Characterization of F1 hybrid lines of cassava (Manihot esculenta Crantz)

Studies were carried out to characterise 27 putative F1 Hybrid lines of cassava (Manihot esculenta Crantz), obtained through artificial hybridization among five parents, based on agro-morphological data generated by using 30 descriptors from IBPGR and IITA. Further investigations were conducted to establish the true genetic identity of the presumed hybrids and to determine genetic relationships among them using data generated from agro-morphological studies, supported by molecular traits data. Scoring for molecular work was done at 12 months after planting using all 27 hybrid lines whilst that for agro-morphological traits was done at 18 months after planting (harvest) and involved 24 hybrid lines which survived up to this stage Data obtained were subjected to Principal Component Analysis (PCA), bi-dimensional graph and one-way analysis of variance (ANOVA). Phenotypic coefficient of variation (PCV) was calculated for each trait and correlations among traits determined. Jaccard similarity between accessions was calculated from the standardised trait mean values and accessions grouped together based on hierarchical cluster analysis. The results show that the 27 lines differed from the parents in agro-morphological traits (i.e. 6.67%) but differed for 28 others (i.e. 93.33%). Medium to high heterosis was detected among most hybrids for yield parameters studied with AFxSEC02, AFxSEC03, AFxSEC07 AFxSEC09 and AFxSEC13 exhibiting high heterotic effects over the others. Number of levels of branching and distribution of anthocyanin pigmentation; have been identified as traits conferring resistance to Cassava Mosaic and Cassava Bacterial Blight Diseases. The total of 23 SSR markers used showed a total of 382 bands out of which 290 were polymorphic, at a rate off 85.52% per locus, indicating the highly hybrid status of the lines investigated. Gene diversity per locus was 42.3. Overall heterozygosity (Ht) was 64.9% with one individual expressing 75.7% heterozygosity. Fis over loci was 0.468. Dendogram based on Nei's (1972) genetic similarity was generated using the SSR data. Cluster analysis based on both morphological and molecular markers revealed one major and minor group of cassava lines. The bi-dimensional plot confirmed the cluster pattern revealed by the dendogram. The result would be useful for further collection, conservation and improvement of cassava. [au]