Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2003
Publication Date: 5/1/2004
Citation: Pedersen, J.F., Bean, S., Funnell, D., Graybosch, R.A. 2004. Rapid iodine staining techniques for identifying the waxy phenotype in sorghum grain and waxy genotype in sorghum pollen. Crop Sci.44:765-767. Interpretive Summary: The waxy phenotype in grains is associated with starch containing little or no amylose giving it unique cooking and industrial properties. Visual assessment of sorghum lines with this character is subjective and can be confounded by genetic background, grain maturity, environment, and by the experience of the classifier. It is also limited in application to mature grain. We adapted iodine staining techniques to sorghum grain that allows rapid and accurate identification of waxy lines using pollen or grain. These techniques provide considerable flexibility for sampling in experimental protocols, and when using fresh pollen allow identification of the genetic makeup of individuals prior to making crosses. This will make genetic experiments and germplasm improvement more efficient.
Technical Abstract: Rapid iodine staining methods for identifying the waxy phenotype in mature sorghum grain and waxy genotypes in sorghum pollen were developed. For mature grains, single sorghum seeds were placed in 48-well micro-plates and crushed. Water was added and the mixture heated to 95 °C for 1 hr to gelatinize the starch. After cooling, iodine solution was added and color scored after 10-60 seconds. With this methodology it was possible to stain up to 384 seeds per hour using four micro-plates, thus allowing for very high sample throughput. Sorghum pollen was analyzed for waxy genotype by mixing isolated pollen with iodine solution and viewing under at microscope at 40x. Waxy pollen was visually distinguished from wild-type pollen. This method was found to be effective on freshly collected as well as aged pollen. These methods will allow large scale screening of both mature sorghum grains as well as sorghum pollen for waxy characteristics.