Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 1/27/2003
Publication Date: 2/1/2003
Citation: Gealy, D.R., Yan, W., Rutger, J.N. 2003. PHENOTYPIC AND GENOTYPIC CHARACTERISTICS OF HAND-CROSSED MALE STERILE RICE X RED RICE HYBRIDS IN THE SOUTHERN U.S.. Proceedings of Southern Weed Science Society. 56:185. Interpretive Summary:
Technical Abstract: Concerns over the consequences of outcrossing between rice and red rice in the U.S. have increased in recent years with the development of herbicide resistant rice cultivars. In this study we investigated the phenotypic characteristics of parental, F1 and F2 populations resulting from hand crossed hybrids between non-resistant rice (female) and non-resistant red rice (male). The rice parents were Kaybonnet-1789 (dominant male sterile) and Cypress-1819 (recessive male sterile), and produced glabrous leaves, long-grain, white seeds, and few tillers. The red rice parents were StgS (strawhull, awnless, early flowering) and LA3 (straw-brownhull, awned, late flowering), and produced pubescent leaves, medium-grain, red seeds, and many tillers. F1 and F2 hybrids and parental plants were planted in a greenhouse in Stuttgart, AR in early June 2002, and later transplanted to the field. All F1 plants produced red seed indicating that red is dominant over white seed color. To date, all F1 populations have produced plants with red:white seeds in a 3:1 ratio. Occasionally, the red seeds in the F2 were light red or pink. All F1 plants produced pubescent leaves confirming that the pubescent trait found in red rice is dominant over glabrous. To date, our analysis has revealed that F2 populations derived from LA3 crosses produced pubescent:glabrous plants in a 3:1 ratio suggesting single gene inheritance whereas F2 populations derived from StgS crosses produced ratios substantially greater than 3:1 suggesting a more complex inheritance. F1 plants from crosses between either Kaybonnet or Cypress rice and awned red rice (LA3) had purple lower stems even though both parents had green stems. In the F2, 65 and 67%, respectively of Kaybonnet and Cypress plants had purple stems, some of which were very dark purple. Conversely, all F1 plants and nearly all (96%) F2 plants from StgS crosses had green stems suggesting that the gene(s) controlling this trait may be different in LA3 and StgS. Crosses that included LA3 produced F1 plants with awns and F2 plants with awn lengths ranging from zero to the length of the LA3 parent. All of the F1 and F2 offspring from StgS crosses were awnless. F1 plants had culm angles (GRIN rating 3) similar to the red rice parents while F2 plants produced culm angles ranging from erect (GRIN rating 1) to more open (GRIN rating 5) than the red rice parent. F1 plants from LA3 crosses headed during the same time period as both parents while F2 plants headed over a period extending earlier and later than the F1, as well as the parents. Conversely, F1 plants from StgS crosses headed long after the parents and about half of the F2 plants headed later than the parents. Based on our results, true F1 hybrids of rice and red rice (assumed homozygous) should be characteristically pubescent and red seeded with an open plant type. Depending on the red rice parental type, F1 hybrids may be awned or awnless, have purple or green stems, and have normal or delayed heading. F2 hybrids can possess a much broader range of phenotypic characteristics including combinations of all parental traits. For instance, some are pubescent with white seeds, others glabrous with red seed, and still others erect and pubescent with purple stems and red seeds, suggesting independent inheritance of these traits.