Abstract
The population structure of the Phytophthora infestans populations that caused the recent 2013–14 late blight epidemic in eastern India (EI) and northeastern India (NEI) was examined. The data provide new baseline information for populations of P. infestans in India. A migrant European 13_A2 genotype was responsible for the 2013–14 epidemic, replacing the existing populations. Mutations have generated substantial sub-clonal variation with 24 multi-locus genotypes (MLGs) found, of which 19 were unique variants not yet reported elsewhere globally. Samples from West Bengal were the most diverse and grouped alongside MLGs found in Europe, the UK and from neighbouring Bangladesh but were not linked directly to most samples from south India. The pathogen population was broadly more aggressive on potato than on tomato and resistant to the fungicide metalaxyl. Pathogen population diversity was higher in regions around the international borders with Bangladesh and Nepal. Overall, the multiple shared MLGs suggested genetic contributions from UK and Europe in addition to a sub-structure based on the geographical location within India. Our data indicate the need for improved phytosanitary procedures and continuous surveillance to prevent the further introduction of aggressive lineages of P. infestans into the country.
Highlights
The late blight pathogen Phytophthora infestans (Mont.) de Bary has had a major impact on both science[1,2] and society[3,4] and continues to do so even 170 years after the first reported outbreaks
Sub-clonal variation in simple sequence repeat (SSR) fingerprints revealed some sub-structure in the local population that was linked to region and host
Most isolates from eastern and north-eastern India differed from global populations and those previously observed in southern India
Summary
The late blight pathogen Phytophthora infestans (Mont.) de Bary has had a major impact on both science[1,2] and society[3,4] and continues to do so even 170 years after the first reported outbreaks. In the plains of eastern India, crop rotation is routine with potato grown between November and February in fields that are used for rice cultivation for the rest of the year These host dynamics affect the pathogen population through repeated extinction and re-colonization events and this may affect gene flow as well as evolutionary trajectories. In eastern India the four major potato producing states are Assam, Bihar, Meghalaya, and West Bengal These regions comprise approximately 45% of the total potato production in the country[33]. In 2014, a late blight epidemic in this region, primarily in West Bengal, led to dramatic social upheaval, including farmers committing suicide due to crop losses and policy changes such as setting minimum export values on potatoes[28]. A close examination of the pathogen populations during recent epidemics could provide insight into the source of P. infestans populations in India and spread within the country and help guide Indian growers to more effective disease management practices
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