Spear Quality Research Articles

Genome-wide analysis of genetic diversity in a germplasm collection including wild relatives and interspecific clones of garden asparagus.

The Asparagus genus includes approximately 240 species, the most important of which is garden asparagus (Asparagus officinalis L.), as this is a vegetable crop cultivated worldwide for its edible spear. Along with garden asparagus, other species are also cultivated (e.g., Asparagus maritimus L.) or have been proposed as untapped sources of variability in breeding programs (e.g., Asparagus acutifolius L.). In the present work, we applied reduced-representation sequencing to examine a panel of 378 diverse asparagus genotypes, including commercial hybrids, interspecific lines, wild relatives of garden asparagus, and doubled haploids currently used in breeding programs, which enabled the identification of more than 200K single-nucleotide polymorphisms (SNPs). These SNPs were used to assess the extent of linkage disequilibrium in the diploid gene pool of asparagus and combined with preliminary phenotypic information to conduct genome-wide association studies for sex and traits tied to spear quality and production. Moreover, using the same phenotypic and genotypic information, we fitted and cross-validated genome-enabled prediction models for the same set of traits. Overall, our analyses demonstrated that, unlike the diversity detected in wild species related to garden asparagus and in interspecific crosses, cultivated and wild genotypes of A. officinalis L. show a narrow genetic basis, which is a contributing factor hampering the genetic improvement of this crop. Estimating the extent of linkage disequilibrium and providing the first example of genome-wide association study and genome-enabled prediction in this species, we concluded that the asparagus panel examined in the present study can lay the foundation for determination of the genetic bases of agronomically important traits and for the implementation of predictive breeding tools to sustain breeding.

Application of MAP and ethylene\u2013vinyl alcohol copolymer (EVOH) to extend the shelf-life of green and white asparagus (Asparagus officinalis L.) spears

In this study, ethylene vinyl alcohol copolymer (EVOH) and polypropylene/polyethylene (PP/PE) films combined with MAP packaging were developed to enhance the shelf-life of green and white asparagus spears. The scope of the research included measurements of weight loss, pH, acidity, color, texture, and sensory analysis as indicators of green and white asparagus spear quality for up to 17 days of storage at 2 and 10 °C. The application of modified atmosphere packaging combined with EVOH-based packaging material and refrigeration at 2 °C promoted a reduction in asparagus weight loss, preventing changes in color and texture as well as sensory quality, thereby extending the shelf-life of the asparagus. According to the obtained results, it was possible to maintain good quality of green and white asparagus for up to 17 and 10 days, respectively, when packed in MAP using EVOH-based packaging stored at 2 °C. Asparagus stored in packaging with PP/PE film showed lower quality during storage at 2 and 10 °C. These results suggest that EVOH films are potential candidates for advanced packaging materials for the asparagus packaging application.

Effects of asparagus decline on nutrients and phenolic compounds, spear quality, and allelopathy

Asparagus (Asparagus officinalis) decline is an important issue that decreases both crop production and quality causing economic losses. The main bioactive compounds in asparagus are phenolics. Several studies have related these compounds with the decline and also with the replanting issues in which when asparagus plants are replaced by new plants, their productivity is low. The asparagus physiological state and the spear quality have not been studied yet in field plots showing decline symptoms. Therefore, the aim of this study was to study the effect of asparagus decline on leaf nutrients accumulation and on the yield and quality of commercial spears. Another aim was to analyze the possible allelopathic effect on another species. For this, mineral nutrients, phenolic compounds and quality indicators were analyzed in plants and spears from two asparagus plots (with and without decline symptoms) and germination tests were conducted using lettuce seeds. Decline plants did not show great changes in macronutrient concentration but they showed low B and high Fe concentrations. Leaves and rhizomes from the plot with decline presented higher phenolic compounds, highlighting caffeic acid in rhizomes. However, spears did not present higher phenolic compounds. Likewise, decline decreased the market spear quality and yield but slightly increased some quality indicators such as chlorophylls, carotenoids, ascorbate, and antioxidant capacity. On the other hand, extracts from the decline plot reduced lettuce germination and epicotyl growth suggesting an allelopathic effect. The obtained results are useful to a better understanding of the decline issue and provided valuable information for producers to manage and control its effects on asparagus quality.

Seasonal and temporal changes during storage affect quality attributes of green asparagus

Asparagus is a perennial crop with a short UK harvest season. Methods to extend the storage life of asparagus have proven difficult. To gain insight into the physiological (viz. colour, respiration rate, cutting energy, and stiffness measured using laser Doppler vibrometry), and biochemical (viz. sugars, ascorbic acid, and abscisic acid and its catabolites) changes throughout the UK season, two cultivars were harvested weekly and stored under shelf life conditions (7 °C). Results were compared to spears (plus one additional cultivar) cold stored (1 °C) for three weeks followed by one week of shelf life. Concentrations of sugar, abscisic acid (ABA) and catabolites at harvest were subject to seasonal variation, directly affecting storage potential. A generalised linear model with stepwise feature selection was applied to select the most important parameters for the prediction of total sugars and phaseic acid (PA). More favourable growing conditions at harvest increased sugars and lowered ABA content and catabolites, which coincided with better maintenance of spear quality during storage; including maintaining textural characteristics. Storage time had a negative impact on spear texture and sugar content, with cutting energy increasing and stiffness decreasing both during cold storage and subsequent shelf life. A partial shift in sugar biosynthesis occurred during shelf life increasing sucrose concentrations. Results suggest that the temporal flux in ABA and catabolites, and individual sugars could be used to model storage potential of asparagus spears.

Selenium fern application and arbuscular mycorrhizal fungi soil inoculation enhance Se content and antioxidant properties of green asparagus (Asparagus officinalis L.) spears

Asparagus can be considered as target crops for Se biofortification for producing spears with enhanced Se content and antioxidant proprieties. Arbuscular mycorrhizal fungi (AMF) inoculation may affect selenium uptake from soil and the level of antioxidant compounds in vegetable crops. However, for this species the response to selenium fertilization is scarcely known as well as the role of AMF in the biofortification process. Two-year experimental trials on Se fertilization of cultivar Grande were performed on two farms a) to assess the effect of 0 (Se0), 25 (Se25), 75 (Se75) and 125 (Se125) g ha−1 of Se as selenate sprayed onto ferns on crop productivity, spear quality, and Se enrichment; b) to consider the potential synergic effect between Se fern fertilization and AMF inoculation (+AMF and –AMF). The cvs. Atlas and ‘Italo’ were also tested against ‘Grande’ to measure their genotype-specific responses using a medium rate of Se application (Se75).Neither fern injury nor changes in spear yield, quality (commercial and organoleptic) or essential/non-essential element contents were observed in Se-treated asparagus plants, whereas an increase in Ca2+ level was detected. Averaged over all the trials, Se content in Se0 spears was close to 150 μg kg−1 DW. It always rose linearly with increasing Se rate, to a much greater extent when Se application was associated with the AMF inoculation, reaching with the highest Se rate values of 1893 and 844 μg kg−1 DW with and without AMF inoculation, respectively. However, AMF inoculation was not effective in enhancing the uptake of Se from soil. Variability in Se spear fortification was observed between farms, probably depending on the crop management affecting the growth of the green biomass. The highest Se dose (Se125) also resulted in an improved content of sucrose in spears and in crowns one year after the Se application. In all trials, total phenols (TP) and carotenoid content, as well as antioxidant capacity (AC) in spears linearly enhanced with the rising of Se dose. A significant correlation between TP and AC in spears of not AMF-inoculated crop was highlighted, while AC in +AMF spears seems to be affected by other antioxidant compounds besides TP. Among the cultivars tested, ‘Atlas’ seems more prone than ‘Grande’ and ‘Italo’ to Se enrichment and, irrespectively to the Se treatment, it had the highest antioxidant capacity. The annual application of Se on asparagus fern is a promising technique for obtaining stable Se enrichment of the asparagus spears over both years and it can be usefully associated with AMF inoculation.

Segmental and Tandem Duplications Driving the Recent NBS-LRR Gene Expansion in the Asparagus Genome.

Garden asparagus is an important horticultural plant worldwide. It is, however, susceptible to a variety of diseases, which can affect the potential yield, spear quality, and lifespan of production fields. Screening studies have identified resistant germplasm. The genetic resistance is usually complex, and the genes underlying that resistance are still unknown. Most often, disease resistance is determined by resistance genes (R). The most predominant R-genes contain nucleotide binding site and leucine-rich repeat (NBS-LRR) domains. Using bioinformatics and data mining approaches, we identified and characterized 68 NBS predicted proteins encoded by 49 different loci in the asparagus genome. The NBS-encoding genes were grouped into seven distinct classes based on their domain architecture. The NBS genes are unevenly distributed through the genome and nearly 50% of the genes are present in clusters. Chromosome 6 is significantly NBS-enriched and one single cluster hosts 10% of the genes. Phylogenetic analysis points to their diversification into three families during their evolution. Recent duplications are likely to have dominated the NBS expansion with both tandem genes and duplication events across multiple chromosomes. Transcriptome sequencing data provided evidence for their transcription and tissue-specific expression. The total number of cis-regulatory elements as well as their relative positions within the NBS promoters suggests a complex transcriptional network regulating defense responses. Our study provides a strong groundwork for the isolation of candidate R-genes in garden asparagus.

Cultivation of asparagus as an annual crop in the tropics: growth, spear yield and -size of two cultivars harvested at different plant age

In and subtropical regions, asparagus is cultivated as a perennial crop; respectively one year old seedlings are transplanted to the field and spear harvesting starts in the spring of the second year. During the summer this crop grows leaves, producing plant reserves for growth and their winter dormancy. Such a crop possesses a production cycle of more than 10 years. In the tropics the asparagus crop grows faster and does not have any dormancy period and harvesting continuously causes both spear yield and quality to decline rapidly. More efficient spear yield could be attained by treating this crop as an annual crop rather than intensive cultivation over longer periods of time. Harvesting spears of annual crops could commence when spear diameter reaches marketable size (>0,8 cm), while smaller size spears are left to grow for photosynthesis. In the warm and humid conditions of the tropics spears reach marketable size about 3 months after transplanting. However, harvesting spears too early caused growth stress, while harvesting too late resulted in a lower yield. The objective of this experiment was to study the effect of different harvesting time (plant age) on plant growth, spear yield and size of two cultivars, respectively ‘Atlas’ and ‘Jaleo’. The experimental design used was a split-plot design with four replications. Four months old seedlings were transplanted into a ditch, prepared on a 30 cm high soil bed, harvesting of marketable spears were conducted daily starting from 12, 15 and 18 weeks after transplanting for a period of 12 weeks. The ‘Jaleo’ cultivar grew stronger during the early stages of growth than did ‘Atlas’, but its spear yield was slightly lower. Spear yield and size diagrams were compared and discussed.

Irrigation effects on asparagus yield and spear quality vary with cultivar and season in Michigan

Irrigation effects on asparagus yield and spear quality vary with cultivar and season in Michigan

Different Oxygen Transmission Rate Packing Films During Modified Atmosphere Storage: Effects on Asparagus Spear Quality

The aim of this study was to determine suitable oxygen transmission rate (OTR) films for modified atmosphere (MA) storage of asparagus spears (Asparagus officinalis L.), and to examine the related changes in asparagus spear quality. Asparagus spears were packed with 10,000, 20,000, 40,000, 70,000, and 100,000 cc/m2·day·atm OTR film treatments for MA storage, and perforated film (conventional storage) was used as the control. The fresh weight loss rate was less than 1% in all OTR film treatments but not in the control. In all OTR film treatments, ethylene content rapidly increased on the first day of storage, and gradually decreased thereafter to 2.0 μL·L-1 by the final storage day. In the 10,000 cc and 20,000 cc OTR film treatments, carbon dioxide content was maintained within the permissible range for asparagus spears under recommended controlled atmosphere (CA) and MA conditions (5-12%). The oxygen content was maintained between 12% and 20% in all OTR film treatments. Hue angles and total chlorophyll content were highest in the 10,000 cc OTR film treatment in both tips and stems. Visual quality was maintained at a saleable level only in the 10,000 cc OTR film treatment until the final storage day (25 days). Based on sensory evaluation, the least off-odor was detected in the 10,000 cc OTR film treatment, and the most in the control treatment. While the soluble solids content decreased with all film treatments, it was maintained at the highest level in the 10,000 cc OTR film treatment. Vitamin C content decreased with all film treatments during storage, but was maintained at higher levels in the 10,000, 20,000, and 40,000 cc OTR film treatments. The firmness of tips and stems increased with storage duration in all film treatments, stems were firmer under the perforated film, 10,000, and 20,000 cc OTR film treatments. Given these results, the 10,000 cc OTR film treatment is considered the most appropriate for MA asparagus spear storage since visual quality and soluble solids content were maintained, and fresh weight loss, vitamin C content, off-odor, and yellowing were suppressed during storage.

Effect of Mother Stem Training on Spear Quality and Yield of Asparagus (Asparagus officinalis L.) in the Greenhouse

This study examined the effects of mother stem training on spear quality and yield of asparagus (Asparagus officinalis L.) in the greenhouse. The training was performed with the “mother stem bending method” (Sakamoto et al., 2011). No significant differences were found in the diameter, soluble solid content, firmness, and index of spear tightness of asparagus spears between the untreated group and the mother stem training treatment group. However, the mother stem training method was effective in improving the spear color quality owing to the increase in incident light intensity. On the other hand, the mother stem training treatment resulted in a decrease in the fresh weight of the spear, marketable yield, and marketable yield ratio of the LL (over 33 g) spear size when compared to that of the untreated group. The cause of this decrease in summer yield in the treated group was hypothesized to be a failure in nutrient translocation and low light interception in close proximity to the other stems.

PRODUCTIVITY OF BROCCOLI (Brassica oleracea) PLANTS TREATED WITH BIO , ORGANIC AND N FERTILIZERS UNDER ALLUVIAL SOIL CONDITIONS

A Field experiment was carried out on broccoli (Broccoli oleraceae L. var. Italica cv. Red acare), Brassicaceae family, in Faculty of Agriculture, El-Mansoura University, Egypt during 2010 season to study the effect of both farmyard manure and Agrisbone (Commercial fertilizer) as biofertilizer source and N fertilizer rates on vegetative growth, yield and flower spear quality of broccoli plants grown on alluvial soils. Treatments were represented all combination of FYM rates (control and 20 m3 fad-1) and N fertilizer rates (control, 50,100 and 150 kg fad-1 as ammonium sulphate, (20.5 % N) in presence of Agrisbone (with and without addition) in split split plot design with three replicates. The obtained results could be summarized as follows: - Statistical analysis revealed that the highest mean values of leaves number, and branches number of broccoli plants were obtained from 150 kg fad-1 mineral treatment jointly with inoculated plants in absence of FYM, while the highest mean values of fresh and dry weight were produced from the inoculated plants with 100 N kg fad-1 under FYM treatment. On the other hand, the lowest mean values of aforementioned characteristics obtained from untreated broccoli plants. - Data indicated that the maximum mean values of height and diameter spear flower produced from plants received FYM and Agrispone combined with 100 N kgfad-1 as compared to the other treatments. - The broccoli plants that fertilized with FYM + Agrispone + 100 N kgfad-1 gave the highest increments in the two stages of spear flower broccoli yield; 1st and 2nd cuts. Meanwhile, unfertilized broccoli plants gave the lowest mean values of aforementioned traits in the two stages; 1st and 2nd cuts, respectively.

Plant Density and Genotype Effects on Wild Asparagus (Asparagus acutifolius L.) Spear Yield and Quality

Wild asparagus (Asparagus acutifolius L.) is becoming an interesting niche crop for marginal areas in Europe, but little information is available regarding cultivation techniques, which differ from those of cultivated asparagus (A. officinalis). We experimented with the cultivation of wild asparagus using two different ecotypes planted at two plant densities. We measured yield and number of spears per hectare and spear quality (average weight, portion of edible part, diameter, and dry matter content). There were no significant effects of either genotype or density on the spear yield and number per hectare. No differences among treatments were found on spear quality parameters. Spear yield and number per plant decreased proportionally with increasing plant density, resulting in constant spear yield and number per hectare. Harvest efficiency was ≈1.2 kg of spears per hour of labor when the prickly evergreen vegetation was not removed before harvest and ≈3 kg per hour when the vegetation was cut and removed. In the latter case, harvest would cost approximately one-third of the gross income of the crop suggesting that the crop could easily be economically viable. Further studies are needed to assess whether cutting the vegetation affects plant vigor and longevity in the following years, but also to further study suitable techniques for crop cultivation, especially weed control.

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 Δ t 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 Δ w per plant at the reference temperature was 17.4 g d −1. The temperature dependence of Δ t and Δ w 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.

Postharvest life of asparagus (Asparagus officinalis) under warm conditions can be extended by controlled atmosphere or water feeding

Green asparagus (Asparagus officinalis) is known to respond to controlled atmosphere storage (CA) at 20°C with increased shelf‐life, reduced respiratory rate, slower loss of soluble carbohydrates and protein, and slower accumulation of asparagine. This work investigated the likelihood of interactive effects of storage of spears in CA along with spear feeding solutions, including 2% sucrose. Standing the spears in a feeding solution extended shelf‐life in air but conferred little additional benefit in CA. Feeding the spears with 2% aqueous sucrose reduced asparagine accumulation and protein loss, but gave no visual benefit over water alone. Spears in the feeding solutions gained weight, particularly during the first 2 days after harvest, but weight gain was slower in CA than in air. Sensory assessment indicated that spears held in CA for 6 days had similar flavour and acceptability to spears held in air for 1 day. Spear quality was more strongly influenced by CA than by feeding solutions. Both approaches could assist in asparagus quality retention where a good refrigerated cool chain is not available, but these technologies are technically challenging to apply to air‐freighted asparagus.

INFLUENCE OF VARIETY AND CULTIVATION ON MINERAL ELEMENTS AND PROTEIN CONTENT OF ASPARAGUS (ASPARAGUS OFFICINALIS L.)

The aim of this research work was to study the effect of variety and cultivation region on mineral elements and protein content of white asparagus spears (Asparagus officinalis L.). Therefore an extended field survey was conducted in the regions of Braunschweig (Lower Saxony) and Erfurt (Thuringia). Statistically significant differences between cultivation regions were found for Ca, Mg and sulphate. Additionally, spear samples of crop performance experiments with new varieties and genotypes in Lower Saxony and Schleswig-Holstein were analyzed. For nitrate and sulphate significant differences were found between varieties in Schleswig-Holstein. In Lower Saxony, genotypical differences were determined for nitrate, sulphate, Ca, S, Fe, Zn, Mn and Cu. INTRODUCTION White asparagus (Asparagus officinalis L.) is an important vegetable crop in Germany, with a production area of about 12,000 hectare (Anon, 2002). The selection of a variety is crucial for the successful commercial production, because asparagus is a perennial crop (Nichols and Fisher 1999). The economical profit depends on the variety and differences may be as high as three times in terms of total yield and even seven times in marketable yield (Nichols and Fisher, 1999). Variety and growth conditions will, however, not only affect crop productivity, but also spear quality (Poll, 1995; Paschold et al., 1996 and Mullen et al., 1999). Asparagus is a medicinal plant, which has a diuretic effect and is beneficial for humans with heart problems (Leung and Foster, 1996). The quality assessment of new varieties is an important part of any research program. Information on genotypical and regional differences in the content of primary and secondary compounds of asparagus is limited. It was the aim of this research work to study the influence of cultivation region and variety on quality parameters such as protein, nitrate, sulphate and the mineral composition of white asparagus in Germany. MATERIALS AND METHODS Experimental Design In 2000 an extended field survey was conducted in the regions of Braunschweig (52°19.0`N; 10°29.1`E) and Erfurt (51°01.4`N; 11°02`E). Spear samples were taken simultaneously on 15 May from 24 production fields in the area of Braunschweig and 27 samples were collected in the region of Erfurt. In 2001 spear samples of different asparagus varieties and genotypes (Ariane, Eposs, Gijnlim, Hannibal, Ramada, Ramos, Ramses, Rapid, Ravel, Stamm 12, Stamm 14, 17/24, 17/30 and 96012) were taken in crop performance trials on 11 May in Burgwedel (52° 37.4' N; 9° 50.2' E), Lower Saxony. At Wiemersdorf (53° 52.7' N; 10° 20.6' E) in Schleswig-Holstein samples from in total five varieties (Boonlim, Eposs, Gijnlim, Huchels Alpha and Thielim) were taken on 15 May. Both experiments were laid out in a completely randomized design with four repetitions in Burgwedel and three repetitions in Wiemersdorf. Proc. XXVI IHC – Future for Medicinal and Aromatic Plants Eds. L.E. Craker et al. Acta Hort. 629, ISHS 2004 Publication supported by Can. Int. Dev. Agency (CIDA) 314 Sample Preparation The spear samples were carefully cleaned with distilled water and cut to a length of 15 cm. Afterwards, the samples were dried at 80 °C until constancy of weight and fineground to a particle size < 0.12 mm employing an ultra-centrifugal mill (RETSCH ZM 1). Chemical Analysis The total nitrogen content was determined according to the Kjeldahl method. Nitrate and sulphate were extracted by de-ionized water and determined colorimetrically according to Kuecke and Schnug (1996) and Novozamsky et al. (1986), respectively. A dry ashing procedure was applied in order to determine the total content of K, Ca, P, Mg, Cu, Fe, Mn, and Zn: the dry sample material (0.5 g) was incinerated at 490 °C for 16 hours. After cooling to room temperature 10ml 2N HCl were added and afterwards the solution was completely evaporated on a hot plate. Then 10 ml 2N HCl were added and the solution quantitatively transferred into 50 ml volumetric flasks, made up to volume with de-ionized water and finally filtered (Schleicher & Schuell 593 1/2). For determination atomic absorption spectroscopy (AAS) was employed for Fe, Zn, Mn, and Cu, flame emission spectroscopy for K and Ca and colorimetry for P. S was determined by X-ray fluorescence spectroscopy according to Schnug and Haneklaus (1999). Statistical Analysis The analysis of variance using the General Linear Model (GLM) was performed by SPSS program version 10 (Anon, 1998).

SECOND INTERNATIONAL ASPARAGUS CULTIVAR TRIAL FINAL REPORT

This trial was initiated at the 8th International Asparagus Symposium in 1993 to establish a systematic evaluation for yield, spear quality and disease tolerances of commercially available asparagus cultivars. Seeds of 45 asparagus cultivars were provided by seed companies and asparagus breeders for distribution to the participants of the trial. The seed suppliers designated the climatic zones in which their respective cultivars would perform best. The trials were conducted in 19 countries by 25 researchers who have selected the cultivars they are evaluating under a uniform experimental protocol. The cultivars UC 157 F1, Gijnlim and Jersey Giant are included in all of the trials as standards. The addresses of the active trial participants and their cultivar selections are presented. The ranking of marketable spear yields and the ratings for tolerance to Puccinia asparagi, Stemphylium sp. and Botrytis sp. are presented.

Effects of cooling treatments and physical damage on tip rot and postharvest quality of asparagus spears

The effects of postharvest cooling rates and physical damage to tips, on the incidence of tip rot and other quality attributes of asparagus spears (Asparagus officinalis L. ‘New Zealand Beacon Syn 2'), harvested early and late in the season, were investigated. The half cooling times were 1 1/2 min, l 1/2 h, and 53/4 h for hydrocooled, forced‐air cooled, and passively cooled spears, respectively. Apical tissue cooled more rapidly than middle and basal zone tissues. Incidence of tip rot, and visible quality and toughness of asparagus spears, was not affected by the method of cooling, or delays after harvest of up to 12 h at ambient temperatures before hydrocooling. However, overall spear quality was marginally higher, and weight loss significantly less, in hydrocooled spears than in forced‐air or passively cooled spears. It is recommended that spears are hydrocooled or forced‐air cooled within 4–12 h of harvest. In this study, the incidence of tip rot was not linked to the time of harvest within a season. Incidence of tip rot increased with increasing severity of non‐visible impact damage to spear tips. Impact on apical tissues after drops from 0, 50, 100, and 150 mm resulted in 0, 34, 36, and 64% tip rot, respectively, after 5 days at 20°C and 93–95% relative humidity (RH). Washing spears after impact increased the incidence of tip rot. Although adverse physiological stress may be a factor involved in the expression of tip rot, results indicate that physical damage may be a major contributing factor, exploited by micro‐organisms present on the asparagus spears and in packhouse wash water, leading to spoilage.

Modified atmosphere packaging of white asparagus spears: composition, color and textural quality responses to temperature and light

Freshly harvested white asparagus ( Asparagus officinalis L.) spears (about 500 g per package) were over-wrapped with a 16 μm stretch film. Packages were kept at 2.5°C, 5°C, 10°C, 15°C, 20°C and 25°C under continuous darkness or light (15 ± 1.9 W m −2) for 6 days. At all temperatures, an atmosphere of 4.5–6.9% CO 2 and 3–6.7% O 2 developed during the first hour; after 8 h, CO 2 increased to a maximum of 5.8–9.8%, whereas O 2 decreased to a minimum of 0.7–1%. At equilibrium, the atmosphere had 4.6–7% CO 2 and about 1% O 2. Bract opening (‘feathering’), toughening, anthocyanin synthesis and ascorbic acid breakdown were suppressed in the packages during 6 days. However, at temperatures above 15°C visual deterioration and development of severe off-odors occurred. The presence of light in the storage environment had no significant effect on spear quality.

Effects of soil type and depth on spear yield and quality of asparagus (Asparagus officinalis L.)

A field experiment was conducted to study the effects of soil type (sandy loam and silt loam) and soil depth (5, 10, 15, 20 cm) over the crown during harvest on the yield and quality of asparagus (Asparagus officinalis L.) spears. It was found that covering the crowns with sandy loam produced significantly higher spear yield, spear number, and better spearhead quality than covering with a heavier soil (silt loam). The increase in spear yield was because of an increase in spear numbers. Spear‐head quality decreased with soil depth.

Incidence of Fusarium spp. in Asparagus Spears.

Fusarium proliferatum and F. oxysporum have been identified as causal agents of asparagus decline in the field and have been associated with reduction in spear quality (1,2). Our objective was to determine the origin and incidence of spear infection by these fungi during the cropping years 1994 to 1997. From 15 to 40 asparagus samples were randomly selected from the field, packing houses, and retail markets and assayed for Fusarium spp. Collections were made in California, Connecticut, Peru, Mexico, and Australia. The number of samples varied between sampling sites and for the time of harvest season. One Mexican collection site was sampled at the beginning, mid-point, and end of the harvest season to evaluate influence of decreasing carbohydrate levels and increasing temperatures on infection and growth of the fungi. Isolations included sections (5 to 6 cm) from the basal and terminal portions of the spear to evaluate postharvest growth in the spear. Fusarium spp. were recovered from spear samples that included all geographical sampling locations (mean 45%, range 20 to 90%). F. proliferatum was the dominant species isolated consistently from the desert areas regardless of harvest period. The frequency of F. oxysporum isolation ranged from 2 to 32% with no correlation to time or location of sampling. Basal sections were more frequently infected (94%) than terminal portions of the spear (less than 6%). No major differences in the percentage of infected spears were found in collection sites regardless of country sampled. There were differences in the incidence of infection between harvest sample dates. Spears sampled late in the harvest period were 57% more infected than spears of early or mid-season collections. Samples from the same fields, regardless of whether collected directly from the field, from packing sheds, or from the retail market, had higher infection rates later in the harvest season compared with earlier harvests. This may be attributable to warmer temperatures, changes in levels of carbohydrates, or other physiological factors. Spears harvested from the field that were infected with both Fusarium spp. had a greater incidence of infection than spears recovered from packing houses or from retail sources. This supports the theory that the source of spear infection is diseased crowns and not postharvest sources. Isolates from the spears of both Fusarium spp. were found to be pathogenic when challenged to asparagus seedlings.