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

Sorghum genetic resource and current utilization  The genetic pool used in sorghum breeding is very small

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

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

Leaf/canopy temperature 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 Thermal camera IR sensors

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

Limitation in Transpiration rate under varying VPD

Leaf area and regression results for 17 genotypes that were found to fit the two-segment regression model GenotypeLeaf AreaBreakpointSlope1Slope2 R2R2 With a breakpointSC982295[20.6]1.62(0.23)50.0(12.6)6.3(4.8)0.79 SC [17.7]1.99(0.17)45.8(9.5)1.0(4.1)0.84 BTX623265[10.0]2.05(0.18)56.3(10.7)10.4(5.2)0.90 SC979290[14.4]2.06(0.18)47.7(7.8)0.0(6.5)0.84 BTX [13.0]2.08(0.20)52.0(9.0)11(6.7)0.89 SC [13.7]2.08(0.25)43.8(8.1)1.3(10.1)0.81 SC630277[15.2]2.16(0.31)40.1(9.7)-1.5(8.2)0.74 SC599286[15.1]2.23(0.27)35.5(7.0)3.4(8.4)0.80 SC [14.8]2.24(0.23)32.2(5.6)1.1(6.5)0.84 SC803267[12.8]2.29(0.19)39.8(6.5)-6.1(6.8)0.84 BTX [13.2]2.29(0.29)38.8(6.5)3.2(9.2)0.85 SN149294[17.4]2.30(0.19)38.2(5.2)-1.8(8.8)0.87 Macia270[12.6]2.51(0.27)35.7(3.8)4.0(12.4)0.91 BTX378268[16.0]2.55(0.39)30.2(3.3)11.3(11.0)0.91 B35265[22.2]2.61(0.18)40.3(6.8)2.4(7.7)0.88 TX [13.8]2.69(0.23)33.5(4.6)-0.5(11.4)0.89 TX [17.4]2.72(0.23)37.7(6.0)1.4(10.2)0.88 With no breakpointDK28311(14.7) 28.6(2.5) 0.89 BTXARG-1277(22.4) 27.5(2.4) 0.90 SC (14.3) 27.5(3.0) 0.84 Hegari280(14.9) 26.3(2.8) 0.84 DK54300(20.4) 25.4(2.9) 0.83 RTX430289(19.7) 25.4(2.8) 0.87 SC489298(15.6) 24.8(2.8) 0.83 SC532283(13.9) 23.9(2.8) 0.81 SC299283(14.1) 23.1(2.3) 0.86 Gholipoor et al., 2010 (Field Crops Research)

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.  Sorghum genotypes could be selected to pursue soil water conservation as a way to improve yields under water-deficit conditions. 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. 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. Gholipoor et al (Field crops Research

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

Canopy temperature and yield  CTD was positively correlated to yield, harvest index and CWSI while canopy temperature was positively correlated to CWSI

Variation in biomass and TE  There was significant genotypic variation in biomass produced and TE

Genotype ranking based on TE Total  Genotypes SC1019, SC720, SC1047, SC1074 and SC979 had high TE

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