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Dormancy release dynamics in olive tree (Olea europaea L.) reproductive buds as affected by cold accumulation, tree bearing status, and budburst temperature was studied under natural and controlled conditions, using both cuttings and container- and field-grown plants. The chilling necessary for dormancy release was acquired at different times within the bud population, presenting a progressive pattern of reproductive budburst. Once sufficient chilling is accumulated, 20 °C is a suitable temperature for reproductive budburst, although higher temperature, e.g., 30 °C, during dormancy release can inhibit budburst. While the bearing status of trees determined the amount of return bloom, dormancy release followed a similar pattern for previously bearing and non-bearing trees. Concurrent with investigating budburst factors, the use of shoot cuttings was tested as a method for olive dormancy release studies by contrasting with results from whole trees. It was found it to be valid for studying reproductive budburst, thus providing a useful method to screen chilling requirements in cultivar evaluation and the breeding programs currently ongoing in this species. However, the method was not valid for vegetative budburst, with varying results between cuttings and the whole plant.

Winter rest and release of axillary buds from dormancy have been frequently noted but scarcely studied systematically in the olive tree (Olea europaea L). A series of experiments was carried out over three consecutive fall-winter periods, with one-node and three-node leafy and defoliated explants from shoots sampled from nonbearing (OFF) and bearing (ON) trees and forced in a growth chamber at different constant temperatures (12.5, 15, 20 and 30 °C). Buds acquired reproductive budburst capacity after a period of chilling accumulation on the tree for both OFF and ON explants, with percentage of reproductive budburst substantially higher in the OFF explants. Reproductive budburst occurred on explants sampled from early January to the second half of February, with slight variation in dates among the different experiments and seasons. During this period, forcing temperatures and defoliation influenced bud growth and development. Reproductive budburst activity indicated that 12.5 °C forcing temperature added effective chilling and promoted earlier budburst, while 20 °C forcing was only effective in promoting reproductive budburst after buds had accumulated enough natural chilling and 30 °C forcing produced a delay in reproductive budburst. From early sampling dates defoliation promoted vegetative budburst, which was then substituted by reproductive budburst as natural chilling accumulation increased. In histological comparisons of the buds a “shell-zone” of active morphogenetic activity was observed in the third node axils of OFF buds at the start of reproductive budburst capacity, later forming an inflorescence branch by the end of the sampling period. Starch presence shown by staining increased during the natural chilling accumulation period and then progressively disappeared with reproductive budburst. These results indicate dormancy release in the potentially reproductive buds following chilling and prior to inflorescence initiation and development. In addition to th

Verticillium wilt, caused by the fungus Verticillium dahliae, is currently the most important disease affecting olive in the Mediterranean basin. There are no effective treatments for controlling this disease. The use of infected nursery stocks has largely contributed to the spread of the pathogen, and therefore the development of treatments to preventively sanitize the propagation stock is critical in the nursery industry. This study describes novel techniques to achieve this aim. The effects of several temperature–exposure time combinations were evaluated: (i) the survival of pathogen on culture medium (PDA); (ii) the pathogen viability on infected shoots and plants; (iii) the vegetative growth of plants of several cultivars; and (iv) the rooting ability of cuttings. The colonies of the pathogen growing in PDA were killed after 8 h and 60 min of exposure at 40 and 47°C, respectively. Temperatures ≥42°C for at least 2 h were lethal for the pathogen infecting the shoots. Likewise, moist hot air treatments at 42–44°C for 6–12 h eradicated the pathogen, without compromising the viability of the plants. Five olive cultivars were also evaluated and classified according to their thermotolerance as follows: sensitive (Chiquitita), moderately sensitive (Koroneiki, Frantoio and Picual) and heat tolerant (Arbequina). However, the optimized sanitation methods were applicable to all of the cultivars. Finally, heat treatments were applied to unrooted cuttings, which severely affected their rooting ability. Thus, this study developed a hot air treatment to produce V. dahliae-free olive nursery plants.

Observations of olive bud lnttlatlon, growth and dormancy and new experimcnts with olive shoot explants have broadcncd our understanding of bud dormancy in potentlally reproductave buds, the role of chllling, and biennial beanng. Shoot apex and lcaf removal al differcnt limes and the effcct of temperat:ure on reproductive budburst wcrc tcsted on shoots ilnd shoot explants samplcd from ON (high cropping) and OFF (low cropping) lrees. Ovcrall the results indicatc and/or confirm: 1) a long period of dormancy onset in the axilary buds during vegetative shoot growth; 2) floral transation ofbuds from undefined to reproductive is mhib1ted by the presence offruits; 3) dormancy becomes generalized in all axillary buds (winter rest) with autumn low temperatures; 4) leaves play a major role in triggcnng and maintaining dormancy in ax illary buds; S) chilhng accumulation releases potential reproductive buds from dormancy; 6) reproductivc bud development 1s morphologically initiated after wanler rest; and 7) similar dormancy release dynamics occur in polcntial reproductive buds on explants from shoot.s sampled from ON and OFF trees and in shoots remalning on lhosc trces. Rega rding the significance of cold temperaturc. we hypotheslzcthat chllling-imposed winter rest ampedcs the relnitiation of growth of potcntlally reproductive buds in winter and promotes a synchronized budburst process that standardizes the timing of inflorescence and flowcr development in buds formed over a long time the previous ycar, thus providing a s hort and synchronized blooming period.

The evaluation of the relative susceptibility of new cultivars to the main diseases of a crop is a key point to consider prior to their release to the nursery industry. This study provides a rigorous characterization of the resistance of 15 new olive cultivars and their genitors (‘Arbequina,’ ‘Frantoio,’ and ‘Picual’) to the three main aerial diseases, peacock spot, anthracnose, and cercosporiosis caused by Spilocaea oleagina, Colletotrichum acutatum, and Pseudocercospora cladosporioides, respectively. To do so, developing leaves and detached green-yellowish fruit were inoculated in laboratory tests with S. oleagina and C. acutatum, respectively, using conidial suspensions of both pathogens. Additionally, a previously validated rating scale was used to assess the incidence of leaves with symptoms of S. oleagina or P. cladosporioides and the fruit rot incidence of C. acutatum in the trees for four years under field conditions. As a result, only two of the cultivars were susceptible to peacock spot, most likely because these new cultivars were previously screened for resistance to the disease on previous phases of the breeding program. Conversely, the 15 cultivars were susceptible or moderately susceptible to cercosporiosis. Five of the 15 new cultivars were classified as resistant to anthracnose, with four of them descendants of ‘Frantoio’ × ‘Picual’ crosses. In addition, the cultivars resistance to C. acutatum showed a negative linear correlation with the total phenols content of olive oil. This information regarding disease reaction of the new olive cultivars is essential for nursery industry and growers.

Shortening the juvenile period (JP) is one of the main strategies to increase the efficiency of olive breeding programs due to the long generation time of this species. Seedling vigor has been reported to be negatively associated to the length of the JP. In the present work we analyzed the influence of the female genitor on the length of the JP of olive seedlings, their vigor (plant height and trunk diameter), and the relationship between seedling vigor and JP using 3650 seedlings from 10 female genitors evaluated over 14 years. Overall, the length of the JP significantly varied for the female genitor and year of germination. Female genitors evaluated were classified into three groups according to the length of the JP of their progeny, as follows: short (‘Arbequina’ and ‘UCI 7-34’); medium (‘Lechín de Sevilla’, ‘Manzanilla de Sevilla’, ‘Picual’, ‘UCI 11-28’ and ‘Zaity’); and long JP (‘Frantoio’, ‘Memecik’ and ‘UCI 10-30’). Vigor, measured as the height of the seedling at planting, was significantly correlated (P < 0.001) with the length of the JP for all progenies except for those of ‘Lechín de Sevilla’, ‘Memecik’ and ‘UCI 10-30’ because most of their seedlings did not flower during the studied period. The highest proportion of flowering plants was obtained when the height of the plants was from 126 to 150 cm at planting. In addition, flowering, measured as presence or absence of flowers, was significantly related to the plant height according to a logistic regression. Nevertheless, for each female genitor, the inflection point of the curve (height at which 50% of the seedlings flowered) presented different values, suggesting that height selection thresholds should be specific for each female genitor.

Hybrid cucumbers were cultivated on the red clover/grass ploughed in the autumn (control). Aditionally in the spring compost (25 t.ha-1) and the liquid manure (20 m3.ha-1)were applied. Enrichment of the soil with the composition of effective microorganisms (EM - 5l.ha-1) or 3-times foliar spray of 0.2% sea-algae extract was also applied in the experiment. The soil surface was mulched with the straw, red clover/grass and black polypropylene (PP-50 g.m2) or left coverless (control). The earliness and structure of the yield, the content of mineral nutrients in the soil and in the plant and the biological value of fresh and dill pickled cucumbers were determined. The fertilization with the liquid manure significantly increased the content of N-NO3 in the soil in the first period of plants growth, more than in the case of compost. The use of EM had no effect on available nitrogent content in the soil. The content of N-NO3, during vegetation period, in the soil mulched with clover was higher than in control as well as in soil covered with straw or polypropylene fleece. The additional use of organic fertilizers or the soil enrichement with EM asa well as foliar spraying with the sea-algae extracts, in cucumbers cultivated on ploughed 2-years red clover/grass, did not increase early and marketable yield of cucumber. The fertilization with the liquid manure and straw mulching had unfavorable effect on the yield and crop quality, increasing the share of misshaped fruits and occurence of hollow seed cavity. Compost fertilization, foliar spraying of sea-algae extract and red clover mulch secured the best quality of dill pickled cucumbers.

The research cycle encompass year-long organic vegetable greenhouse production. Spring crop was grown pickling cucumbers followed by autumn tomato. During winter month without heating annual cover crops (mixture of oat, hairy vetch and field peas) were grown and as an green manure incorporated to the soil in spring before cucumber cultivation. Additional organic fertilizers (compost and chicken manure) were applied before cucumber and tomato planting. In the period between cucumber and tomato cultivation the soil in greenhouse was solarizated. In both crops soil surface was mulched with black fleece or fresh red clover biomass. Transplants of both species were produced in organic substrate. Cucumbers were planting in the soil but tomatoes in bottomless containers of 0,5 dm3, placed directly on the soil surface. The period of cucumbers growing was 90 days and tomatoes 120 days. Every 2 – 3 weeks in cultivation period nutrients concentration in soil solution was monitored on the depth of 30 and 60 cm. Growth development, earliness, yield and quality of fruits were determined. Red clover mulch positively influenced on cucumber and tomato growth and yield when applied early in the season, soon after transplant planting. In the initial period of plant growth (till fruiting) considerable amounts of nutrients (mainly nitrogen and potassium) were leached to the soil depth of 30 and 60 cm. After fruits setting and during fruits growth nutrient contents in soil solution considerably decreased and necessity of additional nutrients supply appeared. It was done by fertigation. In Polish climate condition soil solarization in summer months decreased the total number of soil microorganisms and was more effective while good insolation.

RAPD markers generated by mixtures of two different 10-mer primers were developed for eight different olive cultivars used as parental lines in olive-breeding programs. Two RAPD bands were converted into dominant SCAR markers by direct sequencing of the RAPD products, avoiding the costly and time-consuming cloning step. The SCARs generated have maintained the original RAPD polymorphism among the cultivars and segregated according to Mendelian inheritance. Preliminary results suggest the use of the SCAR SCOeMS-2 for the marker-assisted selection of the high flesh/stone ratio. This strategy provides a rapid method for the characterization of RAPD markers and for the development of PCR-based markers with applications in olive mapping, paternal testing and germplasm characterization. The use of these markers in multiplexed PCRs, and the direct ethidium bromide detection of the PCR products in the test tube, facilitate their efficient and reliable breeding applications.

When developing SCARs by sequencing RAPD markers useful for olive variety identification, one RAPD sequence of 407 bp has been identified that shows significant DNA homology with more than 160 retrotransposon-like sequences. A generally coherent phylogenetic tree has been constructed based on the homologous retrotransposon-like sequences, reflecting genetic distances in 35 species belonging to eight kingdoms. The implications of this finding in the development of SCAR markers are discussed. In addition, specific oligonucleotide primers have been developed to amplify the DNA region and have a practical application as an internal amplification control in SCAR-based multiplexed PCRs. To our knowledge, this is the first report of a retrotransposon-like element in olive.

In the olive (Olea europaea L.), inflorescence and flower differentiation occur in the early spring following a period of winter chilling and dormancy of the potentially reproductive buds. We examined the size, structure, and starch content of these buds during winter rest in the field and during forcing under standard growth-chamber conditions. Basic bud structure and dimensions remained unchanged during the rest period, but starch content increased in the bud’s central axis. When cuttings were forced in the growth chamber, the buds followed a morphogenetic pattern similar to that observed in the field, but the sequence of developmental events could be timed more precisely. The first changes observed were the onset of axis growth and the differentiation of axillary primordia within 3 days of transfer to the growth chamber. This was followed by the initiation of new nodes, and, at 15 to 18 days, by the first signs of floral differentiation in the terminal and axillary bud apical meristems. Bud growth and differentiation were accompanied by a decrease in starch content.