ABSTRACT
In June 2011, lettuce (Lactuca sativa) plants cultivated in major lettuce growing areas in Malaysia, including the Pahang and Johor states, had extensive leaf spots. In severe cases, disease incidence was recorded more than 80%. Symptoms on 50 observed plants initially were as water soaked spots (1 to 2 mm in diameter) on leaves, and then became circular spots spreading over much of the leaves. In this research, main lettuce growing areas infected by the pathogen in the mentioned states were investigated and the pathogen was isolated onto potato dextrose agar (PDA). Colonies observed were greyish green to light brown. Single conidia were formed at the terminal end of conidiophores that were 28.8 to 40.8 µm long and 11.0 to 19.2 µm wide, and 2 to 7 transverse and 1 to 4 longitudinal septa. To produce conidia, the fungus was grown on potato carrot agar (PCA) and V8 juice agar media under 8-h/16-h light/dark photoperiod. Fourteen isolates were identified Stemphylium solani based on morphological criteria described by Kim et al. (1). To confirm morphological characterization, DNA of the fungus was extracted from mycelium and PCR was done using universal primers ITS5 (5'-GGAAGTAAAAGTCGTAACAAGG-3') and ITS4 (5'-TCCTCCGCTTATTGATATGC-3'), which amplified the internal transcribed spacer (ITS) region of rDNA (2). The sequencing result was subjected to BLAST analysis which was 99% identical to the other published sequences in the GenBank database (GenBank Accession Nos. AF203451 and HQ840713). The nucleotide sequence was deposited in GenBank under Accession No. JQ736022. Pathogenicity testing of representative isolate was done using 20 µl of conidial suspension with a concentration of 1 × 105/ml in droplets (three drops on each leaf) on four detached 45-day-old lettuce leaves cv. BBS012 (3). Fully expended leaves were placed on moist filter paper in petri dishes and were incubated in humid chambers at 25°C. The leaves inoculated with sterile water served as control. After 7 days, disease symptoms were observed, which were similar to those symptoms collected in infected fields and the fungus was reisolated and confirmed as S. solani based on morphological criteria (1) and molecular characterization (2). Control leaves remained healthy. Pathogenicity testing was completed twice. To our knowledge, this is the first report of S. solani on lettuce in Malaysia and it may become a serious problem because of its broad host range, variability in pathogenic isolates, and prolonged active phase of the disease cycle. Previous research has shown that S. solani is a causal agent of gray leaf spot on lettuce in China (4). References: (1) B. S. Kim et al. Plant Pathol. J. 20:85, 2004. (2) Y. R. Mehta et al. Current Microbiol. 44:323, 2002. (3) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002. (4) F. L. Tai. Sylloge Fungorum Sinicorum, Sci. Press, Acad. Sin., Peking, 1979.
ABSTRACT
In 2011, a severe gray leaf spot was observed on eggplant (Solanum melongena) in major eggplant growing areas in Malaysia, including the Pahang, Johor, and Selangor states. Disease incidence was >70% in severely infected areas of about 150 ha of eggplant greenhouses and fields examined. Symptoms initially appeared as small (1 to 5 mm diameter), brownish-black specks with concentric circles on the lower leaves. The specks then coalesced and developed into greyish-brown, necrotic lesions, which also appeared on the upper leaves. Eventually, the leaves senesced and were shed. Tissue cut from the edges of leaf spots were surface-sterilized in 1% NaOCl for 2 min, rinsed in sterilized water, dried, and incubated on potato dextrose agar (PDA). Fungal colonies were greyish green to light brown, and produced a yellow pigment. Single, muriform, brown, oblong conidia formed at the terminal end of each conidiophore, were each 21.6 to 45.6 µm long and 11.5 to 21.6 µm wide, and contained 2 to 7 transverse and 1 to 4 longitudinal septa. The conidiophores were tan to light brown and ≤220 µm long. Based on these morphological criteria, 25 isolates of the fungus were identified as Stemphylium solani (1). To produce conidia in culture, 7-day-old single-conidial cultures were established on potato carrot agar (PCA) and V8 juice agar media under an 8-h/16-h light/dark photoperiod at 25°C (4). Further confirmation of the identification was obtained by molecular characterization in which fungal DNA was extracted and the internal transcribed spacer (ITS) region of ribosomal DNA amplified using primers ITS5 and ITS4 (2), followed by direct sequencing. A BLAST search in the NCBI database revealed that the sequence was 99% identical with published ITS sequences for two isolates of S. solani (Accession Nos. AF203451 and HQ840713). The amplified ITS region was deposited in GenBank (JQ736023). Pathogenicity testing of a representative isolate was performed on detached, 45-day-old eggplant leaves of the cv. 125066-X under laboratory conditions. Four fully expanded leaves (one wounded and two non-wounded leaflets/leaf) were placed on moist filter paper in petri dishes, and each leaflet inoculated with a 20-µl drop of a conidial suspension containing 1 × 105 conidia/ml in sterilized, distilled water (3). The leaves were wounded by applying pressure to leaf blades with the serrated edge of forceps. Four control leaves were inoculated similarly with sterilized, distilled water. Inoculated leaves were incubated in humid chambers at 25°C with 95% RH and a 12-h photoperiod. After 7 days, symptoms similar to those observed in the original fields developed on both wounded and non-wounded inoculated leaves, but not on control leaves, and S. solani was reisolated consistently from the symptoms using the same method as the original isolations. Control leaves remained asymptomatic and the fungus was not isolated from these leaves. The pathogenicity testing was repeated with similar results. To our knowledge, this is the first report of S. solani on eggplant in Malaysia. References: (1) B. S. Kim et al. Plant Pathol. J. 20:85, 2004. (2) Y. R. Mehta et al. Curr. Microbiol. 44:323, 2002. (3) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002. (4) E. G. Simmons. CBS Biodiv. Series 6:775, 2007.
ABSTRACT
OBJECTIVE: Most published results about the characteristics of NiTi wires are based on the mechanical laboratory tests on the as-received wires.The purpose of this study was to investigate the effect of saliva on load-deflection characteristics of superelastic NiTi wires. MATERIALS AND METHODS: In this experimental study, 15 wires of three kinds of superelastic NiTi wires (Sentalloy, Force I and Truflex) were prepared. Five specimens of each wire were tested in the as-received condition (T0) to provide baseline information and the remaining wires were divided into two groups of five. Half of them were kept inside artificial saliva for one month (T1), while the others were kept in air (T2). After 30 days, three-point bending test was done in a dental arch model and data from selected points on the unloading phase of the generated graphs were used for statistical analysis. RESULTS: Force I and Truflex showed significantly greater force than Sentalloy. The load values of Truflex and Force I after one month exposed to artificial saliva (T1) decreased significantly, but Sentalloy was not affected significantly. The plateau gap values were not considerably different among T0, T1 and T2. CONCLUSION: Saliva decreased the load of Force I and Truflex significantly, but it did not have a statistically significant effect on Sentalloy.
