Castor (Ricinus communis L.) is one of the oldest cultivated crops, but currently it represents only 0.15% of the vegetable oil produced in the world. Castor oil is of continuing importance to the global specialty chemical industry because it is the only commercial source of a hydroxylated fatty acid. Castor also has tremendous future potential as an industrial oilseed crop because of its high seed oil content (more than 480 g kg−1), unique fatty acid composition (900 g kg−1 of ricinoleic acid), potentially high oil yields (1250–2500 L ha−1), and ability to be grown under drought and saline conditions. The scientific literature on castor has been generated by a relatively small global community of researchers over the past century. Much of this work was published in dozens of languages in journals that are not easily accessible to the scientific community. This review was conducted to provide a compilation of the most relevant historic research information and define the tremendous future potential of castor. The article was prepared by a group of 22 scientists from 16 institutions and eight countries. Topics discussed in this review include: (i) germplasm, genetics, breeding, biotic stresses, genome sequencing, and biotechnology; (ii) agronomic production practices, diseases, and abiotic stresses; (iii) management and reduction of toxins for the use of castor meal as both an animal feed and an organic fertilizer; (iv) future industrial uses of castor including renewable fuels; (v) world production, consumption, and prices; and (vi) potential and challenges for increased castor production.

In Mediterranean Europe, winter cereals can experience soil waterlogging starting from crop establishment up to stem elongation and, in late sowings, this stress is combined with temperatures favorable to plant metabolism. Oats response to waterlogging has been rarely investigated, but these species seems to recover better than other cereals. In a 2-year experiment, Avena sativa and Avena byzantina were sown at the end of winter in pots placed outdoors. At the two-tiller stage, plants were exposed to waterlogging for periods ranging from 0 to 35 days. The dry weight and the N-concentration of shoots and roots were determined on waterlogged plants and drained controls at the start and the end of each waterlogging period, and at maturity. At maturity, the grain yield and its components were determined. To relate oat response to its specific morphological and developmental traits, results were compared to the published results in wheat and barley. Both oat species suffered severe damage during waterlogging: the uptake of nitrogen and the N-concentration of shoots were reduced after 7 days, tiller initiation and root growth after 14 days, and shoot growth after 21 days. All plants survived waterlogging, and the relative growth rates of roots and shoots and the net uptake rate of nitrogen were resumed during recovery. Nevertheless, at maturity, the straw and root biomass were markedly lower with all waterlogging durations, and grain yield decreased by 42% up to approximately 81% following an asymptotic equation. The most affected yield components were the number of panicles per plant and the number of kernels per panicle, but their relative sensitivity changed according to waterlogging duration. The slight increase in tiller fertility in response to short waterlogging and the small and irregular decrease in the number of kernels per spikelet suggest that the two oats could recover the initiation and size of inflorescences better than other winter cereals. Despite this, waterlogging in spring was highly detrimental to these oats because of severe damage under waterlogging and because of the inability to initiate new tillers and adequately resume root growth during recovery, once plants had achieved the phase of stem elongation.

A 5-year selection programme was conducted to obtain an unbranched type of castor plant suitable for efficient mechanical harvesting. Each population (Sn) consisted of several progenies obtained from the selfed main raceme of unbranched plants selected in the previous generation (Sn.i). After self-fertilization of all individuals, selection was conducted in the autumn, at the end of the cycle, so as to have fully developed plants. Unbranched plants were counted in each generation. Comparisons between populations showed significant differences owing to increased recovery ofthe selected phenotype over the generations. The final population could be useful as a source for the development of improved cultivars in future breeding programmes.

The seed oil of castorbean (Ricinus communis, Euphorbiaceae) is highly appreciated in several sectors of the chemical industry. A tropical perennial, with sympodial branching, this plant presents, at the same time, both vegetative shoots and inflorescences, as well as racemes with ripe seeds. This architecture is an obstacle to harvesting the plants using the standard combine harvester which requires, as with any other seed crop, that the plants be dry. One agronomic solution is to spray the plants with desiccants. However, in this paper a genetic solution is suggested, that is, an 'annual plant'. This model is discussed within the present knowledge of plant monocarpic senescence. A mutation that changes the quantity and/or the quality of cambial activity could reduce the secondary growth in castorbean, thus favouring the plant's death. Moreover, to stop iterative growth which is at the base of the perennial form of castorbean, a non-branching model is also proposed. The occurrence of this phenotype in some crops (maize and sunflower) and mutants (tomato, barley, etc.) is examined. Considering apical dominance as the primary mechanism at the base of a non-branching form, a mutation capable of inducing permanent dormancy of axillary buds is discussed. Both mutation breeding and genetic engineering are suggested as major tools to obtain an annual plant of castorbean.

No abstract