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Effect of Gamma Irradiation on Physiological and Biochemical Traits in
Cowpea, Vigna unguiculata (L.) Walp Inoculated with New
Recombinant Isolates of Bradyrhizobium |
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Zaied K.A. ,
F.S. Faris and A.M. Assar |
Abstract:
The symbiotic interaction between rhizobia and legume roots is characterized
by a high degree of specificity. Two varieties of cowpea were gamma irradiated
as a one method to create genetic variation resulting in new varieties with
better characteristics in nodulation and nitrogen fixation processes.
Conjugation is the second method used in this study, a cell contact-dependent
DNA transfer mechanism, which has served as elegant tool in the development of
genetic engineering technology. The possibility of horizontal gene transfer to
other rhizobia, revealed that it is necessary, in view of possibility of
deliberate release of a variety of recombinant rhizobia into the environment for
such agricultural purposes as improving nitrogen fixation. New recombinants
revealed higher amounts of indole compounds from tryptophan above the
mid-parents in two out of six transconjugants resulted from the cross between P1
x P3. Significant number of nodules were developed on the root system
of V2-variety in M4 generation treated with 20 krad in
response to inoculation with the parental strains (P2 and P3)
and also in response to inoculation with triparental transconjugants (Tr4
and Tr5), above that developed on the plants fertilized with
recommended dose of N. The results revealed the success of rhizobial strains and
their recombinants to colonize and infect roots of cowpea, because of
significant dry weight of nodules per plant which can be obtained in V1-variety
treated with 20 krad in M4 generation inoculated with the parental
strain (P3), above that on the plants fertilized with recommended
dose of N. Total chlorophyll formation in V1-variety inoculated with
di-parental transconjugants (DPM-Tr2 and DPM-Tr3) at all
doses of gamma irradiation was significantly increase above that in the plants
fertilized with recommended dose and the mid-parents, with the exception at 30
krad if compared with the mid-parents. Significant increase was resulted in
fresh weight of pods developed per plant above the mid-parents in M3
generation of V1-variety at doses zero and 10 krad, in response to
inoculation with di-parental transconjugant, DPM-Tr2. While, the same
trend was also achieved above the full dose in M3 generation at 10
krad in response to inoculation with DPM-Tr2, DPM-Tr3,
TPM-Tr4 and TPM-Tr5. The highest nitrogen content was
appeared in the shoots of V1-variety at all doses of gamma
irradiation in response to inoculation with diparental transconjugant (DPM-Tr2).
However, V2-variety had the lowest nitrogen content in relation to
the plants fertilized with recommended dose of nitrogen and to the mid-parents
of rhizobial transconjugants. The genetic variability of grain-protein content
appeared that V2-variety treated with 10 krad had significant
increase in protein content above that in the plants fertilized with recommended
dose of N among M3 and M4 generations, in response to
inoculation with parental strains and most of their transconjugants. The same
trend was also shown in M4 generation of V1-variety
treated with 20 and 30 krad above the plants fertilized with recommended dose of
nitrogen, in response to inoculation with di-parental transconjugants. All
biochemical traits studied were more affected by biofertilization than the doses
of gamma rays and the interaction between biofertilization x doses. This
indicated that the significance of treatments was mainly due to inoculation and
particularly to gamma irradiation and the interaction between both of them.
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How to cite this article:
Zaied K.A. , F.S. Faris and A.M. Assar , 2005. Effect of Gamma Irradiation on Physiological and Biochemical Traits in
Cowpea, Vigna unguiculata (L.) Walp Inoculated with New
Recombinant Isolates of Bradyrhizobium. Pakistan Journal of Biological Sciences, 8: 1173-1191.
DOI: 10.3923/pjbs.2005.1173.1191
URL: https://scialert.net/abstract/?doi=pjbs.2005.1173.1191
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