Identity and variability of Pythium species associated with yield decline in aerobic rice cultivation in the Philippines. (15th March 2012)

• Record Type: Journal Article
• Authors: Van Buyten, E.; Banaay, C. G. B.; Vera Cruz, C.; Höfte, M.
• Is Part Of: Plant pathology. Volume 62:Number 1(2013:Feb.)
• Page Start: 139
• Page End: 153
• Publication Date: 2012-03-15
• Subjects: Agricultural pests -- Periodicals; Plant diseases -- Periodicals; 632
• DOI: 10.1111/j.1365-3059.2012.02607.x
• Languages: English
• ISSNs: 0032-0862

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The cultivation of aerobic rice in the tropics enables farmers to save water without lowering productivity. Unfortunately, this system suffers from declining yields due to a disease complex involving nematodes, pathogenic <italic>Pythium</italic> spp. and nutrient deficiencies. Assessing the impact of each underlying factor can contribute to efficient disease control measures. This study therefore investigated pathogenic and genotypic variability among <italic>Pythium</italic> species from affected aerobic rice fields in the Philippines using pathogenicity assays and sequence information from the internal transcribed spacer (ITS) region and β‐tubulin gene. Three closely related <italic>Pythium</italic> spp., <italic>P. arrhenomanes, P. graminicola</italic> and <italic>P. inflatum</italic>, were recovered from affected aerobic rice fields. All <italic>P. arrhenomanes</italic> isolates reduced rice seedling growth, whereas only a few <italic>P. graminicola</italic> isolates and no <italic>P. inflatum</italic> isolates were pathogenic, indicating that <italic>P. arrhenomanes</italic> is probably the most important species affecting rice. Both <italic>P. arrhenomanes</italic> and <italic>P. graminicola</italic> isolates showed little genetic variation, despite the observed pathogenic variation within <italic>P. graminicola</italic>. Intraspecific variation was higher among <italic>P. inflatum</italic> isolates, but again no correlation was observed with phenotype. When screening <italic>P. arrhenomanes</italic> isolates from other hosts such as sugarcane, maize and several grasses, a link between pathogenic and genetic variability was detected. However, rice and maize isolates seemed to lack host specificity, and therefore crop rotation with maize might be a risky strategy to manage yield decline in Philippine aerobic rice fields.</p> </abstract>