The recovery of the recurrent parent in upland cotton

Abstract

Breeders have made numerous improvements in upland cotton (Gossypium hirsutum L.) over the past century. The future improvement of yield and quality in upland cotton may rely on greater use of exotic accessions to expand the genetic diversity. The utilization of primitive accessions of Gossypium hirsutum L. has been limited due to their photoperiodic nature, but the release of day-neutral BC₄F₄ lines of these primitive accessions, converted race stocks (CRS), will aid in the investigation and incorporation of variability into modern breeding strains. The primary or initial breeding method used for the introgression of exotic traits from the CRS should be the backcross. Twenty-three populations, each containing a CRS donor parent, TAM 94L-25 recurrent parent, their F₂ generation, and their BC₁F₂ generation were grown in 2000 and 2001. TX0074 was the only CRS to produce average micronaire readings lower than or equal to the recurrent parent in the BC1F2 generation. The upper half mean fiber length of the recurrent parent was recovered in eight BC₁F₂ populations compared to only one F₂ population. There was little variability for short fiber content existing in these CRS/TAM 94L-25 and CRS/*2/TAM 94L-25 populations. Eleven BC₁F₂ populations compared with seven F₂ populations had gin turnout percentages that resembled those of TAM 94L-25. A single backcross resulted in the recovery of six populations with either the same or shorter plant height as TAM 94L-25 while only one F₂ population averaged the plant height of the TAM 94L-25 parent. Seventeen BC₁F₂ populations exhibited the inter-node length of TAM 94L-25 while only two F₂ populations equaled TAM 94L-25 for inter-node length. Broad sense heritability values of 0.50 or higher were observed along with mean values equal to the desirable parent for seven traits, micronaire, fiber bundle strength, fiber uniformity index, fiber bundle elongation, short fiber content, and seed cotton yield, when TX0017 was crossed with TAM 94L-25.