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Maximum-likelihood method identifies meiotic restitution mechanism from heterozygosity transmission of centromeric loci: application in citrus.

Cuenca J, Aleza P, Juárez J, García-Lor A, Froelicher Y, Navarro L, Ollitrault P - Sci Rep (2015)

Bottom Line: Most researchers consider sexual polyploidisation leading to unreduced gamete as its main origin.Simulating data demonstrated the importance of selecting markers very close to the centromere to obtain significant conclusions at individual level.No significant conclusions were obtained for 14.1% of the hybrids.

View Article: PubMed Central - PubMed

Affiliation: Crop Protection and Biotechnology Center. Instituto Valenciano de Investigaciones Agrarias (IVIA).

ABSTRACT
Polyploidisation is a key source of diversification and speciation in plants. Most researchers consider sexual polyploidisation leading to unreduced gamete as its main origin. Unreduced gametes are useful in several crop breeding schemes. Their formation mechanism, i.e., First-Division Restitution (FDR) or Second-Division Restitution (SDR), greatly impacts the gametic and population structures and, therefore, the breeding efficiency. Previous methods to identify the underlying mechanism required the analysis of a large set of markers over large progeny. This work develops a new maximum-likelihood method to identify the unreduced gamete formation mechanism both at the population and individual levels using independent centromeric markers. Knowledge of marker-centromere distances greatly improves the statistical power of the comparison between the SDR and FDR hypotheses. Simulating data demonstrated the importance of selecting markers very close to the centromere to obtain significant conclusions at individual level. This new method was used to identify the meiotic restitution mechanism in nineteen mandarin genotypes used as female parents in triploid citrus breeding. SDR was identified for 85.3% of 543 triploid hybrids and FDR for 0.6%. No significant conclusions were obtained for 14.1% of the hybrids. At population level SDR was the predominant mechanisms for the 19 parental mandarins.

No MeSH data available.


Related in: MedlinePlus

Half tetrads resulting from no crossover and single crossover events under FDR and SDR mechanisms of unreduced gamete formation.
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f1: Half tetrads resulting from no crossover and single crossover events under FDR and SDR mechanisms of unreduced gamete formation.

Mentions: The origin of 2n gamete formation greatly impacts the gametic structures and, therefore, the polyploid populations and the efficiency of breeding strategies. Under FDR, non-sister chromatids retain parental heterozygosity from the centromere to the first crossover point,. Under SDR, the two sister chromatids are homozygous between the centromere and the first crossover point (Figure 15). As a consequence, several studies based on genetic markers indicate that FDR gametes transmit 70–80% of the parental heterozygosity, but SDR gametes transmit only 30–40%91939404142. Thus, a tighter distribution is expected in FDR-derived populations than in SDR ones because a higher percentage of the parental genome is transferred intact, resulting in a more uniform gamete production43. Therefore, insights into the meiotic nuclear restitution mechanisms that produce unreduced gametes are crucial for the optimisation of breeding strategies based on sexual polyploidisation44.


Maximum-likelihood method identifies meiotic restitution mechanism from heterozygosity transmission of centromeric loci: application in citrus.

Cuenca J, Aleza P, Juárez J, García-Lor A, Froelicher Y, Navarro L, Ollitrault P - Sci Rep (2015)

Half tetrads resulting from no crossover and single crossover events under FDR and SDR mechanisms of unreduced gamete formation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4403285&req=5

f1: Half tetrads resulting from no crossover and single crossover events under FDR and SDR mechanisms of unreduced gamete formation.
Mentions: The origin of 2n gamete formation greatly impacts the gametic structures and, therefore, the polyploid populations and the efficiency of breeding strategies. Under FDR, non-sister chromatids retain parental heterozygosity from the centromere to the first crossover point,. Under SDR, the two sister chromatids are homozygous between the centromere and the first crossover point (Figure 15). As a consequence, several studies based on genetic markers indicate that FDR gametes transmit 70–80% of the parental heterozygosity, but SDR gametes transmit only 30–40%91939404142. Thus, a tighter distribution is expected in FDR-derived populations than in SDR ones because a higher percentage of the parental genome is transferred intact, resulting in a more uniform gamete production43. Therefore, insights into the meiotic nuclear restitution mechanisms that produce unreduced gametes are crucial for the optimisation of breeding strategies based on sexual polyploidisation44.

Bottom Line: Most researchers consider sexual polyploidisation leading to unreduced gamete as its main origin.Simulating data demonstrated the importance of selecting markers very close to the centromere to obtain significant conclusions at individual level.No significant conclusions were obtained for 14.1% of the hybrids.

View Article: PubMed Central - PubMed

Affiliation: Crop Protection and Biotechnology Center. Instituto Valenciano de Investigaciones Agrarias (IVIA).

ABSTRACT
Polyploidisation is a key source of diversification and speciation in plants. Most researchers consider sexual polyploidisation leading to unreduced gamete as its main origin. Unreduced gametes are useful in several crop breeding schemes. Their formation mechanism, i.e., First-Division Restitution (FDR) or Second-Division Restitution (SDR), greatly impacts the gametic and population structures and, therefore, the breeding efficiency. Previous methods to identify the underlying mechanism required the analysis of a large set of markers over large progeny. This work develops a new maximum-likelihood method to identify the unreduced gamete formation mechanism both at the population and individual levels using independent centromeric markers. Knowledge of marker-centromere distances greatly improves the statistical power of the comparison between the SDR and FDR hypotheses. Simulating data demonstrated the importance of selecting markers very close to the centromere to obtain significant conclusions at individual level. This new method was used to identify the meiotic restitution mechanism in nineteen mandarin genotypes used as female parents in triploid citrus breeding. SDR was identified for 85.3% of 543 triploid hybrids and FDR for 0.6%. No significant conclusions were obtained for 14.1% of the hybrids. At population level SDR was the predominant mechanisms for the 19 parental mandarins.

No MeSH data available.


Related in: MedlinePlus