|De La Vega, O|
|Alvarado Balleza, M|
Submitted to: Revista Mexicana de Fitopatologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2001
Publication Date: 12/1/2001
Citation: PECINA-QUINTERO, V., DE LA VEGA, O.M., ALVARADO BALLEZA, M., VANDEMARK, G.J., WILLIAMS-ALANIS, H. COMPARACION DE DOS SISTEMAS DE MARCADORES MOLECULARES EN EL ANALISIS DE LASRELACIONES GENETICAS DE MACROPHOMINA PHASEOLINA. REVISTA MEXICANA DE FITOPATOLOGIA, 19(2):72-80. 2002. Interpretive Summary: The fungus Macrophomina phaseolina lives in soil and causes stem and root disease in over 500 different species of plants. An improved understanding of the levels of genetic diversity present in this fungus would help researchers to group isolates of the fungus based on important traits, such as the range of plant hosts on which a particular isolate of the fungus is capable of causing disease. This knowledge would help growers in the process of deciding which type of crop could be grown in particular fields. However, different methods can be used to examine genetic diversity at the level of differences in DNA sequences. We tested two different methods. The two methods, known as RAPD (Randomly Amplified Polymorphic DNA) analysis and AFLP (Amplified Fragment Length Polymorphisms) analysis primarily differ in the degree of complexity of the required chemistry, with RAPDs being simpler than AFLPs. We found that very little difference was observed dbetween results obtained with both methods. We also found that levels of genetic diversity observed in our sample population of Macrophomina phaseolina were much greater than levels of diversity observed for other fungi. Use of RAPDs, the least complex of the two methods tested, should allow scientists to efficiently examine genetic diversity among pathogenic fungal isolates. This will enhance the rate of discovery and lead to improvements in method available to growers for controlling losses due to soilborne fungi.
Technical Abstract: Two systems of molecular markers (RAPDs and a simplified AFLP protocol) were compared to determine their utility in determining genetic relationships among 21 isolates of the soilborne plant pathogenic fungus Macrophomina phaseolina. Both systems were capable of discriminating among isolates from Arizona. Among loci scored based on RAPD analysis, 98.7% were epolymorphic, and 91.7% of the loci detected using AFLPs were also polymorphic. For each marker system, Nei and Li's Similarity matrix and Skroch's Genetic Distance matrix was calculated. Dendrograms were produced based on the matrices for each marker system. Grouping of the isolates did not conform to differences among isolates in geographic origin. The Pearson product moment correlation between pair-wise genetic relationships obtained with both marker systems was positive (P = 0.77) and highly significant, as was the Spearman Rank Correlation (P = 0.90).The diversity index observed for RAPDs and AFLPs was 0.84 and 0.71, respectively. The effective multiplex ratio index observed for RAPDs and AFLPs was 12.66 and 17.5, respectively. The marker index observed for RAPDs and AFLPs was 10.65 and 12.7, respectively. Results are discussed in terms of the selection of the appropriate marker system to be used for determining genetic relationships.