Researchers crossed high strength female cotton lines with Bt bollworm-resistant male lines to study their combining ability and heterosis. They found significant variances for seed cotton yield, lint yield, boll number, boll weight, lint percentage, fiber strength, and other traits. The hybrids showed significant heterosis for yield, fiber quality, and other characteristics compared to common varieties. Overall, the hybrids exhibited improvements in lint yield, fiber strength, fiber length, and fineness.