Phytophthora infestans in Poland from 1987–1989; Nuclear DNA Content, Mating Type Distribution and Response to Metalaxyl

Abstract

Isolates of Phytophthora infestans were collected from all potato growing regions of Poland during the blight seasons of 1987—1989. All 1987 isolates were of Al mating type and were sensitive to metalaxyl. In 1988 and 1989, 46.5 % and 55.3 % of the isolates were sensitive to metalaxyl, respectively. The percentage of highly resistant (R) isolates increased from 25.6 % in 1988 to 39.5 % in 1989; however the percentage of intermediately resistant (I) isolates decreased during that period from 27.9 % to 5.3 %. A significant association was observed between the A1 compatibility type and metalaxyl resistance. The A2 mating type first appeared in 1988, and its frequency increased from 4.7 % of the population in 1988 to 47.6 % in 1989. Coincident with this change in mating type frequency, changes in ploidy levels of isolates were observed. Whereas 3 % of the 1988 isolates were diploid, 90 % of the 1989 A2 isolates and 28.6 % of the 1989 Al isolates were diploid. The approximate 1:1 ratio of the two mating types encountered in 1989, and the predominance of diploidy, indicates that the Polish population of P. infestans has the potential to become sexual.

Genome Size Determination in Peronosporales (Oomycota) by Feulgen Image Analysis

“…In addition, the recent introduction into new geographic regions and further rapid spread offer interesting clues to evolutionary processes on the cytological level, which can help to explain the observed genome size phenomena of other plant pathogens. In P. infestans, diploid, triploid, and tetraploid strains but also diploid-polyploid heterokaryons were identified by Feulgen absorbance photometry (Tooley and Therrien, 1987;Therrien et al, 1989Therrien et al, , 1993Tooley et al, 1989;Daggett and Goetz, 1992;Daggett et al, 1995;Ritch and Daggett, 1995) and by DAPI microfluorimetry (Whittaker et al, 1991). These data were shown to be correlated with the geographic origins of the isolates.…”

“…A few exceptions to be mentioned here are Uredinales (Eilam et al, 1992(Eilam et al, , 1994, Pythium spp. (Martin, 1995), and P. infestans (e.g., Tooley and Therrien, 1987;Therrien et al, 1989Therrien et al, , 1993Tooley et al, 1989;Whittaker et al, 1991;Daggett and Goetz, 1992;Daggett et al, 1995;Ritch and Daggett, 1995). In several of these publications polyploidy series of closely related taxa have been presented.…”

“…Populations in central Mexico, the supposed place of origin, were found to be sexual and genetically diverse, which was combined with prevailing diploidy and low genome size variation. The other populations in regions where P. infestans has been recently introduced (e.g., Europe, the United States, Peru, Japan) showed a high percentage of polyploid isolates in combination with an apparent lack of sexual recombination; the broad range of genome size variation within a proposed ploidy level further indicated frequent occurrence of chromosomal rearrangements and aneuploidy (Whittaker et al, 1991;Therrien et al, 1993). As can be concluded, sexuality poses strong selection pressure against polyploidy and aneuploidy, whereas in asexual lines this selection pressure seems to be far less strong, which leads to rapid changes in genome size within a short period of time.…”

“…Most data have been obtained by Feulgen absorbance photometry (Typas and Heale, 1980;Jackson and Heale, 1985;Tooley and Therrien, 1987;Therrien et al, 1988Therrien et al, , 1989Therrien et al, , 1993Tooley et al, 1989;Daggett and Goetz, 1992;Daggett et al, 1995); propidium iodide microfluorometry (Eilam et al, 1992) or flow cytometry (Eilam et al, 1994); and DAPI microfluorometry (Whittaker et al, 1991;Rutherford and Ward, 1985). Most of these investigations report only relative DNA values, as their main aim has been to record the relative genome size variation within a species or within closely related taxa, and usually no attempt has been made to report also absolute DNA content values.…”

Phenotypic and genotypic structure of Phytophthora infestans populations on potato and tomato in France and Switzerland

“…The proportion of A2 mating type isolates collected from commercial potato fields has remained low in the UK, France, Germany and Switzerland (Gisi & Cohen, 1996; Day et al ., 2001), whereas in the Netherlands and Scandinavia it has reached over 50% (Hermansen et al ., 2000; Turkensteen et al ., 2000). High proportions of A2 mating type isolates have also been detected in allotment gardens in the Netherlands (Drenth et al ., 1993a), and in certain years in potato fields in Poland (Therrien et al ., 1993). In addition, both A1 and A2 isolates were recovered in 1995 and 1996 from tomato in private gardens in France and Switzerland; the frequency of A2 isolates was often higher on tomato than on potato (Lebreton et al ., 1996; Duvauchelle et al ., 1997; Lebreton & Andrivon, 1998).…”