INVESTIGATING THE ROLE OF PHENOTYPIC PLASTICITY IN TERMINAL HEAT STRESS TOLERANCE IN WHEAT (Triticum aestivum L.)
Loading...
![Thumbnail Image](assets/images/Item.jpg)
Date
2022
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Dr.RPCAU, Pusa
Abstract
The global mean temperature is increasing at a rapid pace due to atmospheric
warming. Consequently, heat stress events are becoming more frequent and severe
and affecting global food production. For the current study, we gave grown thirty
wheat genotypes at two (timely and late) sowing dates and two planting densities viz.
optimum and low density (LD) resulting in three treatments viz. Control, terminal
heat stress (HT), and terminal heat stress with low planting density (LD+HT).
Genotype HD-2967 was used as a check variety for heat stress tolerance. Timely
sowing in control treatment was done on 26th Nov, 2021 while for the HT and
LD+HT treatments, sowing was delayed by 19 days. Late sowing of genotypes
exposed them to a higher temperature of 6.6 oC and 4.5 oC at flowering and active
grain filling stages, respectively. As a result, a reduction in the grain yield of up to 59
% and biomass reduction of up to 55 % were observed under HT conditions.
Conversely, 15 days reduction in total crop duration and 10 days reduction in grain
filling duration has been under HT condition, which was a crucial determinant of seed
weight, and grain yield. There was significant (P<0.05 to <.001) genetic diversity
observed for traits across the genotypes. Key traits that contributed to yield loss under
heat stress were reduced spike weight, grains per spike (seed set) and spikelet fertility.
Correlation analysis of traits showed that there was a significant negative correlation
between canopy and spike temperature with yield and yield components. In general,
spike temperature was significantly higher than canopy temperature across the
treatments. Moreover, higher spike temperature was negatively correlated with
spikelet fertility, seed set and seed weight. Canopy cover was observed as helpful in
maintaining a lower canopy and spike temperature. On the other hand, traits such as
tillering ability, SPAD, relative water content and spike weight were positively related
to yield and biomass accumulation under control and LD+HT conditions. Lower spike
temperature with a better canopy cover was crucial to maintain a high grain number
under reproductive heat stress. A significant variation was noted in the phenotypic
plasticity where all the traits measured showed higher variations under low planting
density. Moreover, genotypes under low density showed higher yield per plant due to
better space and light helping accumulate more biomass and dense canopy. Low
density helped in maintaining a higher seed set and fertility ratio in responsive
genotypes under reproductive heat stress. However, low density did not show similar
effectiveness under heat stress at the grain filling stage, as the minimum temperature
was the dominant factor where a merely cooler canopy was ineffective. The
cumulative response index for 8 key traits showed a wider range in phenotypic
plasticity in wheat genotypes, which can be utilized in crop improvement programs
for terminal heat stress tolerance.