Studies of the genetic diversity of Macrophomina phaseolina isolates from Argentina using AFLP markers

S. REZNIKOV, G.R. VELLICCE, V. GONZÁLEZ, M.G. GARCÍA, C.M.L. ROCHA, L.D. PLOPER AND A. P. CASTAGNARO.

Conferencia; World Soybean Conference South-Africa; 2013

Approximately 40 infectious diseases have been reported on soybean in Argentina causing annual losses of up to 900,000 metric tons, costing over US$ 250 million (Ploper, 2004; Wrather et al, 2010). Charcoal rot, caused by Macrophomina phaseolina (Tassi) Goid, is one of the most prevalent diseases affecting roots and lower stems in northern Argentina, especially when warm and dry conditions prevail during the soybean reproductive stages. Severe epidemics of charcoal rot occurred in recent years (2000/2001, 2002/2003, 2004/2005, and 2011/2012), causing heavy losses in various provinces and total losses in some fields. In addition to soybean, this soil borne fungus can also infect more than 500 cultivated and wild plant species.The objective of the present study was to evaluate molecular diversity, gene flow, and genetic structure in M. phaseolina, critical information for soybean breeders. An AFLP (Amplified Fragment Length Polymorphisms) technique was used to assess the genetic diversity of M. phaseolina isolates from different provinces of Argentina (19 from Tucuman, 5 from Santiago del Estero, 3 from Buenos Aires, 3 from Salta, and 1 from Santa Fe), which had been obtained from different hosts (22 from soybean, 3 from dry bean, 2 from chickpea, 1 from lentil, 1 from sunflower, 1 from peanut, and 1 from gerbera).From the 31 isolates of M. phaseolina, a total of 662 bands were amplified with 16 pairs of AFLP primers. From the total number of bands, 89.81% were polymorphic. Cluster analysis showed no clear association among geographical origin or host with AFLP profiles. Analysis of molecular variance (AMOVA) showed no genetic differentiation of M. phaseolina among provinces; the total variation (100%) was detected within provinces, with a PhiST value of 0.0. AMOVA results, considering host origin, showed no genetic differentiation of isolates among hosts; the total variation (100%) was detected within hosts, with a PhiST value of 0.0. These results indicated that there is no enough isolation that led to a genetic differentiation, confirming in this way a gene flow among these areas and hosts.