Chromosome numbers for the Italian flora: 11

In this contribution, new chromosome data obtained on material collected in Italy are presented. It includes counts for Centaurea aegusae, Hieracium racemosum subsp. lucanum, H. australe subsp. australe, Lysimachia arvensis subsp. arvensis, Micromeria graeca subsp. graeca, and M. graeca subsp. consentina.

Method. Squash preparations were made on root tips obtained from germinating seeds. Root tips were pre-treated with 0.4% colchicine for 3 hours and then fixed in Carnoy fixative solution for 1 hour. After hydrolysis in HCl 1N at 60 °C, the tips were stained in leuco-basic fuchsine for 7-8 minutes.
Observations. Hieracium racemosum subsp. lucanum is a scapose hemicryptophyte, flowering from August to early September. It is currently known only from Timpa Rossa (Lauria, province of Potenza, Basilicata, S Italy) (Di Gristina et al. 2019). The aggregate of H. racemosum Willd. is one of the most polymorphic aggregates in the genus Hieracium L. s.str. The chromosome number 2n = 3x = 27, reported here for the first time on material from the locus classicus of this subspecies, is included in the variability (2n = 27, 2n = 36) reported for the H. racemosum aggregate by Sell and West (1976), Brullo et al. (2005), Di Gristina et al. (2006) and Geraci et al. (2007). Method. Squash preparations were made on root tips obtained from germinating seeds. Root tips were pre-treated with 0.4% colchicine for 3 hours and then fixed in Carnoy fixative solution for 1 hour. After hydrolysis in HCl 1N at 60 °C, the tips were stained in leuco-basic fuchsine for 7-8 minutes.
Observations. Lysimachia arvensis subsp. arvensis is an annual plant native to the Mediterranean Basin, but widely distributed around the world (Jiménez-López et al. 2019). It displays a petal colour polymorphism. Indeed, blue-and orange-flowered plants occur in monomorphic and polymorphic populations across its native range in Europe (Sánchez-Cabrera et al. 2021). The chromosome number 2n = 40, found here in material with orange flowers, agrees with previous reports from Italy and abroad (Löve and Löve 1982;Moneim et al. 2003). Method. Squash preparations were made on root tips obtained from seeds germinating on 1% agar in Petri dishes. Root tips were pre-treated with 0.4% colchicine for 3 hours and then fixed in Carnoy fixative solution for 1 hour. After hydrolysis in HCl 1N at 60 °C, the tips were stained in leuco-basic fuchsine.
Observations. This taxon is endemic to Italy, where it occurs in Calabria and Sicily, doubtful in Abruzzo and Basilicata, and no longer found in Campania and Puglia (Bartolucci et al. 2018). We here report the first chromosome count for this subspecies, 2n = 30, which attests for a diploid status in contrast with the allegedly polyploid chromosome number 2n = 60 reported for the typical Micromeria graeca subsp. graeca  Method. Squash preparations were made on root tips obtained from seeds germinating on 1% agar in Petri dishes. Root tips were pre-treated with 0.4% colchicine for 3 hours and then fixed in Carnoy fixative solution for 1 hour. After hydrolysis in HCl 1N at 60 °C, the tips were stained in leuco-basic fuchsine.
Observations. This taxon is distributed throughout the Mediterranean region from Morocco to the Near East (Govaerts 2021). This is the first count of this subspecies for Italian populations, whereas other counts have been published for the Iberian Peninsula, where two different chromosome numbers have been reported so far, 2n = 20 (Bjorkqvist et al. 1969) and 2n = 60 (Morales Valverde 1990; Luque and Dìaz Lifante 1991). Our count confirms the latter number, which seems the commonest for the species. Concerning the genus Micromeria Benth., it seems that most counts showing x = 10, 11, and 25 have to be referred to species now belonging to Clinopodium L. (Rice 2014+), raising some doubts on the reliability of the count published by Bjorkvist et al. (1969). Assuming x = 15, the autonymic subspecies represents a tetraploid unit. It is of particular interest that the population studied here grows a few dozen metres away from the studied population of M. graeca subsp. consentina .
Method. Squash preparations were made on root tips obtained from germinating seeds. Root tips were pre-treated with 0.4% colchicine for 3 hours and then fixed in Carnoy fixative solution for 1 hour. After hydrolysis in HCl 1N at 60 °C, the tips were stained in leuco-basic fuchsine for 7-8 minutes.
Observations. Hieracium australe is a perennial species distributed in France, Italy, Hungary, and Romania (Greuter and Raab-Straube 2008). Hieracium australe subsp. australe is narrow endemic to Milan, where it grows on the ancient walls of the city and, in particular, on the walls of the Sforza castle (Orsenigo et al. 2019). The chromosome number 2n = 3x = 27, reported here for the first time, is consistent with observations made on other species belonging to H. sect. Italica (Fr.) Arv-Touv., such as those of the H. racemosum aggregate (Brullo et al. 2005;Raimondo and Di Gristina 2004;Di Gristina et al. 2006), and to an apomictic (agamospermy) way of reproduction typical of the genus (Mráz and Zdvořák 2019).