Fruit set has been shown to be a major limiting factor in cranberry (Vaccinium macrocarpon Ait.) productivity. Total nonstructural carbohydrate (TNC) content is lowest during the flowering and fruit set period. This research was undertaken to determine the potential sources of carbohydrates which are important to support fruit set and fruit growth in cranberry. Fruiting uprights had lower TNC content than vegetative uprights beginning at early bloom and continuing through harvest, largely due to lower starch content. Starch from fruiting uprights is apparently remobilized to support flowering and fruit set. This also suggests that uprights on which the fruit are borne are the primary source for carbohydrates for fruit set and fruit growth throughout the season. Net CO2 assimilation rates (NAR) were measured in the field on current season and one year old leaves on cranberry uprights. New leaves had higher NAR than one year old leaves throughout the season. Thus, newly formed leaves on uprights, appear to be an important source for carbohydrates for fruit set and fruit growth. On a diurnal basis NAR peaked at approximately 9:00 a.m. and gradually declined through the day.
Marianna Hagidimitriou and Teryl R. Roper
Marianna Hagidimitriou and Teryl R. Roper
`Searles' (low yielding) and `Stevens' (high yielding) cranberry (Vaccinium macrocarpon Ait.) tissues were collected in 1990 and 1991 to determine the concentration of nonstructural carbohydrates in above-ground (uprights, woody stems) and below-ground tissue. Uprights had the highest total nonstructural carbohydrate (TNC) concentration, followed by woody stems, while below-ground tissue contained the lowest TNC concentration. Total nonstructural carbohydrate concentration in uprights increased early in the season, reached a maximum in late May, decreased as flowering approached, and remained low from late June to late August. The latter period corresponds to flowering, fruit set, floral initiation, and fruit development stages. In late August, when fruit were full size, TNC levels increased, reaching highest concentration in November as the plants were entering dormancy. Most TNC increase in the early season and the subsequent decrease were due to changes in starch. The increase of TNC late in the season was primarily due to increases in soluble carbohydrates. Total nonstructural carbohydrate concentration was greater in vegetative than fruiting uprights for the entire growing season. The lower TNC concentration in fruiting than vegetative uprights during flowering and fruit set was due to greater starch depletion in fruiting uprights. Seasonal changes in TNC in the two cultivars were similar; however, `Stevens' had generally higher TNC concentration and total dry weight as well as more fruiting uprights, fruit, and fruit weight per ground area. The low TNC concentration observed during fruit set and development suggests that the demands for carbohydrates are highest during that period and supports the hypothesis that competition for carbohydrate resources is one factor responsible for low cranberry fruit set.
Teryl R. Roper and Marianna Hagidimitriou
Carbohydrate concentration may be important for flower initiation and fruit set in cranberry (Vaccinium macrocarpon Ait.). Fruit set has been shown to be a major limiting factor in yield component analysis. The objective of this research was to identify carbohydrate concentrations in cranberry tissues at various stages of development under field conditions. Samples of two cranberry cultivars, `Stevens' and `Searles' were collected during the 1989 season using a 13 cm diameter probe. Samples were divided into fruit, uprights, woody stems and roots. Carbohydrates were quantified by HPLC. Nonstructural carbohydrates were primarily sucrose, glucose, fructose and starch. Soluble carbohydrate concentration was stable throughout the season in tissues analyzed, while starch content was high early in the season then decreased during blossom and fruit set. This work shows that starch reserves in leaves and stems apparently are remobilized to support fruit set in cranberry.
Teryl R. Roper, John Klueh, and Marianna Hagidimitriou
Cranberry (Vaccinium macrocarpon Ait.) vines were shaded with either 72% or 93% shadecloth (28% or 7% of full sun) for 1 month before flowering, after flowering, or before harvest. Fruit set was reduced by heavy shade (93%) before flowering in 1991 but not in 1992 or 1993. Heavy shade following flowering reduced fruit set in 1991 and 1992 but not 1993. The number of flowers per upright was generally not affected by shading but was reduced by prebloom shading at either level in 1993. Mean berry weight was usually conserved. Yield was reduced by shading at either level following flowering in 1991 and 1992. Shading just before harvest had no effect on the characteristics measured. Total nonstructural carbohydrate concentration was reduced to about half relative to the controls by either shading level at all treatment dates. Carbohydrate concentrations recovered to control levels by 4 to 8 weeks following removal of shading. Shading always reduced carbohydrate concentrations but did not always reduce fruit set or yield.
Marianna Hagidimitriou, Andreas Katsiotis, George Menexes, Constantinos Pontikis, and Michael Loukas
The aim of the present study was to develop a reliable reference database to discriminate between the major Greek olive (Olea europaea L.) cultivars and reveal their genetic relationships, since Greece is considered a secondary center of diversity. In order to establish genetic relationships among the 26 Greek and eight international cultivars, four amplified fragment length polymorphism (AFLP) primer pairs, 12 randomly amplified polymorphic DNA (RAPD) primers, along with measurements from 10 morphological traits, were used. A total of 576 AFLP and 113 RAPD markers were produced. Genetic similarities, estimated using the Jaccard algorithim, ranged from 0.45 to 0.83 for the AFLP data and 0.27 to 0.87 for the RAPD data. The cophenetic correlation coefficients between the genetic similarities and the unweighted pair group method of arithmetic averages (UPGMA) phenograms were 0.77 for the AFLPs, 0.81 for the RAPDs, and 0.69 for the morphological traits. However, limited clustering similarities among the phenograms derived from the three methods were observed. This was also reflected by the low correlation between the three genetic similarity matrices produced (AFLP and RAPD, r = 0.39; AFLP and morphological traits, r = 0.11; RAPD and morphological traits, r = 0.02). According to the molecular results, olive cultivars are clustered according to fruit size but not according to geographical origin. Three of the cultivars tested, `Vasilicada,' `Throumbolia', and `Lianolia Kerkiras', were found to branch distantly to the others, according to the AFLP results, and can be considered as ancient Greek cultivars.