Application of an orcinol-ferric chloride colorimetric assay in barley and wheat accessions for water-extractable and total arabinoxylan

Arabinoxylan is an important hemicellulose potentially affecting wheat baking qualities, barley malt quality, and may impart prebiotic benefits. Water-extractable (WEAX) and total arabinoxylan (TOAX) were characterized in 204 wheat and barley accessions, respectively, using an orcinol-ferric chloride assay. WEAX measurement accuracy was optimum when glucose concentration was greater than 12-13 times pentose concentration. The modified method removed enough excess glucose spectral absorbance to make the corrected and uncorrected lines different, but still significantly correlated (p = 0.009, R = 0.94). Mean WEAX (expressed as percentage WEAX of TOAX) for the wheat accessions was 15.90%, ranging from 8.82% to 24.87%, and for barley accessions WEAX the mean was 7.10%, and ranged from 2.98% to 13.86%. Conclusions are 1) the assay is useful for a breeding program because of its semi-high throughput design for the simultaneous analysis of 16 (WEAX) to 40 (TOAX) barley lines or 24 (WEAX) to 40 (TOAX) wheat lines, 2) the trichromatic measurement reduces the impact of glucose, and 3) the broad range of WEAX measured showed that barley and wheat accessions vary in their extractable and unextractable components.阿拉伯木聚糖（Arabinoxylan）是一类重要的半纤维素，可潜在影响小麦烘焙品质与大麦麦芽质量，同时可能赋予益生元功效。本研究采用苔黑酚-三氯化铁（orcinol-ferric chloride）分析法，分别对204份小麦与大麦种质资源中的水溶性阿拉伯木聚糖（water-extractable arabinoxylan, WEAX）和总阿拉伯木聚糖（total arabinoxylan, TOAX）进行了表征分析。当葡萄糖浓度为戊糖浓度的12~13倍时，WEAX的检测准确度达到最优。改良后的方法可有效去除过量葡萄糖的光谱吸收干扰，使得校正与未校正的检测结果存在显著差异，但二者仍具有显著相关性（p = 0.009, R = 0.94）。小麦种质资源的平均WEAX占TOAX的比例为15.90%，波动范围为8.82%~24.87%；大麦种质资源的平均WEAX占比为7.10%，波动范围为2.98%~13.86%。本研究得出三点结论：1）该分析法具备半高通量的检测设计，可同时分析16份（WEAX检测）至40份（TOAX检测）大麦种质，或24份（WEAX检测）至40份（TOAX检测）小麦种质，适用于育种项目；2）三色检测法可降低葡萄糖的干扰影响；3）本次检测得到的宽范围WEAX数据表明，小麦与大麦种质资源在可提取与不可提取木聚糖组分上存在显著差异。