Search Results

You are looking at 81 - 90 of 708 items for :

Clear All

Abstract

Seeds from ‘Bartlett’ and ‘Winter Nelis’ and ovules from seedless ‘Bartlett’ pears were collected periodically between 25 days after full bloom and harvest. Extracts were analyzed for hormones by combined gas chromatography-mass spectrometry, using the technique of selected ion current monitoring. Levels of 6 gibberellins were low in all samples prior to appreciable embryo growth (25 days after full bloom). Content of gibberellins A17, A25, A45 and a presumed 3β-hydroxy gibberellin A45 rose dramatically during rapid embryo growth between 65 and 85 days after full bloom, while the gibberellin content of embryoless ovules of ‘Bartlett’ did not change during this period. Two unidentified gibberellin-like compounds, one isomeric with gibberellin A25 and the other corresponding to a hydroxy gibberellin A45, were detected 85 days after full bloom. Abscisic acid content was also maximal between 65 and 106 days, ovules of seedless ‘Bartlett’ exhibiting considerably higher concentration than seeds of either cultivar. Levels of 5 abscisic acid metabolites varied with seed type and sampling period. Phaseic acid levels remained low in ‘Bartlett’ seeds and ovules during all developmental stages but increased in ‘Winter Nelis’ seeds at 122 days. Concentration of cis, Trans-dihydrophaseic acid, although low, rose as ‘Winter Nelis’ seeds matured while ovules of seedless ‘Bartlett’ showed no such increase. Levels of 2 metabolites, tentatively identified as trans, trans-dihydrophaseic acid and a hydroxylated derivative of dihydrophaseic acid, varied only slightly with development. A third metabolite, characterized as a keto derivative of dihydrophaseic acid or a hydroxy-derivative of phaseic acid, was present in large quantities in unfertilized ovules during the early period of fruit growth, but increased in seeds only after 65 days. The possible roles of these compounds are discussed in relation to seed, fruit, and flower development.

Open Access

A new spontaneous mutation of the pear variety Dr. Jules Guyot, named `IGE 2002', was selected from a pear growing area in Catalonia. The clone was established in vitro from a 40-year-old tree, a highly recalcitrant material unable to root by cuttings. An in vitro micropropagation protocol, with an average multiplication rate of 5, a 90% rooting, and an acclimation of 79% of the plantlets, was defined. Self-rooted plants were grown in two experimental stations, covering two distinct fruit growing areas. The main agronomic characteristics of the clone `IGE 2002' were evaluated during six seasons, 1997 to 2002. Blooming and harvest period were at a similar time than `Dr. Jules Guyot'. Soluble solids concentration and acidity are also similar to `Dr. Jules Guyot'. However, at the same harvest time, a lower fruit firmness of `IGE 2002' in comparison to `Dr. Jules Guyot' indicated an advanced ripening. In addition, a finer flesh texture of `IGE 2002' than `Dr. Jules Guyot', distinguished the former from the later variety. Important differences between both plot sites were found on cumulative fruit yield, fruit size, and fruit size distribution, of `IGE2002' grown on its own roots. However, the site did not affect the fruit quality parameters. Superior fruit yields were associated with higher vigor and yield efficiency of the self-rooted variety.

Free access

The aim of this study was to investigate the roles of spur characteristics and carbon partitioning in regulating cultivar differences in fruit size of two late-maturing japanese pear cultivars, `Atago' and `Shinkou'. The study of spur characteristics showed that the two cultivars displayed different patterns in leaf development, flower characteristics, fruit growth, and shoot type. In contrast to `Atago' with dramatically larger fruit, `Shinkou' is a heavily spurred cultivar with a higher total leaf area and leaf number per spur early in fruit growth, less vegetative shoots, and smaller fruit but larger core. No significant differences were obtained in specific leaf weight, leaf thickness, chlorophyll content, and net photosynthesis of mature leaves, and seed number per fruit between the two cultivars. The results of trace experiment with 13C revealed that on a spur basis, there were no significant differences in the amount of 13C assimilate produced by spur leaves on each labeling date except at 190 days after anthesis, however, there were highly significant differences in the amount of 13C allocated to fruit between cultivars. Moreover, a higher amount of 13C assimilates was allocated to `Atago' flesh (or fruit) than that in `Shinkou'. Analysis of relative sink strength (RSS) indicates that the sink strength of fruit was dominant over those of other organs in the spur measured in both cultivars except at the early stage of fruit growth. `Atago' exhibited a greater RSS of fruit and lower losses of 13C for respiration and export than `Shinkou'. These results suggest that the movement of photosynthates into the fruit was determined by sink strength of the fruit rather than the source strength in the two cultivars.

Free access

‘Hanhong', tested as 86-1-32, is a progeny resulting from a cross between ‘Nanguoli’ ( Pyrus ussuriensis Maxim.) × ‘Jinsu’ ( Pyrus bretschneideri Rehd.) made in 1986 ( Fig. 1 ) at the Pomology Institute Academy of Agriculture Science of Jilin

Free access

, a French Pyrus communis cultivar named Nain Vert, originating from a chance seedling ( Fideghelli et al., 2003 ; Rivalta et al., 2002 ) and exhibiting the dwarf characteristic, was released. This cultivar forms a bush between 0.9 and 1.2 m high

Free access

). Reimer ranked species material for fire blight almost 100 years ago ( Reimer, 1915 ). He listed Pyrus ussuriensis as the most blight-resistant species, followed by Pyrus calleryana , Pyrus betualaefolia , P. pyrifolia , and P. communis , which was

Free access

., 1998 ). Moreover, the expression of the self-incompatibility (SI) reaction in Pyrus L. has been shown to vary depending on the cultivar or the experiment ( Crane and Lewis, 1942 ; Ishimizu et al., 1999 ; Tassinari et al., 2004 ; Zhang and Hiratsuka

Free access

Iron (Fe) plays an important role in several basic physiological functions and is an important factor involved in pear ( Pyrus spp.) tree growth and development. Iron deficiency chlorosis (IDC) is a worldwide problem that began in the 1930s

Open Access

-compatibility has been shown to occur as a result of mutation in the S-RNase gene: the self-compatible Japanese pear ( Pyrus pyrifolia ) cv. Osa-Nijisseiki carries a deletion in the S4 locus that includes the S - RNase gene ( Okada et al., 2008 ) and the

Free access

shoots with flower buds in the endodormant stage (Dec. 2006) were cut from mature japanese pear trees ( Pyrus pyriforia Nakai, ‘Kosui’) at the National Institute of Fruit Tree Science (Tsukuba, Japan). Branches were sprayed to runoff with distilled water

Free access