Performance and quality of <Emphasis Type="Italic">Cupressus sempervirens</Emphasis> L. mini-plug seedlings under reduced photoperiod

Short-day treatment has been used for some conifer species to improve planting stock quality. The aim of this paper was to study the effect of short-day treatment on performance and quality of young seedlings of Italian cypress (Cupressus sempervirens L.), a conifer species abundant in the Mediterranean area. Seeds of Italian cypress were sown in mini-plug cavities. After 5 weeks of growth, seedlings were subjected to four different photoperiods: (a) 14 h (control), (b) 8 h, (c) 6 h, and (d) 4 h for a period of 1–3 weeks, before they were transplanted to bigger size containers. Reducing photoperiod did not result in bud formation or shoot inhibition although it increased the number of lateral shoots. Seedlings subjected to 6-h photoperiod for 2 weeks during pre-cultivation in mini-plugs had improved root characteristics, giving them a higher potential for outplanting success, especially in Mediterranean areas.     

Effects of clonal selection on biomass production and quality in Robinia pseudoacacia var. monophylla Carr.

In this paper, the results of the effects of clonal selection on biomass production and quality in monophylla black locust (Robinia pseudoacacia var. monophylla Carr.) were studied. The genetic material included seedlings of open pollinated families, ramets of selected clones within them and seedlings of common black locust (Robinia pseudoacacia L.) as a control. Both seedlings and ramets were planted in the field in April 1994. At the end of the first and the subsequent growing seasons (1994–2002) all of them were cut at 20 cm aboveground. Measurements were done at the end of October–beginning of November and included height and oven-dry weight of saplings, stem number, leaf/stem ratio of oven-dry weight and length of the longest thorn. It was found that height and oven-dry weight were increased in the first three years but they declined thereafter both in clones and families. Overall, however, clones were superior to families. Stem number was increased with age more in families than in clones. Leaf/stem ratio of oven-dry weight declined with time but clones were superior to families. Thorn length, finally, increased over the years but clones had significantly lower values than families. The results showed that the most productive clones were also better in quality characteristics (leaf/stem ratio of oven-dry weight and thorn length) than most families and the control. It is concluded that clonal selection can result in significant increase of biomass quantity and improvement of its quality.     

Artificial hybridization between Robinia pseudoacacia L. and R. pseudoacacia var. monophylla Carr.

Results regarding artificial cross- and self-pollination betweenRobinia pseudoacacia L. and R. pseudoacacia var. monophyllaCarr. are reported. Parental clones involved in a diallel matingscheme were selected according to leaf type phenotype and included(1) single-leaf type, (2) 25-leaf type, (3) three-leaf typeand (4) common Robinia. Artificial pollination proved to bea difficult and delicate procedure. A total of 33 pollinationswere made that resulted in the formation of 84 pods, of which24 developed fully and produced 65 seeds. Fifteen seeds weregerminated, resulting in the production of two putative fertilehybrids. The success of hybridization was assessed by geneticmarkers, while parental clones and hybrid progeny were assignedmultilocus genotypes. The mode of inheritance of the leaf typetrait was studied in open-pollinated families where the monophyllatype was the maternal parent. The study indicated that leaftype in the monophylla variety may be associated with majorgene effects.     

Effects of age and frequency of cutting on productivity of Mediterranean deciduous fodder tree and shrub plantations

Deciduous fodder trees and shrubs are important feed resources for the critical summer period in semi-arid and sub-humid Mediterranean environments. Eleven such species were established in central Macedonia, Greece as 1-year old seedlings in 1987 and studied through 1994. Height and biomass were statistically different among species and tended to increase with the age of plants. Common Robinia pseudoacacia was the tallest and the most productive species, reaching more than 3 m height and 4 kg DM/plant 8 years since planting; it was followed by Ostrya carpinifolia, the variety monophylla of Robinia, Colutea arborescens and Amorpha fruticosa. Grazeable proportion of total biomass was about 50% and decreased as the age of plants increased. Repeated annual cutting resulted in significant reduction of both height and total biomass by 51% and 88%, respectively as compared with uncut plants at the end of the eighth year while frequent cutting tended to increase the grazeable proportion of biomass after the fourth year. To attain an optimum combination of quantity and quality of biomass in deciduous fodder tree and shrub plantations cutting or grazing should not start earlier than the third year since establishment.     

Productivity of deciduous woody and fodder species in relation to air temperature and precipitation in a Mediterranean environment

Productivity and its relation to air temperature and precipitation of 11 deciduous woody fodder species was studied in a semi-arid Mediterranean environment with cold winters in Macedonia, Greece. The species studied included six shrubs: Amorpha fruticosa L., Carpinus orientalis Mill, Colutea arborescens L., Corylus avellana L., Fraxinus ornus L. and Ostrya carpinifolia Scop.; and four trees: Pirus amygdaliformis Vill., Quercus pubescens Wild., Quercus sessiliflora Salish. and Robinia pseudoacacia L., with two accessions, common and spineless. Fodder species were established as one-year-old seedlings in 1987 and studied through 1994. Productivity was measured by clearcutting of the aboveground annual biomass (DM) at the end of each growing season. Samples of biomass were hand separated to determine the grazeable material (leaves and twigs). In addition, monthly values of air temperature and precipitation were correlated with annual biomass through a multiple linear regression analysis. It was found that annual biomass was statistically different among species in all the study years with Robinia being the most productive of all the species tested followed by the other two legumes Colutea and Amorpha. Proportion of grazeable material ranged widely among species and years with an overall mean of 50%. Robinia produced grazeable biomass more than 1000 kg/ha followed by Amorpha and Colutea with about 800 and 700 kg DM/ha, respectively, while all the other species produced less than 500 kg DM/ha. Yearly variation in annual biomass was found to be affected much more by air temperature, especially during the beginning of the growing season (March), than by precipitation. Coefficients of determination (r ²) were found to be high (0.50–0.80) in Amorpha, Pirus, Quercus and Robinia but only in the latter two species they were high enough (>0.70) so that the relations produced can be used for predictive purposes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Insecticide resistance status of Myzus persicae (Hemiptera: Aphididae) populations from peach and tobacco in mainland Greece

The susceptibility of 88 and 38 field samples of Myzus persicae (Sulzer) to imidacloprid and deltamethrin respectively was examined using the FAO dip test bioassay. The field samples were collected from tobacco and peach from various regions of Greece in the period from 2004 to 2006. In addition, 497, 349 and 370 clones originating from peach and tobacco were screened for the three known resistance mechanisms, elevated esterases, modified acetylcholinesterase (MACE) and knockdown resistance (kdr) respectively, using biochemical and DNA diagnostics. Most of the samples assayed with imidacloprid showed low resistance factors (RFs)-39% below 5 and 21% between 5 and 10. However, 9% of the samples (all from tobacco) showed relatively high RF values (24-73). Differences were found between crops, with higher RF values recorded in samples from tobacco than in those from peach. Bioassays with deltamethrin revealed the development of strong resistance in the populations examined. The RFs were mostly higher than 23, and in 29% of the samples they were extremely high (152-436). Finally, the three known resistance mechanisms were found in high frequencies in the populations examined, although some differences between crops and years were detected. The implications of the study for management schemes against M. persicae are discussed.