical floral malformation symptoms in 40% of the buds, up to 10 weeks after inoculation. The Fusarium isolates recovered were identical in colony and mycelia morphology and conidia dimensions to the original F. mangiferae isolates. No Fusarium species were recovered from control flower buds. To our knowledge, this is the first report of MMD in the inflorescence and the vegetative shoots caused by F. mangiferae in Sri Lanka. Isolation of other Fusarium spp. that were not identified as F. mangiferae in this study suggests that additional Fusarium spp. may be associated with the MMD in Sri Lanka. Further studies are needed to confirm the identity of these Fusarium isolates, their role in MMD, and the distribution over the island. Since the disease is likely to drastically reduce productivity, measures will be required to protect 12,160 ha of mango cultivation from this devastating disease. References: (1) S. Freeman et al. Exp. Mycol. 17:309, 1993. (2) S. Freeman et al. Phytopathology 89:456, 1999. (3) Q. I. Zheng and R. C. Ploetz. Plant Pathol. 51:208, 2002.
RESUMEN
Anthracnose development by Colletotrichum musae was observed to be significantly less in the fruits of the banana cultivar 'Embul' (Mysore, AAB) infected with Phyllosticta musarum than in fruits without such infections. Anthracnose disease originates from quiescent C. musae infections in the immature fruit. P. musarum incites minute, scattered spots, referred to as freckles, in the superficial tissues of immature banana peel which do not expand during maturation or ripening. P. musarum does not appear to have a direct suppressive effect on C. musae as conidia of C. musae germinate on both freckled and non-freckled fruit forming quiescent infections. Our investigations have shown that P. musarum infection induced several defence responses in fruit including the accumulation of five phytoalexins, upregulation of chitinase and ß-1,3-glucanase, phenylalanine ammonia lyase (PAL) activity and cell wall lignification. (1)H and (13)C NMR spectral data of one purified phytoalexin compared closely with 4'-hydroxyanigorufone. Some of the P. musarum-induced defences that retained during ripening, restrict C. musae development at the ripe stage. This paper examines the potential of P. musarum-induced defences, in the control of anthracnose, the most destructive postharvest disease in banana.
RESUMEN
Use of bottled water in Sri Lanka has increased over the last decade, while new brands of bottled water are often introduced to the market. However, the manufacturers' adherence to bottled water regulations is questionable, raising concerns regarding the quality of bottled water. The objective of the current study was to investigate the microbiological and chemical quality of bottled water in Sri Lanka. Thirty bottled water brands were sampled and their chemical and microbiological parameters were analyzed. Microbiological analysis was carried out within 1 to 3, 3 to 6, 6 to 9, and 9 to 12 mo after the date of manufacture. The results indicated that 63% of brands tested exceeded the levels permitted by the Sri Lanka Standards Institution (SLSI) for presumptive total coliforms (TC) (<10 cfu per 100 mL) whereas 97% brands exceeded the World Health Organization (WHO) permitted level. Thirty percent of brands exceeded the limit for presumptive fecal coliforms (FC) (0 cfu per 100 mL in accordance with WHO permitted levels, SLSI and the Sri Lanka Health Ministry requirement). Eighty percent of brands showed higher heterotrophic plate counts (HPC) which exceeded the WHO guidelines for bottled drinking water. Throughout their shelf life, the counts of TC, FC, and HPC bacteria decreased. Bacteria identified were Klebsiella pneumoniae ssp. pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa, and Pasteurella haemolytica, the most frequently being P. aeruginosa. The dominant fungi identified were Aspergillus sp. and Penicillium sp. Inorganic chemical parameters were within permitted levels for all brands except for initial content of ammonia. The results of this study show the need for the bottling industry to be monitored closely by relevant authorities, in order to provide safe bottled drinking water to consumers in Sri Lanka.
