表观直链淀粉含量（Ａｐｐａｒｅｎｔａｍｙｌｏｓｅｃｏｎｔｅｎｔ，ＡＡＣ），是通过稻米直链淀粉和枝链淀粉的长链Ｂ与碘发生显色反应来测定的。决定米饭质地的不是直链淀粉的含量，而是枝链淀粉的长链Ｂ的含量及其性质。在多数品种中，稻米ＡＡＣ主要受控于蜡质基因（ｗｘ）座位上的不同等位基因。在该座位上，根据Ｗｘ蛋白的有无及特性，已发现ｗｘ，Ｗｘａ和Ｗｘｂ３个不同的等位基因；根据Ｗｘ基因ＤＮＡ的微卫星多态性，该位点的等位基因可多达８个。除Ｗｘ座位外，迄今已发现另外１３个基因座位也可影响ＡＡＣ。此外，遗传背景和其它非遗传因素，如开花后２０天内的气温等，对ＡＡＣ也有一定的调节作用。已对Ｗｘ基因进行测序，发现其总核苷酸长度约５．５ｋｂ，由１４个外显子和１３个内含子组成，其成熟ｍＲＮＡ的长度为２．３～２．４ｋｂ。 Apparent amylose content (AAC) is determined by the chromogenic reaction of long chain B amylose and amylopectin with iodine in rice. It is not the amylose content that determines the texture of the rice, but the content and properties of the long chain B of amylopectin. In most varieties, rice AACs are mainly controlled by different alleles at the locus of the waxy gene (wx). At this locus, wx, Wxa and Wxb3 different alleles have been found based on the presence or absence of Wx protein. Based on the microsatellite polymorphism of Wx DNA, the allele at this locus can be up to 8 A In addition to the Wx seats, so far it has been found that an additional 13 loci can also affect AAC. In addition, genetic background and other non-genetic factors, such as air temperature within 20 days after flowering, also have some regulatory effects on AAC. The Wx gene has been sequenced and found to have a total nucleotide length of about 5.5 kb consisting of 14 exons and 13 introns with a length of 2.3-2.4 kb for mature mRNA.