Impact of High Temperature Stress on Pulse Crops

P.V. Vara Prasad1*, Harsh Nayyar2, and Kadambot H.M. Siddique3

1 Kansas State University, Manhattan, Kansas, USA2 Panjab University, Chandigargh, Punjab, India

3 University of Western Australia, Perth, Australia

*E-mail: vara@ksu.edu

Phot

o C

redi

t: G

oogl

e Im

ages

1. Past Trends and Future Projections of Climate Change (Temperataure)

2. Impact of Short Episodes of High Temperature Stress

3. Responses to High Day vs. High Night Temperature Stress

4. Responses to High Temperature Stress Under Field Conditions

5. Mechanisms of Reproductive Failure

6. Genetic Variability and Opportunities for Targeting Breeding

7. Future Research Directions (Personal Views)

Outline

Results from mung bean and chickpea are presented. Data from other crops are available.

Climate Change: Past Trends and Future Projections of Temperature Stress

Frequency and intensity of temperature stress in future climates.

Climate Change: Temperature Stress

IPCC

Year 2015 was the warmest year on the record.Most months of that year were warmer than normal.

Global Temperature: Past Trends and Deviation

NASA and IPCC

Annual temperature have changed more rapidly in recent years.Greater increases in nighttime temperatures.

Climate Change: Past Frequency of Extreme Temperatures

IPCC

Climate Change: Future Increased Frequency of Warm Days

In future climates the number of warm days will be greater.This change include both day and night temperatures.

IPCC: RCP (Representative Concentration Pathways)

Climate Change: Early and Intense Summer Heat Waves

Spring and summer starting early.Intensity of heat waves is increasing.

BBC (15 April 2016)

High Temperature Stress: Mung Bean

Photo Credit: Google Images

Short Episodes of High Temperature Stress: Sensitive Stages and Thresholds for Temperature

and Duration

High Temperature Stress: Sensitive Stages and Thresholds for Temperature and Duration – Methods

Multiple experiments were conducted with objectives to determine most sensitive stages during floral development for high temperature stress; and to quantify responses of seed-set to short episodes of high temperature stress of varying intensify and duration. Plants were grown in controlled environment growth chambers under optimum temperature from sowing to start of floral bud development. At a specific reproductive stage, set of plants were transferred to various temperatures for different durations of stress, and returned back to optimum temperatures after treatments. Floral buds were marked and specific stage noted at start of temperature stress. After the stress period, data on seed-set (pods with seed) from tagged floral buds were determined.

All experiments were fully irrigated to avoid water stress.

High Temperature Stress: Sensitive Stages – Mung Bean

Seed-set decreased by short episodes (5 or 2 d) of stress. Maximum decreases occurred when stressed at gametogenesis

(2 to 4 d before anthesis) and at pollination/fertilization.

Prasad et al. (Unpublished)

High Temperature Stress: Thresholds – Mung Bean

Seed-set decreased with mean daily temperature of >33°C; with a ceiling temperature of 38.5°C. There was a linear decrease in seed

set with increasing duration of stress with a ceiling of ~ 24 d.

Prasad et al. (Unpublished)

High Temperature Stress: Thresholds – Mung Bean

Photosynthesis also decreased with increasing temperatures even for short duration stress.

There was slight decreases in stomatal conductance.

Prasad et al. (Unpublished)

High Day and Night Temperature: Comparison

High Temperature Stress: Day vs. Night – Mung Bean

Seed-set decreased with increasing day or night temperature stress. The rate of decrease is greater with increasing night

temperatures compared to day temperatures.

Prasad et al. (Unpublished)

Reproductive Success/Failure: Mechanisms

High Temperature Stress: Thresholds– Mung Bean

Pollen germination and stigma receptivity decreased with increasing temperatures.

Kaur et al. (2015): Scientia Horticulture 197: 527-541

High Temperature Stress: Thresholds – Mung Bean

Increasing temperature decreased seed number and seed weight.

Kaur et al. (2015): Scientia Horticulture 197: 527-541

High Temperature Stress: Impacts – Mung Bean

High temperatures (late sown) decreased pod-set, pod number, seed number and seed weights.

Kaur et al. (2015): Scientia Horticulture 197: 527-541

Reproductive Failure: Pollen Viability - Mung Bean

74% 51%

75% 48%

Normal Shriveled Kaur et al. (2015): .Scientia Horticulture 197: 527-541

Decreased pollen viability

Decreased pollen germination

Damaged structure of pollen

Reproductive Failure: Pollen / Stigma - Mung Bean

Kaur et al. (2015): Scientia Horticulture 197: 527-541

Decreased Pollen load and Stigma Receptivity

Reproductive Failure: Pollen / Stigma - Mung Bean

Kaur et al. (2015): Scientia Horticulture 197: 527-541

Decreased Pollen Germination and Pollen Tube Growth

High Temperature Stress: Chickpea

Photo Credit: Google Images

High Temperature Stress: Impacts – Chickpea

Kaushal et al. (2013). Functional Plant Biology 40: 1334-1349

High Temperature Stress: Impacts – Chickpea

Kaushal et al. (2013). Functional Plant Biology 40: 1334-1349

Reproductive Failure: Pollen / Stigma - Chickpea

Kaushal et al. (2013). Functional Plant Biology 40: 1334-1349

Decreased Pod-set, Pollen Load and Stigma Receptivity

Normal Late : Temperature Stress

Reproductive Failure: Pollen / Stigma - Chickpea

Kaushal et al. (2013). Functional Plant Biology 40: 1334-1349

Decreased Pollen Germination and and Stigma Viability

Normal Late : Temperature Stress

High Temperature Stress: Thresholds – Chickpea

Pollen germination and decreased with increasing temperature.Differential genotype responses – tolerant had higher thresholds.

Kaushal et al. (2013). Functional Plant Biology 40: 1334-1349

Opportunities: Germplasm Resources and Wild Relatives

Genetic Differences: Germplasm / Wild Types

Harsh Nayyar

Chickpea

Genetic Differences: Germplasm / Wild Types

Chickpea

Genetic Differences: Germplasm / Wild Types

P.M. Gaur (ICRISAT)

Chickpea

Genetic Differences: Germplasm / Wild Types

P.M. Gaur (ICRISAT)

High Temperature Stress: Personal Thoughts

Producers and scientific communities acknowledge high temperature stress decrease grain yields and quality of produce (even under fully irrigated conditions).

Limited tolerance in the current breeding pool for all food grain crops – need to systematically screen germplasm collections and wild relatives.

Focus should be on all types of traits components of tolerance:– Escape (early morning flowering; short duration cultivars)– Avoidance (transpirational cooling of canopy or floral buds)

– True tolerance (higher reproductive fertility)

Need to identify quick, reliable and high-throughput morphological, physiological screens or biochemical or molecular markers to screen large collection of germplasm or populations.

Improved understanding of interaction of temperature stress with other abiotic (drought, VPD, salinity and nutrients) and biotic factors (weeds, diseases and pests) is required to quantify true impacts.

Future Research Direction

Acknowledgements

Students and Scholars of Prof. Harsh Nayyar Lab at Panjab University

Students and Scholars of Prof. Kadambot Siddique at Institute of Agriculture at University of Western Australia

Collaborators at Punjab Agricultural University

Collaborators at ICRISAT