Jules Janick

Plant Breeding Reviews

Plant breeding reviews , Plant breeding reviews , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Floral Morphology of Artemisia annua with Special Reference to Trichomes

Floral morphology of Artemisia annua L. was described using light and scanning electron microscopy. Floral trichomes include nonglandular T-shaped filamentous trichomes, which occur on the basal bracts and pedicel of the capitulum, and 10-celled biseriate glandular trichomes on receptacle and bracts of capitula and corolla of florets. The heart-shaped biseriate glandular trichomes, composed of two columns of five cells each, are similar to those described for the leaf. During floral development, the cuticle surrounding the apical cells of biseriate glands detaches and forms a saclike reservoir for fluids excreted by the apical cells. The cuticle ruptures at anthesis, discharging its contents on the inflorescence. Artemisinin was detected by HPLC-EC from flowering branches dipped for 60 s in petroleum ether or acetonitrile, providing corroborating evidence that biseriate glandular trichomes were the likely site of artemisinin sequestration.

Initiation and Development of Asexual Embryos of Theobroma cacao L. in vitro

Summary Zygotic embryos of Theobroma cacao «Amelonado» from 2.5 to 28.0 mm in length were cultured on a basal medium consisting of MURASHIGE and SKOOG salts, vitamins, glycine, casein hydrolysate, and sucrose. Asexual embryogenesis occurred only from immature white (2.5 to 10.0 mm in length) and white/pink (10.5 to 18.0 mm in length) zygotic embryos, with the highest number of asexual embryos arising from the white embryos. Although embryogenesis occurred at low frequency on basal medium alone, the combination of auxin (indole-3-acetic acid, α-naphthaleneacetic acid, or 2,4-dichlorophenoxyacetic acid) and coconut water greatly stimulated embryogenesis; the addition of each separately had little effect on the embryogenic process. A higher incidence of embryogenesis was observed with liquid than with semisolid medium. Enhanced growth of zygotic embryos was also observed in liquid medium. Microscopic examination revealed two distinct patterns of asexual embryo initiation: 1) a «budding» process in which embryos arose from glandular hair-like structures; and 2) a «nonbudding» process with differentiation from internal cotyledonary meristematic tissues. Tissues from embryogenic cultures transferred to basal medium without auxin and coconut water continued to initiate asexual embryos.

Roots as an enhancing factor for the production of artemisinin in shoot cultures of Artemisia annua

Artemisinin was produced in differentiated shoot cultures of Artemisia annua L. but was undetected in callus or cell cultures. The growth regulators benzyladenine, kinetin, chlormequat, and daminozide, at concentrations which severely reduced rooting, reduced artemisinin production. A highly significant correlation (1% level) was observed between shoot artemisinin content and number of roots (r=0.775**), but shoot number and artemisinin content were unrelated (r=-0.198). Benzyladenine increased shoot proliferation at 0.5 and 5.0 μM, but decreased root production at 0.5, 5.0, and 50 μM. The highest levels of artemisinin production (0.287% DW) were obtained in hormone-free medium when root production was maximized. Removal of roots from shoots cultured in hormone-free liquid medium reduced shoot artemisinin by 53% and shoot arteannuin B by 60%. Neither artemisinin, arteannuin B, or artemisinic acid were detected from roots developed in semi-solid or liquid medium.

Abscisic acid and proline improve desiccation tolerance and increase fatty acid content of celery somatic embryos

Desiccation tolerance of celery (Apium graveolens L.) somatic embryos was increased by supplementation of embryo-production medium with 1 μM abscisic acid (ABA) or 1 mM proline, with highest survival obtained with a combination of 1 μM ABA and 1 mM proline. Addition of ABA and proline increased fatty acid accumulation by somatic embryos; the effect on fatty acid composition was inconsistent. Somatic embryos capable of germination differed from mature zygotic embryos by greater size, lower fatty acid level, and substantially lower proportion of oleic acid (18:1) as compared to linoleic acid (18:2).

Immunoquantitative analysis of artemisinin from Artemisia annua using polyclonal antibodies

Artemisinin was derivatized to dihydroartemisinin carboxymethylether in three steps, without disturbing the peroxide bridge, and then linked to either thyroglobulin (TGB) or bovine serum albumin (BSA). The artemisinin-TGB and -BSA conjugates were injected in female New Zealand rabbits but only the artemisinin-TGB conjugate generated polyclonal antibodies. An enzyme-linked immunosorbent assay (ELISA) was developed and the specificity of the antibodies was confirmed by comparison with pre-immune serum and by competitive assays using different dilutions of artemisinin standards. Although anti-artemisinin antibodies cross-reacted with artemisitene and dihydroartemisinin at all dilutions used, cross-reaction with deoxyartemisinin, artemisinic acid, and arteannuin B occurred only at high concentrations. ELISA successfully detected artemisinin from crude extracts in concentrations as low as 1.5 ng ml-1; and was epsilon 400-fold more sensitive than the HPLC-EC. The ELISA successfully detected and quantified artemisinin in different organs of greenhouse-grown plants and in eight clones of Artemisia annua grown in tissue culture but artemisinin was overestimated owing to cross-reactivity of the antibodies with artemisinin-related compounds present in the samples. Despite overestimation of artemisinin content, the correlations between ELISA and HPLC-EC were r = 0.92 when samples were diluted 100 times, and r = 0.90 when samples were diluted 500 times, indicating that ELISA is a potential tool for screening large A. annua populations.

PRODUCTION OF SYNTHETIC SEED BY DESICCATION AND ENCAPSULATION

SummaryProducing synthetic seed of carrot consists of coating in-vitro grown embryos with a synthetic seed coat such as Polyox WSR-N 750, drying under controlled conditions, and hardening to prevent precocious germination. Survival of such embryos declines over time. Similar procedures have also been used with celery. Somatic embryos have several advantages compared to conventional tissue culture which include proliferacy, singulation, and the development of bipolar structures. The factors which most limit the use of synthetic seeds are the inability to use such procedures with economically important genotypes, lack of understanding of the maturation of somatic embryos and poor conversion rates to greenhouse and/or field.

In vivo and in vitro lipid accumulation inBorago officinalis L.

Seeds of 13 accessions of borage (Borago officinalis) varied in total fatty acid content from 28.6 to 35.1% seed weight, with linoleic, γ-linolenic, oleic and palmitic as the predominant fatty acids, averaging 38.1%, 22.8%, 16.3% and 11.3% of total fatty acids, respectively. There was an inverse relation between γ-linolenic acid (25.0 to 17.6%) and oleic acid (14.5 to 21.3%). Fatty acid content of leaf tissues was 9.1% dry weight, with α-linolenic acid 55.2% and γ-linolenic acid 4.4% of total fatty acids. Cotyledons were the major source of fatty acids in seeds. Seed fatty acid content increased from <1 mg at six days postanthesis to about seven mg at maturity (22 to 24 days). Individual fatty acid content of seed was relatively constant after day 8. When immature embryos from 6 to 16 days postanthesis were cultured in a liquid or semisolid basal medium, fatty acid composition was similar to that of in vivo-grown seeds. Growth of cultured embryos decreased as sucrose concentration was increased from 3 to 20% in the basal medium, and most embryos did not survive 30% sucrose; fatty acid as a percentage of dry weight was maximal at 6% sucrose.

Accumulation of lipids, proteins, alkaloids and anthocyanins during embryo development in vivo ofTheobroma cacao L.

Developing embryos ofTheobroma cacao ranging in weight from 0.01–2.2 g dry weight, equivalent to 100–180 days postpollination, were analyzed for lipids, alkaloids, proteins, and anthocyanins. Total lipid, fatty acid, triglyceride, alkaloid, and anthocyanin accumulation increased linearly after an initial lag with embryo dry weight. Palmitic, stearic, arachidic, and oleic acids had constant rates of accumulation per micromole of total fatty acid (0.29, 0.27, 0.38, and 0.01, respectively); however, linoleic and linolenic acid accumulation decreased from 0.2 and 0.02 below 0.2 g dry weight to 0.035 and 0.0035 above 0.2 g dry weight, respectively. Monounsaturated triglycerides [palmito-oleo-stearin (POS), oleo-distearin (SOS), and oleo-dipalmitin (POP)] continued to accumulate as dry weight increased but polyunsaturated triglycerides [palmito-diolein (POO), stearo-diolein (SOO), linoleo-dipalmitin (PLP), and palmito-linoleo-olein (PLO)] ceased to accumulate at about 0.4 g dry weight. Theobromine accumulation increased linearly with dry weight after an initial lag but the rate differed with cultivar. Caffeine accumulation was low until the final stages of development. The protein pattern became dominated by 4 protein species with apparent molecular weights of 43, 34, 22, and 14 kDa as embryos matured.

Asexual embryogenesis via callus of Theobroma cacao L.

Summary Callus of Theobroma cacao L. (cacao) possessing embryogenic competence occurred spontaneously with two clones of asexual embryos proliferated in vitro in a hormone-free basal medium by hypocotylary budding. Asexual embryogenesis via callus occurred at low frequency in the hormone-free basal medium. High concentrations of 2,4-D plus coconut water stimulated callus production and suppressed embryo production. Maximum frequency and intensity of embryogenesis occurred at 10−3 to 10−2 mg·l 2,4-D. Embryos originated from meristematic tissue at the periphery of callus clumps. During development asexual embryos either remained embedded in the callus or were connected through suspensor-like structures.