The effects of derived B-chromosomes on meiosis in pearl millet Pennisetum typhoides

Rao, M. Nageswara; Pantulu, J. V.

doi:10.1007/bf00327386

Cited by 24 publications

(18 citation statements)

References 8 publications

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confidence: 99%

“…This information is of interest because when there is a distal localization of chiasma formation as is the case in pearl millet, the occurrence of interstitial chiasmata may bring about a recombination of otherwise tigtly linked genes (Rees and Jones 1977). Particular attention has therefore been paid in this paper to the effect of B-chromosomes on chiasma distribution.In an earlier paper, Subba Rao and Pantulu (1978) speculated that the differenti al effects of the three types of Bs present in pearl millet on A-chiasma frequency were due to relative amounts of euchromatin and heterochromatin present in them. This conclusion was arrived at particularly from the effects observed when the three types of Bs were present in different combinations and ratios.…”

mentioning

confidence: 99%

“…In an earlier paper, Subba Rao and Pantulu (1978) speculated that the differenti al effects of the three types of Bs present in pearl millet on A-chiasma frequency were due to relative amounts of euchromatin and heterochromatin present in them. This conclusion was arrived at particularly from the effects observed when the three types of Bs were present in different combinations and ratios.…”

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The effect of B-chromosomes on A-chromosome chiasma formation in pearl millet.

Jayalakshmi

Pantulu

1984

CYTOLOGIA

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Pantulu and Manga (1975) studied the influence of standard B-chromosomes while Subba Rao and Pantulu (1978) studied the effect of the derived B-chromosomes on mean cell chiasma frequency in pearl millet, Pennisetum typhoides (Burm.) S. & H. (2n=14). No critical assessment of the effects of Bs on A-chromosome chiasma distribution is, however, available. This information is of interest because when there is a distal localization of chiasma formation as is the case in pearl millet, the occurrence of interstitial chiasmata may bring about a recombination of otherwise tigtly linked genes (Rees and Jones 1977). Particular attention has therefore been paid in this paper to the effect of B-chromosomes on chiasma distribution.In an earlier paper, Subba Rao and Pantulu (1978) speculated that the differenti al effects of the three types of Bs present in pearl millet on A-chiasma frequency were due to relative amounts of euchromatin and heterochromatin present in them. This conclusion was arrived at particularly from the effects observed when the three types of Bs were present in different combinations and ratios.The B-chromosomes of pearl millet are, however, unstable and exhibit numeri cal variation between cells of the same tissue and between tissues of the same plant (Jayalakshmi and Pantulu 1982). The earlier workers carried out observations and analyses at the individual plant level. For this purpose, they classified the B-carry ing plants on the basis of 'modal' number, i.e., that number which is most frequent. How far the Bs present in numbers deviating from the modal number are liable to influence the results is not known. In the present study, therefore, analyses were carried out after pooling the cells with the same B-chromosome type and number from different plants.

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The effect of B-chromosomes on A-chromosome chiasma formation in pearl millet.

Jayalakshmi

Pantulu

1984

CYTOLOGIA

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“…Work in pearl millet gave different results. Manga (1975) andSubba Rao &Pantulu (1978) showed that the standard B chromosome in pearl millet produces a strong increase in chiasma frequency among Bs, but has little effect n the A chromosomes. Apparently, the B has an effect on crossing-over that is specific for B chromosomes.…”

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Crossover effects of B chromosomes may be 'selfish'

Carlson

1994

Heredity

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“…Barlow and Vosa (1970) suggested that the presence of B-chromosomes reduced the negative interference between the sites of chiasma formation and prolong the time of effective pairing in proportional increase in the total chiasma frequency of A-chromosomes. Subha Rao and Pantulu (1978) showed that it is the balance between euchromatin and heterochro matin that decides the effect of B-chromosomes on the chiasma frequency of A chromosomes. However it is possible that the presence of B-chromosomes might be effecting more than one factors influencing the chiasma formation in the A chromosomes.…”

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Cytogenetical studies of accessory chromosomes in the genus Cymbopogon Spreng.

Verma

Sobti

1985

CYTOLOGIA

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Cymbopogon, an important genus of aromatic grasses, consists of nearly 140 species (Verma 1981) of these only a few have been studied cytologically. In India the genus is represented by about 22 species, many of which are cultivated (Jagadish Chandra 1975a, b).The genus is monobasic with x=10 and B-chromosomes have been reported in 7 out of 22 Indian species (Verma 1981). In the present study supernumerary chromosomes were detected in two species, C. martinii var. motia (2n=20) and C. jwarancusa (2n=20) out of the 9 species investigated. No B-chromosomes were detected in the polyploid species. The B-chromosomes were found both in the root-tip meristematic cells as well as the PMCs. The present paper deals with the nature and behaviour of these supernumerary chromosomes in the above two species, their Fi hybrids with other Cymbopogon species and in the F2 population raised from one of the partially fertile F1 hybrid. Material and methodsThe plants were collected from their wild habitat during routine collection and grown in the experimental garden of the laboratory. C. jwarancusa was col lected from Nanital while C. martinii var. motia plants were collected from Haldwani. Herbarium sheets of these plants are deposited in the herbarium of the Regional Research Laboratory, Jammu.Root-tip and male meiosis squashes were made by the standard methods using aceto-orcein and aceto-carmine stains, respectively. Observations and photo micrographs were taken from the temporary preparations which were later made permanent. For denoting the position of centromere in the chromosomes the terminology adopted is reported earlier (Verma and Sobti 1982). ResultsFollowing types of studies were made: 1. Study of B-chromosomes in two parental speciesThe two parental species C. martinii var. motia and C. jwarancusa were taken up for the present study after screening 9 species and varieties for the presence of B-chromosomes.In C. martinii var. motia (2n=20) the frequency of B-chromosomes ranged

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The effects of derived B-chromosomes on meiosis in pearl millet Pennisetum typhoides

Cited by 24 publications

References 8 publications

The effect of B-chromosomes on A-chromosome chiasma formation in pearl millet.

The effect of B-chromosomes on A-chromosome chiasma formation in pearl millet.

Crossover effects of B chromosomes may be 'selfish'

Cytogenetical studies of accessory chromosomes in the genus Cymbopogon Spreng.

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