Chinese scientists unlock "longevity genes" in wild rice, paving way for perennial crops

SHANGHAI, March 20 (Xinhua) -- Can rice be planted once and harvested for multiple years, just like fruit trees in an orchard? A groundbreaking study by Chinese scientists may turn this vision into reality, offering significant potential to reduce agricultural costs and promote sustainable development.

A research team from the Center for Excellence in Molecular Plant Sciences (CEMPS) of the Chinese Academy of Sciences (CAS) has identified key genes that determine the perennial growth habit of wild rice and created wild-rice-like plants capable of surviving for at least two years. The study was published in the journal Science on Friday.

Cultivated rice ranks among the world's most important annual food crops. Yet its ancestor, wild rice, persists as a perennial creeping grass. Han Bin, an academician at CAS and one of the leading scientists on the team from CEMPS, studied how wild rice gradually evolved into the annual, upright-growing cultivated varieties during domestication, a long-standing evolutionary puzzle.

The team conducted a systematic analysis of 446 wild rice accessions. They found that, unlike annual cultivated rice, certain wild rice varieties do not senesce and die after seeds mature. Instead, they continuously generate new branches from axillary buds at the nodes. These branches extend and take root upon touching the ground, developing into new plants and exhibiting a clonal perennial growth habit.

To isolate the genes responsible for this perennial habit, the researchers performed genetic analysis using a wild rice strain and an annual indica rice variety. They ultimately pinpointed the genomic region and named it Endless Branches and Tillers 1 (EBT1).

The researchers found that EBT1 comprises two tandemly arranged microRNA genes -- MIR156B and MIR156C.

These genes serve as the "aging switch" in plants. Classical theory holds that these genes are highly active during the juvenile stage and gradually decline as plants age, thereby triggering the transition from vegetative growth to flowering and reproduction, said Wang Jiawei, another key scientist of the team.

Unexpectedly, the researchers found that while MIR156B and MIR156C in wild rice follow this pattern during early growth, they become reactivated in the axillary buds of tiller nodes after flowering, allowing the continued production of new shoots and enabling asexual reproduction and sustained growth.

"During the domestication of cultivated rice, this perennial capacity may have been inadvertently lost as humans selected for higher yields and compact plant architecture," Han said.

By combining EBT1 with two known rice creeping genes, PROG1 and TIG1, the research team created wild-rice-like plants that exhibit strong clonal reproduction capacity and can survive for at least two years in the fields in China's southern island province of Hainan.

Humans domesticated perennial wild rice into annual cultivated rice, which improved the per-season yield but also increased cultivation costs, according to Han.

"If rice could be planted once in suitable locations and harvested multiple times, farmers would save labor and soil erosion would be reduced. Our research provides valuable genetic information and resources for achieving this goal," Han said.

Perennial rice is suitable for sloping farmland and hilly mountainous areas where machinery cannot be used on a large scale, serving as an effective supplement to conventional annual crops and helping ensure China's food security, Han added.