Glandless seed and glanded plant research in cotton. A review

Recently the world has been entangled by insufficient food such as the lack of rice which threatens the safety of world food and affect sustainable development of the world economy, resulting in rising of food price. To address this issue, cotton appears as a possible source of both fiber and food. The research in recent years indeed showed bright prospects for this expectation. However, gossypol stored in the glands of cotton is toxic to nonruminant animals and humans, which wastes large amounts of cottonseed protein that could potentially provide the annual protein requirements for half a billion people. Gossypium species are characterized by their lysigenous glands containing terpenoid aldehydes, important secondary phytoalexins consisting mainly of gossypol, which constitute one of the important plant's defense system against pests and diseases. The best approach to address this issue is to create glandless seed and glanded plant cotton. A breakthrough in this field would realise the fulfilment of making cotton both a fiber and a food crop, which would be a feat of great magnitude for sustainable development of agriculture. Research on the relationship between glands and their secondary inclusions at the molecular level would be one approach for genetic engineering to control the glands and gossypol content. In this article, we review recent progress on glands and gossypol content for diverse gland types in Gossypium species, inheritance of glands and gossypol content, traditional breeding of glandless seeds and glanded plant cotton, the terpenoid aldehyde biosynthesis pathway, molecular cloning of the related genes, the strategy for genetic engineering, and future prospects.