Abstract
Dipping asparagus crowns (Asparagus officinalis L.) in 1000 ppm (2-chloroethyl)phosphonic acid (ethephon) solutions before planting significantly increased the number and fresh weight of both shoots and roots in pot studies. Ethephon treatment did not affect time of emergence, height, diameter of the shoots and root length. Of the concentrations tested (0, 250, 500, 750 and 1000 ppm), the 1000 ppm was the most effective; 750 ppm was partially effective while 250 and 500 ppm were ineffective. Under field conditions, ethephon and/or the potassium salt of gibberellic acid (KGA3) at 1000 ppm, did not affect the time of emergence of shoots from crowns treated before planting. Ethephon was effective in increasing the number of shoots while KGA3 alone or in combination with ethephon was not. Both chemicals reduced stand. Increasing exposure from 15 to 60 minutes increased the effectiveness of ethephon at 1000 ppm on inducing shoot emergence.
Abstract
Asparagus spears (Asparagus officinalis L. var altilis L.) were cut to 21, 14, and 7 cm in length and stored at 2.5°C for one week. Apical tissue had higher rates of respiration than basal tissue, and cuts to produce 7-cm apical sections caused a significant 15% increase in respiration that lasted a few days. Cuts made 14 cm from the apex had no effect on respiration. Over the 7-day storage period, CO2 production declined by 50%, with most of the decline occurring within the first 3 days. The composition of 3.5 cm incremental segments of the stored spears were analyzed. Storage resulted in significant declines in soluble carbohydrates along the entire 21 cm of the spear, in amino acids for 14 cm, and in protein along the apical 7 cm of the 21-cm spear. Apical 7-cm spears had at least double the rate of losses of these components during storage as did 21-cm spears.
Commercially available biocontrol agents Trichoderma harzianum Rifai and the arbuscular mycorrhizal fungus Glomus intraradices Schenck and Smith were tested for their efficacy in controlling fusarium root rot in potted asparagus (Asparagus officinalis L.) seedlings. High and low concentrations of Fusarium oxysporum (Schlect.) emend. Snyd. & Hans. f. sp. asparagi Cohen & Heald (FOA) were combined with G. intraradices and/or T. harzianum treatments. In both experiments included in this study, T. harzianum and G. intraradices alone and in combination effectively reduced root rot caused by FOA when asparagus seedlings were grown in low levels of FOA-infested medium. When seedlings were grown in high levels of FOA-infested medium, the combination of T. harzianum + G. intraradices significantly increased dry shoot mass and limited root rot compared to the control.
Abstract
In propagating Asparagus officinalis L. through the method of shoot apex culture, apices of terminal buds of spears produced in vitro were found to be equally satisfactory as explants as those of lateral buds of spears obtained from the field. A maximum number of plants was obtained when the cultures were illuminated 4-20 hr daily with white fluorescent or Gro-Lux lamps at an intensity of 1000 lux. A constant 27°C temp was also optimum for plant formation in vitro. Histological examination revealed that roots arose adventitiously from callus which formed at the base of the explant, whereas spears originated from axillary buds.
Successful transfer of plants from laboratory to soil required a prior reculture in a medium lacking NAA and with the light intensity increased to 3000 or 10,000 lux. Examination of the chromosome numbers of plants propagated through shoot apex culture showed that the original diploid status had been retained in every plant.
Asparagus officinalis L. cv. Centennial established with seedling transplants in 1983 was maintained with a conventional tillage (CT) or a no-till) (NT) system with either metribuzin or metribuzin + napropamide being applied for weed control. Marketable yield was assessed from 1985-1989. In 1989, in addition to yield data, destructive harvests were made every three weeks from March to November to evaluate the effects of tillage on fern, crown and bud growth and root carbohydrate levels. Yields were reduced in CT when compared to NT during all years. Asparagus growth (crown and fern weight, bud cluster, bud and fern numbers) was greater in NT than CT throughout the year although seasonal patterns of growth were similar for both tillage systems. Root carbohydrate levels were higher in NT than CT before the harvest season began. Carbohydrates for both tillage systems reached their lowest level in late July before recovering to pre-harvest levels in late September. Use of metribuzin + napropamide did not reduce fern number or yield but significantly reduced the number of bud clusters, buds and fern when compared to metribuzin alone.
We have developed tissue culture and protoplasts isolation protocols for Asparagus densiflorus in order to use this genetic material in the breeding of Asparagus officinalis. For tissue-culture of A. densiflorus, the conditions which optimize the induction and the production of callus are a full MS medium with 1 mg/L of both pCPA and BAP and 0.5 mg/L of thiamine. HCL in the dark. on this medium, we obtained a friable white callus. Indirect organogenesis was obtained if pCPA was omitted from the medium. Replacement of the plant growth regulators by 2,4-D and Kinetin produced a hard and compact callus which did not differentiate. Protoplast have been isolated from 10 days old friable callus. cell wall was digested with 0.3% macerase, 1% cellulase and 0.8% rhozyme for a period of 16h at a temperature of 27°C in a CPW medium. Protoplast yield was 2 ×106 protoplasts/g callus. osmolarity of the digestion solution was 0.8 M provided with a mixture of glucose (0.6 M) and mannitol (0.2 M). cells were then plated at a density of 1 × 105 cells per ml. Microcolonies formed on a 1/2 MS medium with 0,5 mg/L NAA and ZEA and 1 g/L glutamine in the dark.
Several cinnamic acids have been identified as principal toxic components of asparagus (Asparagus officinalis L.) root autotoxin and have been shown to synergize Fusarium infection of asparagus. The basis for this synergism was studied by exposing asparagus seeds and radicles from pregerminated seeds to ferulic (FA), caffeic (CA), or methylenedioxycinnamic (MDA) acids alone and in combinations of two or three of these acids. After treatment, seeds were placed in pots of peat-lite mix, and, depending on the experiment, all or half were inoculated with F. oxysporum (Schlecht) f. sp. asparagi (Cohen). Seedling emergence from each pot was used as a measure of toxicity. All cinnamic acids at 1% suppressed emergence compared with the control. Solutions combining FA and CA (0.5%/0.5%, v/v) were substantially more toxic than 1% solutions of either alone. Exposure of radicles (early postgermination) for 10 minutes to combined FA/CA before planting decreased emergence from pots, whereas emergence following a 10-minute exposure to 1% CA or FA alone did not differ from the controls. The 2-hour exposure to FA or to FA/CA and the 24-hour exposure to CA, FA, or FA/CA decreased emergence, with toxicity progressing as follows: CA < FA < FA/CA. Root tip squashes showed fewer mitotic figures in treated than in untreated radicles, and scanning electron microscopic (SEM) examination of the radicle epidermis revealed damage to the surface of epidermal cells and precocious root hair development, the extent of which paralleled treatment toxicity.
Precocious flowering can be induced in asparagus (Asparagus officinalis L.) seedlings with N-phenylcarbamate herbicides, such as n-propyl N-(3,4-dichlorophenyl) carbamate (NPC); however, only ≈50% of the treated seeds produce flowering plants because these compounds inhibit germination and seedling emergence. We have improved the treatment method by determining the environmental conditions, timing, dose, and duration needed to maximize the percentage of germination, emergence, and flowering. Imbibing seeds in water for 5 days, and then treating germinated seeds with 0.4 mm NPC for 5 days after radicle emergence, with seedling aeration in the light, resulted in the production of flowering seedlings from >90% of the treated seeds. For freshly harvested seeds, in which germination rates are more variable than aged seeds, individual seedlings must be transferred to NPC within 1 day after radicle emergence to produce a high percentage of flowering plants. For seven male asparagus cultivars, chemical induction of flowering in seedlings with NPC produced a sex ratio similar to that of field-grown plants, demonstrating that NPC induces flowering without altering floral differentiation or sex expression. This method can be used for rapidly and accurately identifying the percentage of females in “male” cultivars.
Net photosynthesis from whole plants of eight asparagus (Asparagus officinalis L.) genotypes was measured at two locations in an open infrared gas analysis system. Measurements started at about the completion of full fern growth, which occurred at the end of July and lasted through the season until fern senescence in late September. Net photosynthesis of the eight genotypes ranged from 15.67 to 27.79 μmol·m-2·s-1. Significant differences (P < 0.1) in net photosynthesis were found among the eight genotypes. Both yield and specific leaf mass (SLM) were correlated significantly with net photosynthesis. We suggest that specific leaf mass can be used as a criterion for selecting genotype of high photosynthetic ability. Daily photosynthetic rate patterns were studied and appear to be related to daily changes of stomatal conductance. Seasonal changes of asparagus' photosynthetic activity were studied. High photosynthetic activity was observed from July through August. Photosynthetic activity decreased greatly in September along with the fern maturation and unfavorable changes in environmental conditions.
Three studies were conducted at Clinton, N.C., to investigate the relationship between number of rows per bed, in-row spacing, and spear yield of asparagus (Asparagus officinalis L.) over 11 to 13 years. In the first study, increasing plant densities from 21,550 to 43,100 plants/ha by doubling the number of rows/bed increased the cumulative yield from 64% to 80% for three hybrid lines (`UC 157', `WSU 1', and `WSU 2') but only 6% for `Rutgers Beacon'. The effects of doubling the plant density were still apparent 13 years later. In the second study, yields of `Princeville' (`Mary Washington' selection) crowns, grown at densities from 14,000 to 86,000 plants/ha, were also increased for 8 years by doubling rows at various in-row spacings. In a third study, in which densities ranged from 21,000 to 387,900 plants/ha, the magnitude of the response to rows/bed was dependent on in-row spacing. Efficient use of bed space and the avoidance of crowding exerted a larger influence on productivity than did average planting density. The yield response to rows/bed was greater and more persistent through the years for wider in-row spacings. Spear size was only marginally responsive to rows per bed and in-row spacing.