STUDIES ON MUTAGENIC EFFECT OF GAMMA IRRADIATION IN TUBEROSE (Polianthes tuberosa L.)
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Date
2019-11-07
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COLLEGE OF HORTICULTURE, ANANTHARAJUPETA, KADAPA – 516105 ANDHRA PRADESH
Abstract
Tuberose (Polianthes tuberosa L.) is a vegetatively propagated crop used
as loose flowers, cut flowers and also as raw material for the extraction of the
highly valued natural flower oil. Genetic improvement of tuberose is hampered
by meager genetic variability, self incompatibility, seed sterility and these factors
impair the conventional improvement programme. Mutation breeding is one of
the best options for supersizing the genetic base and enhancing the crop diversity.
Hence the present experiment entitled “Studies on mutagenic effects of gamma
irradiation in tuberose (Polianthes tuberosa L.)” was carried at Floriculture
block, College of Horticulture, Anantharajupeta, Y.S.R. Kadapa District, Andhra
Pradesh during 2017-19 with the objective to estimate the lethal dose of physical
mutagen, gamma rays, to evaluate the growth, yield and qualitative traits of
tuberose cv. ‘Hyderabad Single’, subjected to gamma irradiation at LD50 (20 Gy)
and to conduct molecular analysis of desirable mutants obtained from mutant
population with RAPD and ISSR markers.
The bulbs of tuberose cv. ‘Hyderabad Single’ were treated with different
doses of gamma rays viz., 5 Gy, 10 Gy, 15 Gy, 20 Gy, 25 Gy and 30Gy at
BARC, Mumbai. Untreated bulbs were used as control and the experiment was
laid out in a CRD. The sprouting percentage decreased with gradual increase in
dose of irradiation. The plant height was maximum in 5 Gy (44.8 cm), as the
gamma irradiation dose increased all vegetative (survival per cent, plant height,
plant spread, leaf area, width of leaves, number of shoots per clump), floral
(spike length, rachis length, number of florets per spike, weight of floret, number
of spikes per plant and flower yield), bulb (number of bulbs per clump, weight of
bulbs, average diameter of bulbs, average length of bulbs and circumference of
clump) and biochemical characters (SPAD chlorophyll content) recorded a
gradual decline. The irradiation doses higher than 20 Gy recorded no flowering
through out the period of study. Leaf variegation was observed for plants treated
with 15, 20 and 25 Gy. The LD50 value was assessed based on mortality
percentage and the probit analysis revealed that the LD50 value was 20 Gy.
Subsequently, a total of 500 bulbs were treated with LD50 (20 Gy) value
at BARC, Mumbai. The results indicated that, the growth, yield and quality
parameters of some irradiated plants at LD50 value (20 Gy) showed superiority
over control. Out of 265 mutants, 88 mutants were superior to control with
regards to days to sprouting, 35 mutants were superior to control with regards to
plant height, 35 mutants were found superior for leaf length, 21 mutants were
found superior interms of leaf width, four mutants were found superior for
number of shoots per clump, two mutants showed variegated leaves (M185 and
M243) and 34 mutants with respect to number of primary branches.
Among 265 mutants 69 mutants showed flowering. Among the floral
components the mutants exhibited a superiority in the characters viz., early spike
emergence (3 mutants), days to first floret opening (2 mutants), spike length (11
mutants), rachis length (6 mutants), number of florets (8 mutants), weight of
floret (2 mutants), length of floret (23 mutants), perianth tube diameter (29
mutants), number of spikes per plant (1 mutant) and flower yield per plant (3
mutants) compared to control.
Among 265 mutants, 5 mutants showed more number of bulbs per clump
and weight of bulbs per clump, 45 mutants recorded maximum average diameter
of bulb, 14 mutants recorded maximum average length of clump and four
mutants recored maximum circumference of clump. Seventeen mutants were
recorded superior for SPAD chlorophyll content and 180 mutants recorded
superior for per cent disease index of Alternaria leaf spot compared to control.
Wide spectrum of variation was observed in M1V1 generation for leaf colour.
M185 had showed yellowish green (151C) at centre and green (137 A) at perifery,
while, M243 showed green (138B) at centre with yellowish green (151C) at
perifery. All the mutant population including control bore white colour flowers.
There was a positive correlation among majority of the significant
estimates, for flower yield per plant. Maximum positive correlation was recorded
for number of florets per spike with flower yield, while minimum positive
correlation was recorded for circumference of clump with flower yield per plant.
Among the 113 significant correlations, 99 showed a positive trend, this
correlation suggests that the improvement of those individual traits would
simultaneously improve other pair wise traits due to correlated response. Traits
which are significant with the flower yield per plant will also be useful in
selection of desirable plants from the mutant population.
From the mutant population molecular analysis was conducted for seven
mutant plants, M2 (mutant plant showing compact floret arrangement and more
number of florets), M 185 and M243 (Chlorophyll mutants), M308 (Dwarf statured
mutant) M349, M395, M398 (branched inflorescence mutant) with 25 RAPD and 29
ISSR primers, which enabled to know the diversity among mutants and control.
Maximum PIC, He, Ho, EMR and Rp registered with the RAPD and ISSR
primers prompts insight of molecular complexity involved.
Mutant population showing novelity, superiority in quality and yield were
selected for progressing them to the next generation. The mutants M2, M50, M63,
M83, M120, M185, M212, M243, M308, M319, M336, M337, M349, M395, M398, M436, M490
showed superiority in yield and quality traits. Hence, these mutant plants have
been selected for progressing to M2 generation
Description
1. To determine the lethal dose of the physical mutagen gamma rays in
tuberose cv “Hyderabad Single”
2. To study genetic variability in mutant population
3. Molecular characterization of desirable mutants using molecular markers