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Results and
discussion
Seedling data recorded on the parents showed that all the parents
produced only green seedlings except a monosomic line 3A of a variety
Pb. C591 which produced green and albino seedlings. The frequency of
albino seedlings in this line was 12.6% which agreed to 13.7% of
albino seedlings (nullisomics) produced upon selfing of a monosomic
line 3A of the variety Pb. C591(Singh, 1986).
All the F1, hybrid seedlings produced chlorophyll.
Complete absence of chlorophyll-deficient seedlings in the
F1 seedlings suggested that all the F1
seedlings possess at least one gene for chlorophyll synthesis because
the chlorophyll synthetic gene is hemizygous effective (Singh and
Joshi,1979).
The F2 seedlings of monosomic F1 hybrids
involving monosomic 3A (var. Pb. C591) and Mara were found to
segregate for green and albino seedlings while the F2
seedlings of disomic F1 hybrids produced only green
seedlings (Table
1). The
occurrence of only green seedlings in the F2 generation of
the disomic F1 hybrids showed that the variety Mara
possess at least one gene for chlorophyll synthesis on chromosome 3A.
The variety Pb. C591 was shown to carry a gene for chlorophyll
synthesis. It was therefore presumed that a gene on chromosome 3A of
the variety Mara for chlorophyll synthesis might be allelic to the
gene present on chromosome 3A of the variety Pb. C591. The monosomic
F1 hybrid plants produced albino F2 seedlings
with an overall frequency of 4.0% which was much lower than 12.6% of
albino seedlings observed in the selfed population of a monosomic 3A
of the variety Pb. C 591 (Table
1). This reduced
frequency of albino seedlings in the F2 generation of the
monosomic hybrids suggested that the variety Mara might carry an
additional chlorophyll synthesis gene which reduced the occurrence of
albino seedling (nullisomics) form 12.6% to 4.0%.
The results suggested that the variety Mara might carry two
independent genes involved for some critical function in the
biosynthesis of chlorophyll. One of the genes is located on
chromosome 3A, which may be allelic to the gene present in the
variety Pb. C591.
References
Austin RB, Morgan CL and Ford MA (1986) Dry matter yield and
photosynthetic rates of diploid and hexaploid Triticum
species. Annals of Botany 49: 177-189.
Singh D (1986) Nullisomic frequency, its occurrence and placement in
the selfed monosomic plants of Triticum aestivum. Indian J
Genet 46: 526-529.
Singh D and Joshi BC (1979) Chlorophyll synthetic gene(s) in T.
aestivum (var. Pb. C591). Wheat Inf Serv 50: 45-46.
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