Sopone Wongkaew

Evaluation of Grapevines for Resistance to Downy Mildew (Plasmopara viticola) under Laboratory and Field Conditions

Downy mildew of grapevine (Vitis vinifera L.), caused by the oomycete Plasmopara viticola, can seriously devastate grapevine production in tropical countries, such as Thailand. Four susceptible grapevine cultivars, four potentially resistant lines and 18 F1 hybrids, propagated by air layering and chip budding, were evaluated for resistance to downy mildew at laboratory (using a detached leaf assay) and field (natural infection in 2011 and 2013) levels. Significant differences in the disease scores among grapevine genotypes, ranging from 0.54 (resistant) to 4.83 (susceptible) and 3.30 (resistant) to 7.70 (susceptible), were observed under the laboratory and field conditions respectively. No significant difference in disease severity was observed between the two propagation methods or between the two different years of field evaluations. Resistance evaluations under both conditions consistently classified ‘NY88.0517.01’ and ‘NY65.0550.04’ as resistant lines what would be useful as parents for future breeding programmes. Moreover, one F1 hybrid, ‘SUT0403.09’, was reported to have considerable resistance to downy mildew under both laboratory and field conditions for the first time. The field resistance level of this hybrid was almost comparable to its highly resistant parent ‘Wilcox 321’, suggesting its potential for the future development of resistant cultivars in Thailand. Although the ranking of genotypes varied between screening methods, the resistance levels of the 26 grapevine genotypes evaluated under laboratory and field conditions were comparable based on the Spearman’s rank correlation coefficients of 0.73 (p ≤ 0.01). These results suggest that the laboratory screening assay is efficient for the rapid, reliable and economical identification of resistant hybrids in grapevine breeding programmes.

Salicylic acid-induced accumulation of biochemical components associated with resistance against Xanthomonas oryzae pv. oryzae in rice

ABSTRACT Seed treatment and foliar sprays of salicylic acid (SA) provided protection in rice against bacterial leaf blight (BLB) caused by bacterial Xanthomonas oryzae pv. oryzae (Xoo). Treatment of rice with exogenous SA reduced disease severity by more than 38%. Superoxide anion production and hypersensitive response increased approximately 28% and 110% at 6 and 48 h after Xoo inoculation, respectively, for plants treated with SA. Moreover, the Xoo in treated rice plants grew more slowly, resulting in a population that was half of that observed in the control. Fourier transform infrared spectroscopy analysis revealed that the higher ratios of 1233/1517, 1467/1517, and 1735/1517 cm−1 observed in treated rice suggested alteration of monomer composition of lignin and pectin in the rice cell wall. Exogenous SA-treated rice had more amide I β-sheet structure and lipids as shown by the peaks at 1629, 2851, and 1735 cm−1. These biochemical changes of rice treated with SA and inoculated with Xoo were related to primed resistance of the rice plants to BLB disease.

Foliar application of systemic acquired resistance (SAR) inducers for controlling grape anthracnose caused by Sphaceloma ampelinum de Bary in Thailand

Chitosan and benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) are active-elicitors that induce protection in grapevine against several diseases. In this study, treatment of grapevine with chitosan and BTH provided protection to anthracnose, caused by Sphaceloma ampelinum. Chitosan and BTH treatment also increased chitinase, s-1,3-glucanase and peroxidase activities levels in leaves over non-treated plants. Differential accumulation of these traits was more rapid and pronounced when chitosan and BTH treated plants were infected with S. ampelinum; this pattern indicating priming. The induced resistance by chitosan and BTH was also associated with increased production of salicylic acid (SA) in grapevine leaves, suggesting that SA-dependent signaling pathways are systemically triggered by these compounds. Apart from proteins with defense-related function, most of the proteins induced by chitosan and BTH were involved in defense mechanism, reflecting the strong direct positive effect that chitosan and BTH has on grapevine tolerance to anthracnose disease infection. Keywords: Anthracnose, grapevine, induce resistance, systemic acquired resistance (SAR) biochemical markers, Sphaceloma ampelinum African Journal of Biotechnology Vol. 12(33), pp. 5148-5156

Morphological, pathogenicity and virulence characterization of Sphaceloma ampelinum the causal agent of grape anthracnose in Thailand

Grape anthracnose caused by Sphaceloma ampelinum is one of the most common fungal disease of grape in Thailand. The objective of this study was to examine the morphological diversity among Sphaceloma isolates from grapes and compare their pathogenicity and virulence on a susceptible grape cultivar. 24 isolates of Sphaceloma were isolated from diseased grape samples collected from different geographical regions of Thailand. Their colony morphology consisting of surface texture, elevation, aerial mycelium production, size and coloration were studied along with their conidial size. Subsequently 11 representative isolates having the same morphology were compared for their pathogenicity and virulence on Black Queen susceptible grape cultivar. According to the colours, the 11 isolates could be divided into 8 groups. The average colony size on potato dextrose agar measured at 35 days was 3.70 ± 0.10 × 3.82 ± 0.08 cm. Most isolates produced single – celled, hyaline, cylindrical shaped with rounded – end conidia containing a cellular gutter inside. The average conidial size was 2.1 to 3.6 × 3.4 to 6.7 μm. From the 11 isolates tested on Black Queen grapes, only 7 isolates had pathogenicity with different degree of virulence. Among the isolate GSH from the SUT farm, Nakorn Ratchasima was the most virulent.