Polyembryonic Cultivars Research Articles

Characterization of embryogenic mango cultures selected for resistance to Colletotrichum gloeosporioides culture filtrate and phytotoxin

Embryogenic nucellar cultures of two polyembryonic mango cultivars, ‘Hindi’ and ‘Carabao’, were selected for resistance to the culture filtrate and phytotoxin of a virulent strain of Colletotrichum gloeosporioides Penz. that was isolated from mango leaves. The cultures were recurrently selected either with progressively increasing concentrations of culture filtrate or by continuous challenge with the same concentration of either culture filtrate phytotoxin. Mycelium growth was inhibited when the pathogen was cocultured with the selected, resistant embryogenic cultures. Conditioned plant growth medium containing macerated resistant embryogenic cultures did not inhibit mycelium growth, confirming that extracellular antifungal compounds were involved in the defense response. Enhanced secretion of chitinase and glucanase was observed in the plant growth medium in which resistant embryogenic cultures and regenerated somatic embryos were grown in comparison with the controls.

Isolation and Characterization of Soluble Polysaccharides and Insoluble Cell Wall Material of the Pulp from Four Mango (Mangifera indica L.) Cultivars

Mature green fruits from monoembryonic (Amélie and Palmer) and polyembryonic (M'Bingue and Tête de Chat) mango cultivars were initiated to ripen with ethylene (10 ppm, 24 h) and then left to reach full ripeness (6 days). After elimination of skin and kernel, pulp was added with HEPES (1/5, w/w) and centrifuged. Soluble polysaccharides were obtained from the supernatant by precipitation with ethanol and freeze-drying. Cell wall material (CWM) was isolated from the pellet by the buffered phenol procedure and further enzymatically destarched. Soluble polysaccharides (∼0.5−0.8%/pulp fresh weight) were essentially highly esterified pectic substances (uronic acids content ∼50−60%; degree of methyl esterification ∼89−97%) and their molecular weights were higher in the polyembryonic cvs. CWM, ∼1%/pulp fresh weight, was mainly built of cellulose (∼20%) and highly esterified pectic substances (uronic acids ∼13−24%; degree of esterification ∼63−73%). Hemicellulosic glucans were more abundant in the monoembryonic (∼9%) than in the polyembryonic (∼4%) cultivars. Keywords: Mango; Mangifera indica L.; cultivars; pulp; soluble polysaccharides; cell wall material

Frequency of Zygotic Seedlings from Five Polyembryonic Mango Rootstocks

Five isozyme systems were used to detect zygotic seedlings from five polyembryonic cultivars of mango (Manifera indica L.). Significant differences were found between cultivars (x2 = 35.53, P < 0.001) for the percentage of zygotic and nucellar seedlings detected. The range of variation in the percentage of off-types was from 0% in 13-1 to 64% in Golek. The percentage in Sabre was 4%, and 24% and 36% in Tupentine and Madoe, respectively. Three of eight rootstock mother trees of Turpentine were determined to be off-types.

Factors Affecting in Vitro Embryogenesis from Undeveloped Ovules of Mature Citrus Fruit

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.

Adventive Embryogenesis inCitrus

SUMMARYThe mechanism of adventive embryogenesis was studied at ultrastructural level. Three Citrus cultivars were used as material, two poly-embryonic and one mono-embryonic. The adventive embryos in Citrus are initiated in the nucellar tissue adjacent to the embryo sac in the micropylar half and incidentally from the chalazal end. The nucellar embryoids derive from initial cells. Initial cells are present already at the time of flowering in the poly-embryonic cultivars: in the mono-embryonic cultivar initial cells are absent. At the mature embryo sac stage the initial cells have a « meristematic » character. Before division they develop new cell walls and become « zygote-resembling » cells. During this development they are isolated and their original cell walls are disintegrated. Simultaneously the surrounding nucellar cells degenerate and disappear and the initial cells become embedded in the endosperm.

Somatic embryos from culture ovules of polyembryonic Mangifera indica L.

Ovules were aseptically removed from 2 month old fruits of 9 naturally polyembryonic cultivars and 1 monoembryonic cultivar of mango (Mangifera indica L.). Ovules were placed into culture on solid Murashige and Skoog medium that had been modified by the addition of half strength major salts and chelated iron, 6% sucrose, 400 mg/l glutamine, 100 mg/l ascorbic acid with or without the following growth regulators: 20% (v/v) CW, 1 or 2 mg/1 BA. Somatic embryogenesis occurred from the nucellus excised from the ovules of 5 of the naturally polyembryonic cultivars after 1-2 months in culture. Somatic embryogenesis was not apparently affected by the growth regulator composition of the media; however, efficient somatic embryogenesis only occurred in liquid containing 20% CW.

カンキツ類の珠心胚形成に関する研究 (第2報)

The mechanism of nucellar embryogenesis was studied in histological experiments and ovule cultures. Seven citrus cultivars were used as materials.A primordium cell of the nucellar embryo, designated by the authors in a previous paper (6), was observed in the ‘Trovita’ orange ovule from 4 days before anthesis. The primordium cell was observed in the other polyembryonic cultivars from the time of flowering. However, the primordium cell was not observed throughout the developmental stages of the ovule in any of the monoembryonic cultivars studied. In the culture of ovules excised from flower buds and young fruits, nucellar embryoids were formed only in the polyembryonic cultivars. The embryoids formed in the monoembryonic cultivars originated in the fertilized egg. The nucellar embryoids formed in the polyembryonic ones were derived either from the primordium cell of the nucellar embryo or other cells which might have such a potential as to develop into the primordium cell. Moreover, the nucellar embryoids were formed in an agar medium containing sucrose only. The mechanism of nucellar embryogenesis is discussed on the basis of these results.

Time-dependent Coagulation of Young Shoot Homogenates of Citrus1

Abstract Young shoot homogenates from some noncoagulating taxa coagulated either within 5 or 30 minutes depending on the taxon; others did not coagulate even after 30 minutes. Such time-dependent coagulation behavior or its absence is taxon-specific and appears to have uses as an additional marker in taxonomic and genetic studies in Citrus and to identify zygotic and maternal seedlings from crosses of 2 polyembryonic cultivars if the parents have the contrasting traits. Genetic data obtained from two F1 populations, an F2 population, and a presumed back-cross indicate that the character may be controlled either by 1 or 2 gene pairs.

A Numerical Taxonomic Study of the Mango Mangifera indica L.1

Abstract Variability among 40 cultivars of Mangifera indica L. and one specimen each from M. odorato Griff, and M. zeylanica Hook f. were measured and classified using the unweighted pair group method of cluster analysis of distance coefficients based on 73 characters. Neither M. odorata nor M. zeylanica showed a close overall similarity to any of the cultivars of M. indica. Most cultivars clustered into 1 of 4 major groups. One group contained the polyembryonic cultivars with oblong fruit common to Southeast Asia. Another group consisted of monoembryonic cultivars with roundish fruit common to India. A third group, intermediate in fruit shape, included cultivars from India and one from the West Indies. The final group involved several hybrids developed in Florida and Hawaii. This group, as a rule, has large fruit and is designated as the Sandersha-Haden complex. A tentative pedigree based on both reported parentage and distance coefficients is given for this group. A few cultivars from Indo-china, the West Indies, and Réunion did not show close enough affinity to be placed into any of the above groups.