Evaluating the potential of new testing methods for cotton (Gossypium hirsutum L.) breeding

Rapid and precise measurements of cotton fiber quality are necessary to be able to breed for these essential traits. Fiber qualities like maturity, fineness, length distribution, and short fiber content have a large impact on processing performances and yarn quality but they are not used in the current classification system due to higher variability in their measurement and/or unavailability of instruments to measure these properties accurately and rapidly. Processed cottons have lower amount of within sample variability than raw cotton and require fewer replications than raw cotton to obtain accurate results. Sampling protocols need to be adjusted according to the type of sample being tested. High Volume Instruments (HVI) and Advanced Fiber Information System (AFIS), widely used to determine fiber properties, base their length by weight calculations on the assumption that fiber fineness is constant across length groups within a sample. Our experiments show that fiber fineness and maturity vary across length groups within a sample. Generally, shorter fibers are finer and more immature than longer fibers. The assumption of constant linear density across length groups within a sample leads to an over-estimation of short fiber content by weight. Use of the short fiber content measurement is limited due to its high within sample variability. Transformation of short fiber content could give more reliable and sensitive estimates. The lack of a rapid and accurate measurement of maturity limits the use of maturity for screening in a breeding program. Two instruments that measure maturity, namely the AFIS and the cottonscope, are compared to the reference method to establish their accuracy and assess their performance. The cottonscope gives a relatively rapid and accurate measurement of the maturity of cotton fibers. This could enable the breeding community to screen for maturity.