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Combining ability of latent period and
pustule size in wheat
J. SINGH, O.P. LUTHRA and V. CHAWLA
Department of Genetics, Haryana Agricultural University,
Hisar-125004, India
Slow rusting is a form of resistance which restricts the
rate of pathogen development without showing typical
hypersensitive response. Slow rusting cultivars can be
identified by various ways under controlled conditions.
Different slow rusting parameters like latent period,
pustule size are taken into account for identifying slow
rusting genotypes. (KUHN et al. 1978). Information on
the combining ability of these parameters is scanty.
Therefore, the present investigation was undertaken to
estimate combining ability variances and effects of latent
period and pustule size in wheat.
Materials and Method
Eleven genetic stocks viz; WH283, WH291, WH337, WH157,
WH331, P1438, P1501, P10015, P1486, P1523 and Agra local
were selected for present investigation. Agra local is known
to be susceptible cultivar of leaf rust. All possible
crosses among the eleven genetic stocks (excluding
reciprocals) were attempted. Sixty-six enteries (55
F2 + 11 parents) were grown in plastic pots in
the galsshouse. About 25 plants of each of the
F2's and parents were inoculated with a mixture
of most virulent races of leaf rust at the seedling stage
and after inoculation the seedlings were incubated for 48
hours at 20 + or - 1C and 100 percent relative humidity.
Observations were made on the 2nd leaf for latent period and
pustule size. Latent period was recorded from the 8th day
after inoculation. Pustule size was measured on the 18th day
of inoculation with the help of a stage and ocular
micrometer under low power objective (i.e. 10X) of compound
microscope. The size of each pustule was estimated as the
product (pi) half width x half length. The analysis of
variance for combining ability and effects were calculated
according to the method II, model I as proposed by GRIFFING
(1956).
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