Abstract
The study was carried out to investigate genetic diversity among kenaf germplasms, to assess combining
ability of the selected parents and their hybrids, and to estimate heterosis and the nature of gene actions
for different yield characters in kenaf. Four experiments were conducted during 2007 to 2010 to achieve
the main objectives of the research work. Of them three were field experiments conducted at the Central
Station of Bangladesh Jute Research Institute (BJRI), Dhaka and the other was laboratory experiment
carried out at Genetic Fingerprinting Laboratory of the Department of Genetics and Plant Breeding, and
Central Laboratory of Bangladesh Agricultural University, Mymensingh. Field experiments were
conducted in three replicated plots following RCBD. Data were recorded on different morphophysiological traits. Genetic diversity was investigated based on multivariate analysis and RAPD
markers. Principal component analysis based on correlation matrix of 12 morpho-physiological traits
showed that the first five axes accounted for 92.85% of total variation among the genotypes. Cluster
analysis grouped the 25 indigenous and exotic kenaf germplasms into six clusters. The distribution
pattern indicated that the genotypes collected from the same location were grouped into different
clusters. The results on intra and inter-cluster distances showed that the genotypes were highly
divergent from each other. Amplification of the isolated genomic DNA from each of the 25 germplasms
using 6 decamer random primers generated 48 RAPD markers, of which 38 (79.17%) were polymorphic.
The UPGMA dendrogram based on Nei's genetic distance segregated the genotypes into two major, two
minor and one single genotype clusters. Comparison between two clustering indicated that grouping of
genotypes based on morpho-physiological traits slightly differed with the grouping based on RAPD
markers. The parental genotypes G4(Acc.2731), Gs(Acc.2922), G,(CPI-72126), Gs(Acc.4659), G19(4197) and
G25(Acc.5030) were chosen from different clusters for hybridization work. Selected six parental lines were
crossed in a half diallel method. The performance of the parental lines and 15 Fi hybrids were assessed
and various traits were measured. ANOVA shows that variances for general combining ability (GCA)
and specific combining ability (SCA) were highly significant for all the characters studied suggesting the
presence of both additive and non-additive gene action for the inheritance of the concerned characters.
The magnitude of GCA variance was considerably higher than that of SCA variance for days to 1st
flowering, fibre weight/plant and 1000 seeds weight indicating the importance of additive gene action for
these traits. For all other characters non-additive genetic effects were more important for their
inheritance. Ranking of parents on GCA performance indicated that P3(Acc.2922) was the best general
combiner for earliness of flowering and smaller seed size followed by P4(Acc.5030) and P2(Acc.4197),
respectively. For fibre yield and yield attributes, P6(Acc.2731) was the best general combiner followed by
P2(Асс.4197) and P₁(CРІ-72126). On the other hand, parents P2(Acc.4197) and Ps(Acc.4659) were found to
be the best for maximum number of seeds/fruit' On SCA performance, the cross P3 x Ps was the best for
fibre related all traits except green bark thickness. This was followed by Pi х P6, P3 x P6 and P4 x Ps. The
crosses P2 x P3 and Pз x P4 showed maximum SCA for earliness and number of fruits/plant, while the best
specific cross for smaller seed size was P2 x P4. Genetic analysis study in Fi, F2 and backcross generations
revealed that both additive and non-additive genetic effects were important in the expression of morphophysiological traits examined, with however a predominance of additive gene effects. The extent and
direction of heterosis in Fi varied greatly for different characters and for different crosses. Vr,Wr graph
suggested that partial dominance and/or overdominance gene actions were involved for all the
characters studied in Fi, F2 and backcrosses. The narrow sense heritability (h²ns) as estimated from
genetic components was very high for stick weight/plant, fibre weight/plant, green weight/plant, stemmid diameter, plant height and days to 1st flowering in Fi and backcross, where as in F2, it was highest for
fibre weight/plant (0.69) followed by plant height (0.62), stem-mid diameter (0.59) and stick weight/plant
(0.52). Considering combining ability and genetic analysis study together, the crosses P2(Acc.4197)
P3(Acc.2922), P3(Acc.2922) x Ps(Acc4659), P4(Acc.5030) x Ps(Acc.4659) and P2(Acc.4197) x P4(Acc.5030)
were found promising for their heterotic response to earliness, higher fibre yield, smaller seed size and
other seed related characteristics. Multi-location trial is suggested for further evaluation of selected
crosses for specific purpose like earliness or higher yield characters.