First report of leaf spot caused by Phytophthora capsici on chili pepper (Capsicum frutescens L.) in Pakistan

Abstract

A survey was conducted in chili and a leaf spot disease with approximately 46% incidence was observed in the field. Morphological characteristics of the isolates correspond to those reported for Phytophthora capsici. The resulting sequences of ITS and TEF1 gene had high similarity after BLAST analysis with those of P. capsici isolates. The pathogenicity of one isolate was tested by spraying the zoospore suspension and symptoms of leaf spots similar to those observed in the field developed on all the inoculated leaves.Keywords Chili . Phytophthora . ITSIn June 2016, a survey was conducted in chili (Capsicum frutescens L.) growing areas of Punjab Province (Pakistan) and a leaf spot disease with approximately 46% incidence was observed in the field. The symptoms on leaves appeared as small brown-red spots that slowly enlarged with the central part light brown and dark brown to black margin. Leaf samples (number of plants = 10, number of leaves per plant = 3-4) were cut into small pieces (3 × 3 mm), excised from the edge of lesions, surface disinfected with 70% ethanol, then placed on plates containing corn meal agar (CMA) at 25 ± 2°C. White cottony colonies appeared on plates and ovoid, papillate sporangia produced on long pedicels ranging from 30 to 238 μm long. Sporangia were 43.2 to 56.4 μm in length and 24.5 to 42.2 μm in breadth. Chlamydospores 25 to 37 μm in diameter were observed by inoculating isolates into clarified V8 broth for three weeks in darkness at 18 ± 2°C. Morphological characteristics of the isolates correspond to those reported for Phytophthora capsici Leonian (Erwin and Ribeiro 1996). The ITS1/ITS4 primers were used for the amplification of ITS region (White et al. 1990) and translation elongation factor 1α (TEF1) was amplified with EF1-728F/ EF1-986R primers. The resulting sequences of ITS (LT707525) and TEF1 gene (LT707545) had high similarity (99%) after BLAST analysis with those of P. capsici isolates (EU515171 and KF318773, respectively). The pathogenicity of one isolate was tested by spraying the zoospore suspension of P. capsici (1 × 10 5 zoospores/ml) on healthy chili plants maintained in a greenhouse at 30°C. The control plants were sprayed with sterile water. After 6 days, symptoms of leaf spots similar to those observed in the field developed on all the inoculated leaves. No symptoms were observed on control plants. From affected leaves, colonies were reisolated with morphological characteristics identical with P. capsici. According to our knowledge, this is the first record of P. capsici causing leaf spot on chili in Pakistan.

Characterization of native plant growth promoting rhizobacteria and their anti-oomycete potential against Phytophthora capsici affecting chilli pepper (Capsicum annum L.)

“…A research study suggested that P. capsici isolates from pepper and pumpkin differ in virulence levels 32 . Morphologically identification confirmed the production of papillate sporangia on long pedicels, and Chlamydospores and these findings are supported by a study of 36 . According to 37 , Chamydospores production is not much common in Capsicum isolates but the formation of Chamydospores in P. capsici isolates depends on the cultural methods and the origin of the host 38 .…”

Comparative Genomic Analysis Reveals Genetic Variation and Adaptive Evolution in the Pathogenicity-Related Genes of Phytophthora capsici

“…(D) Heterozygosity levels in each gene family where total genes represent all annotated genes. 17 P. capsici isolates when characterized using pepper as a host (Nawaz et al, 2018). Our characterization study, based on root inoculation and a detached leaf assay, revealed the striking variation in the aggressiveness levels of three P. capsici isolates.…”

“…Different levels of aggressiveness among P. capsici isolates have been observed depending on the host and geographical variation (Granke et al, 2012;Nawaz et al, 2018;Siddique et al, 2019), however, the genomic comparison has not been performed. The broad distribution of P. capsici isolates with diverse aggressiveness levels impacts the breeding and deployment of resistant varieties of host crops (Foster and Hausbeck, 2010).…”

Rhizosphere bacteria induce programmed cell death defence genes and signalling in chilli pepper

“…Chilli peppers have been cultivated worldwide and are one of the essential vegetable fruits in some regions (FAOSTAT, 2016). Significant constraints to pepper fruit production include pests and diseases (Barchenger et al, 2018; Duarte et al, 2015; Nawaz et al, 2018; Saxena et al, 2016). Much progress has been made on increasing knowledge on function of various defence genes in pepper (Jaiswal et al, 2019; Zhang et al, 2019; Zheng et al, 2019).…”