Biomass, Seed and Energy Yield of Cynara cardunculus L. as Affected by Environment and Season

Cynara cardunculus is a perennial plant that adapts well to Mediterranean climate conditions. The possibility of cultivating C. cardunculus with low or zero input and in low productivity or marginal lands makes it one of the most promising crops for bioenergy production in the Mediterranean areas. The objective of the research was to study the effects of two marginal and contrasting southern Italian environments (plain, 42 m a.s.l. and hilly area, 419 m a.s.l.) during a three-year period on biomass, seed, energy yield, and oil composition of two genotypes of C. cardunculus (cultivated cardoon and wild cardoon). When compared to the plain, plants that were grown in the hills gave higher biomass yield (10.9 vs. 9.7 t DM ha−1 year−1), higher seed yield (0.46 vs. 0.44 t DM ha−1 year−1) and, consequently, higher total energy yield (190 vs. 172 GJ ha−1 year−1), attributable to higher average annual rainfall (680 vs. 565 mm year−1). The season, although only evaluated for three years (short cycle), showed a different effect based on the genotype, highlighting a greater over-time production constancy of wild cardoon (though less yielding) as compared to cultivated cardoon. Oil yield and composition were only slightly affected by environment and genotype. Overall, the results of this research suggest using C. cardunculus in marginal hilly areas, where, in addition to the production of bioenergy, it may represent a good chance to fight erosion and improve soil fertility, without competing with food crops.

Seed Transcriptome Annotation Reveals Enhanced Expression of Genes Related to ROS Homeostasis and Ethylene Metabolism at Alternating Temperatures in Wild Cardoon

The association among environmental cues, ethylene response, ABA signaling, and reactive oxygen species (ROS) homeostasis in the process of seed dormancy release is nowadays well-established in many species. Alternating temperatures are recognized as one of the main environmental signals determining dormancy release, but their underlying mechanisms are scarcely known. Dry after-ripened wild cardoon achenes germinated poorly at a constant temperature of 20, 15, or 10 °C, whereas germination was stimulated by 80% at alternating temperatures of 20/10 °C. Using an RNA-Seq approach, we identified 23,640 and annotated 14,078 gene transcripts expressed in dry achenes and achenes exposed to constant or alternating temperatures. Transcriptional patterns identified in dry condition included seed reserve and response to dehydration stress genes (i.e., HSPs, peroxidases, and LEAs). At a constant temperature, we observed an upregulation of ABA biosynthesis genes (i.e., NCED9), ABA-responsive genes (i.e., ABI5 and TAP), as well as other genes previously related to physiological dormancy and inhibition of germination. However, the alternating temperatures were associated with the upregulation of ethylene metabolism (i.e., ACO1, 4, and ACS10) and signaling (i.e., EXPs) genes and ROS homeostasis regulators genes (i.e., RBOH and CAT). Accordingly, the ethylene production was twice as high at alternating than at constant temperatures. The presence in the germination medium of ethylene or ROS synthesis and signaling inhibitors reduced significantly, but not completely, germination at 20/10 °C. Conversely, the presence of methyl viologen and salicylhydroxamic acid (SHAM), a peroxidase inhibitor, partially increased germination at constant temperature. Taken together, the present study provides the first insights into the gene expression patterns and physiological response associated with dormancy release at alternating temperatures in wild cardoon (Cynara cardunculus var. sylvestris).

Allelopathic potential of leaf aqueous extracts from Cynara cardunculus L. on the seedling growth of two cosmopolitan weed species

The search for sustainable alternatives to synthetic herbicides for weed control, has led the scientific community to an increased interest for plant allelopathic mechanisms. The utilisation of plant extracts as possible bioherbicides represents an important solution. In the present study, laboratory experiments were carried out to investigate, for the first time, the differences in the allelopathic activity of the three Cynara cardunculus L. botanical varieties (globe artichoke, cultivated and wild cardoon) leaf aqueous extracts on the seedling growth of Amaranthus retroflexus L. and Portulaca oleracea L. In addition, the autoallelopathic effect on wild cardoon growth and the qualitative profile of the aqueous extract through high-performance liquid chromatograpy (HPLC) analysis were evaluated. Overall, the allelopathic effects were both genotype- and weed species-dependent. Wild cardoon showed the highest allelopathic potential (–23.4%), followed by cultivated cardoon and globe artichoke, and P. oleracea was the most sensitive target species (–32%). Besides, root system length was the most affected parameter (–32.6%). The autoallelopathic effect of wild cardoon extract was also demonstrated on root system length, hypocotyl and epicotyl length and total dry weight. C. cardunculus leaf aqueous extract was characterised by 5 sesquiterpene lactones, 2 caffeoylquinic acids, 6 flavones and 1 lignan. From the HPLC analysis we found that apigenin and luteolin 7-O-glucoronide were detected only in wild cardoon, apigenin 7-O-glucoside was typic of globe artichoke, and 11,13-dihydro-deacylcynaropicrin and 11,13-dihydroxi-8-deoxygrosheimin were characteristics of cultivated cardoon.