Quantitative trait loci associated with longevity of lettuce seeds under conventional and controlled deterioration storage conditions

Lettuce (Lactuca sativa L.) seeds have poor shelf life and exhibit thermoinhibition (fail to germinate) above ∼25°C. Seed priming (controlled hydration followed by drying) alleviates thermoinhibition by increasing the maximum germination temperature, but reduces lettuce seed longevity. Controlled deterioration (CD) or accelerated ageing storage conditions (i.e. elevated temperature and relative humidity) are used to study seed longevity and to predict potential seed lifetimes under conventional storage conditions. Seeds produced in 2002 and 2006 of a recombinant inbred line (RIL) population derived from a cross between L. sativa cv. Salinas×L. serriola accession UC96US23 were utilized to identify quantitative trait loci (QTLs) associated with seed longevity under CD and conventional storage conditions. Multiple longevity-associated QTLs were identified under both conventional and CD storage conditions for control (non-primed) and primed seeds. However, seed longevity was poorly correlated between the two storage conditions, suggesting that deterioration processes under CD conditions are not predictive of ageing in conventional storage conditions. Additionally, the same QTLs were not identified when RIL populations were grown in different years, indicating that lettuce seed longevity is strongly affected by production environment. Nonetheless, a major QTL on chromosome 4 [Seed longevity 4.1 (Slg4.1)] was responsible for almost 23% of the phenotypic variation in viability of the conventionally stored control seeds of the 2006 RIL population, with improved longevity conferred by the Salinas allele. QTL analyses may enable identification of mechanisms responsible for the sensitivity of primed seeds to CD conditions and breeding for improved seed longevity

Influence de la teneur en eau sur les processus d'altération associés au vieillissement des semences de tournesol ( Helianthus Annuus L.)

L objectif principal de ce travail a été de préciser l influence de la teneur en eau sur les mécanismes d altération associés au vieillissement des semences de tournesol (Helianthus annuus L.). Les akènes ont subi un traitement de détérioration contrôlée à 25, 35 et 45C à des teneurs en eau de 0,043 à 0,488 g H2O g-1 MS. La diminution de la vigueur germinative puis de la viabilité des semences a été mise en relation avec le métabolisme énergétique (teneur en ATP, charge énergétique : CE) et l efficacité du système antioxydant (activité catalase, glutathion réductase, superoxydase), à l origine de l augmentation de la teneur en H2O2 et en malondialdéhyde (MDA), indicateur de la peroxydation des lipides. Les mécanismes biochimiques mis en jeu dans la perte de viabilité sont discutés en fonction de la teneur en eau des organes et du métabolisme énergétique.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF