Alexandros Doitsinis’s research while affiliated with Aristotle University of Thessaloniki and other places

Safflower (Carthamus tinctorius L.) growth and productivity are influenced by many factors like genotype, environment and agronomic practices. This field study was conducted to investigate the effects of phenotypic variation in physiological traits on development and yield of spring sown safflower under Mediterranean conditions. Twenty-one genotypes of varying origin were grown for two growing seasons without irrigation. Data were recorded on phenological development stages and seed yield, seed oil content, harvest index (HI) and, seed growth rate (SGR), biomass growth rate (BGR) and economic growth rate (EGR) were determined. Seed yield varied greatly among genotypes and ranged from 1333 to 2870 kg ha−1. There were large variations in SGR and EGR, which were linearly and positively related to seed yield and explained a large amount of the variation in yield, with r2 values between 0.83 and 0.99. The relative contribution of biomass and HI to the variation in seed yield among genotypes appeared to be dependent on the growing season. When the environmental conditions allowed the genetically controlled variation in biomass production to become more apparent, most of the variation (87%) among genotypes in seed yield were due to the differences in biomass and were not resulted by genotypic differences in HI. Genotypes differed in seed oil content that ranged from 26.7% to 35.8%. Oil yield was mainly determined by seed yield in both seasons. Results indicated that spring sown safflower could be considered as an alternative rainfed crop in cool Mediterranean areas where winter kill is a problem. In conclusion, SGR, BGR and EGR were found to be important physiological determinants of seed yield, which could be used as additional selection criteria for yield improvement.

The identification of the factors determining nutrient utilization of safflower (Carthamus tinctorius L.) is useful for the successful introduction of the crop to the cropping system of a region. A field study was conducted to compare and analyze the relative importance of the various component traits causing variation in nitrogen utilization efficiency (NUE) of safflower under Mediterranean conditions. Ten genotypes, four hybrids and six open-pollinated varieties, were grown for two growing seasons without irrigation, on a silty clay (Typic Xerorthent) soil. Seed yield varied greatly among genotypes and ranged from 923 to 3391 kg ha−1. Hybrids showed a mean seed yield superiority of 12.5% against varieties. Seed yield was the most important component of seed N yield and its contribution to the total variation in seed N yield among genotypes was at least 53%. NUE for biomass production during the seed-filling period was lower compared to that during the vegetative period. Genotypes differed in NUE for seed production (NUEs) and the differences followed those of nitrogen harvest index (NHI). The contribution of NHI to the total variation in NUEs among genotypes was much greater compared to that of yield per unit seed nitrogen and accounted for more than 79%. NUEs is positively correlated with seed yield, suggesting that high yield was probably associated with more efficient exploitation of nitrogen. NUEs is negatively correlated with (leaf + stem) N concentration at maturity, meaning that low straw N concentration may be indication of higher NUEs. Results indicated that selection for NUE in safflower should be based on multiple criteria rather than just one criterion and also should be accompanied by evaluation for seed yield to ensure an improvement in both traits.

In crops grown under Mediterranean environments, translocation of pre-anthesis assimilates to the seed is of great importance for seed growth, because hot and dry conditions during the seed filling period diminish photosynthesis and crop nitrogen uptake. This field study was conducted to assess the genetic and seasonal variation in the amount of pre-anthesis dry matter and nitrogen accumulated and translocated to seed by safflower (Carthamus tinctorius L.) plants, and the possible N losses occurring between anthesis and maturity. Ten genotypes, 4 hybrids and 6 open pollinated cultivars, were grown for 2 growing seasons without irrigation, on a silty clay (Typic Xerorthent) soil. The proportion of dry matter and N content at anthesis that was translocated to seed differed among genotypes and ranged from 14.9 to 39.6 and from 24.8–59.3%, respectively. Genotypic differences in dry matter and N translocation were mainly associated with dry matter and N accumulated during the vegetative growth of the plants. Greater amounts of dry matter and N content at anthesis resulted in a greater dry matter and N translocation to seed during the filling period. When the N contents of aboveground plant parts at anthesis and maturity were compared, both gains and losses were observed, and were mainly related to the sink size. No N losses were detected when yield was high. When yield was low, N losses depended on N content at anthesis; high N content resulted in N losses, otherwise no N losses were observed. The contribution of pre-anthesis accumulated reserves to seed weight ranged from 64.7 to 92.2%, indicating the importance of pre-anthesis storage of assimilates for attaining high safflower yield.

A field study was conducted to assess the effect of irrigation on castor (Ricinus communis L.) and to define the water requirements of the crop. Three irrigation regimes, corresponding to 0.0, 0.5 and 1.0 fractions (kd) of the evapotranspiration (ETm) in the area were compared, factorially combined with the varieties Pronto and Negus in 1995. In 1996 and 1997 one more irrigation treatment corresponding to 0.75 of the ETm was included, and Negus was replaced by HD912. Irrigation was found necessary for castor production since seed and oil yields obtained with irrigation were much higher compared to yields of rainfed plants, and also castor could not be competitive to winter cereals in rainfed areas. In 1995 seed yield increased to kd = 1.0, but the response of both varieties was curvilinear. In 1996 kd = 0.50 was enough for the maximum yield by both varieties, while in 1997 higher amounts of water were needed (kd = 1.00 and 0.75 for Pronto and HD912, respectively). The beneficial effect of irrigation was mainly due to the increased number of secondary racemes. Oil yield was mainly determined by seed yield. Thus, the aim of the growers should be to increase the seed yield. The suggested amount of water for the irrigation of castor in the Northern Greece is equal to 75 % of the evapotranspiration of the plant in the area. With this amount the yield is satisfactory and the management of water resources is doing in a rational way.

Successful castor (Ricinuscommunis L.) cropping in Greece depends on the yielding ability and yield stability of the cultivars (hybrids or inbreds) as well as the reliability of production systems. The adaptation and yielding ability of 19 modern castor oil genotypes were studied for 3 years in two sites of Northern Greece. Genotypes combining high seed and oil yield and desirable morphological characteristics were tested for 2 or 3 years, whereas the rest were tested for 1 year only. The growing period in both locations was long enough for ripening the first raceme and a number of secondary racemes depending on the genotypes. The plant height was dependent mainly on the genotypes but also was affected by the site and the year of the experimentation and ranged from 79 to 278 cm. The seed yield varied between 2.5 and 5.0 Mg ha−1, values that are among the highest reported in the literature. The seed yield was higher in the site where plants produced and ripened more secondary racemes. The seed oil content was dependent mainly on the genotype and ranged from 44.5 to 54.2%. The oil yield followed the changes in seed yield. The variation in seed yield between years was low and in most genotypes less than 20%. Results indicate that the castor oil crop was satisfactorily adapted in the area.