Genetic improvement of rice seed vigour for dry direct-seeded conditions

水稻是发展中国家最重要的主要作物。据估计，亚洲有超过30亿人依靠大米提供30%到75%的卡路里。种植水稻最广泛使用的方法是在苗圃里让种子发芽，然后把幼苗移栽到淹水的稻田里。这种水坑移栽水稻（PTR）方法占全球水稻种植面积的约55%和世界产量的约75%。然而，在南亚和东南亚的许多地区，农民正在转向直接播种水稻（DSR），因为劳动力和水的可用性正在下降，其相关成本正在上升。西非也正在发生类似的转变。要想利用DSR获得好收成，种子必须在土壤中迅速发芽，幼苗必须茁壮成长。然而，由于育种者把重点放在开发PTR品种上，因此对种子活力的选择很少或没有。农学家强调了开发种子活力更好的水稻新品种的必要性，以便它们在干燥的直接播种条件下表现更好。该项目的第一个目标是通过拍摄约1000个不同水稻品种的发芽情况，确定与强活力相关的关键遗传差异，从而确定控制水稻种子活力的基因。这些知识可以被育种者用来培育新品种。该项目的第二个目的是确定是否可以通过提高一种称为中胚轴的特定幼苗组织中植物生长调节剂赤霉素的产生来改善现有的优质半矮秆水稻品种的茎部生长。中胚轴伸长的增加有助于种子在较深的土壤中萌发。这是当前品种的一个关键弱点。

Rice is the most important staple crop in the developing world. It has been estimated that over three billion people in Asia rely on rice to provide 30 to 75% of their calories. The most widely used method for cultivating rice involves germinating the seeds in nurseries and transplanting the seedlings to flooded 'paddy' fields. This puddled transplanted rice (PTR) method accounts for ~55% of global rice cultivation and ~75% of world production. However, in many parts of South and Southeast Asia, farmers are switching to direct seeded rice (DSR) because the availability of labour and water is in decline and their associated costs are rising. A similar transition is also occurring in West Africa. To obtain a good crop using DSR it is imperative that the seeds germinate quickly in the soil and that the seedlings grow vigorously. However, because breeders have focused on developing varieties for PTR there has been little or no selection for seed vigour. Agronomists have highlighted a need for the development of new rice varieties with improved seed vigour so that they perform better in dry direct seeded conditions. The first aim of this project is to identify which genes are responsible for controlling seed vigour in rice by filming the germination of ~1000 different rice varieties that have had their genomes sequenced and identifying the key genetic differences that are associated with strong vigour. This knowledge can be used by breeder to develop new varieties. The second aim of this project is to determine whether the shoot growth of existing elite semi-dwarf rice varieties can be improved by enhancing the production of the plant growth regulator gibberellin in a specific seedling tissue called the mesocotyl. The increase in mesocotyl elongation could help seedlings to emerge from the soil when the seed has been planted at a greater depth. This is a key weakness of current varieties.