Sunflower (Helianthus annuus L.) - Physiology and Genetics.
1995
Diepenbrock W. | Pasda G.
Generally, breeding efforts should be directed to some of the economically important traits, i.e. yield components, architecture of the canopy and plant, such as harvest index, and early maturation. Many genotypic differences for different characters are related to the duration of vegetation period. Consequently, genotypic differences should be investigated within base populations with equal duration of the entire vegetation period. The desirable characters of late-maturing genotypes are, for example, leaf area and leaf area duration, total biomass, effective partitioning of biomass to the reproductive organs, extension of the root system and drought resistance characters. The duration of the vegetation period is easy to determine but, a defined developmental period is necessary which is closely related to the entire vegetation period. Examining the whole duration of the vegetation period is rather time-consuming. So, investigations on juvenile - mature correlations in sunflower are becoming increasingly important. Further, introduction of desirable traits from late-maturing genotypes has to be attempted in the future. The weak correlation between leaf photosynthesis and crop net assimilation, together with limited intraspecific variation, suggest that selection for high leaf photosynthesis is not effective in improving crop C fixation. Single growth and developmental periods are easy to determine. For achenes per plant the period 'sowing/emergence to budding' and for IAW only the period after flowering is decisive. Generally, the importance of these developmental stages is clearly related to successive formation of the corresponding yield components during the entire vegetation period.
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