Genetic improvement of sunflower in Argentina between 1930 and 1995: Part III. Dry matter partitioning and grain composition

Abstract

We compared the partitioning of dry matter and the oil and protein content in the grain of sunflower ( Helianthus annuus L.) cultivars released in Argentina between 1930 and 1995. At anthesis, the fraction of plant dry matter partitioned to leaf and head increased, whereas the fraction in the stem decreased with year of cultivar release. Improved oil yield was related to the increase in: (i) harvest index (grain mass/shoot mass) from about 0.3 to 0.5; (ii) kernel-to-grain ratio from 0.6 to 0.8; and (iii) kernel oil concentration from 58 to 70%. The duration of the period of grain growth as a fraction of season length accounted for half of the variation in harvest index. Kernel oil concentration was negatively associated with protein concentration which dropped from 23 to 13%. Further improvement in partitioning may be possible, including increase in harvest index resulting from enhanced contribution of stored assimilate to grain growth. Owing to the dramatic improvement in partitioning achieved in the last seven decades, however, further increase in yield may need to focus on increasing biomass production.