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., Bryant, R.J. 2005. Development of early maturing, intermediate amylose, indica germplasm. Rice Technical Working Group Meeting Proceedings. Abstract p. 48 Technical Abstract: Indica/indica crossing was initiated as a means of base broadening in US rice, where very narrow genetic bases, essentially all in japonicas, have evolved because of need for adaptation to temperate climate and to specific grain quality requirements. The indica cultivar Zhe 733 from China, which has higher amylose than desired for US markets, was used as a donor of very early maturity. It was crossed as a female with the indica cultivar IR64 and six indica experimentals graciously provided by G.S. Khush of IRRI. The IRRI materials have intermediate amylose contents similar to US long grain cultivars but generally are later maturing than desired in the US. Grain dimensions of the IRRI materials are similar to US long grain cultivars, while Zhe 733 has shorter and heavier grains. Crosses were made in the greenhouse during the winter of 1997/98, then materials were expeditiously advanced in the field in Stuttgart, Arkansas, and the winter nursery in Lajas, Puerto Rico. Selection for early maturity was conducted in the 1999 F2 and 2000 F5 generations in Stuttgart. Selection for intermediate amylose content was conducted in the 2000 F5 and 2001 F7 generations grown in Stuttgart. Yield tests were conducted in 2001 and 2002 on 59 recombinants with nitrogen fertilizer applied preflood at the rate of 112 kg ha-1. In 2002 the weak straw of the indicas became apparent, when severe lodging following 10 cm of rainfall in one week shortly after heading resulted in inconclusive yield data. For 2003 the number of lines was reduced to nine that had performed well in 2001, and the nitrogen rate reduced to 55 kg ha-1. The male parent of one line was IR64, the male parent of five lines came from selections from the IRRI cross IR65629, and one line each came from male parents IR65450, IR53936, and IR60864. These nine indica germplasms are similar to or earlier than the Arkansas tropical japonica check cultivar Francis and have similar intermediate amylose contents. Weak straw is a problem at higher nitrogen levels. These lines are being considered for release as improved indica germplasms.