Repeatability, genetic gain and path coefficient analysis in sugarcane (Saccharum Officinarum L).

Abstract

A set of 16 sugarcane genotypes comprising two check cultivars (CP-77/400 and Mardan-93) were assessed for repeatability, genetic gain and path coefficient analysis during 2012-14 and 2013-15 at Sugar Crops Research Institute (SCRI) Mardan, Khyber Pakhtunkhwa, Pakistan. The data were recorded on growth, cane, quality and yield traits for three crop seasons. Analysis of variance showed significant differences among genotypes, crops and genotypes x crops interaction. Repeatability (h2 broad sense) under plant crop, for different characters showed varying levels and it was moderate for internode length (43%), cane yield (41%), number of nodes (39%), cane length (39%), millablecane (35%) and 2nd plant height (30%). Low repeatability was noted for 2nd tillering (12%) and 1st tillering (10%) under plant crop. Under ratoon crop, moderate repeatability was noted for 2nd tillering (47%), 1st tillering (39%) and internodes length (34%). Low repeatability was noted for brix (28%), cane yield (25%), cane diameter (23%), 1st plant height (19%), millablecane (17%), number of node (16%), recovery (16%) and cane length (15%) under ratoon crop. Across crops low repeatability was noted for internode length (26%), number of nodes (23%), 2nd tillering (14%) and 1st tillering (10%). Genetic gain under plant crop was higher for cane length (36.53 cm), 2nd plant height (31.84 cm) and 2nd tillering (12.98 tillers per 9 m2). Under ratoon crop, the genetic gain was higher for 2nd tillering (54.86 tillers per 9 m2), 1st tillering (40.88 tillers per 9 m2) and 1st plant height (15.63 cm). Genetic gain across crops was higher for 2nd tillering (15.52 tillers per 9 m2), cane length (9.55 cm) and 1st tillering (9.24 tillers per 9 m2). Under plant crop, highly significant and positive correlation of 1st tillering (rg = 1.00 , rp = 0.85), 2nd tillering (rg =0.96, rp =0.83 ), 1st plant height (rg =0.89, rp =0.77), 2nd plant height (rg =0.95, rp = 0.81 ), cane length (rg =0.90, rp = 0.76 ), number of nodes (rg =0.79 , rp = 0.67), internode length (rg =0.80, rp =0.74) and millablecane (rg =0.96, rp = 0.87) was noted with cane yield at genotypic and phenotypic levels. Similarly brix showed positive and highly significant phenotypic correlation with POL (rp =0.84) and recovery (rp = 0.71). Under ratoon crop, highly significant and positive correlation of 1sttillering (rg = 0.89 , rp = 0.81), 2nd tillering (rg = 0.92 , rp = 0.84), 1st plant height (rg = 0.86 , rp = 0.75), 2nd plant height (rg = 0.96 , rp = .78), cane length (rg = 0.97 , rp = 0.69), internode length (rg = 0.77 , rp = 0.71), recovery (rg = 0.83 , rp = .64) and millablecane (rg = 0.85 , rp = 0.67) was noted with cane yield at genotypic and phenotypic levels. Brix showed positive and highly significant phenotypic and genotypic correlation with POL (rg = 0.99, rp = 0.98) and recovery (rg = 0.68, rp = 0.65). POL also has highly significant and positive correlation with recovery (rg = 0.72, rp = 0.70) at both the levels. Across crops, highly significant and positive correlation of 1st tillering (rg = 0.78 , rp = 0.70), 2nd tillering (rg = 0.86 , rp = 0.76), 1st plant height (rg = 0.95 , rp = 0.73), 2nd plant height (rg = 1.00 , rp = 0.77), cane length (rg = 0.77, rp = 0.63), internode length(rg = 0.85 , rp = 0.77) and cane diameter (rg = 1.00 , rp = 0.72) was observed with cane yield at phenotypic and genotypic levels. Millablecane showed highly significant and positive correlation at genotypic level while significant at phenotypic level (rg = 0.64, rp = 0.57) with cane yield. Brix showed highly significant and positive correlation with POL (rg = 1.00, rp = 0.95) and recovery (rg = 0.66, rp = 0.67) at genotypic and phenotypic levels. POL also has highly significant and positive correlation with recovery (rg = 0.74, rp = 0.79) at both the levels. Path analysis showed direct positive phenotypic effect on cane yield by 2nd tillering (P1,10 = 0.12), 2nd plant height (P2,10= 0.13), number of nodes (P3,10= 0.14), internode length (P4,10=0.32), brix (P5,10= 0.39), purity (P7,10=0.36) and millablecane (P9,10=0.39)under plant crop. However at genotypic level direct positive effect on cane yield was showed by 2nd tillering (P1,10=0.21), 2nd plant height (P2,10=0.42), number of nodes (P3,10=0.03) and millablecane (P9,10=0.63. Under ratoon crop, path analysis showed direct positive phenotypic effect on cane yield by 2nd tillering (P1,10=0.28), 2nd plant height (P2,10=0.04), cane length (P3,10=0.33), internode length (P5,10=0.32), cane diameter (P6,10=0.08), recovery (P8,10=0.06) and millablecane (P9,10=0.37). The direct positive genotypic effect on cane yield was exhibited by 2nd tillering (P1, 10= 0.16), 2nd plant height (P2, 10=0.40), cane length (P3,10=0.07), internode length (P5,10=0.24) and recovery (P8,10=0.73). Across crops, direct positive phenotypic effects on cane yield was showed by 2nd tillering (P1,10=0.20), 2nd plant height (P2,10=0.27), cane length (P3,10=0.19), internode length (P5,10= 0.28), recovery (P8,10=0.42) and millablecane (P9,10=0.05), however cane length (P3,10=2.36) and recovery (P8,10=1.94) had direct positive genotypic effect on cane yield. GenotypeMS-91-CP-523 had the highest path index values of 240.39 and 439.69 and performed better than rest of the genotypes under plant and across crops, respectively. Under ratoon crop genotype MS-2000-Ho-360 had the highest path index value of 141 and performed better than rest of the genotypes. Results further suggested that path analysis technique combined with development of path index could be successful in selection of sugarcane genotypes for improving overall selection approaches. The parameters with more broad sense heritability and genetic gain can be exploited in sugarcane breeding programs. The parameters having direct effect on cane yield must be given more importance in the breeding and selection strategies. Research should be focused on the selection of genotypes which has good performance both under plant and ratoon crops conditions. The genotypes with good performance may be tested further.