Prelims – Current events of national and international importance | Science & Technology.
Why in News?
Recently, scientists in China discovered a gene that helps prevent rice grains from breaking during milling.
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Layers of Rice
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- Husk – The outermost layer of the rice that has to be removed.
- Bran – It is inside of husk that is also removed to whiten the rice.
- Removal of layers – Traditionally, these were removed by pounding the paddy rice with grinders in a mortar, then winnowing the grains from the chaff.
- Currently, mechanical rollers graze the layers by a process called milling.
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- Chalkiness – It is a trait found in rice grains that significantly increases breakage during milling.
- Chalky grain rate – It is measured by the proportion of chalky grains among all rice grains and the degree of chalkiness, which reflects the extent of chalkiness in them.
- Properties – Chalky rice grains have an opaque appearance after milling and a brittle structure, which leads to higher breakage during milling.
- Determinants – Chalkiness in rice varieties is influenced by many genes and by environmental factors like high temperature and nutrient availability.
- Small stretch DNA on chromosome 9
- If present - Strongly associated with low chalkiness
- If absent – It is associated with high chalkiness.
- Low-chalkiness varieties showed higher expression of Chalk9 in endosperms compared to high-chalkiness varieties.
The endosperm is the part of the paddy grain that makes up the bulk of the milled rice.
- Impact - Higher chalkiness leads to more breakage during milling, reduces the yield and affects rice quality.
- It disappears during cooking and does not affect the taste & aroma.
- Modern breeding technique – It has selected for the low-chalkiness version (Chalk9-L), improving rice quality over time.
- Breeders can directly introduce the Chalk9-L variant into high-chalkiness varieties to reduce breakage and enhance grain quality.
Reference
The Hindu| Chalkiness in Rice
