15e CONFERENCE INTERNATIONALE TOURNESOL Sunflower ecophysiology: some unresolved issues

Abstract

Summary :Major unresolved issues in sunflower ecophysiology constrain efforts to improve crop modelling, management, genetic analysis and breeding. Three issues are used here to illustrate this point. Firstly, much of the work on the duration of the emergence to flowering phase has considered the phase as a whole. It is argued that a more detailed analysis based on sub-phases is required, particularly in view of possible intraspecific variability in the durations of the basic vegetative and juvenile phases and evidence that photoperiod responses before, during and after floral initiation may differ between genotypes and even be of opposite sign for the same genotype. Secondly,contrasting responses of grain oil proportion to manipulation of plant population density and incident radiation appear to be linked to variations in kernel oil proportion rather than to kernel: hull ratio, and responses of grain oil proportion to changes in sowing date seem to have a similar origin. More effort should be focused on understanding the controls of oil mass per kernel. It is speculated that there may be a genotype-dependent limit to this variable. A third unresolved issue relates to the nature and strength of the linkage between post-anthesis stay-green and leaf photosynthetic functionality. These variables are poorly related during pre-anthesis senescence of leaves in the lower portion of closed canopies, and for sunflower this linkage appears much weaker than in other crop species. Current interest in post-anthesis stay-green as a possibly useful crop attribute requires clarification of this uncertainty.Keywords : sunflower, crop development, grain oil content, stay green.Résumé : D'importants points non résolus chez le tournesol limitent les efforts pour progresser dans la modélisation des cultures, leur conduite, les analyses génétiques et l'amélioration. Trois aspects sont considérés ici pour illustrer ce point. Premièrement, la plupart des travaux concernant la durée de la période comprise entre la germination et la floraison traitent cette phase comme un tout. Le besoin d'un analyse plus détaillée en considérant des sous-phases est évoqué, particulièrement face à la possible variabilité intraspécifique dans la durée de la phase végétative de base et la phase juvénile et à l'évidence d'une réponse photopériodique différente avant, pendant et après l'initiation florale. Cette réponse différente peut aller jusqu'à être de signe contraire pour le même génotype. Deuxièmement, des réponses contrastantes dans la proportion d'huile de la graine comme conséquence de la manipulation de la densité de la population et du rayonnement incident paraissent être plus liées à la variation dans la proportion d'huile de l'amande qu'au rapport coqueamande. La réponse de la proportion d'huile de la graine aux variations de la date de semis semble Article disponible sur le site http://www.ocl-journal.org ou http://dx

Genetic Analysis of Seed‐Oil Concentration across Generations and Environments in Sunflower

“…1) and produced less seed‐oil than early flowering genotypes. Decreases in temperature and in incident radiation have negative effects on seed growth rate and seed oil concentration (Andrade and Ferreiro, 1996; Connor and Hall, 1997; Hall, 2000; Dosio et al, 2000). Moreover, in areas with short seasons, the probability of sudden interruption of the seed filling period is high.…”

Integration of Biotechnology, Plant Breeding and Crop Physiology

“…Also, these additive effects were largest at high latitudes. This is because low temperature and radiation have negative effects on grain growth rate and grain oil concentration (Andrade and Ferreiro, 1996;Connor and Hall, 1997;Hall, 2000;Dosio et al, 2000; Section 2 in Chapter 16). Moreover, the highest LOD score for this QTL in association with grain oil percentage was also observed at Fargo (Table 1), the environment with the highest rate of decline in temperature and radiation during the grain filling period.…”