TAGGING OF THE SPECIFIC GENOME AND CHROMOSOME(S) OF HEXAPLOID WHEAT TRIGGERING CHROMOSOME ELIMINATION IN WHEAT x IMPERATA CYLINDRICA SYSTEM OF DOUBLED HAPLOIDY BREEDING
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Date
2013
Authors
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Journal ISSN
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Publisher
CSK Himachal Pradesh Krishi Vishavavidyalaya, Palampur
Abstract
The present research endeavour entitled as “tagging of the specific genome and chromosome(s) of
hexaploid wheat triggering chromosome elimination in wheat x Imperata cylindrica system of doubled
haploidy breeding” was undertaken at Molecular Cytogenetics & Tissue Culture Lab and Experimental
Farm of the Department of Crop Improvement, CSK HP Agricultural University, Palampur, Himachal
Pradesh, India during 2010- 11 and 2011- 12 with the objective of identifying the wheat genomes and
chromosomes responsible for elimination of whole I. cylindrica chromosome complement in wheat x I.
cylindrica hybrids during early embryogenesis. Upon hybridization of different species of wheat viz.,
Triticum monococcum, T. tauschii and T. durum with I. cylindrica, haploid embryos were recovered in T.
tauschii and T. durum only which revealed that the D and B genomes of hexaploid wheat are triggering the
paternal chromosome elimination process. The possibility of enhancing the efficiency of embryo formation
via increasing the exogenous supply of 2,4-D was also exploited and 0.03 % and 0.04 % of 2,4-D
concentration were found optimum for haploid induction in T. durum and T. tauschii, respectively. The
induction of haploid embryos in these species was also confirmed by cross-sectional studies of fertilized
ovules derived after their hybridization with I. cylindrica. For further resolution of the genetic control of
paternal chromosome elimination in wheat x I. cylindrica crosses, cytogenetic stocks viz., complete set of
monosomic and nullisomic lines derived from ‘Chinese Spring’ cultivar of hexaploid wheat and D genome
substitution lines of tetraploid wheat cultivar ‘Langdon’ were crossed with I. cylindrica. Statistical analysis
of embryo formation frequency in monosomics revealed the role of 4D, 1D, 6B and 6D chromosomes as
the absence of these chromosomes resulted in reduction of haploid embryo formation frequency from
control as well as mean. These results were also supported by data obtained from nullisomics and
substitution lines. Morphological characterization of monosomic series was carried out on the basis of 24
traits to identify visual markers for differentiation of aneuploids from disomic plants. Eight morphological
descriptors were identified for differentiation of nullisomics, that is, seed size, plant height, spike length,
number of tillers, florets per spike, seeds per spike, days to flowering and 100 seed weight. Whereas, two
descriptors were identified in case of monosomics viz., spike shape for 5A and days to flowering for 2B
monosomic.
Description
Doctoral Dissertation
Keywords
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