Zora Singh

Somatic embryogenesis and plantlet regeneration in mandarin (Citrus reticulata Blanco)

Abstract Callus cultures were initiated from leaf, epicotyl, cotyledon and root segments of in vitro grown nucellar seedlings of Citrus reticulata Blanco ‘Local Sangtra’. Callus initiation was seen on cut ends of all the explants within 10 days of culture. The epicotyl segments were the best explant for callus induction. Best callus induction occurred on MS medium containing NAA (10 mg l−1) and kinetin (0.5 mg l−1). MS medium supplemented with NAA (10 mg l−1), kinetin (1 mg l−1) and vitamins (10 × normal MS levels) were best for induction of somatic embryogenesis. The epicotyl-derived callus exhibited significantly higher (83.0%) mean somatic embryogenesis than calli derived from other explants. Most of the somatic embryos germinated like normal embryos, but some only produced shoots. The time taken for root initiation from separated shoots was 7–10 days. The number of roots per shoot and root length also varied with culture media. Plantlet survival in vitro was directly proportional to the number of roots produced per shoot. In vitro derived plantlets were successfully transplanted to soil.

Somatic embryogenesis and plantlet regeneration on calluses derived from seedling explants of ‘Kinnow’ mandarin (Citrus nobilis Lour, × Citrus deliciosa Tenora)

SummaryCallus cultures of ‘Kinnow’ mandarin (Citrus nobilis Lour, × Citrus deliciosa Tenora) were established from a range of different somatic explants excised from three week old in vitro-grown nucellar seedlings. The explants tested included leaf, epicotyl, cotyledon and root segments. All cultured explants initiated callus from the cut ends after a week, when cultured on a modified Murashige and Tucker (1969) medium; cotyledon segments were the best explant for callus induction. The calli derived from epicotyl segments were also the best source of somatic embryos. Embryogenic calluses were subcultured on MS medium fortified with BAP (3 mg l−1) +NAA (0.5 mg l−1) + malt extract (500 mg l−1) showed further growth, development, budding and germination of somatic embryos. Root initiation took 7−10 d after culturing on various rooting media. The number of roots per shoot varied from 1−2 to 6−8 on MS medium containing NAA and/or IBA. Plantlet survival in vitro was directly related to the number of roots prod...

Increased fruit set and retention in mango with exogenous application of polyamines

SummaryAqueous solutions of putrescine, spermine and spermidine of different concentrations (10−3, 10−4, 10−5, 10−6M) were sprayed onto panicles prior to anthesis or at full bloom, to study effects on fruit set and retention of the two self-incompatible cvs Langra and Dusheri, of mango (Mangifera indica L.). Putrescine (10−4M) increased fruit set in ‘Dusheri’ when applied prior to anthesis whereas spermine (10−4M) was most effective in stimulating fruit set in ‘Langra’ when applied at full bloom. The application of polyamines at full bloom resulted in higher fruit retention than when applied prior to anthesis. Spermine was more effective than putrescine or spermine in increasing fruit retention in both cultivars. Spray application of spermine (10−3M) prior to anthesis and putrescine (10−4M) at full bloom were most effective in increasing the final fruit retention in cvs Dusheri and Langra, respectively.

Nutrient levels in malformed and healthy tissues of mango (Mangifera indica L.)

Samples of malformed and healthy panicles of mango (Mangifera indica L.) as well as leaves and shoots bearing them were collected at different stages of development (fully swollen buds, bud inception, fully grown panicles prior to full bloom and at full bloom) over two consecutive years and were analysed for their macro- and micronutrient status. In addition, malformed and healthy seedlings were collected and analysed. Malformed panicles were found to be significantly higher in N at all the developmental stages except at bud inception. Phosphorus and K also tended to accumulate in malformed panicles at later stages of their development. In general, malformed panicles exhibited lower levels of P, K and Ca than healthy panicles. The differences in levels of Mg and S in malformed and healthy panicles were not significant. All micronutrients were in much lower concentrations in malformed panicles except for Mn which appears to accumulate in malformed panicles particularly at the early stages of development. The leaves on the shoots bearing malformed panicles also showed a tendency to accumulate N, while P, Mg and S were always higher in leaves on shoots bearing healthy panicles. The leaves on shoots bearing healthy panicles had lower levels of Fe, Cu and Mn, whereas levels of Zn and B tended to be higher in leaves on shoots bearing malformed panicles. The nutrient concentration differences between the two kinds of shoots were generally nonsignificant (P=0.05), except for K and S which were significantly lower in shoots bearing malformed panicles. The shoots bearing malformed panicles showed significantly (P=0.05) higher levels of almost all nutrients compared with shoots bearing healthy panicles. Vegetative malformation was found to be associated significantly (p=0.05) with higher amounts of all nutrients except Ca which was significantly higher in healthy seedlings. The present study, therefore, seems to point to lower Ca as one of the pre-disposing factors causing malformation in mango.

Floral malformation, yield and fruit quality of Mangifera indica L. in relation to ethylene

A three-year study of malformation in mango (Mangifera indica L.) revealed significantly higher levels of ethylene (46%, 145%, 67% and 34%) in malformed panicles than in healthy ones at development stages (I) fully swollen buds, (II) bud inception, (III) full grown panicles prior to full bloom, and (IV) full grown panicles at full bloom, respectively. Similarly, the shoots bearing malformed panicles showed significantly higher levels of ethylene (110%, 90%, 106% and 104%) over shoots bearing healthy panicles at the four developmental stages. Leaves borne on shoots bearing malformed panicles had significantly more ethylene (198%, 120%, 79% and 159%) than leaves on shoots bearing healthy panicles at all four stages. In a two year trial, exogenous sprays of ethephon at 400 ppm a.i. at bud inception stage were more successful in reducing floral malformation (8.9% and 10.2%) than ethephon sprays of 300 ppm, 500 ppm and water control sprays. Highest yields were obtained following application of ethephon (400 pp...

Effect of cobalt ions on floral malformation, yield and fruit quality of 'Dusheri' mango (Mangifera indica L.).

A four year study of malformation in mango (Mangifera indica L.) revealed that a single foliar spray application of 1000 ppm cobalt sulphate prior to flower bud differentiation in the first week of October successfully reduced floral malformation by 93,94,87 and 84% in each year respectively, as compared with the earlier recommended treatment of naphthalene acetic acid (100 ppm) and with unsprayed control trees. The single foliar spray of cobalt sulphate was more effective in reducing floral malformation than a double spray. This treatment also increased fruit yield in all four years. The foliar application of cobalt improved fruit weight, size, TSS/acid ratio and the total sugars in the fruit. Experimental findings based upon three years’ data clearly demonstrated that the deficiency or toxicity of cobalt is not related to the cause of mango malformation because the concentrations of cobalt did not vary between healthy and malformed organs.

Effect of (2RS, 3RS)-paclobutrazol on endogenous indole-3-acetic acid in shoot apices of pear cv. Doyenne du Comice

The possibility that the stimulation of pear flower initiation by (2RS, 3RS)-paclobutrazol (PP333) might be caused by changes in shoot apex IAA as apical activity is slowed, affecting apical dominance, was studied. Applied directly to the shoot tip, 30 mg 1-1 of PP333 inhibited growth of cv. Doyenne du Comice as effectively as 100, 300 or 1000 mg P1. Retardation of shoot growth by these concentrations did not reduce IAA production by the shoot apex, as measured by gas chromatography-mass spectrometry (GC-MS). On the contrary, at 100, and to a lesser extent 300 mg 1-1 the chemical induced a large, but transient increase in IAA within two days after treatment. Full mass spectral evidence for the presence of native IAA in the pear shoot apex was obtained.

Effect of cobalt, cadmium, and nickel as inhibitors of ethylene biosynthesis on floral malformation, yield, and fruit quality of mango

Abstract Among the treatments of exogenous foliar spray application of sulphates of cobalt (Co) and cadmium (Cd) at 0, 250, 500, 1000, and 1500 ppm, and nickel (Ni) at 0, 100, 200, and 400 ppm prior to flower bud differentiation in the first week of October, cobalt sulphate (1000 ppm) or cadmium sulphate (1500 ppm) significantly (P=0.05) reduced floral malformation of mango (Mangifera indica L) cv. Langra by 65 to 71% and increased the fruit yield by 35 to 37%. The physical characteristics of the fruit were not affected significantly at the lower concentrations but higher concentrations of Co and Cd caused reduction. Total and non‐reducing sugars in the fruit were adversely affected by the higher rates of Co and Ni applied, but exhibited no effect on total soluble solids percentage (TSS%) or reducing sugars. The foliar spray application of the sulphates of Co, Ni, and Cd increased their respective concentrations in the leaf tissue without any phytotoxic symptoms. Most of the desirable effects were achieve...

Induction of high frequency somatic embryogenesis and plant regeneration in Mandarins

Mandarins constitute an important group among the citrus fruits. Kinnow (C. nobilis Lour x C. deliciosa Tenora) is now extensively grown commercially in North Indian plains, owing to its high yield and relative resistance to insect-pests and diseases. However, it has a tendency towards higher seediness, bitterness in juice, thick and tight rind and late maturity. Likewise, in C. reticulata Blanco cv. Local Sangtra, poor productivity, high incidence of sunburn and granulation warrant the incremental improvement in these two mandarins, via tissue culture. The paucity of the information, on the induction of high frequency somatic embryogenesis and plant regeneration in these cultivars necessitates this investigation.

In-ovulo embryo culture in seedless grapes(Vitis vinifera L.)

Seedless table grapes are preferred by consumers, which demands breeding work to develop improved seedless cultivars. Vitis vinifera L. cvs. Perlette, Thompson Seedless and Beauty Seedless are stenospermic in which embryos abort after few days of anthesis (Stout, 1936). Embryos and endosperm breakdown occurs during third to fourth weeks after anthesis. Embryo development in aborting seeds ranged from few cell stage to globular stage (Stout, 1936). In-ovulo embryo culture prior to embryo abortion provide an attractive alternative to conventional breeding methods. In conventional method breeding of seedless grapes, the crossing of seeded cultivars with seedless cultivars resulted in 10–15% seedless progeny (Winberger and Harmon, 1964). Theoratically by crossing seedless cultivars with seedless cultivars result in high percentage of seedless progenies in one breeding cycle. Two distinct methods, viz. culturing in liquid medium (Emershad and Ramming, 1984; Gray et al., 1987) and on solid medium (Cain et al., 1983; Spiegel-Roy et al., 1985) have also been reported. The present report deals with in-ovulo embryo culture of stenospermic Perlette, Thompson Seedless and Beauty Seedless grapes.