Contribution of host plant resistance and geographic distance to the structure of Potato virus Y (PVY) populations in pepper in northern Tunisia

Abstract

The genetic structure of Potato virus Y (PVY) populations was investigated in naturally-infected pepper ( Capsicum annuum ) fields, collected at eight different localities in northern Tunisia, where 23% of the sampled plants were homozygous for the pvr2 1 recessive resistance allele, while the other plants carried the dominant susceptibility alleleRestriction fragment length polymorphism analysis at three PVY genome segments revealed a high level of viral diversity, with a majority of cases showing co-infection of individual plants by several PVY haplotypes and a strong genetic differentiation of viral populations collected in the different localities. Geographic distances affected the differentiation of PVY populations and isolation by distance among these populations was significant. However, the occurrence of the pvr2 1 resistance allele did not contribute to the structure of viral populations, suggesting that the virulence properties of the virus did not significantly affect its fitness. Consequently, greater deployment of the pvr2 1 gene would probably not be a suitable strategy to control PVY, and other resistance genes should be preferred.

Genetic diversity and geographic differentiation analysis of duckweed using inter-simple sequence repeat markers

“…The results indicated that geographic region had significant influence on the populations' genetic diversity. These results correspond with the report of Bergmann et al that large differences among geographic isolates of duckweeds were found when they selected superior duckweed (Lemnaceae) genotypes for the utilization of nutrients in animal wastes [32], and the geographic differentiation of some other plants [33][34][35][36]. Different communities may have resulted in the significant genetic differentiation between duckweed populations; local selective forces may greatly affect genetic diversity within duckweed populations.…”

Cucumber mosaic virus populations in Tunisian pepper crops are mainly composed of virus reassortants with resistance‐breaking properties

“…Moreover, genetic drift due to strong bottlenecks during both CMV movement within the plant (Ali & Roossinck, ) and aphid transmission (Ali et al ., ; Betancourt et al ., ) could also favour genetic differentiation between CMV populations. Similar conclusions were drawn for PVY populations in peppers in Tunisia (Ben Khalifa et al ., ), a virus submitted to similar strong bottlenecks (Moury et al ., ; Fabre et al ., ).…”

“…Moreover, this unexpected result was confirmed for the samples collected in 2009 (Table ). Total RNAs previously purified from fruits of naturally infected peppers collected in 2006 for the study of Tunisian PVY populations (Ben Khalifa et al ., ) were then analysed. The situation was similar for samples collected in 2006.…”

“…The two viruses often occur in mixed infection, which results in increased severity of the disease through synergy (see review by Syller, ). The molecular and biological properties of Tunisian PVY populations have been studied in detail (Ben Khalifa et al ., , ), but very little is known about CMV populations in Tunisia.…”

“…Pepper (Capsicum annuum) is an important vegetable crop in Tunisia, grown mostly for local consumption. It is affected by different viral diseases, among which those induced by Cucumber mosaic virus (CMV) and Potato virus Y (PVY) seem to be the most damaging (Fakhfakh et al, 1999;Ben Khalifa et al, 2009). The two viruses often occur in mixed infection, which results in increased severity of the disease through synergy (see review by Syller, 2012).…”