Coimbatore: After a gap of nearly three years, the Tamil Nadu Agricultural University (TNAU) has resumed its efforts to develop naturally coloured cotton varieties that come in shades of brown and green.
Scientists say it would take at least six to seven years to commercially release the varieties as only two trials could be done a year after crossing, as the cotton is a six-month crop.
While they had attempted to develop such a variety back in 2015, the plan was shelved as there wasn’t a huge demand for the coloured cotton, which could contaminate any pure white cotton varieties growing nearby.
However, naturally coloured cotton seems to be the solution to the water pollution caused by dying units, which often let untreated effluents into waterbodies.
With the Nagpur-based Central Institute of Cotton is doing research on coloured cotton and developing cultures that are in pre-release stage, TNAU has also restarted its efforts.
Dr S Geetha, director, Centre for Plant Breeding and Genetics, says there are some naturally occurring varieties of coloured cotton in India. “We are in the process of identifying them, crossing them with stabilized cultivated cotton varieties, and then trying to find the superior coloured variety with good fibre length, strength and micro layer counts.”
It is only the colour gene that scientists are transferring through conventional breeding to cultivated species to improve the quality, colour, stability and yield.
Geetha says they will keep finding natural varieties and crossing them, until they come up with a variety of cotton with a stable amount of colour, high yield and good fibre qualities. “The target is to develop the cotton with enough colour and minimize the requirement for dyeing.”
TNAU too says there are many limitations to cultivating naturally coloured cotton. “First of all, cotton comes only in a few natural colours like shades of brown, green and blue. If you further colour the garments made of naturally coloured cotton fabric with chemical dyes for designs, the point is lost” says Geetha. The fear is that pollen from the coloured cotton might fall onto the white cotton that is cultivated in the vicinity and mate, contaminating the latter’s colour. “At least 99% of the cotton demand is for the pure white, so we can’t afford to get that contaminated. Hence, coloured cotton has to be cultivated on a small, niche and isolated area.”