Improvement of crops requires genetic variability. Sources may extend from wild or exotic species to varieties commonly grown by farmers. Primitive race stock accessions of cotton, Gossypium hirsutum L. contain genetic diversity, but many are photoperiodic. A program has been in progress for a number of years to incorporate day-neutral genes in the primitive accessions. Seventy-nine accessions with the day-neutral flowering habit have progressed through the program.

The day-neutral backcross four progenies have been evaluated for agronomic and fiber traits. Day-neutral lines had more main stem nodes, were taller and the node of the first fruiting branch in 50% of the lines was significantly higher than cultivars. Lint percentage for most of the day-neutral lines was in the mid to low 30's; however, a few were near the cultivars. Two of the day-neutral lines had larger bolls than did the cultivars. Seed size of most day-neutral lines was equal to the cultivars. Seed gossypol level was in the same range as in cultivars; however, cultivars generally had a higher tannin level in seed. Several day-neutral lines had greater fiber strength than Delta cultivars. The micronaire tended to be equal to or higher than cultivars. Most of the day-neutral lines had short fibers while fiber elongation was similar to cultivars. Useful variability was measured for several agronomic and fiber traits and is available to expand genetic diversity of cotton.