Production and characterization of new interspecific hybrids of pearl millet (Pennisetum glaucum (L.) R. Br.) × Napier grass (Pennisetum purpureum (K.) Schum) and their amphiploids
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
Pearl millet [Pennisetum glaucum (L.) R. Br.] with 2n = 2x = 14 chromosomes (AA)
and Napier grass [Pennisetum purpureum (K.) Schum] with 2n = 4x = 28 chromosomes
(A’A’BB) belongs to two different gene pools of Pennisetum but are sexually compatible and
undergo hybridization that favours introgression of favourable alleles such as high biomass
production, perennial nature, winter hardiness coupled with multicut behaviour into
interspecific pearl millet Napier hybrid. In the production of interspecific hybridization, 20%
seed setting has been reported. The major constraint in utilizing this interspecific hybrid for
breeding purpose lies in its sterile behaviour owing to its triploidy (2n=3x=21) nature. To
overcome this problem, amphiploid induction by chromosome doubling has been identified as
the most efficient approach. The present study describes an efficient in vitro method using
colchicine treated triploid interspecific hybrids to produce hexaploid hybrids and their
subsequent characterization using stomata frequency and morphology, trichome study and
cytological investigation. Colchicine was used at three different concentrations i.e. 0.05%,
0.1% and 0.2% for two different time durations i.e.12 hours and 24 hours to the root slips and
stem cuttings. The treated plants were analysed for confirmation of ploidy and compared with
control plants. It is confirmed that stomata frequency and trichome density decreases whereas
stomata size increases with an increase in the ploidy level. Pollen staining was also used as an
indicator for doubling of chromosomes. The plants which have fertile pollens were considered
as putative hexaploid plants. Therefore, the cytological investigation was taken up only in
plants identified as hexaploid. In nutshell, 0.1% colchicine concentration applied to root slips
for 24 hours was found to be the most effective treatment to induce the amphiploidy.
Chromosome doubling has numerous applications in Pennisetum breeding once the fertility
restoration of bajra x napier hybrids is achieved satisfactorily.
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