Detection of a highly heterozygous locus in recombinant inbred lines of rice and its possible involvement in heterosis

Abstract

Forty-seven recombinant inbred (RI) lines derived from a cross between two indica rices, cv 'Phalguna' and the Assam land race ARC 6650, were subjected to restriction fragment length polymorphism (RFLP) analysis using cloned probes defining 150 single-copy loci uniformly dispersed on the 12 chromosomes of rice. Of the probes tested, 47 detected polymorphism between the parents. Heterozygosity was calculated for each line and for each of the polymorphic loci. Average heterozygosity per line was 9.6% but was excessive (>20%) in the 5 lines that seemed to have undergone outcrossing immediately prior to harvest. Average heterozygosity detected by each probe across the 47 RI lines was 9.7%. The majority of probes revealed the low level of heterozygosity (<8%) expected for F5-F6 lines in a species showing about 5% outbreeding. On the other hand, 7 probes exhibited heterozygosity in excess of 15%, while with a eighth probe (RG2 from chromosome 11) heterozygosity varied according to the restriction enzyme employed, ranging from 2% with SaII to 72% with EcoRV. The presence of 34 recombination sites in a segment of the genome as short as 24 kb indicates a strong selection for recombination between two neighbouring loci, one required as homozygous for the 'Phalguna' allele, and the other heterozygous. Since selection was principally for yield advantage over that of the high-yielding parent, 'Phalguna', one or both of these loci may be important for heterosis in this cross. The results also indicate that heterozygosity as measured by RFLP can depend on the particular restriction endonuclease employed.

Chalcone synthase in rice (Oryza sativa L.): Detection of the CHS protein in seedlings and molecular mapping of the chs locus

“…It follows that the chs gene is active in Whiteputtu although anthocyanin biosynthesis is blocked in this plant due to a genetic change at any of the other anthocyanin loci. The RG2 locus is an important locus and has been previously shown to be highly heterozygous in recombinant inbred lines of rice and could be potentially contributing to heterosis [34]. The observation that young leaves have more CHS protein than the old leaves of Purpleputtu reflects developmental specificity of CHS expression and regulation (Fig.…”

Impact of seasonal changes on spikelets per panicle, panicle length and plant height in rice (Oryza sativa L.)

“…Many researchers have begun to develop a series of populations based on molecular marker technology, such as double-haploids, F 2 , F 3 , backcross, and recombinant inbred lines (RILs) for quantitative trait locus (QTL) M. R. Kovi Á X. Bai Á D. Mao Á Y. Xing (&) National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan 430070, China e-mail: yzxing@mail.hzau.edu.cn identification (Fan et al 2006;Nair et al 1995;Pooni and Jinks 1978;Xing et al 2001). However, among the different types of populations, RILs have several advantages, including reproduction, which favors the genetic analysis of quantitative traits, because experiments can be replicated over several years and locations, and the use of dominant markers with the same efficiency as the co-dominant ones (SalibaColombi et al 2000).…”

Wide Crossing Technology for Pigeonpea Improvement

“…Homozygous plants offer a promising alternative to recurrent selfing for many years/ generations, for rapid inbred line development. Even if the inbred lines are developed after repeated selfing, it is known that certain regions of the genome retain heterozygosity (Nair et al 1995). In none of the leguminous crops, this phenomenon of homozygosity through wide crosses has been reported.…”