Large sub-clonal variation in <i>Phytophthora infestans</i> from recent severe late blight epidemics in India

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

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Different cellulose synthase genes are prominently expressed during fiber elongation in <em>Gossypium arboreum</em> and <em>G. hirsutum</em>

200-206Quantitative expression analysis of three cellulose synthases/subunits encoding genes (cesA1, cesA1b, and cesA2) during three fibre development stages [3, 15 and 35 days post anthesis (dpa)] in Gossypium arboreum, G. anomalum, and G. hirsutum was undertaken. Exceptionally high expression was observed in G. hirsutum at 15 dpa stage for cesA1 and cesA2 (6.5 and 7.7 magnitude increase over β tubulin) genes, which might be responsible for longer fibre in G. hirsutum. Moderately high expression of cesA1 gene was recorded in G. arboreum (at 15 dpa), and in G. anomalum (at 3 and 15 dpa). However cesA1 gene expression was negligible in G. arboreum, and G. hirsutum at 3 dpa and in all three species at 35 dpa. Strong increase in expression levels of cesA1b gene (6.4 magnitude increase over β tubulin) was observed in G. arboreum at 15 dpa stage. Expression levels of cesA1b gene were moderate in G. hirsutum (at 3 and 15 dpa) and in G. anomalum (at 15 dpa); while its expression was low to negligible in rest of the samples. The cesA2 gene expressed at moderate to low levels at 3 dpa in G. anomalum and G. hirsutum; at 15 dpa in G. arboreum and G. anomalum; and at 35 dpa in all three species. During fibre initiation, expression of all three cellulose synthase genes was negligible in G. arboreum. In fuzzy fibred G. anomalum expression of all three ces genes was low (nil for cesA1 at 3 dpa) at all the stages. These results indicate that different cellulose synthase genes, cesA1 and cesA2 (in G. hirsutum) and cesA1b (in G. arboreum) play a predominant role in fibre development