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Recovery of desirable mutations
through chemical treatments in wheat
C.S. KALIA, M.P. SINGH and R.P. PURI
Division of Genetics, Indian Agricultural Research Inst.,
New Delhi-110012, India
With the discovery of ionizing radiations and mutagenic
chemicals, there was considerable optimism for the practical
utilization of mutagenesis particularly for improving
productivity and for the rectification of specific defects.
Subsequently, the results obtained were not comparable with
the expectations and thus sceptism was expressed about the
relevance of mutagenic techniques (CHOPRA & SHARMA
1985). In the course of present investigation efforts were
made to ascertain the mutagenic efficiency of different
chemicals and the scope of crop improvement with different
mutagenic treatments, particularly with chemosterilants and
antileukemic agents. The comparison for their effectiveness
and relative efficiency was undertaken with the potent
chemical mutagen EMS.
Materials and Methods
Three group of chemical agents viz., Aziridines (Metapa 0.4
and 0.2%, Thiotepa 0.2 and 0.01%), Nitroso compounds (MNG
0.1 and 0.05%, NMU 0.1 and 0.05%), Esters (MMS 0.1 and 0.05%
and EMS 0.1 and 0.05%) were used in direct treatment to one
variety each of tetraploid (HD 4502) and hexaploid (NP 880)
wheat respectively. Two hundred seeds of uniform size were
separated and the chemical treatments were given at 20 + or
- 1C. In field, the M1 population was bagged and
subsequently in M2 mutation percentage was
calculated on the basis of M2 population. For
estimating seedling rust reaction inoculation was done in a
glass house where optimum temperature and humidity
conditions were maintained. After two weeks of inoculation,
pustule infection types were recorded and classified as
described by STAKMAN and LEVINE (1922). Mixture of stem rust
races used for seedling infection included 11, 14, 15, 17,
21, 21A-1, 21A-2, 24, 34, 40, 428, 117, 117A, 117A-1, 122,
184, 194, 222, 295 and observations were recorded on the
basis of three replications. Adult plant rust testing of
selected mutant lines (M8) was undertaken in 1986
crop season (May-Nov.) at Wellington Nilgiri Hill (South
India) which is considered a hot spot for rust infection.
Adult plant rust reactions for black, brown and yellow rust
were separately recorded by Cobb's scaling method. The
protein percentage of checks and selected mutant lines was
done on NIR (Near Infrared Analyser, Model 102).
Result and Discussion
lnduced mutations for specific characters such as disease
resistance and quality aspect in crop plants occur generally
at low frequency. Genes for disease and pest resistance
available in the existing germplasm are mostly associated
with several undesirable linkages, hence their utilization
has certain physical limitations. In order to enlarge gene
pool for resistance in high yielding varieties, induced
mutagenesis has been advocated as an important methodology
(SAWHNEY et al. 1979).
At seedling stage, the selected mutants which were tested
against mixture of stem rust showed variable range of
resistance. In HD 4502 control, the resistance observed on
pustule basis was 0-1 type whereas mutant 104-122 was
completely free from any infection. It also showed
resistance for black, yellow and brown at adult plant stage.
Similarly, line 246 which showed resistance to black rust at
seedling stage was highest yielder and gave high protein
percentage. At adult plant stage it showed only traces of
black rust and complete resistance to yellow and brown rust.
Another line 268 had manifested resistance to black and
brown rust, whereas the parental check was showing moderate
susceptibility (Table 1).
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