Abstract
The genus Hibiscus belongs to Malvaceae, and H. cannabinus (kenaf) and H. sabdariffa (mesta) are the two most important bast fibre yielding cultivated species, next to jute. The present research was conducted on interspecies hybridization involving four species having different ploidy levels of the genus Hibiscus with the objective of transferring spiral borer resistance of wild species to kenaf in the Bangladesh Jute Research Institute. The genomic formulae for these species were determined as H. radiatus (2n = 4x = 72, AABB), H. acetosella (2n = 4x = 72, AABB), H. sabdariffa (2n = 4x = 72, XXYY/AAYY), and H. cannabinus (2n = 2x = 36, AA). Altogether 7 genotypes of 4 species were used in interspecies hybridization. The wild H. radiatus and H. acetosella were represented by single genotype each, Acc. 1822 and Acc. 4300 respectively. H. cannabinus was represented by one variety, HC 95 and H. sabdariffa, was by the variety, HS 24, breeding line 300M (fibre type) and two land races, Raikhali and Acc. 2065 (edible type). To select parental lines variability of 12 genotypes of each of H. cannabinus and H. sabdariffa and 3 genotypes of each of H. acetosella and H. radiatus were evaluated on 12 quantitative characters. The Fis & their parents were identified through 20 morphological, 8 anatomical, 3 spiral borer resistance and RAPD parameters. Transgressiveness for plant height, nodes per plant and fresh weight without leaves were observed in all Fis of single and trispecies crosses compared to their parents, indicated the hybridity of Fis. Dominance of the male parent showed by the F1s for stipule shape, epicalyx shape and capsule dehiscence also indicated hybridity. Trispecies crosses were made to incorporate the spiral borer resistance of H. acetosella into kenaf using H. radiatus as bridging species. The semi-sterile F1 of H. radiatus × H. cannabinus was hybridized with the third species H. acetosella. Out of 8750 crosses 4354 were reciprocals. Number of sterile crosses were 6690 and 18205 seeds were obtained from 2060 fertile crosses. Total number of cross combinations were 20 including reciprocals. Of the cross combinations, the fertile cross combinations were H. radiatus × H. cannabinus, H. acetosella × H. cannabinus, H. radiatus × H. acetosella and with its reciprocal, H. acetosella x F1 (H. radiatus × H. cannabinus), F1 (H. radiatus × H. acetosella) x H. cannabinus and F1 (H. acetosella × H. radiatus) × H. cannabinus. Out of 1995 crosses between 4 genotypes of H. sabdariffa and H. cannabinus, none were successful. Spiral borer resistance status of Fis differed significantly from the susceptible parents in respect of gall length, % plant infestation (PPI) and amount of plant damage (APD). All the Fis showed resistant reaction except F1 of H. radiatus H. cannabinus. Gall length of resistant parent H. acetosella was 4.65 cm which was statistically identical with the Fis of H. acetosella × H. radiatus (6.18 cm) and H. acetosella × F1 (H. radiatus H. cannabinus) (4.90 cm) indicated the transfer of resistance from H. acetosella to the desired F1. Eight amplified bands observed in F1s were absent in their respective parents indicating hybrid specificity. However, none of the five primers alone was able to detect all seven hybrids. Inheritance and infestation pattern in F1 s indicated the chance of getting spiral borer resistant superior breeding lines in F2 and following generations on careful selection.