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Seasonal changes in leaf gas exchange, assimilation response to light and leaf area were monitored in bearing and nonbearing pistachio shoots. Shoot bearing status did not directly affect leaf photosynthetic rate. However, photosynthetic light-response curves strongly varied during the season demonstrating the dominant effect of the tree’s seasonal phenology on assimilation. Early in the season low photosynthetic rates were associated with high rates of dark respiration indicating limited photosynthesis in the young leaves. As leaves matured, dark respiration decreased and assimilation reached maximum values. Photosynthetic efficiency was strongly reduced late in the season due to leaf age and senescence. Fruit load precipitated an early leaf senescence and drop that resulted in a 53% decrease in leaf area in bearing vs. nonbearing shoots, strongly decreasing the seasonal photosynthetic performance of bearing shoots. Bearing shoots produced a 26% lower seasonal carbon gain compared to nonbearing shoots.

In the last decade, high-density olive planting systems have been developed to facilitate less costly mechanical harvesting and pruning by using straddle harvesters. High-density orchards allow faster production since the first crop of fruit starts a few years after planting. In high-density orchards the control of tree size is essential. It is possible to control the vigour and size of the tree by selecting suitable cultivars, by choosing rootstocks capable of controlling scion vigour and, finally, by applying deficit irrigation to reduce plant vegetative growth. Knowledge of tree water requirements is needed for precise irrigation scheduling. In this study, the dwarfing capacity of two Leccino clones, Leccino Dwarf (LD) showing low vigour, and Leccino Minerva (LM) highly vigorous, was investigated under two water regimens, well-watered ( T 100 ) and water deficit ( T 50 ). We analysed growth rates, dry matter production, gas exchanges and water relations of one-year-old plants of Leccino Dwarf (LD) and Leccino Minerva (LM), grown in pots in open fields. The two genotypes showed significant differences in vigour, demonstrated by measuring the trunk diameter, shoot length and leaf area; values were significantly lower in clone LD. Stem water potential, photosynthesis and stomatal conductance were similar in both genotypes under a well-watered regime; they decreased when subjected to water deficit with values significantly lower in LM clone during the summer months, indicating physiological differences among clones and that LD adapts better to water deficit.

Summary This study, as a preliminary step toward the definition of a carbon budget model for pistachio trees (Pistacia vera L.), aimed at estimating and evaluating the dynamics of respiration of vegetative and reproductive organs of pistachio tree. Trials were performed in 2005 in a commercial orchard located in Sicily (370 m a.s.l.) on five bearing 20-year-old pistachio trees of cv. Bianca grafted onto Pistachio terebinthus L. Growth analyses and respiration measurements were done on vegetative (leaf) and reproductive (infructescence) organs during the entire growing season (April–September) at biweekly intervals. Results suggested that the respiration rates of pistachio reproductive and vegetative organs were related to their developmental stage. Both for leaf and for infructescence, the highest values were observed during the earlier stages of growth corresponding to the phases of most intense organ growth. The sensitivity of respiration activity to temperature changes, measured by Q10, showed an increase throughout the transition from immature to mature leaves, as well as during fruit development. The data collected were also used to estimate the seasonal carbon loss by respiration activity for a single leaf and a single infructescence. The amount of carbon lost by respiration was affected by short-term temperature patterns, organ developmental stage and tissue function.

Twelve published simple sequence repeat (SSR; microsatellite) markers, belonging to the ssrOeUA-DCA, GAPU and UDO series, were tested in a panel of 46 accessions of olive germplasm belonging to 30 unique cultivars collected in seven Provinces of Sicily. Four well-known reference olive cultivars were also added. The analysis was carried out on an automatic capillary sequencer using fluorescent dyes, and fragment sizes were determined using internal standards. The results allowed us to rank the SSRs assayed according to their information content and reproducibility. Up to 115 alleles were identified (119, if those unique to sport mutations were included), the frequency of which allowed genetic relationships among accessions to be investigated. The probability that two unrelated genotypes displayed the same SSR pattern at all loci examined was calculated to be as low as 1.18 × 10-11. Sixteen accessions were identified as synonyms. Of these, eight matched perfectly with another accession at all SSR loci examined. The others showed one or two allelic differences from the reference accession. These were interpreted as mutations. Otherwise, all accessions were clearly separated from each other. Two likely parentages were also identified ('Giarfara' = 'Nocellara del Belice' X 'Cacaridduni'; and 'Pizzo di Corvo' = 'Nocellara Etnea' X 'Tonda Iblea'). The genetic diversity of the pool represented by the unique accessions was very high, reflecting the richness of the olive germplasm accumulated in Sicily. A database of the accessions is available to the scientific community (http://www.unipa.it/germolive/ssr.html) to facilitate comparisons of data.

Olive (Olea europaea L.) shows alternate bearing, with unreliable cropping patterns and inconsistent fruit size and quality every year. In many countries, thinning with naphthaleneacetic acid (NAA) is used to minimise alternate bearing behavior in olives. However, in Italy, growers are reluctant to employ this practice and no detailed knowledge is available for specific cultivars. We evaluated the effects of spraying NAA on various dates on the productive and vegetative characteristics of the main Italian table olive cultivar'Nocellara del Belice'. Trunk cross-sectional area, fruit set, fruit drop, fruit size, pit size, yield per tree, crop density and flesh to pit ratio were analysed. The NAA treatment applied on the earliest of the dates selected increased fruit weight and flesh to pit ratio, by reducing crop density and enhancing the leaf to fruit ratio, without reducing yield. Two distinct negative relationships were found between fruit weight and crop density during "on" and "off" years, but a unique relationship between pit weight vs. crop density in both years, suggested that the pit is the strongest sink. Fruit size and quality of'Nocellara del Belice' can be enhanced by NAA application, thereby increasing economic returns in the "on" year.