The reason why BC15 rice variety has empty grains

(Baonghean) -This winter-spring crop, thousands of hectares of BC15 rice in Nghe An, Thanh Hoa, Vinh Phuc have suffered from flat grains. On May 21, the Department of Crop Production (Ministry of Agriculture and Rural Development) held a meeting with scientists and localities to find the cause and discuss timely support solutions. The meeting concluded: The reason why BC15 rice has flat grains is because the variety has biological characteristics that are sensitive to unfavorable weather conditions; for more clarity, we introduce the article "Causes of BC 15 rice having flat grains" by engineer Doan Tri Tue.

To find out and clarify the reason why the pure rice variety BC15 supplied by Thai Binh Seed Corporation when planted in Nghe An has flat grains? Meanwhile, other rice varieties are planted and cared for in the same way but do not have flat grains as severely as the BC15 rice variety. I would like to mention 3 very big disadvantages that can easily lead to risks for producers, which are:

- Very susceptible to blast disease in spring crop.

- Very sensitive to low temperatures, poor cold tolerance. Therefore, in the spring crop, if the air temperature is below 180C or lower, newly planted rice seedlings and rice are very susceptible to mass death.

- Rice grains with exposed husks: this is a major drawback that has been passed down from generation to generation and cannot be overcome. Because its origin is from the IR17494 (13/2) rice variety that has been widely cultivated in Nghe An since the late 90s of the 20th century and the early years of the 21st century. Because of this drawback, Nghe An farmers often call it cracked rice or chapped rice. After harvesting, rice grains are dried, and no matter how well preserved, they are still eaten by weevils.

So what is the basic cause of BC15 rice variety having many empty grains?

Most of the BC15 rice varieties that bloomed from April 23 to 28 had a rate of 60 - 70% of the grains being empty. Similar to BC15 rice, but blooming earlier, the average yield was 70 - 75 quintals/ha and blooming from April 23 to 28, but other rice varieties did not have this problem. Of the 3 major disadvantages mentioned above, 2 have contributed to the cause of many empty grains in the spring crop this year, which are:

BC15 rice variety is inherently a very cold-resistant variety compared to all other pure rice varieties currently cultivated in Vietnam. Most of the BC15 rice area that bloomed on April 23-28 had 60-70% grain loss. In terms of the time of blooming, the average air temperature was 27.10C, the average maximum air temperature was 31.20C and the average minimum air temperature was 24.60C. Such air temperature did not affect the blooming of the rice at all. However, looking back at the time before the blooming of the rice, it can be seen that: On April 7-14, 2013, there were continuous cold air waves, causing the air temperature to drop below 17 and 180C, and on April 12, 2013, the air temperature dropped (below 170C). This is the period coinciding with the stage of panicle differentiation of BC15 rice variety, the area that was severely damaged. With BC15 rice variety in the panicle differentiation stage, if the air temperature drops to 200C or lower, the entire process of rice flower development will be greatly affected, the stamens will be short - small and shriveled, pollen grains will degenerate, vitality will be reduced...

Therefore, when the rice is done blooming, we will see many empty grains on the rice panicle, the end of the rice panicle is severely degenerated, unable to form rice grains.

The reason why the entire rice field, the entire BC15 rice field, was 60 - 70% flat, was because during the flowering period, there was heavy rain and strong winds. Other rice varieties did not fail, only the BC15 rice variety suffered a heavy loss because this rice variety's two husks could not close.

For rice plants when flowering, if they encounter unfavorable weather conditions such as: severe cold, cloudy, lack of light, strong rain and wind, too much sun, too high air temperature... then the two rice husks of the rice flower will close themselves to protect the stamens and anthers. But in the BC15 rice variety, both rice husks will still close but not tightly. Therefore, when encountering heavy rain and strong wind, the stamens and pollen will be partly washed away by the rainwater, and partly blown away by strong wind. According to hydrometeorological observation data, on April 24 and 26, 2013, in the Dien - Yen - Quynh area, there were 2 heavy rains and strong winds (in Quynh Luu, the measured rainfall was 43.7mm and 86mm) right at the time when the BC15 rice variety was severely damaged, flowering and pollinating. The remaining rice fields that flowered before or after the above mentioned time still gave normal high rice yields.

From the above monitoring, analysis and evaluation results, it can be affirmed that the reason why BC15 rice in this year's spring crop has a high rate of flat rice, in some places up to 60 - 70% is not due to poor seed quality but mainly due to unfavorable weather conditions at the stage of rice differentiation at stages 5 and 6 and the stage of flowering and drying of the ears as mentioned above.

Doan Tri Tue