Key phenological events in globe artichoke (Cynara cardunculus var.scolymus) development

Abstract

A priority for the field vegetable grower is to be able to schedule a regular supply of product throughout the growing season. This requires a predictive framework, based on the identification of key developmental events of the crop, and an understanding of how genotypic and environmental factors interact to determine plant development. Four globe artichoke (Cynara cardunculus var. scolymus) cultivars, representing the existing phenological range, were grown in a field experiment, and a range of environmental conditions was imposed by varying both the timing of the first irrigation (which determines the initiation of regrowth) and by repeating the experiment across two locations and 2 years. The timing of the appearance of the main stem capitulum was sensitive to both the growing environment and the cultivar. These differences persisted till flowering and were correlated with final leaf number. As the plant developed, the phyllochron decreased, resulting in three values of phyllochron, each of which was responsive to genotype, and hardly to environment. The timing of the first change in phyllochron was associated with the final leaf number and the appearance of the capitulum. For all the cultivars, the rate of development fell and the final leaf number increased as the length of the photoperiod increased. The later flowering cultivars shared a similar vernalisation requirement, but 'Spinoso sardo' did not require a cold period to flower. Leaf length reached a peak before the beginning of stem elongation, and maximum leaf length was correlated with final leaf number. The sensitiveness of the phyllochron to the genotype, and of the number of leaves and the timing of the appearance of the capitulum to both genotype and environment makes them suitable as variables in developmental models. The importance of the final number of leaves is not only because of its phenological significance, but also because of its effect on the ability of the canopy to intercept radiation. Key phenological events in globe artichoke developmentA. Virdis et al.

Artichoke: botanical, agronomical, phytochemical, and pharmacological overview

“…Starting from the 100 references cited in the present review, 81 studies were selected, whereas 19 items were discarded since reporting not relevant information. These included an international on-line database on crop production (FAO 2013), 3 books of general interest about medicinal plants (Schauenberg and Paris 1977;Chevallier 1996) and herbs (Fleming 1998), 2 monographs on the Cilento National Park (SouthWest Italy) dealing with dyeing plants (De Falco and di Novella 2011) and multifunctional sustainable agriculture (Amato et al 2011), respectively, a review (Verpoorte et al 2008) and a methodological paper (Incerti et al 2013) on plant metabolomics, and 11 book chapters and research articles reporting on artichoke horticulture (Bianco 1990, Cantore andBoari 2009), breeding (Lanteri and Portis 2008), phenology (Virdis et al 2009(Virdis et al , 2014Archontoulis et al 2010), origin and evolution (Rottenberg and Zohary 1996;Sonnante 2004, 2009), and population genetics (Portis et al 2005;Sonnante et al 2008). …”

“…Seed production occurs through free pollination (producing a high genetic, phenotypic and phonological variability) or creation of F1 hybrids which are more uniform in behaviour. Artichoke phenology has been described by Archontoulis et al (2010) according to the BBCH scale and Virdis et al (2009Virdis et al ( , 2014 have studied the genetic factors and environmental requirements for timing of leaf emission (phyllochron) and head production. Flower induction requires a critical photoperiod of at least 10.5 h and a thermal sum of at least 200-250°C with a base temperature of 7-9°C, and aartichoke does not survive at less than -10°C (Bianco 1990).…”

The phenology of seed-propagated globe artichoke

“…This is an important limitation for seed-propagated cultivars, because the market value of capitula sold in early November and December is higher than at other times of the year (Calabrese et al, 2004(Calabrese et al, , 2011. Lateness has frequently been attributed to a failure to fully meet the plant's vernalisation requirement (Harwood & Markarian, 1968;Rangarajan et al, 2000;Mauromicale et al, 2005b), and Virdis et al (2009) have shown that late types do need a longer period of vernalisation than early ones. Artificial vernalisation accelerates development to a rather variable extent (Harwood & Markarian, 1968;Foury & La Malfa, 1976;Mauromicale et al, 2005a), probably because of occurrence of devernalisaing conditions (Foury & La Malfa, 1976).…”

“…Phenological models that are able to establish functional relationships between the environment and the crop development represent a possible way forward. At present, the only developmental model available for globe artichoke is the one based on the developmental framework proposed for wheat by Jamieson et al (1998) and used for globe artichoke by Virdis et al (2009). The rationale of this framework is to assume that crops switch to anthesis at a time that is function of the rate of appearance and final number of leaves.…”

Basic principles of graphing data

“…Compare Figures 1 and 2 and note how well the full box in the latter defines the plotting region compared to the two-axis box in the former. A very important aspect of the box is that the data rectangle (so the region used for plotting) should be slightly smaller than the box itself (Cleveland, 1994) -otherwise the plotting symbols will interfere with the axes (see Figure 9 and Virdis et al, 2009), although Tufte's (1997, p. 45) graph is a very elegant with exception to this rule. Remember also that the data rectangle should be effectively used-for a variable ranging from 50 to 105 it would seldom be wise to start the axis at 10 and end at 170 (see also Figure 1).…”