The ripening inhibitor (rin) and non-ripening (nor) mutants each contribute additively as heterozygotes to delay ripening as measured by time from anthesis to the respiratory peak. The rin mutant as a heterozygote has no effect on the magnitude of the respiratory rise, whereas nor reduces the respiratory peak to about 50% of normal. The respiratory rise is further reduced to about 25% of normal in the double mutant hybrid (+ rin, + nor). Peak ethylene and fruit carotene production is reduced about 50% in single mutant hybrids and to 25% of normal in the double mutant hybrid. Polygalacturonase activity 5 days after the respiratory peak in heterozygotes of rin and nor and the double mutant hybrid was 35, 25 and 10% of normal, respectively. Ethephon treatment hastened ripening in all genotypes, but the magnitude of specific ripening events was determined by genotype. The mode of action of these mutants is not directly through endogenous ethylene but probably via a slow change which precedes the ethylene rise and other concomitant ripening changes. It is proposed that polygalacturonase synthesis or activation may represent the primary genetic event which is inhibited in the mutants and attenuated in mutant hybrids.
Transverse slices of green banana fruit were vacuum� infiltrated with aqueous solutions of 24 potential inhibitors of protein synthesis, respiration, or ethylene production. The effects of these compounds were examined in the absence or presence of 10 p.p.m. ethylene. Of the compounds which produced marked effects mono� fiuoroacetate, 4�hydroxy�2�oxoglutarate (HKG), KCN, and cycloheximide were examined in more detail.
Potassium permanganate reduced the concentration of ethylene and calcium hydroxide reduced the concentration of carbon dioxide in sealed polyethylene bags containing bananas. When the fruit that were not packed in sealed bags were ripe (16 days after the beginning of storage) all the fruit in sealed polyethylene bags were in a firm green condition and there was little difference between treatments in sealed polyethylene bags. After 29 days some of the fruit in sealed bags had softened, but fruit in bags containing potassium permanganate was firmer than fruit receiving other treatments, and this effect was more marked after 38 days. It was estimated that about two weeks additional storage life was obtained by packing potassium permanganate with the fruit.
F1 hybrids of the nor non-ripening mutant tomato in different genotypic backgrounds were evaluated between 1978-81. The nor gene in the heterozygous condition delayed the start of ripening by a few days, increased the interval between breaker and the table ripe stage to 10 d at 21�C compared with 6 d for fixed cultivars and increased the storage life of ripe fruit at 21�C by about 50%. The retention of firmness by ripe fruit of the hybrids was affected by parental genotype. Fruit of some hybrids was firmer or as firm as fruit of the hard commercial Flora-Dade but others were much softer. A major problem with fruit of F1 nor hybrids was poor colour development. The fruit ripened to an orange-red colour, and strains with green shoulders developed an unattractive yellow on the shoulders. This deficiency was most pronounced in fruit picked before the appearance of red colour. The best hybrid found in this study was 75T10-1 x nor backcross 4 or 5 Heinz 1350. Fruit size, soluble solids, pH, titratable acidity, total ascorbic acid levels and acceptability except external colour of table ripe fruit appeared to be influenced by the parental genotype rather than by the nor gene. Since there were marked differences between hybrids with different genotypic backgrounds, it should be possible to breed nor hybrids with improved colour and firmness.
Fruits of Halehaven and Fragar peaches (mid- and late season respectively) were sampled and examined weekly during one complete growing season. The period of rapid growth following anthesis (stage I) was characterized by relatively high respiration and ethylene production rates. Fruits of both cultivars entered the subsequent period of slow growth (stage II) together. Ethylene production was low and respiration declined throughout stage II. Sprays of (2-chloroethyl)phosphonic acid (ethephon), but not succinic acid-2,2-dimethylhydrazide (SADH), resulted in increased ethylene evolution by stage II fruits. Neither chemical altered respiration or the duration of stage II. Both chemicals, however, advanced commercial harvest and promoted ripening of fruits sampled throughout the final rapid growth period (stage III). All fruits sampled during stage III showed a climacteric-like increase in respiration and ethylene production. The horticultural effectiveness of SADH and ethephon appears to be due to a promotion of physiological activity in stage III. Abscisic acid in peach pericarp increased just before and during stage III. Possible roles for abscisic acid and ethylene in regulating the stage II-stage III transition in peaches and other fruits are discussed.
Green bananas were held in humidified gas streams comprising air (control); "high carbon dioxide" (A) (5% CO2, 20% O2,75% N2); "low oxygen" (B) (0% CO2, 3%,02,97% N2); "high carbon dioxide-low oxygen" (C) (5% CO2, 3% O2, 92% N2). Ripening in A, B, and C was delayed at least 2, 8, and 12 times respectively compared with air. These three gas streams also reduced the rates of oxygen uptake by the fruit but increased the total oxygen uptake over the period before the beginning of the respiratory climacteric.
The aim of the experiments described in this paper was to identify determinate cultivars suited to production of fresh market tomatoes on raised beds in the inland irrigation areas of the south-west area of New South Wales from January to April. Cultivars that produce high yields of first-grade medium to large fruit, and are smooth, nearly round, firm and an even bright red when ripe are required. The plants should have good leaf coverage to prevent sunburn, and jointless pedicels to facilitate harvesting. The period of maturation of the fruit should be short to permit recovery of the crop with a maximum of 3 harvests. Ten lines including Sunny, a .reference cultivar with jointed pedicels, were evaluated at Richmond in the Sydney Greater Metropolitan Area and at Leeton in the Murrumbidgee Irrigation Area, 1984-86. The lines were trickle-irrigated and mulched with black polyethylene film except at Leeton in 1985-86 when a trickle-irrigated, no mulch treatment and a furrow-irrigated treatment were included. The experiments showed that it is possible to produce yields of 50-100 t ha-1 of first-grade fruit with trickle irrigation. No significant advantage was obtained at Leeton in 1985-86 by using polyethylene mulch; however, the mulch largely eliminated the need for hand-chipping of weeds from among the plants. The visual quality of fruit grown at Leeton was excellent but total soluble solids levels were low, ripe fruit were unexpectedly soft, and sensory scores for flavour and general acceptability were only satisfactory. Overall, 2 cultivars that have jointless pedicels, Red Chief and Delta Contender, showed promise. A jointless hybrid line, HARU 83-148, which was bred at Richmond, warrants further evaluation. Some signs of incipient field chilling of fruit were observed at Leeton in fruit harvested after the first week in April.
Fuji apples have low rates of ethylene production at commercial harvest maturity, whereas Lady Williams apples, which are harvested commercially in late autumn, produce large concentrations of ethylene. We investigated whether chilling at 0�C, which has previously been shown to stimulate ethylene synthesis in preclimacteric Granny Smith apples, would stimulate Fuji and Lady Williams fruit as well. Preclimacteric Fuji and Lady Williams apples were stored in air at 0�C and were removed at intervals to 20�C. Ethylene production remained low in Fuji apples held continuously in air at 20�C. Fruit held for 32 days at 0�C accumulated 1-aminocyclopropane-1-carboxylic acid (ACC) and developed ACC oxidase activity. On return to 20�C these fruit had a high and sustained level of ethylene production. ACC accumulated in all chilled Lady Williams apples at 0�C but decreased to low levels within 2 days after transfer to 20�C. A sustained increase in ACC was not found until 15 days at 20�C in fruit chilled for 32 days. A distinct temporary increase in internal carbon dioxide (CO2) concentration was observed in Fuji apples but not in Lady Williams apples following chilling. Chilling for 32 days was required to stimulate sustained levels of CO2 in Lady Williams apples.
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