Revista mexicana de fitopatología
Print version ISSN 0185-3309
SILVA-ROJAS, Hilda Victoria et al. Spatio-Temporal Distribution of Pepper (Capsicum annuum L.) Wilt in Chihuahua and Identification of the Causal Agent Phytophthora capsici Leo. Rev. mex. fitopatol [online]. 2009, vol.27, n.2, pp. 134-147. ISSN 0185-3309.
Phytophthora capsici is the oomycete that causes root rot and wilting of jalapeño pepper in the South Central region of Chihuahua State. The zoosporangia release zoospores which can spread by water surface movement, resulting in pathogen dispersion in places where it was not present yet. Therefore, the spatio-temporal distribution of wilting on jalapeño pepper was studied in 2002 and 2003 in the municipalities of Camargo and Delicias, Chih. The spatio-temporal distribution was determined by the Poisson distribution and the spatial autocorrelation analysis. These studies revealed that the disease continuously spreads from a single infected plant up to ten nearest neighboring plants within the row (4.5m), and up to four continuous neighboring plants across the row (2m), this may indicate that the pathogen's dispersal followed the furrow irrigation path and aggregates manly in the waterlogged spots due to a lack of land leveling in the field. Gompertz was the model that best described the progress of the disease, reaching apparent intensity rates from 0,008 to 0,016 gompitz day-1 (R2 = 0,75 to 0,95). In order to determine the causal agent of the jalapeñño pepper wilt the pathogen was isolated from diseased plants and by pathogenicity test. The isolates were identified as P. capsici throughout morphological characteristics, and sequencing of796 bp of the internal transcribed spacers (ITS) of the rDNA. The representative isolate sequence was deposited in GenBank with the accession number EF660564. Compatibility types A1 and A2 were detected among the isolates, and they were sensitive to mefenoxam.
Keywords : Oomycete; Capsicum annum; Poisson distribution; spatial autocorrelation.