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Heat tolerance in cotton cultivars: Physiological and morphological aspects

Heat tolerance in cotton cultivars: Physiological and morphological aspects. Asia Perveen and Fiaz Ahmad Central Cotton Research Institute Multan, Pakistan. Plant responses to stresses. Introduction.

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Heat tolerance in cotton cultivars: Physiological and morphological aspects

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  1. Heat tolerance in cotton cultivars: Physiological and morphological aspects Asia Perveen and Fiaz Ahmad Central Cotton Research Institute Multan, Pakistan

  2. Plant responses to stresses

  3. Introduction • Temperature stress affects seedling growth, root growth, vegetative growth, flowering, fruit set ultimately crops achieve only about 25% of their potential yield and fiber quality (Singh et al., 2007, Boyer, 1982) • Temperature >32°C have adverse effects on reproductive efficacy through inhibition of photosynthesis, decreased metabolism, crop growth rate, pollination, and fertilization (Snider et al., 2009).

  4. Average maximum temperatures 27ºC-32°C are more desirable during the period of boll development and maturation (Gipson and Joham, 1968; Mauney, 1974; Freeland et al., 2006). • Higher temperatures of 35ºC-40°C are frequently associated with cotton sterility, bolls produced and their retention (Reddy et al., 1992b, Prasad et al., 2006)

  5. Threshold high temperatures for some crops plants

  6. Impact of heat stress on dehiscence of anthers

  7. Major effects of high temperature on plants. Inhibition of seed germination Reduction of plant growth Oxidative stress Reduction in Crop Quality Improper development High Temperature Yield Reduction Alteration in Photosynthesis Water Loss Alteration in Phenology Alteration in Dry Matter Partitioning

  8. Physiological responses Waters relations Heat stress perturbed the leaf water relations and root hydraulic conductivity (Morales et al., 2003). Enhanced transpiration induces water deficiency in plants, causing a decrease in water potential and leading to perturbation of many physiological processes (Tsukaguchi et al., 2003).

  9. Acclimation to heat stress 40/32 ⁰C 35/27⁰C Temperature 30/22⁰C

  10. Morphological and Physiological alteration of plants to cope with high temperature stress Physiological Changes Morpho-anatomical changes Accumulation of compatibleOsmolytes Reduced cell size Increased retention of water in Plants Closure of stomata Better stomatal regulation increased permeability of plasma membrane Enhanced Photosynthesis Greater xylem vessels of both root and shoot Improved High Temperature Stress Tolerance (Waraich et al. 2012)

  11. Objectives • To quantify physiological traits contributing to heat tolerance in cotton • Screening of cotton genotypes from across Pakistan against heat stress tolerance

  12. Physiological and morphological aspects Different physiological traits were studied for screening of different genotypes. • Pollen viability • Relative Cell Injury • Boll set on 1st & 2ndpositions • Electrical conductivity • Boll Weight • Number of bolls per plant • Seed cotton yield

  13. Monthly day temperature (°C) during the peak months

  14. Monthly night temperature (°C) during the peak months

  15. The impact of increment in day/night temperature on total fruiting sites (TFS), intact fruit (IF) and fruit shedding (FS%) No. per plant 30/22⁰C 35/27⁰C 40/32 ⁰C Temperature

  16. Pollen Viability • This measurement was made by staining pollen with the vital dye Acetocarmin and observed after 6 h at 200X. • Pollen with bold red color as viable and colorless as non viable.

  17. Pollen germination Cyto-313 NIAB-545

  18. Pollen germination and pollen tube growth at two temperatures Pollen tube length as affected by Temp Pollen germination (%) Pollen tube length (mm) Pollen germination as affected by Temp Time (hrs) Reproduced from Kafizadeh et al.,2008)

  19. Pollen viability vs Seed Cotton Yield

  20. Relative Cell Injury or Cell membrane thermostability • Temperature stress causes: • Cell membrane disruption • Changes in membrane fluidity • Modification in membrane composition • Leakage of ions

  21. Relative Cell Injury vs Seed Cotton Yield

  22. PV vs RCI

  23. Electrical conductivity vs Seed Cotton Yield r = - 0.912

  24. % BSFP & % BSSP vs Seed Cotton Yield

  25. Physiological and Morphological traits for determining heat tolerance in different genotypes

  26. Correlation between PV, %BSFP, %BSSP, RCIL, EC, NBPP, boll weight and seed cotton yield

  27. Conclusion • Pollen viability, RCI % can be used as heat tolerance indicators in cotton genotype to improve and sustain cotton performance under thermally stressed environments. • RCI % or Cell membrane thermostability is more practical indicator for screening in large breeding trials.

  28. Acknowledgment and Thanks • Specially to • ICAC and ICRA • Respected Dr.KeshevKranti ,Dr Michel Fok and Dr. M. A. Negm

  29. THANKS

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