The breeding of two polyploid rice lines with the characteristic of polyploid meiosis stability

Abstract

Polyploidization is a basic feature of plant evolution. Nearly all of the main food, cotton and oil crops are polyploid. When ploidy levels increase, yields double; this phenomenon suggested a new strategy of rice breeding that utilizes wide crosses and polyploidization dual advantages to breed super rice. Because low seed set rates in polyploid rice usually makes it difficult to breed, the selection of Ph-liked gene lines was emphasized. After progenies of indica-japonica were identified and selected, two polyploid lines, PMeS-1 and PMeS-2 with Polyploid Meiosis Stability (PMeS) genes were bred. The procedure included seven steps: selecting parents, crossing or multiple crossing, back-crossing, doubling chromosomes, identifying the polyploid, and choosing plants with high seed set rates that can breed themselves into stable lines. The characteristics of PMeS were determined by observing meiotic behaviors and by cross-identification of seed sets. PMeS-1 and PMeS-2, (japonica rice), have several characteristics different from other polyploid rice lines, including a higher rate of seed set (more than 65%, increasing to more than 70% in their F1 offspring); and stable meiotic behaviors (pairing with bivalents and quarivalents nearly without over-quarivalent in prophase, nearly without lagging chromosomes in metaphase and without micronuclei in anaphase and telophase). The latter was obviously different from control polyploid line Dure-4X, which displayed abnormal meiotic behaviors including a higher rate of multivalents, univalents and trivalents in prophase, lagging chromosomes in metaphase and micronuclei in anaphase and telophase. There were also three differences of the breeding method between PMeS lines and normal diploid lines: chromosomes doubling, polyploidism identifying and higher seed set testing. The selection of PMeS lines is the first step in polyploid rice breeding; their use will advance the progress of polyploid rice breeding, which will in turn offer a new way to breed super rice.

Genome duplication effects on pollen development and the interrelated physiological substances in tetraploid rice with polyploid meiosis stability

“…Meiosis of most polyploid rice triggered by genome duplication was unorganized, leading to low frequency normal pollen; consequently, most lines of polyploid rice had a seed set rate of under 40% and low yields. In our research, polyploid hybrid rice with a PMeS parent background showed stable meiosis and had a high seed set rate (Cai et al 2007). The discovery and application of PMeS in disrupting the low seed set rate would have great potential in contributing to research in polyploid rice in the future.…”

“…japonica lines Balilla-2X (commonly used in Japan), Balilla-4X, HN2026-2X, and HN2026-4X were used in this research. HN2026-4X, which has a high seed set rate, was considered a stable polyploid meiosis rice line (Cai et al 2004a(Cai et al , 2007. The Balilla-4X line without the PMeS background had a low seed set rate with disorganized meiosis behavior, and was applied as CK.…”

“…Ph is the main regulator of recombination in allopolyploid species, was discovered 50 years ago in wheat (Dhaliwal 1977), and was only recently characterized at the molecular level (Griffiths et al 2006). The PMeS HN2026-4X line had a high seed set rate, was selected because of its especially stable meiosis behavior and was considered a Ph-like genetic material (Cai et al 2004a(Cai et al , 2007. The Balilla-4X line without the PMeS background had a low seed set rate with disorganized meiosis behavior.…”

Cytomorphological Characterization of the Backcross Progeny of Synthetic Amphiploid Rice (AABB) and Tetraploid Oryza sativa (AAAA)

“…The cultivated rice Sg99012 (O. sativa, AA, 2n = 2X = 24) is a japonica rice line stored at the Polyploid Genetics Lab of Hubei University, Wuhan, China. Sg99012-4X (AAAA, 2n = 4X = 48) is a high seed set tetraploid rice line with a polyploid meiosis stability (PMeS) gene selected by Cai et al (2007).…”

Dissecting 2 Meiotic Mutations (<i>dmc</i>1 and <i>asy1</i>) in Artificial Autopolyploid <i>Arabidopsis thaliana</i>

“…Polyploidy provides the benefits for plants such as heterosis (hybrid vigor) and gene redundancy which thus cause polyploids to be more vigorous and tolerant than their diploid progenitors. For instance, autotetraploid rice lines pMeS-1 and pMeS-2 (Polyploid Meiosis Stability) were produced and selected to improve the crop yields based on meiotic stability and high fertility (Cai et al 2007). However, little is known about effects of polyploidy on specific meiotic mutations after polyploidization in plants.…”