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Agronomic Potential of Nectariless Cotton¹

ABSTRACT

We compared three BC₆F₄ nectariless strains of cotton (Gossypium hirsutum L.) with their recurrent parent varieties for yield, yield components, and fiber properties at six environments in 1971. A slight decrease (4.3%) in yield for nectariless ‘Stoneville 7A’ and a slight increase (3.8%) in yield for nectariless ‘Deltapine Smooth Leaf’ was detected. Nectaried and nectariless ‘Dixie King’ did not differ in yield. Nectariless strains, especially Deltapine Smooth Leaf tended to mature earlier. Slight but inconsistent differences in yield components of nectariless and nectaried strains were detected. Nectariless cottons tended to have shorter fibers.

Significant genetic variability within BC₆F₃ nectariless populations of Stoneville 7A was detected, indicating that we were not working with isogenic nectariless varieties. Selection within BC₅ nectariless Stoneville 7A resulted in yield improvement equal to that of nectaried Stoneville 7A. Fiber properties between nectaried and nectariless strains were essentially the same.

The nectariless trait reduced boll rot. While the results from large field test were inconclusive, there were fewer tarnished plant bugs, fleahoppers, and less bollworm damage in nectariless cotton. Two predatory insects, lady beetles and big-eyed bugs, were not affected by the presence or absence of nectaries.

We detected no strong deleterious associations of nectariless and agronomic performance. This trait appears to have a good potential for insect and boll rot suppression in the Mississippi Delta.

Key Words: biological control • variety improvement • selection • backcross breeding • boll rot • bollworms • lady beetles • big-eyed bugs

¹ Contribution from the Plant Science Research Division, ARS, USDA, and the Delta Branch of the Mississippi Agr. and Forest. Exp. Sta., Stoneville. 38776. Published as Journal Paper 2325 of the Mississippi Agr. and Forest. Exp. Sta.

² Research Geneticist, Research Plant Pathologist, Plant Science Research Div., ARS, USDA, Stoneville, Miss., and Beltsville, Md.; and Entomologist, and Plant Breeder, Delta Branch of the Mississippi Agr. and Forest. Exp. Sta., respectively, Stoneville, Miss. 38776.

Received for publication March 30, 1972.