Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: February 29, 2004
Publication Date: February 1, 2005
Citation: Rutger, J.N., Beaty, B. 2005. Induction of early maturing indica mutants. Rice Technical Working Group Meeting Proceedings. Sbstract p. 75. Technical Abstract: Several long grain indica lines have shown grain quality comparable to US standards but mature much later than current US cultivars. Six such experimental indica lines obtained from G.S. Khush of IRRI, IR65629-22, IR65629-67, IR65629-157, IR65450, IR53936, and IR60864 (the first three are different selections from the same cross), were irradiated in order to induce early mutants. In 2000, 400 grams of seed of each line were treated with 250, 300, or 350 Gy of gamma radiation. In the 2000/2001M1 generation in Puerto Rico, about 1000 panicles were randomly selected from the 250 and 300 Gy dosages. Only about 300 panicles were taken from the 350 Gy dosage due to severe stand reduction. In order to save space, the M1 panicles were planted panicle-to-hill. A total of 101 early heading M2 plants was identified and tagged within hills. The M3 generation was grown in the 2001-2002 Puerto Rico winter nursery. The M4 was grown in 2002 Stuttgart and selections were made that uniformly headed in < 111 days from the effective planting date, which reduced the total to 49. The M5 was planted in 2002-2003 Puerto Rico, and 20 panicles were bulked together to plant large plots to look for uniformity in 2003 Stuttgart. In 2003 Stuttgart, each selection was planted in 4.5 meter long, 6 row non-replicated plots. The 6 IRRI parents and the Arkansas cultivar Francis were included for comparison. Of the 49, 20 were selected on the basis of earliness, uniformity, and resistance to lodging. These 20 selections range from 9 to 34 days earlier than their respective parents. For reference, the Arkansas cultivar Francis headed 99 days after planting. IR65629-22 headed in 126 days, and had one mutant that headed in 92 days. IR65629-67 headed in 126 days and had mutants that headed in 94, two at 103, and 104 days. IR65629-157 headed in 122 days and had one mutant that headed in 103 days. IR65450 headed in 126 days and had mutants that headed in 101 and 111 days. IR53936 headed in 133 days and had mutants that headed in 108, 109, five at 110, 111, 114, and 120 days. IR60864 headed in 131 days and had mutants that headed in 120 and 122 days. Average heading of the 20 selections was 108 days, which was down from an average of 127 days of the 6 parents. Thus significant progress was made on selections for early maturity in all 6 parent genotypes. These mutants provide indica materials that have heading dates that are more nearly manageable under Arkansas conditions than the parent materials. The parents had grain quality similar to US standards; it is not anticipated these grain quality factors will be changed in the mutants.