Quercus x caroppoi Medagli, Turco, Albano and Accogli, a new oak's hybrid from the Salento

Authors describe a new taxon that belongs to genus Quercus L. probably of hybrid origin. Quercus x caroppoi was found in Salento (Carpignano Salentino, Lecce), it would seem to be originated from hybridization between Turkey oak (Quercus cerris L.) and Kermes oak (Quercus coccifera L. subsp. calliprinos Webb). This is the first ever discovery of this hybrid. The discovery of the new hybrid took place 13th September 2012 along the provincial road S.P. 3, Carpignano Salentino-Borgagne (LE), near a dry-stone wall bordering an olive grove. Q. x caroppoi is an abundantly fruiting tree of about 8-8,5 m high (Fig. 1), with a slim canopy (as in Q. cerris) and not globular (as in Q. coccifera subsp. calliprinos). It has a greyish bark, smooth with slightly accentuated longitudinal striations (Fig. 2) and a bicormic appearance, as it has two distinct trunks about one meter apart, starting from the ground to canopy, apparently, two distinct and twin trees (main shoots) and numerous small basal suckers, which give it a densely bushy appearance (Fig. 3). Leaves have pubescent petioles, with a generally crinkled leaf blade, almost never flat, often asymmetrical in shape, lanceolate-acute as in Q. cerris (elliptical or obovate in Q. coccifera), evergreen, rather shiny and rough to the touch, (but less shiny than respect the leaves of Q. coccifera) (Fig. 4); coriaceous (but less than respect to Q. coccifera) with a glabrous and darker upper leaf page and a lighter lower leaf page (Fig. 5) with evident leaf veins (they are just noticeable in Q. coccifera) all with 4-6 toothed and mucronate lobes per side and an acute and mucronate apex as in Q. cerris, but with non-rigid and pungent mucrons as in the Q. coccifera subsp. calliprinos, with 4-6 dentate and unequal lobes per side. Leaf are flattened at the apex where they have an apical mucron. Cupule covers from half to one third of the acorn; they look similar to that of Q. coccifera calliprinos, but with stiff scales and pointed apex, arched towards the peduncle. The cupules are more delicate, slightly thinner, and less lignified if compared to those of Q. coccifera (Fig. 6). An interesting remark is the biennal fruiting cycle of Q. x caroppoi, as it presents simultaneously acorns at initial development associated with acorns close to maturity (Fig. 7). This biennality in the development of acorns is common to both Thorny oak and Turkey oak. During samplings at the base of the tree, numerous germinating acorns (Fig. 8) and several plants born spontaneously from germinated acorns were observed, which, however, due to the lack of suitable spaces and to interventions of weeding in the adjacent olive grove, they cannot develop undisturbed (Fig. 9). At the Botanical Garden of the University of Salento acorns where seeded and germinating power was analysed (Fig. 10). Acorns show a germinative power of about 52% (6 months after seeding), unlike experiences concerning Quercus coccifera subsp. calliprinos which showed a higher germination around 80-95% in Salento. The seedlings show a strong resemblance to the mother plant, highlighting strongly toothed and mucronate leaves (Fig. 11). It would seem that the specimen is predominantly self-pollinated, which promote conservation of the features that belong to the mother plant; this assumption is also due to the considerable distance of Q. caroppoi from spontaneous specimens of thorny oak. A case that has many similarities is related to the discovery of Q. thracica Stefanov and Nedjalkov, a presumed hybrid between Q. cerris e Q. trojana Webb. that was found in Bulgaria as a bicormic plant, with morphological characteristics very similar to Q. x caroppoi. Unfortunately, in this case, after the death of the only plant described in 2010, this taxon was declared extinct.