Analysis of genetic and virulence variability of Stemphylium lycopersici associated with leaf spot of vegetable crops

Abstract

Stemphylium lycopersici (Enjoji) W. Yamam was initially described from tomato and has been reported to infect different hosts worldwide. Sequence analyses of the internal transcribed spacer (ITS) regions 1 and 2, including 5.8S rDNA (ITS-5.8S rDNA) and glyceraldehyde-3-phosphate dehydrogenase (gpd) gene, random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR), as well as virulence studies were conducted to analyze 46 S. lycopersici isolates. Stemphylium lycopersici isolates used in this study were obtained from diseased tomato (Solanum lycopersicum L.), eggplant (Solanum melongena L.), pepper (Capsicum annuum L.) and lettuce (Lactuca sativa L.) from major vegetable growing regions of Malaysia, including the three states of Pahang, Johor and Selangor between 2011 and 2012. Phylogenetic analysis of a combined dataset of the ITS-5.8S rDNA and gpd regions indicated that all isolates were clustered in the sub-cluster that comprised S. lycopersici, and were distinguished from other Stemphylium species. Cluster analyses using the UPGMA method for both RAPD and ISSR markers grouped S. lycopersici isolates into three main clusters with similarity index values of 67 and 68 %. The genetic diversity data confirmed that isolates of S. lycopersici are in concordance to host plants, and not geographical origin of the isolates. All S. lycopersici isolates were pathogenic on their original host plants and showed leaf spot symptoms; however, virulence variability was observed among the isolates. In cross-inoculation assays, the representative isolates were able to cause leaf spot symptoms on eggplant, pepper, lettuce and tomato, but not on cabbage.

Analysis of virulence and genetic variability of Alternaria alternata associated with leaf spot disease in potato plants in Iran

“…Our current findings were consistent with those of previous studies on A. alternata isolates obtained from citrus hybrids [23], potato plants [10,24], and tomato plants [24,25] throughout Iran. The RAPD and ISSR techniques are extremely powerful tools for distinguishing among individuals that exhibit intraspecific and interspecific variability [26]. In the present study, 100% and 84% of the isolates were found to be polymorphic with respect to the RAPD and ISSR markers, respectively.…”

Characterisation of Magnaporthe oryzae isolates from rice in peninsular Malaysia.

“…All isolates were collected from the MR219 rice variety, which is the most popular variety of rice planted on 70% of all rice plantation areas in Malaysia (Hashim et al 2015), and recently it has shown signs of being susceptible to the rice blast disease. Although the results of RAPD analysis showed quite good congruence with the results obtained from ISSR studies, a greater effective ratio of multi-locus Table 1 Coefficient doi: 10.17221/102/2016-CJGPB markers as well as a higher number of private alleles were observed using ISSR markers (Nasehi et al 2014). (Mishra et al 2006), Korea (Park et al 2003), China (Ngueko et al 2004), Iran (Javan-Nikkhah et al 2004 and India (Chadha & Gopalakrishna 2005), which is in agreement with the findings of this study.…”

“…Because of the low precision and overlapping of some morphological characteristics, more accurate methods such as DNA sequencing have been employed to identify fungal pathogens (Nasehi et al 2014). In this respect, the use of molecular techniques such as sequencing of different regions of DNA is considered as alternatives to morphological methods of identification of Magnaporthe species (Hirata et al 2007).…”

“…The RAPD and ISSR markers have been proved as highly powerful tools in studies of genetic diversity and fingerprinting of Magnaporthe spp. isolates (Chadha & Gopalakrishna 2007;Sirithunya et al 2008), as well as other plant pathogenic fungi (Nasehi et al 2014).…”

“…and 2.5 µl of 10× supportive buffer (100 mM Tris-HCl, 500 mM KCl, pH 9.1) and 10 ng of genomic DNA. RAPD analysis was carried out as described by Nasehi et al (2014). PCR amplification was conducted in a thermal cycler (C1000 Touch TM Thermal Cycler, Bio-Rad Laboratories, Inc.) programmed with the following profiles: 94°C for 4 min initial denaturation, 45 cycles of 94°C for 1 min denaturation, 35°C for 1.5 min annealing and 72°C for 2 min extension and 10 min final extension at 72°C.…”