Introgression of day-neutral genes in primitive cotton accessions: I. Genetic variances and correlations

Many of the primitive accessions of cotton, Gossypium hirsutum L., are phot operiodic and not readily useable by plant breeders. Five generations of da y-neutral progenies (F-5, BC1F5, BC2F5, BC3F5, and BC4F5) derived from 16 a ccessions crossed to 'Deltapine 16' were evaluated for agronomic and fiber traits for 3 yr. Genetic variance components for each trait and correlation among these traits were studied. variation of accession generation was hig hly significant for all traits studied. Main effects for accessions and gen erations were significant; however, the magnitude was relatively small comp ared with the interaction variation. The breeding merit of day-neutral prog enies should be evaluated according to specific accessions. Lint yield had significant but small positive phenotypic correlation with lint percentage, boil size, and 2.5% span length, but not with the other traits studied. Hi ghly significant positive correlations were found for effects of accession, generation, and accession x generation between lint yield and lint percent age. With the use of multiple backcrosses to introgress day-neutral genes i n primitive cotton accessions large interaction can be expected between acc ession and backcross generation; therefore, specific generations should be evaluated for the trait of interest.