Variation parameters for heat tolerance index of wheat

Abstract

Wheat is important rabi crop in Chhattisgarh, which is grown mostly
under irrigated condition. The late sowing and early rise in the
temperature during winter season are the major causes of the lower
productivity. One hundred genotypes were evaluated on two dates of
sowing under late sown conditions and Heat Tolerance Index (HTI) was
calculated for seed yield and seven component characters. Most of the
characters recorded high coefficient of variation for HTI except days to
maturity. HTI for days to flowering ranged from 0.12 (EBWYT 524) to
0.76 (CG 8047). Forty three genotypes have negative index indicating
high grains per spike in second sowing date, moreover, genotypes Raj
4187, LBPY 06-14, ESWYT 104 and CG 8040 have zero HTI and YCSN
102(09), Raj 4174 have near stable grains per spike in two sowing dates.
Three genotypes IBWSN 1156, EIGN 8-83 and HD 2932 (C) recorded
the zero HTI for tillers per plant. The average 1000 seed weight was
33.49 percent higher in first sowing date as compare to second date.
The minimum index value is 0.04 for EGPY 5, CG 8017, moreover
SBR-48, EBWYT 519 and ESWYT 528 recorded less than 0.10 index,
indicating stable seed weight over different sowing dates. The seed
yield per plot ranged from 260 g for IBWSN 1156 to 1100 g for CG
8046 with average yield of 608.5 grams per plot first date of sowing.
Under January sown conditions, mean seed yield was 357.7 gram per
plot resulting in 70 percent reduction in seed yield. The seed yield per
plot ranged from 180 grams for Lok 1 to 575 grams for IBWSN 1133.
The HTI ranged from 0.00 (tolerance) to 0.72 (Susceptible). CG 8020,
CG 8038 and LBPY 6-13 recorded the 0.00 index, but these varieties
are poor yielder than the check, hence can only be used as parent
for heat tolerance.