Laboratory Exercise on the Segregation of Flower Color and Related Genes Using Velvet Flower (Salpiglossis sinuata Ruiz et Pavon)

Abstract

<jats:p>Velvet flower (<jats:italic>Salpiglossis sinuata</jats:italic>, Solanaceae) can be used as an excellent demonstration plant for horticultural crop breeding classes. Salpiglossis produces large trumpetlike flowers exhibiting an assortment of corolla colors and pigmentation patterns. The pistil is large (3 to 4 cm or 1.2 to 1.6 inches long) with a sticky stigmatal tip and flowers can be easily emasculated prior to anthesis. The large pollen grains are shed in tetrads which can be separated and placed on the stigmatal surface. It takes eight to nine weeks from seeding to blooming, with a prolific flowering cycle that comes in flushes. Numerous seeds (about 750 per capsule) are obtained in three weeks after self- or cross-pollination. The influences of three genes that control flower color and pigmentation pattern can be conveniently demonstrated with their dominant and recessive alleles. The <jats:italic>R</jats:italic> gene controls flower color with red (<jats:italic>RR</jats:italic> or <jats:italic>Rr</jats:italic>) being dominant over yellow (<jats:italic>rr</jats:italic>). The <jats:italic>D</jats:italic> gene controls the density of pigmentation with solid (<jats:italic>DD</jats:italic> or <jats:italic>Dd</jats:italic>) color being dominant over dilute (dd) color. Corolla color striping is controlled by the <jats:italic>St</jats:italic> gene with striped (<jats:italic>stst</jats:italic>) being recessive to nonstriped (<jats:italic>StSt</jats:italic> or <jats:italic>Stst</jats:italic>) pattern. By using diploid lines of genotypes <jats:italic>RRDD</jats:italic> (red, solid), <jats:italic>RRdd</jats:italic> (red, dilute), or <jats:italic>rrdd</jats:italic> (yellow, dilute) and their crosses, students can easily observe a dominant phenotypic expression in the F<jats:sub>1</jats:sub> hybrid and the digenic 9:3:3:1 segregation ratio in the F<jats:sub>2</jats:sub> progeny. Another gene (<jats:italic>C</jats:italic>) that controls flower opening can also be used to show its influence on cleistogamous (closed, selfpollinated, <jats:italic>CC</jats:italic> or <jats:italic>Cc</jats:italic>) versus normal chasmogamous (open-pollinated, <jats:italic>cc</jats:italic>) corolla development. In addition, the induction and use of polyploid (4x) plants in plant breeding can also be demonstrated using this species.</jats:p>