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.