Phenotyping for root traits and carbon isotope discrimination in rice genotypes of Kerala

Root traits and water use efficiency play an important role in breeding for drought tolerance in rice. Water captured by roots after flowering, is valuable for grain yield and quality because it is immediately used for grain development and filling. A set of 80 rice germplasm accessions were phenotyped for various root traits and water use efficiency ( D13C) at R.A.R.S., Pattambi for three years from 2011 to 2013. Deep and thick, shallow root genotypes were selected on the basis of phenotypic data. Similarly, based upon D13C values, high and low WUE plant types were selected. Varieties identified for deep and thick roots were Chuvanna modan, Ptb1 (Aryan), Ptb2 (Ponnaryan), Ptb 6 (Athikkiraya) and Ptb15 (Kavunginpoothala). Varieties identified for high WUE (based on D13C value) were Ptb5 (Veluthari kayama), Ptb7 (Parambuvattan), Ptb9 (Thavalakannan), Ptb10 (Thekkancheera) and Ptb19 (Athikiraya). It is found that Uma (MO-18), a high yielding variety with low carbon isotope discrimination (22.17 per mil) having high WUE. Otherwise, most of the high yielding varieties have high carbon isotope discrimination values under normal condition. This variety also recorded the higher SPAD chlorophyll meter reading (SCMR) values in three consecutive years. These selected genotypes can be
used as donor parents for drought resistance breeding programmes in rice.