Phenotyping for Root Traits and Carbon Isotope Discrimination in Rice (Oryza sativa L.)

Root system play an important role in crop adaptation in the changing climate scenario. Water scarcity will be a threatening problem in the coming years. It is recognised now that in dry environments and dry seasons crop yield depends on the ability of the root system to capture as much water from soil as possible between germination and physiological maturity. The contribution of a deep and abundant at depth root system to maintain yield stability in dry seasons depends on its ability to continue extending into moist soil throughout the season, enabling access to more soil volume and water particularly around flowering and grain filling. Water captured by roots after flowering, is valuable for grain yield and quality because it is immediately used for grain development and filling. Thus, in dry seasons and dry environments, if deep soil water is available any breeding or management effort that produced a deeper root system to capture this water will increase grain yields. Phenotyping for root traits and Water Use Efficiency (WUE based on ∆¹³C value) was done using 80 rice genotypes for two seasons. Deep and thick, shallow root genotypes were selected on the basis of phenotypic data. Similarly based upon ∆¹³C values, high and low WUE plant types were selected. Basis of selection for BLA being, the genotype with extreme values on either side of the grand mean is given as either positive (+) negative (-) sign for each trait studied. The genotypes which has scored nearer value to either side of the grand mean is omitted and were not considered for bulking in order to have two very distinct bulks amongst the genotypes. Therefore, the genotypes which scored high value in root length, root volume and root dry weight were considered for deep root bulk and those scored low value for these traits were taken for shallow root bulk. Varieties identified for deep and thick roots were Chuvanna modan, Ptb1 (Aryan), Ptb2 (Ponnaryan), Ptb 6(Athikkiraya) and Ptb15 (Kavunginpoothala). Varieties identified shallow root were Ptb8 (Thavalakannan), Ptb12 (Thekkan chitteni), Ptb17 (Jeddu Halliga), Ptb32 (Aruvakkari) and Ptb27 (Kodiyan). Varieties identified for high WUE (based on ∆¹³C value) were Ptb5 (Veluthari kayama), Ptb7 (Parambuvattan), Ptb9 (Thavalakannan), Ptb10 (Thekkancheera) and Ptb19 (Athikiraya). Varieties identified for low WUE were Ptb27 (Kodiyan), Ptb36 (Rohini), Ptb37 (Aswathy), Ptb38(Triveni) and Ptb39(Jyothi).