Alkaline-tolerance gene identified to improve crop yields on sodic land
A collaborative research team in China found a key gene in a crop that might, via genetic engineering, substantially improve crop yields in alkaline soil.
The study, published on Friday in the journal Science, described the breakthrough in agriculture that could increase the production of crops, including rice and maize, by at least 250 million tons should the newly-identified gene be applied to 20 percent of global under-utilized saline and alkaline soil.
More than 1 billion hectares of saline and alkaline areas globally are cultivation-unfriendly. What is worse, global arable land is expected to become saltier owing to climate change, declines in freshwater availability, and the use of chemical fertilizers.
To cope with the challenge, agriculturalists have made progress in examining plants that could tolerate salty soil with a neutral pH value.
But plant tolerance in alkaline soils with higher pH levels and dominated by sodium carbonate and sodium bicarbonate salts are less known. The alkalinity in soil inhibits a plant's ability to take in nutrients and manage salt stress.
The researchers, led by those from the Institute of Genetics and Developmental Biology under the Chinese Academy of Sciences, China Agricultural University, and Huazhong Agricultural University, investigated the sorghum originally grown in barren African soil instead of the Arabidopsis thaliana, a frequently-used model plant grown in non-alkaline areas.
Sorghum has evolved greater tolerance to multiple abiotic stresses, and can even survive in a sodic soil with a pH of up to 10.0, according to the researchers.
They performed a genome-wide association study in a diverse sorghum panel and identified a vital genetic locus called Alkaline tolerance 1 (AT1), linked with the plant's sensitivity to alkaline soils.
The gene can encode a guanine nucleotide-binding protein's subunit and thus controls alkaline tolerance, said the study.
They clarified the molecular mechanism of such tolerance, finding that the signaling of this protein may regulate the activity of aquaporins called PIP2s, downstream molecules that allow the passage of water transport across the cell membrane.
Then those aquaporins lead to decreased reactive oxygen species levels in plants, thus alleviating the oxidative stress in alkaline soils.
The discovery is valuable since the very mechanism also plays a part in monocot crops like sorghum, rice, wheat, maize, and millet. In rice, the gene was named GS3.
Since the overexpression of the AT1 protein resulted in higher sensitivity to alkaline stress, a gene knockout of it in sorghum and its homologs in rice, maize, and millet increases the plant's alkaline tolerance.
At field trials in northwest China's Ningxia Hui Autonomous Region and northeastern Jilin Province, the team experimentally planted these genetically-modified species in saline and alkaline soils with a pH value of more than nine.
The sorghum's annual yields grew by 20.1 percent, millet by 19.5 percent, and rice by 22.4 to 27.8 percent, and the knockout of the AT1 gene could significantly improve the maize's survival rate, according to the study.
The findings have great potential for guiding the breeding of alkaline salt-tolerant crops and could improve global food security, said the paper's corresponding author Xie Qi from the Institute of Genetics and Developmental Biology.