Genetic variation and seed yield in Tunisian castor bean ( Ricinus communis L.)

Background and hypothesis: Castor bean (Ricinus communis) is spontaneous in Tunisia with a wide geographical distribution. To study seed morphology we introduced J index as the percent of similarity of seed images to an ovoid. Reduced seed size, J index and color intensity were observed in the population grown in the desert (MartIn Gamez et al. 2016). Our objective is to analyze the variability in castor bean grown from seeds obtained from different geographic origins, to describe morphotypes and to find phenotypic parameters to select productive populations. Data description, mathematical model, study site and methods: Seeds collected from twelve populations in 12 Tunisian sites (4 bioclimatic regions) were sown in the experimental field of INRGREF in Gabes (Tunisia). After 10 months, morphological and agronomic characteristics of plants were measured. Morphological traits of seeds were analyzed. Results: Three groups were obtained. The first represented by a single population (northern Tunisia) is characterized by small leaves, large fruit, small seed and early flowering. The second group includes nine populations with intermediate values for fruit and seed dimensions. The third group characterized by reduced fruit length and elevated values of seed length and width. Seed yield varied between populations. Conclusions: Some features of seeds were maintained from the parental generation. Reduced size and color intensity with increased roundness values were maintained in the seeds of the Saharan region. J index values, reflecting the morphological similarity with an ovoid, increased in relation to the previous generation, in general as in particular in the seeds of the Saharan region .