PhD

The present investigation entitled “Characterisation and genetic improvement
in Rose(Rosa spp.) through mutagenesis” was carried out in College of Agriculture
Vellayani and RARS,Ambalavayal during the period 2014-2017.The major objective
of the study was to assess the natural variability available in Hybrid Tea and
Floribunda groups of roses and to analyze the effectiveness of gamma rays and Ethyl
methane sulphonate(EMS) on inducing variability in them for improved plant
architecture and floral characters.
The first part of the programme consisted of evaluation and characterization of
germplasm of Hybrid Tea and Floribunda groups of roses. For assessing genetic
variability and diversity, twenty five varieties under each group were studied with
respect to thirteen morphological characters. ANOVA revealed highly significant
differences among the genotypes for all the traits analysed. In Hybrid Tea accessions,
moderate values of PCV and GCV were obtained for number of leaves at first flower,
number of petals per flower, size of petals and number of flowers per plant. In
Floribundaaccessions, high estimates of PCV and GCV were obtained for number of
days to first flower and prickle density. High heritability coupled with high genetic
advance as percent of mean was observed for number of days to first flower, number
of leaves at first flower and number of petals per flower in accessions belonging to
Hybrid Tea group whereas in Floribunda group, flower size, number of days to first
flower, number of leaves at first flower and number of petals per flower exhibited
high heritability and genetic advance.
The twenty five rose genotypes each under Hybrid Tea and Floribunda were
grouped into ten and nine clusters respectively on the basis of Mahalanobis D2
statistic. The higher number of clusters obtained under each group is an indication of
the genetic diversity within the group. In both the groups of roses, it was observed
that the characters number of days to first flower and number of leaves at first flower
contributed maximum towards genetic divergence. Cluster means of economically
important characters were determined.
The second part of the programme included induced mutagenesis using
physical and chemical mutagens. The physical mutagen used was gamma rays.For
fixing LD50 value,budwoods of four varieties viz., Pink Panther and Demestra(both
under Hybrid Tea) andGolden Fairy and Monnalisa, (both under Floribunda)were
treated with nine doses of gamma rays ranging from 20 to100 Gy along with control.
The doses were fixed specifically based on LD50 values and were administered to the
four different varieties. M1was field planted and was evaluated for thirteen
morphological characters. Statistical analysis of quantitative characters showed that
for an increase in gamma ray doses, a proportionate significant decrease for various
plant growth parameters was evident. Mutants in plant architecture, leaf characters
and floral characters were also recorded.
Chemical mutagen treatment was done using EMS on in vitro cultures of four
varieties viz., SchlossElutin, Jogan, Josepha and Morning Sun. Regeneration
protocols for nodal explants were first standardized. The best
in vitro culture
medium for culture establishment comprised of MS+BA(2.0 mg/l)+ADS(25
mg/l).The best medium for shoot proliferation was BA(2.0 mg/l)+IAA(0.25
mg/l)+ADS(25mg/l) and the best medium for root induction was identified as 1⁄2
M.S+IBA(0.2 mg/l)+sucrose(2%)+BA(2.0mg/l). In vitro cultures of genotypes viz.,
SchlossElutin, Jogan, Josepha and Morning Sun were treated with twelve doses of
EMS ranging from 0.1to1.2% along with control for three durations (30,60 and 90
minutes) for fixing
LD50 value.Maximum survival was recorded in 30 minutes
treatment and hence it was selected. The doses were fixed specifically for the four
varieties based on LD50values. Five doses including control were administered to the
different varieties and field planting of M1 was done. EMS treated invitroderived M1
was evaluated for thirteenmorphological characters. Most of the vegetative and floral
parameters showed a decrease in mean valueswith increase in doses of mutagen.
Induced mutagenesis, both physical and chemical, resulted invariations in
form and colour of flowers and leaves in M1.Variations in form of flowers was
recorded in Pink Panther, Demestraand Monnalisa. Out of these, the variation in form
isolated in Pink Panther at 20 Gyis a novelty. The mutant had very shapely semi-open
flowers in contrast to the fully open flowers of the parent.Demestraat 30 Gyshowed
form and colour variation.In one of the variants, the flower was found to be star
shaped with paleorange colour in contrast to the pale yellow with dark golden yellow
centre in the parent. Among the mutants derived, two leaf variants were also isolated
from Demestra and Monnalisa through gamma rays.In EMS treatment, SchlossElutin
and Josepha yielded desirable colour mutants.No seed setting was observed in M1.
RAPD analysis of the selected parental rose varieties and mutants was done.
Based on the presence or absence of polymorphic bands, variation was detected at the
molecular level. Ten RAPD decamer primers were used to check parental
polymorphism. Among them,twoprimers viz.,OPA-4 and OPD-8that were highly
polymorphic.Polymorphism between the parent cultivar Monnalisa and its mutants
could be demonstrated using two polymorphic primers viz., OPD-8 and OPA-4.
In conclusion, the extent of variability in Hybrid Tea and Floribunda groups
of roses was found to be high as is evident from clustering based on Mahalanobis D 2
statistic. Both gamma rays and EMS could induce variations in form and colour of
flowers andcolour of leaves.Among the mutants derived three flower colour variants
viz., in Demestra at 30 Gy, SchlossElutin at 0.5% and Josepha at 0.8% and one
flower form variant in Pink Panther at 20 Gy were found to be promising and were
carried forwarded to the M1V1generation by budding. The M1 mutants isolated can be
carried forwarded by in vitro means by taking explant from the plant part showing
variation to see if solid mutants can be developed. These may be released directly as
varieties or utilised in further breeding programme.