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  • Author or Editor: G. A. Moore x
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Internodal seedling stem sections of 3 Citrus rootstocks—sour orange (C. aurantium L.), ‘Carrizo’ citrange [C. sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf.], and ‘Cleopatra’ mandarin (C. reshni Hort. ex Tanaka)—were cultured on media containing varying concentrations of BA and NAA. A medium containing 22 μM BA with or without 5.4 μM NAA was optimum for shoot initiation in all 3 rootstock types, but the 3 genotypes varied greatly in numbers of shoots produced. NAA in the medium was inhibitory to shoot production in long-term cultures. Chemical names used: N- (phenylmethyl)-1H-purin-6-amine (BA) and 1-naphthaleneacetic acid (NAA).

Open Access
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Abstract

The effects of genotype and growth additives on the induction of embryogenesis from undeveloped ovules from mature fruit of Citrus were examined. Embryos were produced in cultures of 15 of the 17 representative polyembryonic cultivars examined. Cultured ovules of 5 monoembryonic cultivars did not become embryogenic. Percentages of ovules producing embryos in the responsive polyembryonic cultivars ranged from 5 to 20 after 56 days in culture. Mean numbers of embryos per responsive ovule ranged from 1.9 to 13.2. Effects of growth additives on the production of embryos from undeveloped ovules from mature fruit of ‘Marsh’ grapefruit were tested. A low concentration (0.01 mg/liter) of butanedioic acid mono (2, 2-dimethylhydrazide) (daminozide) was most effective at increasing the induction of somatic embryogenesis over the control treatment of 500 mg/liter malt extract. The presence of abscisic acid or a higher concentration of malt extract (100 mg/liter) in the medium also increased embryo induction, but germination of embryos obtained on the malt extract medium was poor. The use of undeveloped ovules from mature fruits allows the initiation of embryogenic cultures from a wide range of Citrus species.

Open Access
Authors: and

Abstract

Isozyme markers for glutamate oxaloacetate transaminase (GOT), superoxide dismutase (SOD), peroxidase (PER), and malate dehydrogenase (MDH) were identified for Carica papaya L. and the related but sexually incompatible C. cauliflora Jacq. These markers were used to determine the nature of somatic embryos derived from papaya ovules cultured on modified Murashige and Skoog (MS) medium 65 days after controlled pollination with C. cauliflora. Zymograms of plantlets from somatic embryos contained bands specific to either C. papaya or C. cauliflora (PER, GOT) and a unique band not present in the zymogram of either species (PER). Zymograms of somatic embryo-derived plantlets were distinctively different from those of either of the Carica species for all the enzyme systems examined. Evidence from isozyme markers indicates that somatic embryos produced from cultured papaya ovules following pollination with C. cauliflora may be hybrids. The isozyme banding patterns of 60 plantlets derived from somatic embryos from the same ovule were very uniform and suggest genetic uniformity among the regenerated plantlets.

Open Access

Genetically characterized isozyme loci are useful for taxonomic studies. In an initial study a few Ananas genotypes were used to determine which enzyme systems would give well-resolved banding patterns on starch gels. The enzyme-staining systems that resulted in well-resolved banding patterns were used to survey more Ananas genotypes to identify and characterize isozyme polymorphism. Genetic studies were performed using seedling populations to determine the basis of variability observed among genotypes. Two peroxidase loci and three phosphoglucomutase loci were identified and characterized. Information from these studies, was used to formulate a system by which species and plant introductions could be identified and distinguished.

Free access

Abstract

A method for obtaining small (15-25 cm) plants of peach [Prunus persica (L.) Batsch] with all bud types present was developed by rooting peach cuttings following flower bud initiation. These small plants permit studies to be carried out in controlled-environmental chambers. The rest and dormancy periods of the rooted cuttings were similar to large field-grown trees of the same cultivar.

Open Access

Citrus genetic studies and cultivar improvement have been difficult with conventional techniques. Alternative approaches are needed to enhance efficiency of such studies. Our objectives were to characterize the Citrus genome and to initiate development of a linkage map using RFLP and isozyme analysis. Methods of Citrus DNA extraction were developed to allow the isolation of chromosomal DNA of acceptable quality for recombinant' DNA manipulations. A PstI Citrus genomic library was constructed to create DNA clones for the RFLP survey. A rapid, reliable procedure was developed to facilitate screening of the library for useful clones. The methods used and strategy followed minimized contamination with organelle DNA, increased the frequency of single copy clones, and allowed rapid screening of the newly–constructed library. Linkage relationships of 49. markers, including 36 RFLP and 6 isozyme loci, were analyzed and a map comprised of 8 linkage groups was constructed. Insertions or deletions were responsible for at least 30% of the RFLPs identified. A hypothesis of transposon activity in Citrus was proposed based on our observations.

Free access

Abstract

Medium components and characteristics that affect the growth of embryogenic mango (Mangifera indica L.) nucellar cultures and production of somatic embryos in vitro were studied. These included the role of complex organic supplements, basal medium formulations, solidifying agents, and liquid vs. solid media. Growth of embryogenic cultures in suspension was more efficient than on solid medium; however, subculture onto solid medium was essential for high-frequency production of morphologically normal somatic embryos, and Gelrite was more effective in this respect than Difco Bacto-agar. Modified B-5 basal medium was better for maintenance of cultures and for production of morphologically normal somatic embryos than either Murashige and Skoog or Woody Plant Medium. Sucrose concentrations at 5% to 6% were optimal for somatic embryo production, and also increased the frequency of recovery of normally differentiated early heart-shaped somatic embryos. Coconut water (20%, v/v) enhanced somatic embryo production by 18%; other complex organic addenda alone or in combination with coconut water were either ineffective (casein hydrolysate) or highly inhibitory (yeast extract) in comparison with basal medium alone.

Open Access

Abstract

Maturation and germination of mango (Mangifera indica L.) somatic embryos were achieved by sequential transfer of heart-shaped somatic embryos on a series of media based on the B-5 formulation. Precocious germination and other developmental abnormalities were controlled by incorporating 3 μm abscisic acid (ABA) and 6% (w/v) sucrose in the medium. Other factors, including the substitution of Gelrite (0.175%) for agar, the use of solid rather than liquid medium, and the culture of somatic embryos in darkness until physiological maturity also affected normal growth and development. Coconut water (20%, v/v) was also essential for mango somatic embryogeny. Germinated mango somatic embryos were successfully established in planting medium and they have continued to grow in a greenhouse.

Open Access

Abstract

The usefulness of isozyme banding patterns as genetic markers in peach [Prunus persica L. (Batsch)] was investigated using starch gel electrophoresis. Samples for electrophoresis included leaves of both juvenile and mature plants. A survey of 38 enzyme activity stains and five electrophoretic buffer systems was conducted. Only 12 staining systems produced well-resolved banding patterns; of these, nine were monomorphic among all genotypes surveyed and three showed some variation. Genetic analysis of the variable banding patterns observed for diaphorase, malate dehydrogenase, and peroxidase revealed the presence of single independently inherited loci, designated Dia-1, Mdh-1, and Per-1. These loci are inherited in a simple Mendelian manner and are useful as genetic markers in peach. Some possible applications to peach breeding are discussed.

Open Access

Abstract

Starch gel electrophoresis of leaf tissue samples was used to distinguish pineapple [Ananas comosus (L.) Merr.] cultivars. Isozyme genotypes at two peroxidase and three phosphoglucomutase loci allowed the unique identification of 15 of the 27 cultivars examined. The hypotheses that some cultivars originated as either sports or hybrids were confirmed by the allozyme data.

Open Access