KAT 60/8. India. UN-PI/48/1. Kenya. ICP 6927. India. UN-PI/41/2. Kenya .... 34 UN-P1. 24 UN-P1. 23ICEAP. 39ICP. 33 UN-P1. 4 UN-P1. 3 UN-P1. 100. 100. 15.
African Journal of Biotechnology Vol. 4 (11), pp. 1228-1233, November 2005 Available online at http://www.academicjournals.org/AJB ISSN 1684–5315 © 2005 Academic Journals
Full Length Research Paper
Genetic variability and relatedness of the Asian and African pigeon pea as revealed by AFLP S. Wasike, P. Okori*, and P.R. Rubaihayo Department of Crop Science, Faculty of Agriculture, Makerere University P.O. Box 7062 Kampala, Uganda. Accepted 21 February, 2005
Amplified fragment length polymorphism was used to study genetic variability and relatedness between African and Asian pigeon pea cultivars. Forty-one samples, 32 African and 9 Asian varieties were subjected to the analyses. The genetic data was subjected to phenetic and analysis of molecular variation (AMOVA). Phenetic analysis revealed no major clusters and indicated limited genetic variability among the samples. AMOVA at continent wide hierarchical level, revealed a significantly weak population structure (φFST = 0.05, P= 0.001) and Fishers’ exact tests (P 0.05), and revealed that Indian pigeon pea cultivars were more genetically diverse (Table 4). Furthermore, our work revealed no distinct clusters based upon the maturity times and morphological marker traits like flowering time and floral colour of the pigeon peas (data not shown). DISCUSSION The study presents for the first time genetic characterization of pigeon pea using AFLP. The study revealed a close relationship between the test cultivars in this study as shown by presence of a weak population structure and absence of any major clustering patterns from phenetic analysis. The presence of a weak population structure between the two populations, African and Asia, suggests that the cultivars in this study have not been genetically isolated from each other. Two populations deriving from the same original population have got to be reproductively and genetically isolated
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26 UN-P1 25UN-P1 30UN-P1 22UN-P1 20 UN-P1 27UN-P1 21 UN-P1 31ICEAP 18 UN-P1 9UN-P1 12 UN-P1 11 UN-P1 6 UN-P1 10UN-P1 15UN-P1 8 UN-P1 7UN-P1 36ICP 13 UN-P1 14 UN-P1 19 UN-P1 17 UN-P1 38KAT 37ICPL 2 UN-P1 1UN-P1 29 ICEAP 28 ICP 35ICEAP 34UN-P1 32 UN-P1 24 UN-P1 23ICEAP 16UN-P1 39ICP 33 UN-P1 5UN-P1 4 UN-P1 3 UN-P1
B
A
Figure 2. A dendogram showing clusters of African and Asian pigeon pea generated using Treecon 1.3b from Nie and Li Neighbour joining analysis. Two clusters A and B were generated with the latter closer to the local Ugandian varieties.
from each other to permit selection and fixation of unique alleles that will account for divergence and presence of genetic structures (Hartl and Clark, 1997). In this study we obtained negative variance components in AMOVA at the continent hierarchical level. AMOVA estimates variance components and φFST following a multi-allelic (multivariate analysis of variation) (Excoffier et al., 1992), as previously described by Weir and Cockerham (1984). This methodology relies on estimates of relationships between alleles in the same populations relative to alleles of different populations and is designated by the parameter Accordingly, negative variance components can result from very small but positive estimates of from data relative to the true value in nature or if is indeed negative (Weir 1996). In genetic terms, this implies that alleles are more related between than within populations (Weir and Cockerham, 1984; Weir, 1996). When treated as sub-populations of one pigeon pea population, the φFST was still weak, but much higher. This provides
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Table 3. Analysis of molecular variation based on 299 AFLP fragments of pigeon pea from Africa and Asia.
Source of variation 1 Continent level a Among groups Among Populations Within populations Total 2
df
Sum of squares
Variance components
Percentage of variation
1 1 38
61.75 87.00 1641.33
-9.68 11.68 43.19
-21.41 25.85 95.56
40
1790.25
45.58
φFST = 0.05 (P = 0.001) based on 1023 permutations
One population Among populations
2
148.75
3.68
7.84
Within populations Total
38 40
1641.33 1790.10
43.19 46.87
92.16
φFST = 0.09 (P = 0.001) based on 1023 permutations 1
Comparisons done at the continent hierarchical level, that is, Africa and Asia. All cultivars considered as samples from one large population, with samples treated as sub-populations from the Africa and Asia. a Groups refers to continent of origin, that is, Africa or Asia, while populations refers to samples from Kenya, India and Uganda.
2
Table 4. Gene diversity and numbers of polymorphic loci of pigeon pea from Africa and Asia based on 299 AFLP loci examined.
Country of Origin Kenya Uganda India
Number of polymorphic loci 292 72 231
ˆ) Average gene diversity ( H 0.287 0.241 0.304
a
a
Average gene diversity computed according to Nei (1987) and Tajima (1983).
Hˆ values are not significantly different at (P
