PHENOTYPIC AND MOLECULAR EVALUATION OF SUGARCANE (SACCHARUM SPP. HYBRID) CLONES FOR HIGH YIELD AND QUALITY TRAITS USING AN AUGMENTED DESIGN AND EST-SSR MARKERS

Abstract

The present investigation was undertaken at the Kalyanpur Farm of the Sugarcane Research Institute, Dr. Rajendra Prasad Central Agricultural University, Pusa, Samastipur, Bihar to assess genetic variability among sugarcane clones for yield and quality traits to examine the association among yield, quality and related attributes and to characterize the clones at the molecular level using EST-SSR markers. Forty-five CoXK-series clones derived from five bi-parental crosses were evaluated against two check varieties CoP16437 and CoP09437 in an augmented design with three blocks. Nineteen characters were recorded, juice quality being assessed independently at eight, ten and twelve months after planting. Twenty-two of the clones together with both checks were profiled using seven EST-SSR markers that resolved twenty-six allele bands. Treatment differences were significant (P ≤ 0.05) for all nineteen characters. Substantial variability (GCV 11.16-17.28%) was evident for cane yield, CCS yield, cane diameter, plant height, single cane weight, germination and Brix and sucrose content at all three harvest ages, whereas juice purity showed the lowest variability of any character (GCV 1.37-1.57%). Broad sense heritability was uniformly high, interpreted as an upper-bound estimate because the augmented design derives error variance from the replicated checks alone. Correlation analysis resolved the characters into two largely independent blocks: cane yield was most strongly associated with the number of millable canes per hectare (r = 0.86), single cane weight (r = 0.79), germination and plant height (r = 0.77 each) while quality characters were mutually correlated across harvest ages (r = 0.82-0.87) but showed no significant association with cane yield. Path coefficient analysis identified the number of millable canes per hectare as the principal direct determinant of cane yield (direct effect = 0.640; R² = 0.788). Ward's clustering grouped the forty-seven treatments into four clusters, one combining high biomass with low recovery and another the reverse. All twenty-six marker bands were polymorphic (mean PIC = 0.570; mean gene diversity = 0.624), with no two genotypes sharing an identical banding profile. UPGMA clustering of Jaccard distances resolved the panel into five groups (cophenetic correlation = 0.794). Four clones - CoXK25034, CoXK25036, CoXK25079 and CoXK25082 - combined a significant gain in CCS yield with recovery at par with the better check and fell into four different molecular clusters, indicating that superior performance arose independently in more than one lineage; these are recommended for advancement to replicated multi-location testing.