Background

Awns are bristle-like organs at the tips of the glumes. Wild rice has maintained long awns for successful seed propagation through seed dispersal. Seed awning is an interesting trait in rice domestication. Long awns might have been beneficial for seed gatherers in the initial phase of domestication; however, awnless phenotypes were preferably selected in a later phase with non-seed-shattering plants. Investigation of domestication loci associated with awnlessness in cultivated rice will be useful in clarifying the process and history of rice domestication.

Results

Quantitative trait locus (QTL) analysis for seed awning was carried out using a BC₃F₂ population between Oryza sativa IR36 (a cultivated donor parent with awnless phenotype) and O. rufipogon W630 (a wild recurrent parent with awns). As a result, two QTLs on chromosome 4 (corresponding to An-1 and LABA1) and one on chromosome 2 (designated as qAWNL2) were detected. Gene interaction among three seed-awning QTLs were further examined with the plants having eight different combinations of homozygous genotypes. Their awn length variation indicated that the IR36 alleles at these loci had the additive awnlessness effects in the genetic background of wild rice. The shortest awn length was observed for the plants having IR36 homozygous alleles at all loci, giving about 75% reduction in awn length. By the fine mapping, the candidate region of the novel qAWNL2 locus was delimited in a 157.4-kb region containing 22 predicted genes in Nipponbare genome.

Conclusions

QTL analysis revealed that three loci, An-1, LABA1 and qAWNL2, were mainly responsible for the awnlessness of O. sativa IR36. In the wild genetic background, loss-of-function alleles at three awning loci showed additive effects on length reduction. In rice domestication, awnless forms may be gradually generated through the accumulation of mutations at awning loci.

中文翻译：

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稻米栽培中与失芒相关的驯化位点评估

背景

檐篷是刚毛顶端的硬毛状器官。野生稻保持着长芒，通过种子传播成功地繁殖了种子。种子遮篷是水稻驯化中一个有趣的特征。在驯化的初期，长芒可能对种子采集者有利。但是，最好在不播种种子的植物的后期选择无芒表型。调查与栽培稻无芒相关的驯化位点将有助于弄清水稻驯化的过程和历史。

结果

数量性状基因座（QTL）分析用于种子雨篷进行使用BC ₃ ˚F ₂之间人口稻IR36（一个栽培供体亲本与无芒表型）和野生稻W630（野生轮回亲本与芒）。结果，在染色体4上有两个QTL（对应于An-1和LABA1），在染色体2上有一个QTL （称为qAWNL2））被检测到。具有八种不同纯合基因型组合的植物进一步检查了三个种子棚QTL之间的基因相互作用。它们的芒长度变化表明，这些基因座的IR36等位基因在野生稻的遗传背景中具有附加的无芒效应。对于在所有位点具有IR36纯合等位基因的植物，观察到最短的芒长，使芒长减少约75％。通过精细定位，新的qAWNL2基因座的候选区域被划分为157.4kb区域，该区域包含日本晴基因组中的22个预测基因。

结论

QTL分析表明，三个基因座An-1，LABA1和qAWNL2主要负责水稻IR36的无芒。在野生遗传背景中，三个遮阳篷位点的功能缺失等位基因显示出对长度减少的累加效应。在水稻驯化中，可通过在遮篷位点积累突变来逐渐生成无篷形式。