Date of Award
Master of Science
Hybrid rice production using the two-line system requires developing environment genetic male-sterile (EGMS) lines which become male sterile in certain environmental conditions. EGMS lines contain genes that can be induced to express male sterility by temperature (TGMS), day length (PGMS), or both (PTGMS). Eight EGMS were tested including four lines designated as 236s, 801s, 805s, and 811s developed by the University of Arkansas System Division of Agriculture's Rice Research and Extension Center (RREC) near Stuttgart, Ark.; and four mutant male-sterile lines designated as GSOR 1, GSOR 2, GSOR 3, and GSOR 4 developed by the Dale Bumpers National Rice Research Center (DBNRRC-USDA-ARS) near Stuttgart, Ark. The lines were screened in growth chambers using different temperatures and day lengths to identify the genetic source(s) and sterility threshold for each lines. Plants were tested when panicles began to exsert for pollen sterility via the pollen staining method. A two year field test was conducted to determine an optimum planting date for sterile conditions. In summer 2017 the lines were planted in a randomized block design with three replications and three planting dates at RREC. In summer 2018 the four RREC lines were planted in a randomized block design with three replications and three planting dates at RREC, Pine Tree Research Station (PTRS) near Colt, Ark., and Rohwer Research Station (RRS) at Rohwer, Ark. In summer 2018, line 811s was planted in a randomized block design with three replications and three different seed rates - 2, 4, and 8 seeds/m2 - to determine an optimum seed rate to reduce late, potential fertile tillers. The results from the growth chamber screening revealed that the RREC lines are TGMS. The sterility threshold for lines 801s, 805s, and 811s is when day time temperature is >29.4oC, and for line 236s is when day time temperature is >32.2oC. The GSOR lines expressed pollen fertility in most of the environments tested and sterility was inconsistent among the lines, thus the source(s) of sterility and the sterility threshold could not be determined. The results from the two year field study revealed that April 25th is the optimum planting dates for sterile conditions in Arkansas. The results from the seed rate study of 811s suggests that the different seed rates do not affect late, fertile tiller production, however, 4 seeds/m2 is the best seed rate for hybrid seed production.
North, Dustin, "Characterization and application of Arkansas male sterile lines for hybrid rice production" (2019). Graduate Theses and Dissertations. 17068.