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BY JULIO P. YAP JR.
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BASED on a recent study conducted by a team of Philippine Rice Research Institute’s (PhilRice’s) weed science researchers, it apparently appears that the growth and development of weedy rice are higher than cultivated rice.
They found out that it also matures earlier than cultivated rice, and its seedlings can survive even when subjected to adverse environmental conditions.
It was learned that weedy rice (WR) is a type of a grain-bearing weed.
It is also considered as pest, which would eventually result to lower rice yields, affects quality of rice produce, and an alternate host office insects, diseases, and nematodes.
According to Edwin C. Martin, the leader of the team of researchers, it is a product of a natural cross between wild and cultivated species of rice, and it is common in direct-seeded rice system.
He says that this type of rice competes with cultivated rice varieties in terms of sunlight, nutrients, water, and growth space.
Because of these, farmers in direct-seeded areas are more prone to this kind of infestation.
During the 2016 dry season for instance, the team surveyed different ricefields in North Cotabato, Maguindanao, and Sultan Kudarat for possible occurrence of weedy rice.
It was learned that one of the sampling sites in Isulan, Sultan Kudarat, recorded an average of 15 weedy rice panicles per square meter (sqm), the highest across all sites.
Technically, it is said that 15 panicles/sqm means moderate infestation with approximately 70 to 80 percent yield loss.
On the same year during the wet season (WS), ricefields in Koronadal City, South Cotabato, had the most number of weedy rice recorded with about 23 panicles per square meter.
To compare the seed germination rate of weedy rice with a registered rice variety, the researchers incubated the NSIC Rc222 and 21 biotypes of weedy rice seeds that were collected during the 2016 wet season from Central Mindanao.
On the first day after incubation (DAI), results showed that the germination rate of Rc222, which was computed to be 93.33 percent, was the highest compared with other samples.
However, after three DAI, all weedy rice types are recorded to be at 100 percent germination rate, surpassing Rc 222’s germination rate.
The researchers emphasized that in direct-seeded rice, the difference between cultivated rice and WR cannot be distinguished during the vegetative stage as they are quite identical.
They said that the difference becomes obvious during the reproductive stage.
In terms of fertilizers and other inputs, WR competes heavily with cultivated rice during the vegetative stage.
During the reproductive and maturity stages, it can also cause contamination of the seeds if harvested and threshed with cultivated rice.
Because of these findings, the team plans to continue the field surveys to further identify fields with weedy rice because most farmers are not yet aware about the existence of the WR.
They are also planning to conduct molecular characterization of WR to further differentiate weedy rice from cultivated rice in terms of molecular structure/composition or for any other similarities or differences. (jaypeeyap@ymail.com)/PN
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