Some sources of variation in sampling plants of 16B7 strain of cotton for proportion of impermeable seed

A heritable impermeable seed characteristic that restricts water imbibition is present in the 16B7 strain of cotton (Gossypium hirsute L.). Studies have shown that this characteristic is valuable in preserving cottonseed viability (1, 2, 3, 4). Preservation of cottonseed viability has long been a problem. Moisture content of permeable cotton seeds readily fluctuates with changes in relative humidity of the atmosphere. In permeable seeds a high level of moisture supporting a rapid and irreversible loss of viability can be attained in a few hours (4). Christiansen, Moore, and Rhyne (4, p. 81) stated: "In hard seeded types, an impermeable coat restricts water movement into embryos during periods of high atmospheric humidity thus permitting embryos to be maintained at earlier established low moisture contents that are favorable for preservation of seed quality." Germination studies involving samples of 16B7 grown at Knoxville in 1965 showed considerable variation in impermeable seed content. In one germination experiment seeds from bolls produced early in the blooming period were higher in impermeable seed content than seeds from bolls produced later. In another preliminary experiment seeds from self pollinated bolls were higher in impermeable seed content than seeds from open pollinated bolls. This difference in seed coat permeability was thought to be due to metaxenia, the effect of pollen on tissues of the mother plant other than embryo and endosperm. The objectives of this study were; 1. To determine the effect of metaxenia on seed coat permeability, 2. To determine the effect of time of development on the impermeable seed content of self pollinated bolls, 3. To study possible genetic sources of variation among progenies, subprogenies, and Individual plants of 16B7 cotton, and 4. To develop techniques for identifying impermeable seeded plants and maintaining the maximum potential impermeable seed content in samples after harvest.