Starch granule size distribution in storage roots of different types of sweetpotato cultivars | 不同类型甘薯品种块根淀粉粒粒度的分布特征

Chinese. 目的阐明不同类型甘薯块根淀粉粒粒度的分布特征及其与淀粉品质的关系。方法选用6个淀粉型品种、5个食用型品种和1个兼用型品种，研究块根中淀粉粒的体积和数目分布、淀粉粒体积和数目分布与淀粉及其组分含量的相关性。结果甘薯块根含有小（粒径＜3.36 micro;m）、中（粒径3.36―19.76 micro;m）和大（粒径＞19.76 micro;m）3种类型淀粉粒，其粒径范围为0.39―55.14 micro;m。淀粉粒体积和数目都表现为双峰分布，低谷粒径均为3.36 micro;m；其中，粒径＜3.36 micro;m的淀粉粒体积占总体积的9.8%―18.5%，而粒径＜3.36 micro;m的淀粉粒数目占总数目的97.7%―99.1%。与淀粉型品种相比，食用型品种粒径＜3.36 micro;m的淀粉粒所占体积百分比和粒径＜1.00 micro;m的淀粉粒所占数目百分比较高。块根总淀粉、直链淀粉和支链淀粉含量与小型和中型淀粉粒的体积百分比呈显著负相关，与大型淀粉粒的体积百分比呈显著正相关；支/直链淀粉比率与小型和中型淀粉粒的体积百分比呈显著正相关，与大型淀粉粒的体积百分比呈显著负相关。结论食用型甘薯块根中小型淀粉粒所占比例较高，而淀粉型甘薯块根中大型淀粉粒所占比例较高。

English. Objective An experiment was conducted to clarify the starch granule size distribution and the relationship between starch granule size and starch quality properties in storage roots of different types of sweetpotato cultivars. Method Six starchy sweetpotato cultivars, five edible sweetpotato cultivars, and one dual-purpose sweetpotato cultivar were planted at Taian experimental site in Shandong Province, with randomized block design in 2009-2010 growing season. The volume distribution and number distribution of starch granule, and their relationship to the content of total starch and its components in storage root were determined. ResultThe starch granule in storage root was 0.39-55.14 micro;m in diameter, containing smaller type（diameter＜3.36 micro;m）, mid-type（diameter 3.36-19.76 micro;m）and larger type（diameter＞19.76 micro;m）granules. The distribution frequency showed typical two-peak curve in starch granule volume and number, and the grain diameters were all equal to 3.36 micro;m. The volume of smaller type granule accounted for 9.8%-18.5% of the total starch granule, and the number of smaller type granule accounted for 97.7%-99.1% of the total starch granule. The volume percentage of ＜3.36 micro;m starch granule and the number percentage of ＜1.00micro;m starch granule were higher in edible sweetpotato than in starchy sweetpotato. The contents of total starch , amylose and amylopectin were negatively correlated with the volume percentage of smaller type（r=-0.772**, -0.730**, -0.774**）and middling type（r=-0.723**, -0.715**, -0.712**） starch granules, respectively, but positively correlated to larger type（r=0.746**, 0.729**, 0.738**） starch granule. The ratio of amylopectin to amylose was positively correlated with the volume percentage of smaller type（r=0.716**）and middling type（r=0.740**） starch granules, respectively, but negatively correlated to larger type（r=-0.745**） starch granule. ConclusionThe rates of small starch grains in storage root of edible sweetpotato were higher, but the rates of big starch grains in storage root of starchy sweetpotato were higher.