early stages of growth and development as the glucose and fructose concentrations increased slightly through 28 DAA. It has been well established that sucrose accumulates massively during the final stages of maturation and is the dominant sugar in most
ReTain™ is a plant bioregulator containing the active ingredient aminoethoxyvinylglycine (AVG), which inhibits the ethylene biosynthesis pathway. In 1997, the first efficacy studies on `Royal Gala' apple with ReTain™ were conducted under New Zealand conditions in Hawkes Bay. ReTain™ was applied 4 weeks before the anticipated start of harvest on `Royal Gala' at 850 and 1700 g·ha–1 with or without adjuvants. ReTain™ application delayed the onset of `Royal Gala' fruit maturation between 1 and 2 weeks, resulting in enhanced fruit size and fruit flesh firmness at harvest. The optimum response for delaying the onset of fruit maturation was achieved using ReTain™ at 850 g·ha–1 if applied in combination with a wetter. Fruit were also graded for fruit quality and air-stored at 0.5 °C. Fruit after 10 weeks of storage showed no difference in fruit flesh firmness, but all ReTain™ treatments had fruit with less yellow background colour compared with untreated fruit. In 1998, efficacy studies were undertaken in three geographical locations on `Royal Gala'. ReTain™ was applied at a rate of 830 g·ha–1 in combination with Silwet L-77 at 0.1%. All trees with the exception of `Royal Gala' grown in the Hawkes Bay had not received any ReTain™ previously. In all regions, seasonal changes in background color and starch pattern index were delayed by ReTain™ treatment. A concurrent delay of an increase in soluble solids concentration and retention of higher flesh firmness were also induced by ReTain™ treatment.
Leaf samples of Ilex opaca ‘Miss Helen’ were collected over a 2-month period and analyzed on a mg/g basis for total nonstructural carbohydrates (TNSC), individual ethanol soluble sugars (IESS), total ethanol soluble sugars (TESS) and apparent storage carbohydrates (ASC). Samples were preserved for analysis by 4 methods: 1) liquid nitrogen killed freeze-dried (NFD); 2) liquid nitrogen killed oven-dried (NOD); 3) oven-dried (OD) and 4) ambient air-dried (AD). The samples showed significant decreases in TNSC between the NFD and NOD, NOD and OD and OD and AD methods; a significant decrease in TESS with the NOD and OD methods and a further significant decrease in TESS with the AD method. A significant increase in ASC was noted with the AD method. Gas liquid chromatographic analysis of the IESS revealed a significant decrease in D-fructose and D-galactose with the AD method, a significant decrease in α-D and β-D glucose with the OD method and an additional decrease in both sugars with the AD method. Sucrose was undetectable with the NOD method, and was significantly decreased with the OD and AD methods. TNSC, TESS and ASC all decreased significantly with leaf maturation and expansion. Time of day of sampling showed no significant differences in any carbohydrate fraction.
In New Zealand, harvest maturity for kiwifruit is determined by the soluble solids concentration (SSC) of juice (minimum 6.2%). Commercial maturity differs in various regions of the country within each season and between years and may be due to differences in temperatures during growth.
Mature `Hayward' kiwifruit vines were grown in controlled environment temperature treatments of 14/8, 18/8, 22/8, 26/8, 14/12 and 22/12C to determine whether the increase in SSC at low night temperatures recorded in a related study was a result of the mean temperature, the min. daily temperature, or the magnitude of the max./min. temperature difference. Measurement was made of fruit size, firmness, starch and total sugar concentrations in the fruit at 10 day intervals.
SSC increased fastest with the coolest mean temperature irrespective of the min. temperature or max./min. difference. In the coolest treatment the concentration of starch decreased rapidly with a rise in total sugar, in the warmest treatment the change in the carbohydrate components was slower. Data will be used to predict harvest date at commercial orchard sites based on field temperature measurements.
A single-value estimate of maturity response and an independent estimate of the thinning response to treatment can be determined from detailed harvest records. Thinning index is estimated from the total number of fruit per tree; maturity response is estimated from the weighted-average harvest date.
Maturation and germination of mango (Mangifera indica L.) somatic embryos were achieved by sequential transfer of heart-shaped somatic embryos on a series of media based on the B-5 formulation. Precocious germination and other developmental abnormalities were controlled by incorporating 3 μm abscisic acid (ABA) and 6% (w/v) sucrose in the medium. Other factors, including the substitution of Gelrite (0.175%) for agar, the use of solid rather than liquid medium, and the culture of somatic embryos in darkness until physiological maturity also affected normal growth and development. Coconut water (20%, v/v) was also essential for mango somatic embryogeny. Germinated mango somatic embryos were successfully established in planting medium and they have continued to grow in a greenhouse.
To understand the relationship between fruit cracking and gene expression patterns, we identified two expansin genes from litchi (Litchi chinensis Sonn.) fruit and then examined their expression profiles in pericarp and aril at different stages of fruit development, using the cracking-resistant cultivar Huaizhi and the cracking-susceptible cultivar Nuomici. Two full-length cDNAs of 1087 and 1010 base pairs encoding expansin, named LcExp1 and LcExp2, were isolated from expanding fruit using RT-PCR and RACE-PCR (rapid amplification of cDNA ends) methods. LcExp1 mRNA could be detected from the early stage of fruit rapid growth (59 days after anthesis). The LcExp1 mRNA increased and reached to the highest level at the end of growth phase (80 days after anthesis) in pericarp of `Huaizhi', while the mRNA could be detected at the stage of rapid fruit growth, then increased slightly and finally kept remained almost constant in the pericarp of `Nuomici'. Similar accumulation of LcExp2 mRNA was observed in fruit aril of `Nuomici' and `Huaizhi', whereas LcExp2 accumulated only in pericarp of `Huaizhi' but did not appear in pericarp of `Nuomici'. The results indicate that expression of two expansin genes in litchi pericarp are closely associated with fruit growth and cracking.
Field experiments were conducted on organic soil for 2 years to evaluate the influence of frequent irrigation and topdressings with N on growth, maturity and storage life of onions (Allium cepa L.). With no irrigation, growth to midseason, maturity, and final yield were not influenced by increasing amounts of N. The growth to midseason, and the final yield increased and maturity was earlier with increasing amounts of N applied to onions receiving 5 cm of rainfall + irrigation per week. Sprouting in storage was earlier with high N and latest with no N or with the low N rates. The effect was greater with irrigation.
Onions did not respond to N topdressing without irrigation even though rainfall was regular. With irrigation, the highest yield and earliest maturity was obtained with 22 or 34 kg of N/ha applied whenever the crop received 10 cm of water. No advantage in yield or maturity was obtained by applying N after mid-July. Maturity was earlier without irrigation regardless of N treatment.
The notion that ethylene production levels in nonmelting-flesh (NMF) peach (Prunus persica L.) fruit are normally lower than those in melting-flesh (MF) fruit is refuted in our study. In fact, NMF fruit (`Oro A' and FL 86-28C) usually produced higher levels of ethylene than did MF fruit (FL 90-20 and `TropicBeauty'). In both MF and NMF peaches, the rate of ethylene production, rather than the respiration rate, provided a good indication of the developmental stage of the fruit at harvest. Ethylene content in fruit on the tree followed a climacteric pattern, with the level in `Oro A' (NMF) and FL 90-20 (MF) peaking at 50 and 12 μL·L–1, respectively. The respiratory climacteric was not apparent in either `Oro A' or FL 90-20, and levels of CO2 were similar in both genotypes.
Polyphenols were analyzed in expanding buds and developing leaves of pecan [Carya illinoensis (Wangenh.) C. Koch] cultivars with varying responses to Cladosporium caryigenum (Ell. et Lang. Gottwald), the organism causing scab. Plant tissue extracts were examined by high-performance liquid chromatography using a water: methanol gradient to separate polyphenolic components on a C-18 reversed phase column. A diode-array detector was used to identify profile components by retention times and computer matching of ultraviolet spectra to standard compounds in a library. Concentrations of these polyphenols were compared throughout the growing season in leaves of pecan cultivars with low (`Elliott'), intermediate (`Stuart'), and high (`Wichita') susceptibility to scab; during susceptibility to infection by Cladosporium caryigenum from 16 cultivars; and in `Wichita' leaf discs with and without scab lesions. The major polyphenolic constituent of tissues for all cultivars was identified as hydrojuglone glucoside, which was detected in intact buds and leaves throughout the growing season. Hydrojuglone glucoside concentration increased concomitantly with leaf expansion and then declined slowly. Juglone was barely, if at all, detectable, regardless of leaf age. No correlation was found between cultivar susceptibility to pecan scab and the levels of either juglone or hydrojuglone glucoside in the healthy leaves of 16 cultivars. Leaf tissue with scab lesions had significantly higher juglone and hydrojuglone glucoside levels than leaf discs without scab lesions. Chemical names used: 4-8-dihydroxy-1-naphthyl b-d-glucopyranoside (hydrojuglone glucoside); 1,5-hydroxy-naphthoquinone (juglone).