Adverse Effects of Elevated Ambient Ozone on Yield and Protein Loss of Three Thai Soybean Cultivars

Abstract

Various studies in the past have shown that high ozone concentration significantly decreased yield and nutrition in soybean but there is little information in Thailand. Hence, an examination of the aforementioned problem is needed. The purpose of this study is to know the different adverse effects of elevated ambient ozone concentration on yield and protein content of Thai soybean. The research experiment was conducted during December 2007 to March 2008 at the Field Crops Research Center, Phitsanulok, Thailand. Thai native soybean 3 cultivars; Chiang Mai 60, Sorjor 5 and Srisumrong 1; were planted and covered with open top chamber (OTC) since seedling through maturing stage. The OTC with charcoal filtered and non-charcoal filtered were set to control the O₃ level at three different levels ; at ambient level (32 ± 11.1 ppb), lower (12 ± 10.1ppb) and higher than ambient level (62 ± 10.8 ppb). Results indicated that growth and yield loss at maturing stage obviously occurred in all 3 cultivars under high ambient O₃ concentration by statistical significance. However, we found the different reductions in number of total seed/plant of Chiang Mai60, Sorjor5 and Srisumrong 1, by 37, 28 and 33% respectively when they were exposed to 62 ppb O₃ compared to the lower ambient level. The significant reduction by 14% in plant height appeared in only one cultivar, Sorjor 5. The parallel result was shown in protein content; Sorjor5 cultivar showed the most sensitive to high O₃ concentration in protein content reduction by 2.3% but consistent effect was not found in Chiang Mai 60 and Srisumrong 1. The overall results in the study conclude that long-term high O₃ exposure caused different adverse effects in among 3 Thai soybean cultivars. Sorjor5 seems to be more an ozone-sensitivity cultivar than the other cultivars.