The AFLP technique was used to assess the genetic diversity and sectional relationships in 39 accessions representing the four main sections of the genus Musa. Eight AFLP + 3 primer pairs produced 260 polymorphic bands that were used in cluster and PCO analysis. A wide range of variability was observed among the species within the sections of the genus Musa. AFLP data was useful in separating the different sections of the genus as well as differentiating the different genomic groups of section Eumusa. Section Rhodochlamys ( x = 11) appeared as a distinct entity and clustered closely with the Musa acuminata Colla complex of section Eumusa that has the same basic chromosome number. This relationship is congruent with previous studies. However, unlike previous proposals that questioned the identity of Rhodochlamys as a separate taxonomic unit, PCO analysis of the AFLP data showed that it is a distinct entity. Musa laterita Cheesman ( Rhodochlamys) and Musa schizocarpa Simmonds clustered with the M. acuminata complex suggesting that they may be sources of useful genes for the improvement of the cultivated bananas. Callimusa formed a distinct unit and was closer to Australimusa than to the other sections. Although both sections share the same basic chromosome number of x = 10 these sections are genetically distinct

level that could limit continued breeding success. Introduction of new sources of germplasm into the breeding Asian soybean [Glycine max (L.) Merr.] improvement programs pool may provide the genetic variability to permit conhave been conducted for many years almost completely independent of U.S. breeding programs. Productive, modern Asian cultivars may tinued progress in developing high yielding cultivars. be a promising source of new yield genes for U.S. breeding programs. Though plant introductions (PIs) provide genetic vari-However, this hypothesis has not been tested. The objectives of this ability, they are less frequently used as sources of new study were to determine the level of genetic diversity within and yield genes than current cultivars and elite lines because between Asian and North American soybean cultivars (NASC) by they often yield less. Populations developed from crossamplified fragment length polymorphism (AFLP) analysis and to ing cultivars with PIs, which have been selected for good identify Asian cultivars with significant genetic difference from NASC. phenotypic traits, generally have a lower mean yield The genetic diversity and relationships were assessed among 35 North and lower frequency of desirable lines than those popu-American soybean ancestors (NASA), 66 high yielding NASC, 59 lations developed from crossing elite parents (Vello et modern Chinese cultivars, and 30 modern Japanese cultivars. Five al., 1984; Ininda et al., 1996). Recent studies have used AFLP primer-pairs produced 90 polymorphic (27%) and 242 monomorphic AFLP fragments. Polymorphic information content (PIC) molecular markers to help identify genetically diverse scores ranged from zero to 0.50. Only 53 of the 332 AFLP fragments PIs to use in crosses in cultivar improvement programs provided PIC scores Ն0.30. Genetic distance (GD) between pairs (Thompson and Nelson, 1998a,b; Thompson et al., 1998; of genotypes was calculated on the basis of the similarity indices Narvel et al., 2000). These studies have had more success determined by the 332 AFLP fragments. Within each of the cultivar than conventional selection programs in producing progroups, the average GD between pairs of genotypes was 6.3% among ductive lines from PI crosses with elite genotypes. Modern the Japanese cultivars, 7.1% among the NASC, 7.3% among the Asian cultivars, which share no ancestors with NASC, NASA, and 7.5% among the Chinese cultivars. The average GD represent a potential reservoir of new alleles available between the NASC and the Chinese cultivars was 8.5% and between for improving U.S. soybean yield, and is a different apthe NASC and the Japanese cultivars was 8.9%. Although these proach than using other germplasm in crosses with distances were not significantly different, they were greater than the average GD between all pairs of NASC (7.1%). Clustering and princi-NASC. pal coordinate analysis using all 332 fragments showed a separation Acquisition of soybean germplasm from Asia has inof the cultivars into three major groups according to t...

Fifteen AFLP primer pairs (EcoRI+3 and MseI+3) and 60 10-mer RAPD primers were used to detect polymorphisms and assess genetic relationships in a sample of 25 plantains from diverse parts of Western and Central Africa. The discriminatory power of the AFLP technique was greater than that of the RAPD technique, since the former produced markers with greater polymorphic information content (PIC) than the latter. Hence, AFLP analysis appeared to be a more-powerful approach for identifying genetic differences among plantain accessions. In this regard, significant genetic diversity within the plantains was shown by the unweighted pair-group method of arithmetic averages (UPGMA) and the multidimensional principal coordinate (PCO) analyses. The AFLP-derived clusters indicated closer relationships between similar inflorescence types than the RAPD-derived clusters. A small group of cultivars from Cameroon were separated from the bulk of other plantains, suggesting that Cameroon may harbour accessions with useful or rare genes for widening the genetic base of breeding populations derived from the plantains. A greater effort should be directed at collecting and characterizing plantain cultivars from Cameroon.

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Background: Assessment of genetic diversity of Vigna unguiculata (L.) Walp (cowpea) accessions using informative molecular markers is imperative for their genetic improvement and conservation. Use of efficacious molecular markers to obtain the required knowledge of the genetic diversity within the local and regional germplasm collections can enhance the overall effectiveness of cowpea improvement programs, hence, the comparative assessment of Inter-simple sequence repeat (ISSR) and Start codon targeted (SCoT) markers in genetic diversity of V. unguiculata accessions from different regions in Nigeria. Comparative analysis of the genetic diversity of eighteen accessions from different locations in Nigeria was investigated using ISSR and SCoT markers. DNA extraction was done using Zymogen Kit according to its manufacturer's instructions followed by amplifications with ISSR and SCoT and agarose gel electrophoresis. The reproducible bands were scored for analyses of dendrograms, principal component analysis, genetic diversity, allele frequency, polymorphic information content, and population structure.

Genetic diversity and relationships were assessed in 28 accessions of Musa acuminata (AA) Colla and Musa balbisiana (BB) Colla, and some of their natural hybrids, using the amplified fragment length polymorphisms (AFLP) technique. Fifteen AFLP +3 primer pairs produced 527 polymorphic bands among the accessions. Neighbor-joining and principal co-ordinate (PCO) analyses using Jaccard's similarity coefficient produced four major clusters that closely corresponded with the genome composition of the accessions (AA, BB, AAB and ABB). The AFLP data distinguished between the wild diploid accessions and suggested new subspecies relationships in the M. acuminata complex that are different from those based on morphological data. The data suggested that there are three subspecies within the M. acuminata complex (ssp. burmannica Simmonds, malaccensis Simmonds, and microcarpa Simmonds). 'Tjau Lagada' (ssp. microcarpa), 'Truncata' [ssp truncata (Ridl.) Shepherd] and 'SF247' [ssp. banksii (F.Muell) Simmonds] clustered very closely with 'Gros Michel' and 'Km 5', indicating that more than one M. acuminata subspecies may be involved in the origin of triploid AAA bananas. 'Calcutta 4' (ssp. burmannicoides De Langhe & Devreux) and 'Long Tavoy' (ssp. burmannica) were closely related and could be together in the same subspecies. This study also showed that there is much more genetic diversity within M. balbisiana that was split into two groups: (1) 'I-63' and 'HND' and (2) 'Los Banos', 'MPL' (Montpellier), '10852', 'Singapuri', 'Etikehel', and 'Butohan 1' as the other.

Amplified restriction fragment length polymorphism (AFLP) was used to assess the levels of genomic variations among species and isolates of the genus Colletotrichum. Our objective was to characterize at the molecular level two alfalfa pathogens, isolates Arl-NW and 57RR, which are unusually aggressive to anthracnose-resistant alfalfa cultivars and whose taxa has been uncertain based on morphological criteria. The fingerprint patterns obtained were complex but did enable us to place these two isolates within the species C. trifolii and C. gloeosporioides, respectively. The diversity detected with AFLP among and within Colletotrichum species from alfalfa and other crops corroborated their published taxonomy based on morphology, ribosomal DNA sequence, and random amplified polymorphic DNA analyses. Similarity matrices generated with three primer pairs were highly correlated and, thus, were combined to determine the similarity among the fungal species and isolates that were analyzed. Analysis of the data generated with each of the primer pairs individually and application of either distance or parsimony methods supported the placement of these two isolates. The parsimony method of data analysis was more confirmatory in the placement of Phoma medicaginis as an out-group than the distance method, using either simple matching or Jaccard's coefficients to generate the similarity matrices. Our conclusion is that the AFLP technique will be useful for identification of individual isolates within complex genera such as Colletotrichum because of its ability to generate large numbers of polymorphisms and the consistency of polymerase chain reaction amplification.