Isotope discrimination technique (△13C): A possible selection criteria for drought tolerance in Indian mustard (Brassica juncea L.)

摘要

Carbon isotope discrimination has emerged as an accurate and time averaged surrogate for water use efficiency among C3 species. Based on this approach, we determined the genetic variability in WUE among a set of 320 germplasm accession of Indian mustard for drought prone areas. The germplasm accessions were raised in an augmented design at National Research Centre on Rapeseed-Mustard, Sewar, Bharatpur (Rajasthan), India during the rabi season (October. to March) of 2004-05. The observations on △13C, dry matter accumulation, seed yield, SLA and SPAD (SCMR) values were recorded. △13C was estimated using Isotope Ratio Mass Spectrometry. The range for △13C was 18.03- 22.86 per mill, SLA 55.0 - 178.6, dry matter per plant 24.2 - 74.6 g,SPAD value 22.95 - 50.1 and seed yield 6.53 - 21.4 g/plant. The leaf carbon isotope dscrimination values (△13C) showed a significant genetic variability and recorded a strong relationship with yield among these accessions suggesting the possibility of adopting △13C as a selection criterion. Regression analysis revealed up to 71% of the variability in yield could be explained by △13C in these accessions of mustard. To ascertain thits further 40 germplasm accessions with high △13C and 40 accessions with low △13C were compared for yield and yield attributes. The low △13C group showed a significant higher average yield and total biomass when compared with the high △13C group.Furthermore,the fact that a strong correlation exists between △13C and yield and no significant differences in test weight and harvest index suggest that WUE is the major determinant of total biomass and yield. The best genotypes having lowest △13C (BPR 552-9, BPR 349-1, BPR 537- 10, BPR 552-5 and RLM 619) would be utilized in the breeding program. The study revealed for the first time that WUE of these Indian mustard accessions was under the control of photosynthetic capacity and the large variability in this traits can be successfully exploited for firther crop improvement.