Colchicine mutagenesis is associated with substantial heritable variation in cotton

Summary

Seedlings of the cotton cultivar Sicot 1 were treated with either 1%, 2% or 5% colchicine in lanolin which was topically applied to the apical meristem four days after emergence. Of 293 1%-treated seedlings 64 survived to produce fertile C₁ shoots which gave rise to 84 C₂ single boll families. C₂ and C₃ generations were examined in field experiments for morphological variants and for a number of quantitative characters (yield components and fibre quality). No morphological mutants were seen but considerable heritable variation for metrical characters of economic importance was detected. Of 18 extreme C₂ families consisting of 54 C₃ progenies, 19 were shown in a replicated spaced-plant trial to be significantly different to the Sicot 1 parental material for at least one (usually more) characters. The 222 C₃ progenies of the 66 non-extreme C₂ families were tested in an unreplicated plot experiment and at least 14 were suspected of exhibiting variation in metrical characters. Although no light has been shed on the mechanism responsible for the production of variants by this method, it is argued that the colchicine technique results in higher levels of genetic variation than found in commercial cultivars; variation which can be readily exploited by cotton breeders.