Kernel softness in wheat is determined by starch granule bound Puroindoline proteins.

Wheat has a vital position in agriculture because it is a staple food for masses and variation in grain hardness governs its applications. Soft wheats have softer endosperm texture that mills easily, so needs less energy to mill, produces smaller particles, and small amount of starch is damaged after milling as compared to hard wheat. Soft texture results from higher level of friabilin whereas hard texture results from low level of friabilin on starch granule surface. Friabilin, a marker of kernel texture is primarily composed of Puroindolines (PINs) and its genes ( Pins) are located on the Hardness ( Ha) locus. The Pins are the molecular-genetic basis of kernel softness in wheat. When both Pins are in their 'wild state' ( Pina- D1a and Pinb- D1a), wheat kernel is soft. Absence or mutation in one of the Pins results in hard grain texture with different effects on end use and milling qualities. Pina- D1b genotypes gave harder grain texture, higher protein content, water absorption of flour, damaged starch granules and greater flour yield than hard wheat. Recently, other Pins like genes, Pin b variant genes located on the long arm of chromosome 7A were reported in bread wheat with more than 70% similarity to Pinb ( Pinb- D1a) at the DNA level. Other genes located on chromosomes 1A, 2A, 5A, 7A, 5B, 2D and 6D also affect kernel texture. However the main determinants are the variants in the allelic diversity of Puroindoline family genes. Contemporary studies show that Pins are multifunctional family of genes having a range of functions from grain hardness to natural defense against insects and pathogens such as viruses, bacteria and fungi. [ABSTRACT FROM AUTHOR]