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Effects of Seed Density on Stand, Verticillium Wilt, and Seed and Fiber Characters of Cotton¹

Rapid germination and emergence and vigorous seedling growth enhance the opportunities for profitable production of cotton (Gossypium hirsutum L.). Within seed lot, the heavier, more dense seed are most likely to exhibit these traits. In 1976, acid-delinted, gravity-graded seed of ‘Paymaster 909’ and ‘Tamcot SP37’ were separated into four density classes by a liquid separation process. These classes were: D1 = very low density (floaters); D2 = low density; D3 = medium density; and D4 = high density. Seed with cracked coats were included in the D4 class. Commercially gravity-graded (DG) seed of each cultivar were used as standards. All samples were treated with carboxin-captafol {(5,6-dihydro-2-methyl-1, 4-oxathiin- 3-carboxanilide plus cis.N.[(l,l,2,2-tetrachloroethyl) thio]-4.cyclohexene-l,2-dicarboximide)} 2-2 F SP (2 lbs. of each fungicide as aflowable seed protectant) at g/kg of seed. Enough seeds of each class were obtained to conduct tests for 2 years. The Paymaster 909 select seed were representative of the type commonly planted by area farmers. Tamcot SP37 seed were obtained from a planting of registered seed that failed to mature properly and consequently failed to meet germination reqmrements for certification in Texas. Seed index, germination, and stand were highest and the prevalence of Verticillinm wilt (caused by Verticillium dahliae Kleb.) was lowest in plants from D3 seed, but plants from D2 seed performed almost as well. The poorest overall performance was shown by plants from D1 seed, whereas the performance of plants from D4 seed lots equaled or slightly exceeded that of plants from DG seed. The liquid seed-separation process may enable seed proeessors to isolate seed for significantly improved germination, seedling survival, and lint yield, and reduced prevalence of Verticillium wilt. The liquid separation process may be used in breeding and seed-increase programs to select high-quallty planting seed for performance evaluations. The process also may be used to isolate seed of acceptable quality for planting from seed that fail to meet quality standards after commercial gravity grading. Seed index may be used to select density classes for planting seed.

Key Words: Seedling diseases • Seed Index • Seed processing • Plant vigor • Seed quality • Gossypium hirsutum L. • Verticillium dahliae Kleb

² Plant pathologist, AR, SEA, USDA, and area agronomistcotton, Texas Agric. Ext. Serv., Route 3, Lubbock, TX 79401. Present address of the first author: Cotton Physiology and Genetics Laboratory, P. O. Box 225, Stoneville, MS 38776.

Received for publication October 1, 1979.