Generation of doubled haploid maize lines through induced gynogenesis : improvement of the method and integration in selection schemes
Création de lignées haploïdes doublées de maïs par gynogenèse induite in situ : amélioration de la méthode et intégration dans les schémas de sélection
Résumé
The intraspecific crossing technique used to induce the in situ gynogenesis in maize was improved to make reliable the production of doubled haploid (DH) lines. The theoretical and practical interest of DH line integration in a breeding programme was compared to the conventional methods. The development of more efficient inductive genotypes was the main improvement of the technique. Thus, the average percentage of haploid plants obtained in a progeny, increased from approximately 2.5 per 100 for the control inductor WS14 to approximately 5 for PK6 and 7 for FIGH3, the new selected inductors. The introduction of dominant characters, as cherry and purple embryo markers, into the new inductors, makes much easier the identification of haploid plants in the progenies. The mating design varying the number of recombination generations before production of doubled haploid lines (DH), allows to detect linkage disequilibrium and epistasis effects by comparison of means and variances from lines obtained at different generations. The DH technique was applied to genotypes belonging to a large genetic variability pool, and most of the tested material was reactive to the improved gynogenesis induction technique. DH line phenotypes are very similar to those of Single Seed Descent lines (SSD), obtained by repeated selfing. Concerning the hybrid value, particularly grain yield, the genetic variance of DH lines is almost twice higher than genetic variance of the parental S1 families. This result was expected. But, it was not expected the higher DH genetic variance in comparison with genetic variance of SSD lines resulting from the same S1 families. This could mean that a selection deviation was introduced during generations of SSD lines production. Per recurrent selection cycle, a higher genetic variance and a lower residual variance induce a higher heritability and thus, a better efficiency of DH lines compared to S1 families. Per unit of time, and cost-unit, the efficiency of the two methods is equivalent. Applied to an integrated programme of recurring selection for variety creation, the doubled-haploids method seems very effective. The main results from this thesis, demonstrate that the doubled-haploid method elaborated in this work, is now a very effective and interesting method for maize breeding oriented to obtain performing F1 hybrids. This efficiency of the DH method could be increased in combination with molecular marker-assisted selection (MAS).
L'amélioration de la technique, permettant d'induire in situ la gynogenèse afin de fiabiliser la production de lignées haploïdes doublées (HD) de maïs, a été entreprise. L'intérêt de son intégration dans les schémas de sélection, par rapport aux méthodes conventionnelles a été évalué. Le pourcentage moyen de plantes haploïdes obtenues, est passé d'environs 2,5 à environs 5 , puis 7. Dans une très large variabilité génétique il n'a généralement pas été observé de génotypes ne répondant pas à l'induction de la gynogenèse. Les lignées HD ont des phénotypes très semblables à ceux des lignées obtenues par autofécondation. Pour le rendement, la variance génétique des lignées HD est presque deux fois supérieure à celle des familles S1 dont elles sont issues. Par cycle de sélection récurrente, les lignées HD sont plus efficaces que les familles S1. L'haplométhode, mise au point au cours de ce travail, peut donc être considéré comme efficace et intéressante pour la selection d'hybrides de maïs.
Domaines
Biologie végétale
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