MOLECULAR GENETIC EVIDENCE FOR GAMETOPHYTIC SELECTION FOR HEAT TOLERANCE IN MAIZE (Zea mays L.)
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Date
2018-10-29
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
In present study, the effect of pollen selection for heat tolerance in F1 generation
on the frequency of heat tolerant plants in F2 generation was studied. The heat susceptible
line BTM4 was crossed to heat tolerant BTM6 and the true F1 plants were identified
using two SSR markers. Three different methods of pollen selection for heat tolerance;
incubating the freshly dehisced pollen grains of F1 plants at 36 ˚C for three hours in
growth chamber (GRC), dry bath (DB) before selfing and growing F1 plants in summer at
ARS, Bheemarayanagudi were carried out, Thus producing selected F2 (GRC), selected
F2 (DB) and selected F2 (BGD). The control F2 was also produced without heat treatment
of pollen grains. The control and selected F2 population were compared for heat tolerance
by selfing the F2 plants with heat stressed pollen grains. The selected F2 (GRC) showed
significantly higher cob diameter, number of seeds per cob and seed yield per plants
compared to control F2 under stress suggesting its superiority over other methods and
also positive effect of pollen selection for heat tolerance. One selected F2 and one control
F2 populations were studied for segregation of twenty polymorphic SSR markers. The
chi-square test suggested that the control F2 showed 1:2:1 ratio for 19 out of 20 markers
while in selected F2 only two markers recorded Mendelian inheritance. The frequency of
alleles from tolerant parents was more in selected F2 providing molecular evidences for
positive effect of pollen selection. The heat tolerance of F4 generation progenies of the
same cross suggested that the cyclic pollen selection for heat tolerance in F1, F2 and F3
generation has significantly improved the tolerance of progenies. The result suggests that
the pollen selection is an effective strategy for improvement of heat tolerance in plants.