chapter 2 review of literature -...
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CHAPTER – 2
REVIEW OF LITERATURE
Mutation breeding in general is relatively earlier method for crop
improvement. Mutagenic agents can generate a wide spectrum of genetic
variation. Pulse crops generally lack genetic variation due to their highly
autonomous nature. Mutation breeding can be exercised to create genetic
variation.
The present review in connection with the objectives of the current
research programme is restricted to the investigations carried out in induced
mutagenesis in cowpea and to bring out their relative changes.
2.1. Development in mutation breeding
The occurrence of true gene mutations was studied by Muller (1927 ) after
irradiating the sperms of Drosophila with x-rays. After this work, plant
breeders realized the possibility of producing mutation artificially. Sensitivity
studies in pulses, induction of mutation, their manifestation, transmission and
recovery were reported to influence biological, radiological and
environmental factors by Swaminathan (1970).
It’s many work has been done in progress of the induction of variability
through mutagenesis in different crops. In legumes, the seeds in general were
sensitive to doses from 10 kR to 20 kR of x-rays by Gustafsson (1944).
Effect of x-ray and neutron irradiation on seeds of black gram ( Phaseolus
mungo ) was studied by Jana (1964). Santos (1965 ) observed the reduction of
sensitivity to gamma rays in Phaseolus aureus through pre or post irradiation
heat treatments of seeds. The effect of gamma irradiation on seeds, seedling
and callus tissue of Phaseolus vulgaris were found by Bajaj et al., (1970).
Genetic variation by mutation to deleterious alleles at a large number of
loci scattered through the genome by Koteswara Rao et al.,(1983 ). By use of
mutation breeding several mutant cultivars like TAT10 in Cajanus cajan,
TAT in Vigna radiata and TAU1 in Vigna mungo have been successfully
released. The characters depend not only on their additive genetic variances
and co-variances but also on maternal characters that influence them by
Lande and Kirkpateick (1990). Every new deleterious mutation that is
induced in a population will be lost in future generation by Bengtson
(1990 ). Effect of Gamma irradiation on seeds of blackgram was studied by
Ahmed John, (1991 and 1998 ). In Tamil Nadu CO 4 a mutant variety of
blackgram has been released by Tamil Nadu Agricultural University,
Coimbatore. Thus mutation breeding is useful to select the mutant lines with
desired characters by Singh et al., ( 1997 ).
2.2. Physical Mutagens
While x-rays were first used by Muller (1927) other physical mutagens, like
ultra rays by Altenburg ( 1934 ), Beta particles by Ehrenberg et al.,(1949 )
and gamma rays by Sharma (1965) were used for inducing mutations in
different crop plants. The gamma rays are extensively used to induce
mutations and to develop varieties in crop plants.
2.3. M1 generation
2.3.1. Germination
Ahmed John (1991) and Rajasekaran (1973) noticed a gradual reduction of
germination in blackgram. Palanisamy (1975) recorded a gradual reduction
of germination by gamma rays in cowpea. Ashraf yadav et al., (1975) in
mungbean, Alikhan et al., (1973) in redgram, Sivasamy (1976).
Srinivasan ( 1977 ) and Chaturvedi et al., (1982a) in pigeon pea reported
that a gradual reduction in germination with increase in dose of mutation .
Singh et al., (1978) found that gamma rays and EMS reduced the
germination, seedling survival, seeding height and pollen viability in pearl
millet and found that the reduction was positively associated with the dose.
Ahmed and Goud ( 1979 ) reported that the irradiation caused a reduction
in germination survival and in the means of various quantitative characters
in the M1 Generation of sunflower. Chowdry and Sing ( 1980 ) found the
reduction in germination in all the doses of gamma rays in pigeon pea. The
decrease in germination by mutagen was reported by earlier workers in
sesamum by Sree Rengasamy (1988) and Lee et al., (1986 ). Soybean by
Bhadra and Miak ( 1980); Morie et al.,(1981) and Jayaraj (2004).
Thirugnanakumar (1986) obtained a progressive decrease in germination
with increase in dose of gamma rays and the reduction was not mostly dose
dependent. Hermelin et al., (1987) contributed that the gamma radiation
caused a decrease in germination and plant height in M1 generation of
sunflower. Packiaraj (1988) noticed that there was a successive reduction in
germination percentage in parents and hybrid of cowpea. He observed the
increase in dosage of mutagen led to a reduction in germination.
Torres et al., (1991) noticed that the response of sunflower to ultraviolet
radiation and found that the percentage of abnormal seedlings increased with
exposure time. Ahmed John (1991) reported that there was a dose dependent
reduction in all the six genotypes of black gram.
Padmavathi et al., (1992) observed that DES and MH affected the
germination, seedling height and plant survival more drastically than gamma
rays in soybean. They observed that 60kR of gamma rays and 0.3 per cent of
DES and MH delayed the maturity. Rajendiran (1993) observed that the
decrease in seed germination and seedling growth with increasing radiation.
The percentage of decrease in the germination of seeds was observed in
sunflower by Elangovan and Selvaraj (1994). Rao (1988) noticed that the
germination percentage, shoot length, seedling height and seedling vigour
were reduced by the higher concentration of EMS in the M1 plants.
Raveendran (1998) found that the reduction of germination percentage by
gamma rays in cowpea. Ionizing radiation induced germination and
emergence of cowpea seeds, linear relationship between germination with
doses of radiations was noticed by Uma and Salimath (2001). Chaudhuri
(2002) find out that a simple and reliable method to detect gamma-irradiated
lentil seeds by germination efficiency and seedling growth test.
Jayaraj (2004) reported that there was a reduction in germination
percentage in parents and their hybrid in soy been. Chickpea seed
germination was carried out over a period of 6 days, little variation in the
nitrogen and total globulin content was observed in Guilherme Vanucchi
Portari et al., (2005). The parents and their hybrid showed more than 50 per
cent reduction in germination in redgram by Jayaraju (2005).
2.3.2. Survival
Ramasamy (1973) observed that between the two radiations, reduction in the
survival of plants in blackgram was not appreciable in different doses of
gamma rays. A linear reduction in survival with increase in doses in
blackgram Rajasekaran (1973). Palanisamy (1975) obtained a gradual
reduction in survival rate in the doses of gamma rays increased in cowpea.
Shrivastava (1975) noticed a slight increase in survival at 15 krad and
reduction with further increase in doses of gamma rays in pigeon pea.
Tyagi and Gupta (1991) suggested that the reduced survival at the higher
doses of gamma rays. A linear reduction in survival with increase doses of
both physical and chemical mutagen was reported by Chaturvedi et al., (1982
and 1982a) in pigeonpea. Thirugnanakumar (1986) found that a progressive
decrease in survival with increase in dosage of gamma rays.
Ahmed John (1991) reported that the decrease in survival rate in both
parents and their hybrids in blackgram. Jeyamary (1996) observed that the
survival percentage were influenced by mutagenic treatments. Raveendran
(1988) noticed that a gradual reduction in survival percentage of cowpea due
to increasing dose of gamma rays survival percentage decreased due to
gamma rays was observed in soybean Jayaraj (2004). Methods such as
inhibition of seed germination and elongation of roots and shoots from
germinating seeds have been reported for the detection of irradiated seeds of
crop species by Vadivelu and Rathinam (1980).
Vanniyarajan et al., (1991) and Kumar ( 1992). Chaudhuri (2002)
reported a simple and reliable method to detect gamma-irradiated lentil seeds
by germination efficiency and seedling growth test Jayaraju (2005) found
that the highly significant differences were observed among the doses of
mutagen and also among the redgram.
2.3.3. Plant growth
Ashraf et al., (1975) reported that the plant height was adversely affected
ion M1 generation. Chadurvedi et al., (1982 and 1982a) in pigeon pea showed
stimulation of plant growth following lower doses of in ionising radiation
and reduction at higher doses. Thirugnanakumar (1986) observed that the
reduction in seedling height on the 30th
day was dose dependent with gamma
rays. Ignacimuthu and Babu (1988) recorded increased plant height when
seeds were treated with 20kR gamma rays in blackgram.
Ahmed John (1991) found that a differential inhibitory effect of radiation
was observed in shoot length, root length, and number of rootlets and size of
the cotyledonous leaf. Sarkar et al., (1996) suggested that the plant height
15kR gamma was reduced in M1 generation due to gamma rays. Mohanty et
al., (1998) observed, the plant height was increased in M1 Generation with
gamma rays. Mishra (1999) recorded reduced plant height in all mutagenic
treatments in green gram.
Shilpa Girhe and Chaudhary (2002) worked in Lathyrus sativus, treated
with gamma rays and EMS and observed twenty on morphological mutations
in M2 and M3 generations. Jayaraj (2004) observed increased plant height in
soybean due to gamma rays. Maity et al., (2004) indicated that germination
in gamma-irradiated chickpea Bengal gram seeds was reduced upon exposure
to 6 Kgy at 96 hrs. Mishra and Raja (2000) observed improving the
productivity of peas to induce genetic variation through gamma irradiation.
2.3.4. Quantitative characters
Jana (1964) reported that the number of fruits produced per plant varied
inversely to the dosage in blackgram. Kumar and Dubay (1984) observed
more number of branches in winged been due to gamma rays. Verma and
Singh (1984) treated the seeds of greengram with gamma rays 20kR -50kR
and reported more number of pods per cluster.
Verma and Singh (1984) reported more number of pods per cluster in
greengram treated with gamma rays. Thirugnanakumar (1986) observed
that the treatment with gamma rays had a stimulatory effect for most of the
quantitative characters of Vigna unquiculata like number of branches,
number of clusters number of pods and yield.
Waghmare and Mehra (2000) studied gamma rays and EMS induced
root mutant in Lathyrus sativus, and mutant plants were 15 to 18 cm in height
and usually had unbranched stem 2-3 in flowering, partially sterile. The
mutants demonstrate high degree of pleiotropic activity in the mutated genes
or mutation of closely linked genes affecting several characters
simultaneously. Khan (1987 and 1988) reported that more number of pods
per plant in mungbean treated with gamma rays.
Packiaraj (1988) observed that the number of clusters, number of pods
per plant, and pod length declined in cowpea with an increased dosage of
gamma rays. Gunasekaran et al., (1998) noticed increased number of clusters
per plant in cowpea with 20 kR gamma rays treatment. Ignacimuthu and
Babu (1990) reported more number of clusters per plant in blackgram due to
gamma rays and Ahmed John (1991) recorded the number of pods per plant
decreased in all the genotypes as the dose of irradiation increased.
Rajendiran (1993) observed several morphological variations induced by
gamma irradiation in sunflower. The gamma rays at higher dose had gross
retarding effect on the overall growth and yield, where as the lower dose had
beneficial effect on plant growth. He noticed maximum values for plant
height, number of nodes, inter nodal length, length and breath of leaves and
chlorophyll contents. Phenotypic variation like forked stem mutant and
yellow spot leaf mutant were observed more frequently in 50kR-irradiated
plants. Ahmed John (1991) reported that the gamma rays reduced the plant
height, number of leaves, stem thickness and head diameter in the M1 plants
of sunflower. An increase in 100-seed weight was noticed at 10 kR level,
where as 30 kR reduced the test weight.
Elangovan and Selvaraj (1994) noticed that a reduction in leaf area of
the plant in the M1 generation with increasing dose of gamma rays and EMS.
In the M2 generation, the total leaf area showed an increase with increase in
the dose/ concentration of the mutagen. Sarkar et al., (1996) studied the effect
of gamma rays in greengram and observed more number of pods per plant
when compared with control.
Singh and Mohapatra (1997) found that more number of pods in
blackgram treated with EMS. Singh et al., (1997) reported that positive shift
in mean value for number of pods per plant due to induced mutagenisis with
EMS treatment in blackgram. John et al., (2002) noticed that the selected 20
variants in M2 generation were advanced to M3 generation and they were
screened for the quantitative character stability in dose of gamma rays in
Cicer arietinum.
Jayaraj (2004) reported that there were an increased number of pods
per plant, number of seeds per plant in soybean as the dose of gamma rays
increased. The critical dose that prevented the shoot and root elongation
varied among species and also ranged from genotypes to genotype within the
crop species find out that Quiongying et al., (1993), Zhu et al., (1993) and
Muhammad et al., (2005) in Cicer arietinum. Jayaraju (2005) observed that
the all the treatment shifted the mean in positive direction in redgram.
2.3.5. Biochemical analysis of mutant seeds
Ignacimuthu and Babu (1989) reported the variation in protein quantity
and quality in wild and cultivated urdbeans and mungbeans due to gamma
rays and EMS in M2 and M3 generation. They recorded the high protein content.
Ahmed et al., (1995) were also noticed the variations in protein content due to
mutagens in M1 and M2 generations of blackgram. The greengram seeds treated
with EMS and gamma irradiation. The protein content and carbohydrate content
was increased in M3 generation Ignacimuthu (1994).
Sindhan et al., (1999) Gamma rays altered the protein content in
mungbean. Jayaraj (2004) noticed that the carbohydrate content was increased
due to gamma rays in soybean. They observed the maximum increased in
hybrid followed by JS 335 and Punjab1. They also recorded, the increased
protein content and phenol content in soybean.
2.4. M2 Generation
2.4.1. Chlorophyll mutations
Several workers observed differential effects due to different kinds of
mutagen employed both in terms of frequency and spectrum of chlorophyll
mutations. Appa Rao and Jana (1964) observed the different spectrum of
chlorophyll mutations in T-9 of Phaseolus mungo. These chlorophyll mutations
were mostly conditioned by single recessive gene. The frequency of
chlorophyll mutations in Vicia faba under field conditions was about 2 to3
percent after treatment with different ionizing radiations and between 2 to 14
percent after treatment with chemical mutagen, Sjodin et al., (1962).
Ramasamy (1973) observed in blackgram that the chlorophyll mutations
frequencies showed a proportionate increase and reached a maximum at high
doses with a decrease at the highest dose by gamma irradiation. Dahiya (1973)
recorded more albino than xantha and viridis in mungbean. Suresh (1975)
reported that the frequency of chlorophyll mutants was higher due to gamma
irradiation than the EMS in Phaseolus aureus.
Thirugnanakumar (1986) suggested that gamma rays showed an
inconsistent relationship with chlorophyll mutation frequencies. He observed
viridis most frequent than the other types and albino only in higher doses of
gamma rays. High frequency of chlorophyll mutations in pigeon pea has been
recorded by Chopde (1969), Sivasamy (1976) with gamma rays and EMS and
by Natarajan (1976) with gamma rays and DES.
In redgram maximum chlorophyll mutations frequency at 24 krad of
gamma rays, the spectrum of mutants was fairly wide and the four different
types such as chlorina, xantha, viridis and tigring were recorded by Alikhan and
Sivasamy ( 1973). Packikaraj (1988) reported that in cowpea chlorophyll
mutation frequency on M2 seeding basis increased up to 50 krad of gamma
rays and there after it decreased with further increase in dosage. He observed
the type viridis was to be maximum followed by albino, chlorina and xantha.
Bengtson (1990) reported that the mutation is sensitive to change the
segregation ratio. Ahmed John (1991) studied the changes in blackgram due to
gamma rays, in M2 generation. He recorded that the chlorophyll mutation
frequencies increased upto 50 krad of gamma rays and maximum increase
was shown in hybrid (COBG 301 x PDU 1) followed by COBG 301. Gautham
et al., (1992) observed that gamma rays were more effective than EMS in Vigna
mungo. However, the latter was found 2-2.5 times more efficient than the
gamma rays. They also noticed an increase in the frequency of chlorophyll and
viable mutations with increasing mutation dose.
Vannairajan et al., (1993) found that gamma rays were more efficient
than EMS in Vigna mungo inducing chlorophyll mutations and the frequency of
viable mutations was high in the medium doses of both mutagens. Ahmed John
(1997) reported that mutation frequency increased in 20 kR gamma irradiation
in blackgram. Sharma and Haque (1997) identified more number of
chlorophyll mutants in green gram treated with gamma rays.
Khan and Siddique (1993) noticed, that was a increase in chlorophyll
mutation with increasing dose of gamma in greengram. Raveendran and
Jayabalan (1997) reported highest mutation frequency in cowpea treated with
gamma rays. The mutagenic effect of gamma rays and EMS alone or in
combination on chlorophyll frequency and chlorophyll spectrum and macro
mutation on two cultivars namely PDU 1 and T9 of Vigna mungo have studied
by Singh et al., (1999).
Ahmed John (1999) reported that the gamma rays altering the mutation
frequency and chlorophyll mutations in cowpea parents and their F1, hybrid at
different doses. The mutation frequency increased gradually up to moderate
doses of gamma rays and the high frequency rate was found in the variety
high frequency rate was found in the variety CO 4 on M1 plant basis. The
mutant viridis was more frequent in the total spectrum, while chlorina and
xantha were in equal proportions, followed by albino and albino viridis.
Mutagenic effects of physical and chemical mutagens on frequency and
spectrum of chlorophyll mutations were studied in Vigna mungo by Singh et al.,
(1999) and in chickpea by Kharkwal (1998 and 1988a) and in fenugreek by Koli
and Ramakrishna (2002). The effect of three mutagens viz., gamma rays, EMS
and ECH (Epichlorohydrin) in mungbean were studied by Gajraj Sing et al.,
(2000).
They identified four types of chlorophyll mutations like xantha> albino >
viridis > chlorina and reported EMS was the most effective mutagen inducing
2.08% Chlorophyll mutations followed by ECH (1.82%) and gamma rays
(1.66%). Das and Kundagrami (2000) discussed the frequency and spectrum of
chlorophyll mutations in grass pea induced by gamma rays.
Toker and Cagirgan (2004) in chickpea observed five types of
chlorophyll mutations like albino, chlorine, strieta, maculata and marginuta.
They also noticed increased in treatment dose, there was a gradual increase in
chlorophyll mutations. Ahmed John (2004) reported that there was a increasing
mutation frequency gradually upto moderate doses in blackgram and also
recorded the albino, chlorine, xantha, viridis and alboviridis in both the parents
and hybrid.
2.4.2. Viable mutations
Jana (1962) obtained viable mutants in blackgram, variety 7-9 such as
ray leaflet mutant small leaf mutant with dwarf habit, minute leaves mutant,
small leaf mutant, bud mutant with small size buds tall mutant, mall formed
flower mutants, rolled leaf mutant, keel mutant with an extra set of keel petals
in each flower; basal branch mutant and pollen mutant with good proportion of
large pollen which was due to the absence of second meiotic division. Santos
(1969) studied the two leaf form mutants of phaseolus aureus unifoliate from
gammaray series (100 kR) and the multifoliate from the EMS series (0.05m).
Ahmed John (1999) found in Vigna mungo early as well as late flowering lines
as compared to parental variety, in M2 with gamma rays.
Rajasekaran (1973) noticed that the creeping mutants in 75 and 85 krad of
gamma rays treatment in blackgram. Palanisamy (1975) reported that the in
consistent relationship between the dose and mutation rate in cowpea. He
isolated many viable dwarf mutants, spreading mutants, plants with fascinated
stem, plants with basal branching, seedling with multiple leaflets and mutants
for pod and seed characters. He also obtained non-viable mutants such as little
leaf mutants, oblanceolate leaf and undulate leaf mutants, all of them are short
lived.
Appa Rao and Jana (1976) got four new leaf mutants viz., wrinkled leaf,
wavy leaf, narrow leaf, and uniofoliate leaf after treatment of blackgram seeds
with x-rays and EMS. Chopde (1969) reported the viable mutants affecting
stature (height), branching and maturity in pigeon pea.
Sivasamy (1976) observed viable mutants such as fascinated stem multi
clustered pods at axils and non-branching in Cajanus cajan after gamma
radiation and EMS treatments. Thirugnanakumar (1986) reported that the
frequency of viable mutations showed an inconsistent relationship with the dose
of gamma rays.
Packiaraj (1988) found the frequency of viable mutation on M2 plant
basis showed an inconsistent relationship with the dosage of gamma rays in
cowpea. Mutation for growth period was most predominant among the viable
mutants followed by mutants for leaf character and seed coat colour.
A bold seeded early dwarf mutant in cowpea was recorded with increased
pods and seeds following irradiation of seeds with 40 krad of gamma rays by
Chowdry (1983). Borikar et al., (1983) isolated three small leaved mutants from
M2 generation of cowpea variety 2-1 after treatment with 20 krad gamma
irradiation. The leaves mutants were thicker. They also isolated broad leaves
mutants from M2 generation of C 152 after treatment with 20 krad gamma
rays.
Ahmed John (1991) isolated number of viable mutations involving
changes in traits like plan habit, stem, leaves, peduncle exertion, seed size and
seed coat colour. Jeyamary (1996) reported that the viable mutants such as
bilobed leaf at 30mm EMS treatment and 300 Gy, Gamma rays treatment in the
sesame variety TMV 4. They also found the trifoliate leaf and tetra foliate leaf
in sesame variety TMV 6 after treatment with 50 mm EMS.
An extreme dwarf mutant observed in the M9 generation of the dwarf
sunflower variety was reported by Sanjay Jambhulkar, (2002). The significant
attribute of the mutant was the drastic reduction in the plant height (11-66 cm)
compared to 180 cm of control.
Cecconi et al., (2002) have contributed a dwarf mutant (dw1) in redgram
with gibberellic acid treatment. The height of the plant ranges between 10-30
cm. ( normal height 120-150 cm).
2.4.3. Mutagenic effectiveness and efficiency
The mutagenic effectiveness is defined as measure of frequency of
mutations induced by a unit dose of mutagens (Konzak et al., 1965). The
mutation frequency in M2 and M3 generations was computed by pooling the
chlorophyll and viable mutation as percentage of segregating plant progenies
and mutants (Gaul, 1964).
Efficient mutagenesis is in the production of desirable changes free from
association with undesirable ones Konzak et al., (1965). Prabhakara Rao
(1968) compared both the X-ray and DES treatment and observed that X-ray
is more effective than DES in cowpea.
Ramasamy (1973) estimated the effectiveness and efficiency of mutagens
and showed that the gamma rays were most effective and efficiency in inducing
mutation. EMS was more effective in inducing both chlorophyll and viable
mutation by Palanisamy (1975). Jebaraj and Marappan (1981) found that
gamma rays were effective in greengram in inducing chlorophyll as well as
viable mutants. They also noted higher mutagenic effectiveness and efficiency
at lower doses of the mutagen.
Nilan (1965) reported that the gamma rays were found to be more
effective than the DES in redgram and the effectiveness decreased with
increased dose of gamma rays. The mutagenic effectiveness and efficiency in
pigeon pea decreased with increasing doses of gamma rays by Sharma and
Haque (1981).
Thirugnankumar (1986) reported that gamma rays were found to be most
effective and efficient in inducing chlorophyll mutation. Packiaraj (1988) found
that the efficiency for chlorophyll mutation was high on sterility basis in CO 4
and on the lethality basis in TVK 944 – OZE and hybrid.
Sharma (1990) observed the usefulness of a mutagen, in mutation
breeding depends not only on its mutagenic effectiveness but also mutagenic
efficiency in Macrosperma lentil. Efficiency increased in M2 generation with
increase in the dose by Sharma (1990). He also observed the mutation rate of
marked progenies was higher and mutation rate of mutants was lower in M2
generation when compared with M3 generation. Ahmed John (1991) found that
there was a decrease in mutagenic efficiency with increase of mutagenic dose in
parents.
Gautam et al., (1992) reported that gamma rays were more effective than
EMS in blackgram. Ahmed John (1995) found that there was a decrease in
mutagenic efficiency with increase in the dose. He also observed that the
efficiency of gamma rays for chlorophyll mutation induction was high in the
parent PDU 1 on the basis of lethality and found 30 kR was efficient.
Raveendran and Jayabalan (1997) reported that the mutagenic
effectiveness and efficiency was decreased with the increased mutagen
concentration in cowpea. Khan (1999) reported that low doses of gamma rays
were more efficient than high doses of EMS and combined treatment in
producing chlorophyll mutation. Mehraj-ud-din et al., (1999) observed the
mutagenic effectiveness and efficiency was found to be highest at lower doses.
According to Gunasekaran et al., (1998) gamma rays were more effective
than ethidium bromide in inducing viable mutation in cowpea. Ahmed John
(1999) noticed in cowpea, there was a difference in efficiency of gamma rays
in parents and hybrid. Reddy (2000) calculated the induced mutation in wheat
and Triticale mutagenic parameters and reported that individual treatment of
EMS was found more effective, while combined treatment were more efficient
in producing mutation.
Deepalakshmi and Anandha Kumar (2003) contributed that the efficiency
and effectiveness of physical and chemical mutagens in urdbean, gamma rays
were found to be more effective than EMS in producing chlorophyll and viable
mutants in M1 and M2 seeding basis as well as efficient on lethality and sterility
based. They found EMS was more efficient than gamma rays. Ahmed John
(2004) reported that the gamma rays alter the mutagenic effectiveness and
efficiency in blackgram parents ( CO 5 and Vamban1) and their F1 hybrid.
2.5. M3 Generation
The genetic studies in M3 and later generation of the mutants induced by
gamma rays and showed that the induced characters were conditioned mostly
by recessive gene by Moh and Alan (1965). Moh and Alan (1965 and 1968) and
Moh and Nanne (1969) observed dwarf mutants, yellow mosaic mutant,
wrinkled leaf mutant and Phaseolus vulgaris by using gamma rays.
The mean performance of quantitative traits showed equal or positive
shifts in M3 for almost all characters in treatment with gamma rays in blackgram
by Ramasamy (1973) and Ahmed John (1991). Ramasamy (1973) reported that
there was an equal or slight increase in variance for height clusters and pods in
all the doses and for branching seeds and yield at middle doses alone. In M3
generation, dependence was not evident between dose and mean as well as dose
and variance in respect of all the characters. An assessment of phenotypic
frequency in M3 pointed significant deviation in certain classes which may
results from the effect of segregating genes and interactions by Ramasamy
(1973).
In blackgram, Kundu and Singh (1982) recorded increased variability for
number of pods, per plant, and yield per plant, in the irradiated population of M3
generation. Khan (1987) recorded an increased weight in M3 generations, of 30
krad gamma rays treatments in green gram. The estimates of heritability and
genetic advance differed from trait to trait.
Bhat and Dani (1990) selected from each dose of gamma rays treatment
in cotton in M3 generation, 20 normal looking plants with visual improvement
in yield, earliness and other economic characters. Sharma (1990) reported than
the mutation rate of mutants was higher in M3 generation than the M2
generations.
Waghmare and Mehra (2000) recorded that the mutagenic treatments
generation substantial magnitude of genetic variability for all the economic
characters such as days to flowering, days to maturity, plant height, number of
primary branches per plant, number of pods per plant, pod length, number of
seeds per pod etc. in Lathyrus sativus ( L).
2.5.1. Micro-mutations
Micro-mutation is induced variations for polygenitically controlled traits
and is obviously of greater interest to the breeders. Improvement in
quantitative attribute is achieved through accumulation of genes affecting their
expression in a positive of negative direction had increasing the variability by
Ramasamy (1973). Induction of micro-mutation in different crop plants has
been reported by various investigators like Gregory (1968) in peanut, Rawlings
et al., (1958) in soybean.
Palaniamy (1975) found that the mean of the characters viz., number of
pods, per plant, pod length, number of seeds, per pod and seed yield, per
plant were shifted to the negative side. No linear relationship was observed
between dose and variability. The magnitude of genetic variability was high for
seed yield per plant followed by pods per plant. In the case of seeds, per pod,
the variability was higher at maximum doses of gamma rays. High
hereditability and genetic advance were observed for pods, per plants, at 30 kR
and 60 kR of gamma rays.
Mahishi (1986) recorded that the higher values in cowpea, than in the
control for number of branches pod per plant, pod length and number of seeds,
per pod in lines from treatment with 20 krad and 30 krad of gamma rays. He
also reported higher phenotypic and genotypic coefficients of variations,
heritability estimates and expected genetic advance for yields, per plants, in the
lines from treatment with 10 krad than the control.
Koteswara Rao et al., (1983) reported that the variability in polygenic
character influencing yield was much greater in irradiated progenies than in
control in green gram. Seth et al., (1986) observed the high values of mean for
pod number per plant, in the sesame crop.
Packiaraj (1988) reported that in cowpea those gamma rays generated
higher genetic variability for the traits like number of primary branches per
plants, number of cluster per plant and number of pods per plant, than the other
traits. The mean values of yield component traits in all the three genotypes
shifted in both positive and negative directions.
Ahmed John (1991) noticed that the mean values of the yield component
in all the six genotypes showed positive and negative shift for M2 generations
and positive shift for M3 generation in blackgram. There was a mixed
relationship between the doses of mutagen and the genetic variability for the
traits like number of primary branches, per plant, number of cluster, per plant,
and number of pods, per plant, when compared to other traits.
Elangovan (1994) reported that the gamma rays reduced the plant height,
number of leaves, stem thickness and head diameter in sunflower. Samiullah
Khan et al., (1999) observed in mungbean III and reported that a wide range of
variability in number of fertile branches, number of pods, per plants and yield,
per plant of the mutants in M3 generation. Gajraj Singh et al., (2000) and
Rajput et al., (2001) contributed gamma rays, EMS and ECH induced
variability in mungbean.