Male Asparagus Research Articles

Effects of Cultivar and Cropping Type on the Growth and Yield of Female and Male Asparagus Plants

Asparagus (Asparagus officinalis L.) is a dioecious perennial plant. Male plants have a higher yield than female plants; therefore, all-male cultivars are more commonly produced. In contrast, female plants have a higher spear weight than that of male plants. To increase profitability, selective cultivation of only female plants would increase the yield of asparagus with a thick spear, which has a higher unit price. However, the effects of cultivar and cropping type on the growth and yield of male and female asparagus plants have rarely been examined. This study compared the growth and yield of female and male plants of three cultivars grown under various cropping types: a rootstock planting forcing culture; a long-term harvest production system in an open field; and a semi-forcing culture. As a measurement of growth, the rootstock weight was significantly higher for female plants compared with that of male plants with the rootstock planting forcing culture. Regarding yield measurements, the spear weight and yield were not significantly different with the rootstock planting forcing culture. However, with the long-term harvest production system in the open field and semi-forcing cultures, the weight and yield of female plants were equivalent to or significantly higher than those of male plants, regardless of the cultivar, except during some harvest periods. These results indicated that the selective production of female plants may be advantageous in terms of growing heavier spears with a higher unit price in a long-term harvest production system in the open field and semi-forcing cultures in Japan. Additionally, the development of a simple and low-cost method for sex identification would be beneficial.

Andromonoecious outcrossing: a novel method of generating males suitable as parents of male asparagus cultivars

Andromonoecious outcrossing: a novel method of generating males suitable as parents of male asparagus cultivars

Comparison of spear yield and quality between male and female asparagus plants in protected mother fern culture

A higher yield of spears is generally obtained from male asparagus plants than females in outdoor culture. However, recently in Japan, it was reported that the spear weight and yield of female plants was generally greater than those of males in rootstock-planting forcing or mother fern culture. 'UC157' plants were grown in large black polyethylene pots. Spears were harvested daily and their weight and external appearance were recorded for four and two years, respectively. Spear numbers were not significantly different between male and female plants in spring, and tended to be greater per male plant than per female plant from summer to autumn. Mean spear weights per female plant were significantly higher than those per male plant in spring and from summer to autumn. Spear yields per female plant were also significantly higher than those per male plant during spring, whereas no significant differences were found from summer to autumn. Spearhead tightness, an important external quality indicator, was significantly better in female plants than males. From these results, we concluded that in spring, the spear yield and quality of female plants would be better than those of male plants without causing a difference in the annual yield. Therefore, a choice of all-male varieties seems to be not necessary and all female cultivation could be profitable for protected mother fern culture in Japan, since the price of spears in spring and heavier spears is higher in the Japanese asparagus market.

Identification of Homozygous Male Plants by Quantitative Analysis of a Nucleotide Sequence Linked to the Sex-determination Locus in Asparagus officinalis L.

Discrimination of homologous and heterozygous plants at the male-determination locus in asparagus (Asparagus officinalis L.) was examined by quantitative analyses of a diagnostic marker for male asparagus. The quantitative difference of a sequence, AspTaq1, derived from the Asp1-T7 diagnostic marker (Jamsari et al., 2004), was measured using the real-time monitoring PCR and normalized based on the quantitative difference of a sequence, AODEF-Taq1, derived from a single copy gene, AODEF. The normalized difference was higher in established supermales than in regular males grown from commercially available seeds. The averaged values in respective groups are in the approximate ratio of 2 : 1. Homozygous male (MM), heterozygous male (Mm), and female (mm) genotypes were obtained by selfing of an andromonoecious line. The progeny were divided into three groups by the normalized difference; plants showing high values and intermediate values were thought to be homozygous and heterozygous males, respectively. Significant amplification of AspTaq1 was not detected in several plants; therefore, they were judged to be females. Then, to identify supermales, pollen from male plants was crossed separately with female plants, and the sex of the next generation was determined. Pollen from two male plants showing high values of the normalized difference generated only males in the next generation, while pollen from 12 male plants showing intermediate values generated both female and male plants. Pollen from one male plants that showed intermediate values generated only male plants. The normalized difference in homozygous males was comparable to the value obtained using a recombinant sequence that contains an equal number of AspTaq1 and AODEF-Taq1. These results indicate that homozygous and heterozygous males can be identified by quantitative analysis of a nucleotide sequence linked to the sex-determination locus and that the use of an authentic sequence for calibration facilitates the discrimination process of those genotypes in asparagus plants.

Mono- and dinucleotide repeat DNA content differs in dioecious Asparagus (Asparagus officinalis L.)

Asparagus (Asparagus officinalis L.) is a green vegetable with high antioxidant activity among the commonly consumed vegetables. This plant is naturally dioecious and female plants are homozygous for the recessive alleles (mm) while male plants are either homozygous (MM) or heterozygous (Mm) at the sex locus [1]. In the present study we reported that among the expressed gene/gene segments of asparagus deposited into data bases, mononucleotide and dinucleotide repeat contents were significantly different (Table 1) using a computational approach [2]. Results indicated that genes in male asparagus contained more mononucleotides while female contained fewer amounts of mononucleotide repeats containing genes. On the other hand dinucleotide containing genes in female were much higher than that of the male asparagus. Mono- and di-nucleotide repeat content differences between female and male asparagus indicated that microsatellite instability of mono- and di-nucleotide tandem repeat sequences is much higher than tri-, tetra- penta- and hexa-nucleotide repeat sequences. Although repeat content differences among genes have been previously reported in other plant species [3,4] this study is the first report on repeat content differences between plant sexes. Repeat content differences between the sexes may contribute differenzial expression of genes [5] which may affect the chemical properties of asparagus.

Characterization of a Behaviorally Active, Gender-Specific Volatile Compound from the Male Asparagus Fly Plioreocepta poeciloptera

Adult male asparagus flies exhibit typical calling behaviors (suggestive of pheromone production) during which they emit a single volatile compound that was identified as isopropyl (S)-5-hydroxyhexanoate. In laboratory bioassays, synthetic samples elicited an arrestant response in females, but did not appear to attract females. On the other hand, the synthetic material attracted conspecific males in olfactometer bioassays.

Rapid Sex-typing of Asparagus for Male Hybrid Seed Production using n-Propyl N-(3,4-dichlorophenyl)carbamate (NPC)

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.

Recovery of transgenic asparagus plants by particle gun bombardment of somatic cells

Transgenic asparagus (Asparagus officinalis L.) plants were obtained through particle gun bombardment of suspension cells using the pKGUS plasmid containing both neomycin phosphotransferase II (nptII) and β-glucuronidase (uidA) genes. In experiments to optimize bombardment parameters, the combination of 1.1 μm tungsten particles and 1000 psi bombardment pressure was best; 65 cells or cell clumps per plate of 105–106 suspension culture derived cells expressed uidA in transient assays. No significant genotypic effects were detected for the number of cells or cell clumps expressing uidA among four genotypes. A two-step selection procedure was established for the recovery of transformed plants. The bombarded cells were first placed on embryo induction medium with 25 mg l−1 kanamycin for 4 weeks, and the resistant calli were then transferred to the same medium with 50 mg l−1 kanamycin for embryo development. A total of 10 plants from six kanamycin resistant calli were recovered. The expression of uidA was detected in the stems and cladodes of these 10 plants. Southern analysis confirmed the integration of nptII and uidA into the asparagus genome, and revealed that the 10 transgenic plants from six resistant calli were from one transformation event. In addition to the detection of junction fragments where the pKGUS plasmid integrated into the genome, Southern analysis also provided evidence that most of the pKGUS plasmid DNA was integrated intactly and organized as head-to-tail concatemers in these plants. uidA assays of the hybrid seeds from the crosses between one transgenic male asparagus T0 plant and nontransformed female asparagus suggested that uidA activity was inherited as a single locus with Mendelian segregation.

41 Thiocarbamate-Induced Early Flowering Protein is Expressed in Male Asparagus Flower

41 Thiocarbamate-Induced Early Flowering Protein is Expressed in Male Asparagus Flower

Micropropagation of a recalcitrant male asparagus clone (MD 22-8)

TheAsparagus officinalis male asparagus clone MD 22–8 (Howard Scott) is highly prized by asparagus breeders but has been very difficult to micropropagate due to its slow growth rate and reluctance to initiate roots. Shoot tips cultured on indole-3-acetic acid or indole-3-propionic acid, at concentrations of 1.53 and 1.44 μM respectively, resulted in levels of root initiation and elongation equal to or better than those of a female asparagus clone. These culture conditions also improved the rates of shoot initiation and elongation. Root initiation and elongation were further increased by culture conditions that provided enhanced gas exchange.

Monoclonal antibodies to antigens of anthers from a dioecious plant: Asparagus officinalis L.

Monoclonal antibodies were raised by immunizing mice with a crude extract from anthers of mature male flowers of the dioecious plant Asparagus officinalis L. To isolate anther specific antibodies, hybridoma culture supernatants were screened by enzyme-linked immunosorbent assay (ELISA) against extracts from anthers, leaves, roots of male Asparagus plants. We were able to isolate a set of anther specific monoclonal antibodies recognizing four different epitopes, as shown by ELISA experiments, Western blotting and immunolocalization. Only one of the antibodies is periodate-sensitive, implying that the epitope it recognizes is carbohydrate in nature. Indirect immunofluorescence observations and timing experiments seem to suggest that at least three of the antigens are localized in pollen cells and are present in large amounts only at relatively late times during anther development.

Male Asparagus Hybrids: `Jersey Gem', `Jersey General', `Jersey King', `Jersey Knight', and `Jersey Titan'

Five male asparagus hybrids described herein are new members of the series that began with the release of ‘Jersey Giant’ (Ellison and Kinelski, 1985) and ‘Greenwich’ (Ellison and Kinelski, 1986). Male hybrids are extremely desirable because they result from controlled pollination and only F1 seed is available to growers. The integrity of the dioecious cultivars Mary Washington and Martha Washington was lost because growers saved seed from random pollinations (Norton, 1913). Male hybrids are generally higher yielding (Ellison and Scheer, 1959) than dioecious hybrids due to diversion of photosynthate to seed production in female plants. Males also live longer (Ellison and Scheer, 1959) and do not produce seedlings that behave as weeds in the production field.

The value of comparative tests of progenies from open-pollinated female asparagus plants

From seed yield determinations in an isolated seed garden the conclusion has been drawn that a male asparagus plant only pollinates those female plants which grow very close to it. The so-called open pollination of a female plant in a commercial or trial field can therefore only be carried out out by a very limited number of male plants.

The significance of andromonoecy for the breeding of Asparagus officinalis L.

Following a previous publication in this periodical (3), indicating the lines along which an entirely male asparagus variety can be obtained, the above article further discusses the difficulties to be overcome. The combination of andromonoecism and homozygosis for the male sex (andromonoecious MM-plants) is discussed in more detail. These plants, some hundreds of which are now in the possession of the Institute of Horticultural Plant Breeding, have the great advantage that they can be readily used to produce large numbers of MM plants. There is the danger, however, that andromonoecism is transmitted to the commercial seed of the male variety. Although the available figures do not yet provide certainty as to the genetic behaviour of andromonoecism, transmission is likely to depend on some dominant factors. Proceeding from this assumption we could already indicate in principle how to prevent andromonoecism in commercial seed.