Canopy Temperature: A potential trait in selection for drought tolerance in grain sorghum

1. Canopy Temperature: A potential trait in selection for drought tolerance in grain sorghum Raymond N. Mutava, Prasad P.V. Vara, ZhanguoXin SICNA Meeting, Lubbock Texas August 28 – 30, 2013

2. Sorghum genetic resource and current utilization http://www.icrisat.org/crop-sorghum-genebank.htm • The genetic pool used in sorghum breeding is very small

3. Breeding for drought tolerance Some important traits in sorghum breeding • Goal: Increased yield • Improved tolerance to environmental stresses – drought and heat Key trait in drought tolerance: • Staygreen - post-flowering drought stress BUT not tolerance to: • Pre-flowering drought stress • Heat stress • There is need to screen germplasm for other traits for improved drought tolerance

4. The sorghum diversity panel • 300 lines with diverse background representative of sorghum genotypes from all over the world • Identify physiological traits associated with pre- and post flowering drought tolerance • Grown in multi-locations in multiple years in Kansas • Data was collected in several traits (phenology, growth, Physiological, yield

5. Leaf/canopy temperature Thermal camera IR sensors Mutava et al., 2011 (Field Crops Research) • There were genotypes that recorded: • High leaf/canopy temperature with high and also low yields • Low leaf /canopy temperature with high and also low yields

6. Drought coping mechanisms in sorghum High transpirational cooling Cooler canopies Drought escape mechanism Low transpirational cooling Warmer canopies Drought tolerance mechanism Modified from Mutava et al., 2011 • These two mechanisms seemed to exist among sorghum genotypes • Drought tolerance through conservative water use (slow wilting trait)

7. Leaf area and regression results for 17 genotypes that were found to fit the two-segment regression model Gholipoor et al., 2010 (Field Crops Research)

8. Transpiration rate response to Vapor pressure deficit • No BP and low rate of increase in TR with VPD (Red line) • Consistently dry environmental conditions. • Restricted carbon assimilation • Slow growing and probably low yielding even under well-watered conditions. • High initial slope and a low BP, e.g. SC982 • Offer a better approach to developing drought tolerance. • Maximize gas exchange under low VPD and then shift to water conservation at high VPD. • BP selection could therefore be matched with the likelihood of water-deficit conditions • A low BP = greatest water conservation when soil water is still available • High BP = less-restrictive water conservation. Gholipooret al. 2010 (Field crops Research • Sorghum genotypes could be selected to pursue soil water conservation as a way to improve yields under water-deficit conditions.

9. Canopy temperature monitoring using IR IR sensors detected variation in canopy temperature among genotypes between 2:00 and 6:00 PM Genotypes SC1019, SA5330, and SC701 recorded high canopy temperature while Hegari, pioneer hybrid 84G62, SC663 and SC1124 had low canopy temperature consistently between 2:00 and 6:00 PM

10. Canopy temperature and yield • CTD was positively correlated to yield, harvest index and CWSI while canopy temperature was positively correlated to CWSI

11. Variation in biomass and TE • There was significant genotypic variation in biomass produced and TE

12. Genotype ranking based on TETotal • Genotypes SC1019, SC720, SC1047, SC1074 and SC979 had high TE

13. Collaborators T. Tesso Kansas State University Sorghum Breeder ZhanguoXin Plant Stress and Germplasm Development Unit USDA-ARS, Lubbock, TX T.R. Sinclair North Carolina State University Crop Physiologist J. Yu Iowa State University Sorghum Genetics Kansas State University Crop physiology Lab members Maduraimuthu Djanaguiraman George Mahama George Paul Sruthi Narayanan Subramanian Satheesh Kumar NCSU ManoochehrGholipoor SunitaChoudhary Kansas Grain Sorghum Commission