Abstract
We have succeeded in selecting four higher yield mutants from five gamma-ray irradiated high-yielding Japanese rice varieties using a novel approach. A total of 464 M2 plants which had heavier total panicle weights per plant were first selected from 9801 irradiated M2 plants. Their higher yields were confirmed by yield trials conducted for three years with a six to ten-pairwise replicated plot design. FukuhibikiH6 and FukuhibikiH8 were selected from an irradiated high-yielding variety Fukuhibiki and showed 1.2% to 22.5% higher yield than their original significantly. YamadawaraH3 was selected from an irradiated high-yielding variety Yamadawara and its yield advantages were 2.7% to 3.9%. However, there was no difference in the genotypes of the 96 SNP (single nucleotide polymorphism) markers between the higher yield mutants and their respective original varieties. The differences in the measured phenotypical traits between each mutant and its original variety were not constant and the actual differences were marginal. Therefore, the higher yields of the selected mutants were likely to have been caused by physiological traits rather than phenotypical traits. The selection method used in this study is an application of the directed evolution method which has long been commonly used in the substantial improvements of microorganisms and their proteins.
Highlights
Yield is the most important trait of crops and it primarily determines the amount of crop production in a unit area or a nation [1]
1600 were Fukuhibiki M2 and 55 M2 plants were selected from them according to the total panicle weight per plant
For the other 4 M2 mutants, the number of harvested M2 plants were 3001, 3000, 2000, and 200 and the number of M2 plants selected according to their yield were 155, 132, 106, and 16 for Oonari, Yamadawara, Mochidawara, and Akidawara, respectively
Summary
Yield is the most important trait of crops and it primarily determines the amount of crop production in a unit area or a nation [1]. A considerable number of studies have been conducted around the world on the breeding of high yield crops, including rice [2]. A high yield study requires the determination of crop yield under the ideal cultivating conditions for the relevant crop. If we can dissect the genetic architecture of high yield, we can apply it to genomic selection, genetic modifications, or genome editing to pyramid multiple useful genes for obtaining higher yields. This is what we are working on and we look forward to providing further information on this in our future report
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