Shorter stature, stronger future– windproof corn takes root
mutation that reduces the amount of the growth hormone auxin in the stalks. In other studies, researchers focused on gibberellin, anoth- er plant growth hormone. Knocking out the gene in the whole plant results in deformed flowers and ears. Using microRNA to suppress two genes that produce gibberellin, mainly in the
Decades ago, wheat and rice production was dramatically increased by forcing the plants to grow shorter. Short plants spend less energy growing stalks and can be planted more densely. Both mean more grain production per hectare planted. Corn, however, is still a tall crop, growing as tall as 4 meters. For years, breeders selected for stiffer stalks to resist rot and larger leaves, which produce oversized, more starchy ears of corn. Along with those traits came increased height. Tall plants are vulnerable to breaking in high winds. A single 2020 wind storm in the U.S. Corn Belt cost an estimated 12 billion dollars in losses to corn growers. Field trials indicate shorter plants can withstand high winds without sacrificing corn production. Shorter plants have agro- nomic benefits such as less need for anti-fungal treatments, and they thrive with later and fewer fertilizer applications. Two major seed producers, Bayer ® and Corteva ® , are working to produce short-stature corn. Using genetic analysis of seedings, breeders are speeding the rate of traditional cross-breeding. Bred spe- cifically for growers in Mexico, researchers select plants with a
leaves and stalks, produces short plants, but leaf loss reduces crop yields. To avoid this, researchers added a genetic switch from a rice virus to make the inserted genes only active in the stalk. Genetically engineered short corn is currently in field trials in the U.S. and being reviewed by the USDA. Research fo- cusing on gene editing to alter the gibber- ellin pathway is also underway. Since gene editing does not add genes, corn produced this way may face fewer regulatory hur- dles. Long an aspirational goal, short corn seems closer to wide-scale production. n
REFERENCE: Kosola, K.R., et al. Short-stature and tall maize hybrids have a similar yield response to split-rate vs. pre-plant N applications, but differ in biomass and nitrogen partitioning. Field Crops Research (2023) 295: 108880. doi.org/10.1016/j.fcr.2023.108880
Carbon capture with genetically modified trees A biotech company, Living Carbon ® , produced genetically modified poplar trees to cap- ture atmospheric carbon. The modified trees grow faster and produce more biomass in green- house experiments. They have three genes inserted, including
one from pumpkin and one from green algae. Their increased growth is due to increasing the efficiency of photosynthesis and reducing photorespiration. During photosynthesis, plants produce sugars but also a toxic byproduct, phosphoglycerate, that must be broken down, wasting energy from photosynthe- sis. Under increased temperature, more phosphoglycerate forms, reducing unmodified trees' efficiency as carbon capture tools. The genetically engineered poplars include a bypass pathway that blocks the movement of carbon dioxide out of chloroplasts, storing it for future use. Planted on private land, the modified poplars grow 53% larger and capture 23% more carbon dioxide than their unmodified counterparts. The roots absorb metals from soils, meaning they can thrive in contaminated soils and will decay more slowly. The company hopes to plant up to 5 million trees by 2025, which could remove up to 600 megatons of carbon from the atmosphere. That amount is equivalent to removing 133 million gas-powered cars. As promising as these results are, the genetically-
modified trees still face challenges. The company avoided many regulations surrounding vector-based genetic engi- neering by using an older technology so they won't produce pollen. Other genetically modified trees, such as apple or American chestnut, have spent years in regulatory review, while Living Carbon has moved from greenhouse to field trials in less than three years. This speed alarmed some forest conservation groups. To address these con- cerns, the company is planting only female trees. n
REFERENCE: Tao, Y. et al. Enhanced Photosynthetic Efficiency for Increased Carbon Assimilation and Woody Biomass Production in Engineered Hybrid Poplar. Forests (2023) 14, 827. doi.org/10.3390/f14040827
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