Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2000
Publication Date: 7/1/2000
Citation: VANDEMARK, G.J., MARTINEZ, O., PECINA, V., ALVARADO, M. ASSESSMENT OF GENETIC RELATIONSHIPS AMONG ISOLATES OF MACROPHOMINA PHASEOLINA USING A SIMPLIFIED AFLP TECHNIQUE AND TWO DIFFERENT METHODS OF ANALYSIS. MYCOLOGIA, 92(4):656-664. 2000.
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. Unfortunately, methods used to examine levels of genetic diversity often require the use of very expensive laboratory equipment and chemicals that are harmful to both human health and the environment. We found that it was possible to examine levels of genetic diversity in a sample of isolates of the fungus by using a newly developed laboratory approach that did not require the use of either expensive equipment or hazardous chemicals. 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. These results will help other researchers to investigate levels of genetic diversity by using a procedure that is less expensive and more environmentally friendly than many other available procedures. An easier method for examining the genetics of fungi will enhance the rate of discovery and lead to improvements in method available to growers for controlling losses due to soilborne fungi.
Technical Abstract: A simplified protocol for detecting amplified restriction fragment length polymorphisms (AFLPs) was used to evaluate genetic diversity among isolates of Macrophomina phaseolina collected from different hosts and locations. Fifteen different selective primer pairs were evaluated. No significant differences were observed among primer pairs, grouped based on the AT% of the selective nucleotides, for several parameters that define primer utility. Relationship matrices generated with each group of AFLP primers were highly correlated (r2 > 0.92). Isolates were very diverse and could not clearly be grouped based on the geographic locations from which they were obtained. Genetic relationships among isolates were very robust. Relationships were determined using both the ¿genetic similarity¿ method of Nei and Li and the ¿genetic distance¿ method of Skroch. We conclude that both methods are equally effective for determining intraspecific genetic relationships when the majority of markers are polymorphic.