Keynote Presentation 12 by P.V. Vara Prasad at the International Conference on Pulses in Marrakesh, Morocco, 18-20 April 2016

1. 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, USA
2 Panjab University, Chandigargh, Punjab, India
3 University of Western Australia, Perth, Australia
*E-mail: vara@ksu.edu
PhotoCredit:GoogleImages

2. 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.

3. Climate Change: Past Trends and Future
Projections of Temperature Stress

4. Frequency and intensity of temperature stress in future climates.
Climate Change: Temperature Stress
IPCC

5. 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

6. Annual temperature have changed more rapidly in recent years.
Greater increases in nighttime temperatures.
Climate Change: Past Frequency of Extreme Temperatures
IPCC

7. 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)

8. Climate Change: Early and Intense Summer Heat Waves
Spring and summer starting early.
Intensity of heat waves is increasing.
BBC (15 April 2016)

9. High Temperature Stress: Mung Bean
Photo Credit: Google Images

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

11. 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.

12. 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)

13. 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)

14. 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)

15. High Day and Night Temperature: Comparison

16. 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)

17. Reproductive Success/Failure: Mechanisms

18. High Temperature Stress: Thresholds– Mung Bean
Pollen germination and stigma receptivity decreased with
increasing temperatures.
Kaur et al. (2015): Scientia Horticulture 197: 527-541

19. High Temperature Stress: Thresholds – Mung Bean
Increasing temperature decreased seed number and seed weight.
Kaur et al. (2015): Scientia Horticulture 197: 527-541

20. 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

21. 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

22. Reproductive Failure: Pollen / Stigma - Mung Bean
Kaur et al. (2015): Scientia Horticulture 197: 527-541
Decreased Pollen load and Stigma Receptivity

23. Reproductive Failure: Pollen / Stigma - Mung Bean
Kaur et al. (2015): Scientia Horticulture 197: 527-541
Decreased Pollen Germination and Pollen Tube Growth

24. High Temperature Stress: Chickpea
Photo Credit: Google Images

25. High Temperature Stress: Impacts – Chickpea
Kaushal et al. (2013). Functional Plant Biology 40: 1334-1349

26. High Temperature Stress: Impacts – Chickpea
Kaushal et al. (2013). Functional Plant Biology 40: 1334-1349

27. 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

28. 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

29. 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

30. Opportunities: Germplasm Resources and Wild
Relatives

31. Genetic Differences: Germplasm / Wild Types
Harsh Nayyar
Chickpea

32. Genetic Differences: Germplasm / Wild Types
Chickpea

33. Genetic Differences: Germplasm / Wild Types
P.M. Gaur (ICRISAT)
Chickpea

34. Genetic Differences: Germplasm / Wild Types
P.M. Gaur (ICRISAT)

35. High Temperature Stress: Personal Thoughts

36.  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

37. 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