Ultralow oxygen treatment for postharvest control of western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), on iceberg lettuce: II. Effects of pre-treatment storage on lettuce quality

Iceberg lettuce stored under normal atmosphere and controlled atmosphere (CA) with about 3% oxygen at low temperature for 1 week was compared with fresh lettuce for their response to 2 d ultralow oxygen (ULO) treatment with 0.003% oxygen at 10 °C for control of western flower thrips. Lettuce which had been stored for 1 week under normal or CA tolerated ULO treatment while over 30% of fresh lettuce sustained minor injury to heartleaves. Therefore, pre-treatment storage at low temperature enhanced tolerance of lettuce to the subsequent insecticidal ULO treatment. A sequential combination of CA storage and ULO treatment was demonstrated to be effective against western flower thrips and lettuce aphid and safe to all seven lettuce cultivars tested. The study indicated that ULO treatment can be made safer to lettuce through pre-treatment storage to increase lettuce tolerance.     

Semi-commercial ultralow oxygen treatment for control of western flower thrips,Frankliniella occidentalis (Thysanoptera: Thripidae), on harvested iceberg lettuce

Pallet-scale ultralow oxygen (ULO) treatment was applied to iceberg lettuce after various lengths of postharvest storage to determine the effects of pre-treatment storage on lettuce tolerance to ULO treatment for control of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Lettuce from seven cultivars was vacuum cooled and stored at 2 °C after harvest for 0, 2, 3, and 5 d before being subjected to 2-d ULO treatment with 0.003% oxygen at 10 °C ambient temperature. Complete control of thrips was achieved in all three tests. Temperature of lettuce increased from about 5 °C at the start of ULO treatment to 9.6 °C at the end of the treatment. Fresh vacuum-cooled lettuce from three of seven cultivars sustained injury to heartleaves by the ULO treatment. Lettuce that had been stored at the low temperature for 2, 3, or 5 d before the ULO treatment tolerated the ULO treatment and there was no significant quality reduction compared with untreated controls. Heavier heads were significantly more susceptible to heartleaf injury than lighter heads. This study demonstrated that 2-d postharvest refrigerated storage followed by 2-d ULO treatment was effective in controlling western flower thrips with minimal adverse effects on lettuce quality. The ULO treatment protocols developed in this study also have potential to be scaled-up for commercial ULO treatment applications.     

Preharvest and postharvest factors related to off-odours of fresh-cut iceberg lettuce

The influence of different preharvest and postharvest factors affecting off-odour development of fresh-cut iceberg lettuce in low-O₂ modified atmospheres (MA) was investigated. Fresh-cut iceberg lettuce developed undesirable off-odours under low O₂ and elevated CO₂ atmospheres. A strong relationship between CO₂ concentration and off-odour development was observed. Significant differences in off-odour development existed among different cultivars in two harvests in consecutive years. The influence of maturity stage was evaluated, comparing fresh-cut product from immature and over-mature heads with commercial ones. Higher CO₂ concentrations and higher accumulation of ethanol and acetaldehyde were detected in the headspace of MA-packed lettuce from immature heads. Differences in respiration rate of the fresh-cut product from heads cultivated during the winter–spring seasons were around 30%. Respiration rate of fresh-cut iceberg lettuce increased when medium temperature during cultivation increased. Changes in the product weight generated different CO₂ levels which correlated with the production of ethanol and acetaldehyde and other off-odour metabolites related with the lipoxygenase (LOX) pathway such as hexanal, 1-hexanol, and cis-3-hexen-1-ol. Volatile compounds such as cis-3-hexen-1-ol, β-elemene, ethyl acetate and dimethyl sulphide increased their content more than 10 times compared with other volatiles. Moreover, differences in the initial flushed gas-mixture with or without CO₂ showed higher CO₂ concentrations and the development of stronger off-odours when samples were flushed with an enriched CO₂ gas-mixture. In summary, visual quality of fresh-cut iceberg lettuce is important but so are odour and flavour. MAP currently used for fresh-cut lettuce may need some modification to inhibit off-odours and achieve better aroma and flavour qualities for preserving “freshness” of the cut product. Screening for cultivars with low browning potential and fermentation, harvested at optimum maturity stage and with an adequate package design are recommended.     

Response of some Andean cultivars of quinoa (Chenopodium quinoa Willd.) to temperature: Effects on germination, phenology, growth and freezing

This article presents various experiments conducted under semi-controlled conditions to determine the effects of temperature on germination, phenology, growth and freezing in Chenopodium quinoa, a pseudocereal originating from the cold and dry Andean altiplano. Traditional landraces and recently released cultivars from distinct geographical origins were compared in order to look for local adaptation or breeding improvement with respect to low temperatures. Germination was evaluated in 10 cultivars at temperatures between 2 and 20 °C. Plant growth and development were examined in three cultivars over the growing cycle, under minimum temperature between 8 and 13 °C and maximum temperature between 20 and 28 °C. The thermal time concept was used to compare the various treatments and estimate the phyllochron, as well as the base temperature and optimum temperature for leaf appearance, time to flowering and leaf width growth. Two cultivars at the vegetative stage were compared for night freezing tolerance down to −6 °C, registering leaf exotherms and plant survival rate. The influence of plant water status and the possible protective or detrimental role of leaf epidermal vesicles were also examined. Low temperatures down to 2 °C delayed germination without impeding it totally. Base temperature for germination varied between −1.9 and +0.2 °C, with negative values in 9 cultivars out of 10. Thermal sensitivity in germination was not related to the geographic origin of the cultivars. Leaf appearance and time to flowering showed similar base temperatures near 1 °C. Phyllochron varied from 12.9 to 17.2 °C d with lower values in the two recently released varieties than in the traditional landrace. Leaf width increased from a base temperature around 6 °C up to an optimum temperature between 20 and 22.5 °C. Freezing experiments showed that no plant could survive after 4 h at −6 °C, while no serious effect was noted down to −3 °C. Leaf exotherms confirmed that ice nucleation occurred between −5 and −6 °C in most of the plants, the traditional landrace showing a lower freezing tolerance than the selected line. Low leaf water status delayed the freezing process, while leaf vesicles did not seem to play any protective or detrimental role towards leaf freezing. Implications of these results for quinoa crop adaptation to the Andean environment are discussed.     

Controlled atmosphere treatment for control of grape mealybug,Pseudococcus maritimus (Ehrhorn) (Hemiptera: Pseudococcidae), on harvested table grapes

Controlled atmosphere (CA) treatments with ultralow oxygen (ULO) alone and in combinations with 50% carbon dioxide were studied to control grape mealybug, Pseudococcus maritimus (Ehrhorn) on harvested table grapes. Two ultralow oxygen levels, 30 and <0.01 μL L⁻¹, were tested in both ULO and ULO + 50% CO₂ treatments. The ULO treatments with the lower oxygen level were more effective than the ULO treatments at the higher oxygen level. The ULO + 50% CO₂ treatments were more effective than the ULO treatments. Grape mealybug eggs were significantly more tolerant of ULO and ULO + CO₂ treatments than nymphs and adults. A 14 day ULO treatment with 30 μL L⁻¹ O₂ at 2 °C did not achieve 100% mortalities of any life stage. In the presence of 50% CO₂, the 14 d treatment achieved complete mortality of all life stages of the grape mealybug. A 3 d ULO treatment with <0.01 μL L⁻¹ O₂ at 2 °C resulted in 93.3% mortality of nymphs and adults. The 3 d ULO treatment in combination with 50% CO₂ treatments, however, achieved complete control of grape mealybug nymphs and adults and caused 70.5% relative egg mortality. Complete egg mortality was achieved in a 10 d ULO + 50% CO₂ treatment with <0.01 μL L⁻¹ O₂ at 2 °C. Both the 14 d CA treatment with 30 μL L⁻¹ O₂ and 50% CO₂ and the 10 d CA treatment with <0.01 μL L⁻¹ O₂ and 50% CO₂ were tested on table grapes and grape quality was evaluated after two weeks of post-treatment storage. The CA treatments did not have a significant negative impact on grape quality and were safe for table grapes. The study indicated that CA treatments have potential to be developed for postharvest control of grape mealybug on harvested table grapes.     

超低氧处理对采后马铃薯绿变及品质变化的影响

绿变是影响马铃薯采后品质的关键因素。研究了20℃温度、80%~85%相对湿度、24 h荧光灯照射条件下超低氧(ULO,0.3%±0.05%O2,CO20.2%)处理3 d和6 d对经2~4℃贮藏3个月的马铃薯绿变的抑制作用以及对发芽指数、还原糖、淀粉及VC含量等品质指标的影响。结果表明,马铃薯块茎经超低氧3 d和6 d处理,可明显抑制光照引起的马铃薯绿变,并有效抑制其发芽和VC含量的下降,其中超低氧处理6 d的抑制效果显著优于处理3 d,贮藏12 d后,马铃薯的绿变轻微,品质良好。     

Role of commercial sanitizers and washing systems on epiphytic microorganisms and sensory quality of fresh-cut escarole and lettuce

Increasing concerns about the possible formation of carcinogenic compounds and the emergence of new, more tolerant pathogens, have raised questions on the use of chlorine in fresh-cut produce. There is a growing need to investigate the efficacy of new commercial sanitizing and other alternative technologies. In the present study, the effectiveness of chlorine and other commercial sanitizer agents (Sanova, Sanoxol 20, Tsunami 100, Purac FCC 80, Citrox 14W and Catallix) was evaluated on epiphytic microorganisms and their influence on the sensory quality of fresh-cut escarole and lettuce. Different sanitizer concentrations (manufacturer's recommended dose and half of this dose) and application systems (submersion and spray) were also compared. The antimicrobial efficacy of the treatments was evaluated, initially after washing, and after 8 days of storage simulating a commercial shelf-life (3 days at 4 °C + 5 days at 8 °C). All the tested washing solutions were more effective in reducing the microbial load than water washes, particularly in fresh-cut escarole. However, the microbial load of fresh-cut escarole and lettuce after 8 days of storage was very similar for most of the treatments despite the different application systems and concentrations of the sanitizers. Clearly epiphytic microorganisms of fresh-cut escarole and lettuce were able to grow rapidly during storage under low temperature, reaching similar or higher values than the unwashed fresh-cut produce at the day of production. The overall visual quality of fresh-cut salad leaves was scored as good or very good (≥6) after 8 days of storage, except for the product washed with Purac. Thus, despite the high number of mesophilic bacteria present in the product, between 6 and 8 log cfu g⁻¹, it was not associated with a detrimental quality. Therefore, the determination of the initial epiphytic reductions of fresh-cut products after washing with different sanitizing agents provides little information about the microbial or sensory quality of the product at the time of consumption.     

Expression of expansin genes during postharvest lignification and softening of ‘Luoyangqing’ and ‘Baisha’ loquat fruit under different storage conditions

Four expansin cDNA fragments, EjEXPA1, EjEXPA2, EjEXPA3 and EjEXPA4, were isolated and characterized from loquat (Eriobotrya japonica Lindl.) fruit. EjEXPA1 mRNA accumulated consistently with the increase in fruit firmness in 0 °C storage of ‘Luoyangqing’ (LYQ) fruit, where chilling injury with increased fruit firmness due to lignification was observed. EjEXPA1 mRNA levels were lower in fruit that underwent low temperature conditioning (LTC, 6 d at 5 °C then 4 d at 0 °C), and in 1-methylcyclopropene (1-MCP) treated fruit, in both cases where chilling injury was alleviated. Fruit of the ‘Baisha’ (BS) cultivar soften after harvest rather than increase in firmness, and high expression levels of EjEXPA1 and EjEXPA4 accompanied the softening of BS fruit stored at 20 °C; such mRNA accumulation was much lower when fruit were stored at 0 °C, where softening was significantly inhibited by the low temperature. Very low expression of EjEXPA2 and EjEXPA3 was observed during storage of both LYQ and BS fruit under the different storage conditions. Our results showed that of the four genes characterized, EjEXPA1 might be associated with chilling-induced lignification while both EjEXPA1 and EjEXPA4 were closely related to softening of loquat fruit during the postharvest period.     

A high temperature/low oxygen pulse improves cold storage disinfestation

Short periods of elevated temperature under controlled atmospheres (CA) effectively control insect pests. Cold treatment is also an effective non-chemical disinfestation process. If synergistic effects can be found by combining treatments, these may provide opportunities for cost reduction. Tests were performed to evaluate the tolerance of Packham's Triumph pears (Pyrus communis L.) to a range of temperatures (30–40 °C) combined with low oxygen (O₂ < 1 kPa). Treatment duration was 16–48 h and was followed by 1 month storage at 0 °C under air. When held at 30 °C, pears withstood up to 30 h of hypoxia. After cold storage, pears ripened slightly faster than controls but were undamaged. A temperature of 35 °C induced slight skin browning, and 40 °C resulted in substantial skin blackening. Some treatments were also tested on survival of lightbrown apple moth (LBAM), Epiphyas postvittana (Walker). All developmental stages were subjected to either 16 h at 30 °C, or 16 h under hypoxia, or 1 month at 0 °C, or a combination of the three treatments. With all treatments combined, all eggs, larvae and adults were killed. Only 4% of the pupae produced adults and combined treatments led to an increase in pupa mortality of 38%. A combined treatment (tolerated by pears) consisting of 30 h at 30 °C under low O₂ plus 1 month cold storage under air, killed 100% of LBAM pupae, and 100% of 5th instar larvae of both codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck). Implementation of such treatments would not require substantial investments for fruit industries equipped with CA storage facilities.     

Effect of new sanitizing formulations on quality of fresh-cut iceberg lettuce

In the present study, three recently patented decontamination agents: peroxyacetic acid combined with lactic acid, and two different combinations of hydrogen peroxide with citric acid (with and without propylene glycol), were compared with sodium hypochlorite and tap water washing regarding their effect on equilibrium modified atmosphere packaged (EMAP) fresh-cut iceberg lettuce. Effects of these sanitizers on respiration rate, electrolyte leakage, microbial levels, and sensory quality of the product after decontamination and during storage (3 d at 4 °C followed by 4 d at 7 °C) were elucidated. Hydrogen peroxide based sanitizers provoked a significant increase in the respiration rate and the electrolyte leakage of fresh-cut iceberg lettuce compared with tap water washing. Peroxyacetic acid combined with lactic acid resulted in similar results to those of tap water washing for all the parameters analyzed. However, other aspects of the combination of peroxyacetic and lactic acids (e.g. efficacy for cross-contamination avoidance) should be assessed in the future in order to determine its suitability for fresh-cut iceberg lettuce processing.     

Extending the postharvest life of carnations with nitric oxide—comparison of fumigation and in vivo delivery

The ability of nitric oxide (NO) to extend the postharvest life at 20 °C of carnations (Dianthus caryophyllus L. cv. White-Sim) was investigated using delivery by gas-based fumigation and in vivo release via a solution containing the NO donor compound 2,2′-(hydroxynitrosohydrazino)-bisethanamine (DETA/NO). Treatment with NO gas in air at 1 and 5 μl l⁻¹ produced about a 30% increase in postharvest life while DETA/NO applied in solution at 10 mg l⁻¹ extended postharvest life by about 50% when dissolved in water. For flowers, use of solid delivery appears to offer a more convenient and more effective method of NO treatment than gaseous fumigation to extend postharvest life.     

Effect of high-pressure hot-water washing treatment on fruit quality, insects, and disease in apples and pears: Part I. System description and the effect on fruit quality of ‘d’Anjou’ pears

A manually operated high-pressure hot-water washing system consisting of a boiler, hot-water mixing tank, contact loop, heat exchanger, spray mixing tank, high-pressure hot-water washing manifold, low-pressure fresh water rinse manifold, and pressure pump was constructed and installed in a packingline. The system developed 20–50 °C washing water at pressures up to 980 kPa. ‘d’Anjou’ pears (Pyrus communis L.), shortly after harvest, and after storage for 3 and 4 months in regular air (RA) or for 4, 7 and 8 months in controlled atmosphere (CA) at −1 °C were washed through the packingline with different wetting agents (0.1% Silwet, 0.01 and 0.1% Defoamer, and water), water pressures (regular and high-pressure (210–980 kPa)), water temperatures (control (tap water, 4–22 °C), 40 °C, and 50 °C), and brushes (soft and firm), respectively. The effect of the washing conditions on fruit quality was investigated after 1 month of storage at −1 °C to simulate shipping condition, and then again after 1 week at 20 °C to simulate marketing condition. Hot-water caused severe heat scald. When nozzle temperature was 50 °C, the incidence of heat scald increased to over 50% for the fruit stored in RA for 3 months. Combined with hot-water, 540 kPa high-pressure washing increased the incidence of friction discoloration. There were lower incidences of friction discoloration and heat scald for fruit stored in CA for 7 months, in comparison to that in RA for 3 months. However, those fruit did not ripen properly as indicated by a high extractable juice content. Fruit washed at harvest had minor incidences of friction discoloration regardless of different brushes, water pressures, and wetting agents. Fruit washed after storages in either 4 months RA or 4 or 8 months CA suffered a high incidence of friction discoloration including scuffing symptoms and pressure marking. The firm brushes caused a higher incidence of friction discoloration mainly because of scuffing symptoms. However, no differences were found between different water pressures and wetting agents with respect to friction discoloration. Fruit stored for 4 months RA suffered 26–28% friction discoloration in comparison to 16–18% in CA stored fruit with firm brush washing. Extended CA storage increased friction discoloration even with soft brush washing. The results suggest that a washing system with high-pressure spray, <30 °C warm water, wetting agent Defoamer and rotating soft brushes were significantly effective in removing surface pests and decay control without causing internal or external damage of fruit.     

不同钾肥用量对莴笋产量和品质的效应

莴笋是中国南北地区广泛栽培和食用的叶类蔬菜之一, 其对氮、磷、钾三要素的吸收量中以钾最大,氮次之,磷最小。钾素作为作为“品质元素”,对莴笋品质形成至关重要。为寻求大田条件下合适的钾肥用量,在田间试验研究了不同钾肥施用量(K1、K2、K3、K4）对莴笋产量和品质的影响。结果表明：不同施肥处理间莴笋产量有显著差异。不同施肥处理提高莴笋产量2.0%～18.5％,增产幅度以K2＞K1＞K3＞K4,增施钾肥处理的增产效率则以K1＞K2＞K3＞K4。与CK1相比,不同施肥处理提高莴笋茎和叶片硝酸盐含量12.9%～140%;增施钾肥降低莴笋茎和叶片硝酸盐含量12.2%～43.8%和20.6%～35.0%,且茎、叶片硝酸盐含量与钾肥用量呈显著的二次回归关系。与CK1处理相比,不同施肥处理对莴笋Vc和可溶性糖含量茎中以负效应为主,叶片中以正效应为主;低K 处理（K1和K2处理）对Vc和可溶性糖含量正效应较大。不同施肥处理对莴笋茎和叶片氨基酸含量的效应以降低作用为主。综合莴笋产量和品质来看,以K2处理（即K2O 150kg/km2）为莴笋高产优质的最佳处理。     

Effect of combined application of heat treatments and plastic packaging on keeping quality of ‘Oroblanco’ fruit (Citrus grandis L.×C. paradisi Macf.)

Combinations of various heat treatments with individual fruit sealing, packaging in polyethylene liners or waxing were tested as means to control pathological and physiological spoilage of ‘Oroblanco’ fruit (Citrus grandis L.×C. paradisi Macf.). The following heat treatments were used: curing at 36°C for 72 h, hot water dip at 52°C for 2 min or ‘hot drench brushing’ at 52, 56 or 60°C for 10 s. The standard packinghouse treatment included waxing with addition of thiabendazole (TBZ) and 2,4- isopropyl ester. The fruit was stored for 2 weeks at 1°C (simulated low-temperature quarantine treatment), followed by 12–13 weeks at 11°C (simulated sea transportation to Japan) and 1 additional week at 20°C (simulated retail shelf-life period). The lowest weight loss and the highest firmness were observed with individually sealed fruit. Polyethylene liners were usually more efficient for weight loss control than waxing. However, the liner packaging enhanced the risk of postharvest disease development, if not accompanied by appropriate decay-controlling measures. Applying TBZ, hot water dip or curing controlled the development of postharvest pathogens, especially that of Penicillium molds. In another trial, both hot drench brushing at 56 or 60°C and hot water dip reduced decay incidence. Hot drench brushing at 60°C and hot water dip slowed fruit softening and reduced buttons abscission. In addition, the hot drench brushing at 60°C significantly delayed the loss of ‘Oroblanco’ green rind color, especially at the stylar and stem ends of the fruit. The hot dip at 52°C inhibited yellowing only when combined with individual seal-packaging.     

Spear yield and quality of white asparagus as affected by soil temperature

In three consecutive years two asparagus cultivars (Gijnlim, Grolim) were cultivated at three different temperatures in the ridge surface ranging from 12 to 26 °C to assess (1) the onset of spear yield, (2) the mean daily yield increase per plant, and (3) the establishment of spear quality defects. The objective was to determine the temperature dependence of the spear growth and quality of white asparagus with respect to different cultivars and the harvest year.

The mean time interval Δt from the beginning of the temperature treatment to harvest start was 16.5 d at the reference temperature of 20 °C. This time interval corresponded to a thermal time of 255 °C d at a base temperature of 4.4 °C. The mean yield increase per plant at the reference temperature was 17.4 g d⁻¹. The temperature dependence of Δt and was expressed by the relative change of these quantities per 1 °C alteration, which were on average 0.08 and 0.14 °C⁻¹, respectively. The frequency of quality defects (rusted spears, split spears, hollow/club-shaped spears, spears with open heads) and grade I quality depended significantly (P < 0.05) on the temperature, cultivar, and harvest year. Generally, ‘Gijnlim’ showed fewer quality defects than ‘Grolim’, whereas spears without defects were most frequent for those grown between 18 and 22 °C. With rising temperatures, the frequency of split or hollow/club-shaped spears and spears with open heads increased, while the frequency of rusted spears decreased. The derived functions of yield and quality parameters should improve the controlling of the yield and quality of white asparagus spears at varying temperatures in the ridge.     

Chilling-induced oxidative stress and antioxidant responses in mume (Prunus mume) fruit during low temperature storage

Mume (Prunus mume Sieb. et Zucc.) fruit are harvested and consumed at the mature green stage and have a short storage life at ambient temperature. While cold temperature extends their storage life, improper refrigeration causes severe chilling injury (CI), with fruit suffering more severe CI at of 5–6 °C than at 1 °C. The objective of this research was to determine the involvement of reactive oxygen species (ROS) and antioxidant systems in fruit under chilling stress. ‘Nankou’ fruit were stored at 1 °C or 6 °C for 15 days. Hydrogen peroxide, a preventive ROS, decreased at a slower rate at 6 °C than 1 °C during storage. Malondialdehyde (MDA), an indicator of lipid peroxidation caused by ROS, increased during storage and the contents were higher in fruit stored at 6 °C than at 1 °C. On the other hand, fruit stored at 6 °C had a lower total antioxidant capacity (TAC) and lower activities of antioxidant-related enzymes including superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) than at 1 °C. These results indicate that the fruit at 6 °C had more oxidative stress; thus the fruit had more severe CI symptoms than at 1 °C.     

Analysis of the differences in growth between five lettuce cultivars marking the development in lettuce breeding for winter production

Summary Since 1950 growth of lettuce for winter production has been improved considerably by breeding. It has been investigated whether this improvement must be attributed to a more rapid leaf production, to larger leaves or to both. To this end the differences in growth between the cultivars Meikoningin. Proeftuin's Blackpool, Rapide, Deci-Minor and Valentine were analysed at a range of temperatures (10, 14, 17 and 20°C) under natural light conditions in autumn. The last four cultivars represent successive improvements in growth of lettuce for winter production.From the experiments it can be concluded that the improvement in growth of lettuce for winter production was initially brought about through increasing the rate of leaf production and there-after through increasing leaf size. At the same time the heat requirement for optimal growth has become higher.     

The effect of breeding on the phenology of Italian durum wheats: From landraces to modern cultivars

An understanding of the changes in phenology resulting from durum wheat breeding in Italy can inform breeding objectives for durum wheat improvement in Mediterranean environments. The phenology of a set of 20 durum wheat cultivars, grouped according to their period of release into ‘old’, ‘intermediate’ and ‘modern’, was compared in two sowings (September and May) with or without artificial vernalization. The vernalization treatment and the 6 h range in daylength and wide variation in temperature were responsible for the variation in anthesis date from 817 to 2105 °Cd (base 0 °C) from sowing. Old cultivars had the greatest photoperiod sensitivity and cold requirement, intermediate ones the greatest earliness per se and modern ones the least photoperiod sensitivity and greatest earliness per se. The first substantive effect of breeding in Italy on phenology was achieved with introgression from syriacum germplasm, which increased earliness both by an increase in earliness per se and a reduction in photoperiod sensitivity. The next step, characterized by the introduction of the semi-dwarfing gene Rht1, had a specific effect of reducing photoperiod sensitivity, although the modern group of varieties has a relatively low level of earliness per se, which is fundamental for preserving and increasing the length of the TS-anthesis period. Some quantitative cold requirement still persists in Italian germplasm, although all the cultivars tested are classified as spring types. The main phenological events affected by the changes in anthesis date resulting from breeding depend on the mechanism involved. Variability among cultivars within each group is also described.     

Phosphine and its effect on some common insects in cut flowers

The most effective fumigant for insect disinfestation of cut flowers is currently methyl bromide, which will soon be unavailable in several countries. The toxicity of an alternative fumigant, phosphine (2% PH₃ and 98% N₂), was tested at 24 °C on adult greenhouse thrips (Heliothrips haemorrhoidalis), adult aphids (Myzus persicae) and lightbrown apple moth larvae (LBAM; Epiphyas postvittana). These are commonly found as insect pests on many cut flower crops. Thrips were exposed to phosphine concentrations ranging from 20–600 μl/l for 1 or 2 h. All thrips were killed within 18 h of exposure after a treatment of 300 μl/l phosphine for 2 h. Adult aphids and fifth instar LBAM larvae were more resistant to phosphine, and trials were therefore conducted using higher phosphine concentrations (> 500 μl/l) combined with atmospheric (0.035%) or elevated (33%) CO₂. The most effective treatment for aphids was 1000 μl/l phosphine + 33% CO₂ for 4 h, which killed all insects within 36 h of exposure. Under atmospheric CO₂, levels, 92% of aphids were killed within 36 h after exposure to 1000 μl/l phosphine for 6 h, with 100% kill attained after exposure to 5000–8000 μl/l phosphine for 6 h. Elevated CO₂ levels did not improve the efficacy of phosphine on LBAM larvae. The optimal treatment was 2000–2500 μl/l phosphine for 4 or 6 h, which killed 96 or 100% of the larvae, respectively. Under atmospheric CO₂ levels, 4000 μl/l phosphine killed 74% of LBAM larvae after 4 h, and 94% after 6 h exposure.