Scientists believe that the phenomenon of wild rice may be due to genetic degeneration, the presence of wild rice species, and agricultural practices.
In mid-June, as the summer rice harvest is nearing completion, the fields in Thanh Liêm District, Hà Nam Province still have many plots that have not been harvested. According to local reports, this area has been affected by wild rice (also known as grass rice), which means that after 5-6 months of sowing, there is virtually no harvest.
Mrs. Trịnh Thị Loan, from Thanh Hà commune, uprooting wild rice in an unharvestable field. (Photo: Phạm Chiểu)
Explaining the wild rice phenomenon, Professor Võ Tòng Xuân, a scientist in agriculture and currently the honorary rector of Nam Can Tho University, stated that wild rice fields are not a rare occurrence. In the South, this phenomenon has previously appeared in the Đồng Tháp Mười area. This type of rice can grow up to 2 meters high, primarily consisting of Oryza rufipogon (with long grains) and Oryza officinalis (with round grains). The yield of this rice is low, with 1 hectare of wild rice typically producing only 800-900 kg, while high-yield rice varieties can achieve at least 5 tons per hectare.
According to Professor Xuân, wild rice does not reproduce by seeds, but rather from tubers (roots) or rice nodes. When this type of rice falls to the ground, new rice nodes will sprout and continue to grow year after year.
He noted that in Hà Nam, the appearance of wild rice can be explained by the growth of a new type of grass, with seeds that fell to the fields from the previous season, which the locals are unaware of. In the new season, during the plowing process, seeds buried deep in the soil are pushed to the surface, leading to the emergence of wild rice. He explained that these fallen seeds can survive in the soil for a long time, approximately 2-3 years after plowing.
Agreeing with this perspective, Professor Trần Duy Quý, former director of the Agricultural Genetics Institute and the “father” of many rice varieties for Vietnamese farmers, believes that the reason wild rice is referred to as “ghost rice” is due to the appearance of different rice plants that grow taller than regular rice.
Professor Quý stated that in the past, our ancestors would plow deeply and carefully, allowing the fields to be flooded for several months (from May-June until the end of July) so that all the straw roots would decompose, and previous season’s seeds would rot. Nowadays, farmers mainly cultivate short-duration varieties, replanting about ten days after harvest. Meanwhile, wild rice varieties can survive in the soil for a long time, with strong vitality, making them easier to sprout again.
He also emphasized the importance of seed selection. According to him, the seed production companies’ lack of proper filtration leads to genetic degeneration and mixing with wild rice varieties. Another reason is the use of harvesting machines, which causes 3-5% of seeds from the previous season to scatter, mixing with seeds from the next season, resulting in uneven growth.
Professor Nguyễn Thị Lang, director of the High-Tech Agricultural Research Institute of the Mekong Delta, believes that the rice appearing in Hà Nam is grass rice. Grass rice is very prone to shedding, with long, bearded grains, and sometimes red or black grains, resembling improved cultivated rice. This type of rice matures earlier and has beards, making it easy to confuse with wild rice.
Explaining the emergence of grass rice in Hà Nam, Professor Lang noted that from 2000 to 2010, researchers indicated that the appearance of grass rice was due to the hybridization between wild rice and improved varieties grown locally.
“Wild rice travels along water channels and crosses with improved rice over the years, leading to hybridization,” she said, adding that old varieties used for many years without purebred seeds will confirm that they have hybridized. “Hybrid varieties can proliferate rapidly from just one seed.”
Grass rice is common in many countries such as Malaysia, Indonesia, Cambodia, Laos, and Vietnam.
Need to eradicate it completely
Wild rice growing interspersed with regular rice. (Video: Phạm Chiểu)
Because wild rice has long stems and many nodes, each node buried underground can survive for a long time, continuing to sprout when the seeds mature, it is necessary to remove both the roots and rice nodes. Professor Võ Tòng Xuân suggested uprooting wild rice clumps to compare them with regular rice, to determine if the rice developed from fallen seeds or connected together, in order to accurately analyze the quantity and reasons for the emergence of grass rice. To eliminate this phenomenon, farmers should select and cut wild rice, uproot it completely, burn it, and also deal with the wild grass. “Once the fields are clean, normal rice can be harvested; this is the best method,” Professor Xuân stated, adding that thorough plowing is necessary to remove all roots and repeatedly kill this type of grass rice.
Professor Quý warned farmers against purchasing unverified seeds. He also suggested that thorough plowing should be done, using microbial preparations to decompose straw roots quickly and clean up all fallen seeds from the previous season.
Although wild rice has a low yield, experts believe that the genetic traits of wild rice can still be utilized to breed new varieties. Professor Xuân noted that wild rice possesses genes that are resistant to both drought and flooding conditions very well. This species has the dual characteristics of being resistant to drought and flooding. It can withstand acidic conditions, thriving in dry, acidic soils, while during the rainy season, as water rises, wild rice grows higher. “This is a valuable genetic trait that can be harnessed,” Professor Xuân said.
According to Professor Xuân, wild rice is currently difficult to find, mostly seen along canal banks, while it is virtually absent in large commercial fields. “Part of the reason is that the soil has been ‘domesticated’ due to plowing and planting short-duration rice, which has eradicated most types of grass,” he stated.
