Chalkiness in Rice

Why in News?

Recently, scientists in China discovered a gene that helps prevent rice grains from breaking during milling.

• 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