Agronomic performance and genetic diversity of the root crop yam bean (Pachyrhizus spp.) under West African conditions Doctoral Dissertation Submitted for the degree of Doctor of Agricultural Sciences of the Faculty of Agricultural Sciences Georg-August University Göttingen Germany by Ahissou Séraphin Zanklan from Porto-Novo, Benin Göttingen, July 2003 D7 1st examiner: Prof. Dr. Heiko C. Becker 2nd examiner: Prof. Dr. Elke Pawelzik Date of oral examination: 17 July 2003 To my parents, brothers and sisters Table of contents List of Abbreviations...................................................................................iii List of Figures.............................................................................................iv List of Tables...............................................................................................v 1. Introduction and literature review...........................................................1 1.1. Background and objectives......................................................1 1.2. The genus Pachyrhizus............................................................4 1.2.1. Botanical description, taxonomy and ecogeographic requirements.............................................................................4 1.2.2. Agronomy and breeding...........................................................9 1.2.3. Chemical Composition and Nutritional Value...........................14 1.2.4. Biological Nitrogen Fixation......................................................16 2. Evaluation of the root legume yam bean (Pachyrhizus spp.) under West African Conditions...................................................................................18 2.1. Introduction...............................................................................18 2.2. Materials and Methods..............................................................19 2.3. Results......................................................................................25 2.4. Discussion.................................................................................44 2.5. Summary...................................................................................48 3. Genetic diversity in yam bean (Pachyrhizus spp.) revealed by multivariate analyses of morphological and agronomic traits......................................49 3.1. Introduction................................................................................49 3.2. Materials and Methods..............................................................51 3.2.1. Plant material............................................................................51 3.2.2. Field experiments .....................................................................51 3.2.3. Statistical analysis.....................................................................56 3.3. Results......................................................................................57 3.4. Discussion.................................................................................64 3.5. Summary...................................................................................67 i 4. Genetic diversity in yam bean (Pachyrhizus spp.) germplasm revealed by Near Infrared Reflectance Spectroscopy.................................................68 4.1. Introduction................................................................................68 4.2. Materials and Methods...............................................................69 4.3. Results.......................................................................................72 4.4. Discussion..................................................................................76 4.5. Summary....................................................................................77 5. Conclusion.................................................................................................79 6. Summary / Zusammenfassung / Résumé.................................................80 7. References................................................................................................90 Appendix...................................................................................................111 Aknowledgements.....................................................................................121 Curriculum vitae........................................................................................123 ii List of Abbreviations AC Andean yam bean (P. ahipa) accession CC Chuin Cultivar group of the Amazonian yam bean (P. tuberosus) EC Mexican yam bean (P. erosus) accession G Genotype ha Hectar INRAB Institut National des Recherches Agricoles au Bénin L Location NIA Experimental station at Niaouli (Benin) NIRS Near Infrared Reflectance Spectroscopy PC Principal component PCA Principal Component Analysis R Replication SON Experimental station of “Centre Songhai“ in Porto-Novo (Benin) t Ton TC Amazonian yam bean (P. tuberosus) accession iii List of Figures Figure 2.1. Means of tuber fresh matter yield with and without pruning (t ha-1) Figure 2.2. Means of tuber dry matter yield with and without pruning (t ha-1) Figure 3.1. Plot of the first and second component scores for the 34 accessions of yam bean, Pachyrhizus spp. Figure 3.2. Plot of the first and third component scores for the 34 accessions of yam bean, Pachyrhizus spp. Figure 3.3. Cluster analysis on basis of 71 agronomic and morphological traits from a two locations field trial in Benin / West Africa Figure 4.1. Plot of the first and second component scores for the spectral data from 34 accessions of yam bean ( Pachyrhizus spp.) Figure 4.2. Cluster analysis on basis of Near Infrared Reflectance Spectroscopy (NIRS) spectra of seeds from a two locations field trial in Benin / West Africa iv List of Tables Table 1.1. Key to Pachyrhizus species Table 1.2. Literature overview of yield performance in Pachyrhizus spp. Table 2.1. List and passport data of accessions tested Table 2.2. Description of experimental sites Table 2.3. Agronomical characters evaluated, code and procedure of measurement Table 2.4. Effect of pruning on 12 agronomical characters for the Amazonian Yam Bean (P. tuberosus), the Mexican Yam Bean (P. erosus) and the Andean Yam Bean (P. ahipa) obtained from an analysis of variance Table 2.5. Means of agronomical traits after pruning of reproductive parts measured at two locations in Benin West Africa. Table 2.6. Means of agronomial traits without pruning of reproductive parts measured at two locations in Benin West Africa. Table 2.7. Variance analysis for tuber fresh matter yield in Andean Yam Bean (P. ahipa), Mexican Yam Bean (P. erosus) and Amazonian Yam Bean (P. tuberosus) Table 2.8. Variance analysis for tuber dry matter yield in Andean Yam Bean (P. ahipa), Mexican Yam Bean (P. erosus) and Amazonian Yam Bean (P. tuberosus) Table 2.9. Variance components of agronomical traits estimated from treatment pruning of reproductive parts. Table 2.10. Variance components of agronomical traits estimated from treatment no pruning of reproductive parts. Table 2.11. Means of traits of individual accessions within treatment pruned Table 2.12. Correlation coefficients of tuber fresh matter yield and of tuber dry matter yield with important yield components (Treatment with pruning) v Table 2.13. Correlation coefficients of tuber fresh matter yield and of tuber dry matter yield with important yield components (Treatment without pruning) Table 3.1. Morpho-agronomic characters evaluated, code and procedure of measurement Table 3.2. Results of Principal Component Analysis, Eigenvalues of the Correlation Matrix Table 3.3. Pearson Correlation Coefficients for principal components Table 4.1. Results of Principal Component Analysis from the spectral data, Eigenvalues of the Correlation Matrix Appendix Table A 1. Field plan at Centre Songhai, Porto-Novo, for the treatment without and with pruning Table A 2. Field plan at Niaouli for the treatment without and with pruning Table A.3 Coefficients of Correlation of different traits in P. ahipa without pruning of reproductive parts Table A.4. Coefficients of Correlation of different traits in P. erosus without pruning of reproductive parts Table A.5. Coefficients of Correlation of different traits in P. tuberosus without pruning of reproductive parts Table A.6. Coefficients of Correlation of different traits in P. ahipa with pruning of reproductive parts Table A.7. Coefficients of Correlation of different traits in P. erosus with pruning of reproductive parts Table A.8. Coefficients of Correlation of different traits in P. tuberosus with pruning of reproductive parts vi 1. Introduction and literature review 1.1 Background and objectives Many thousand plant species have been used for several purposes by human. About 100 have been developed into important crops (Hill et al., 1998) and only few of these crops have been intensively and widely used in the world´s agriculture. This has lead to the shrinking or erosion of agricultural biodiversity and at the same time to an increasing level of vulnerability of food suply. These concerns have generated growing interest in the research on “underutilized“ crops. Root and tubers are second in importance for human nutrition after cereals. Conventional root crops such as cassava, sweet potatoes, yam and taro are seriously deficient in protein and when used as the main source of nourishment, the local population, especially weaning children, often suffers from protein deficiences. Already in 1979 the FAO (1979) pointed out that due to