Journal of Plant Diseases and Protection

In European QoI monitoring studies from 2019 on Pyrenophora teres, the causal agent of net blotch in barley, an isolate (ISO-2210) was identified with a level of QoI resistance that had never been observed before. ISO-2210 is highly resistant to QoI fungicides, which is caused by the G143A mutation in the mitochondrial-inherited cyt b gene. A part of its cyt b gene around codon 143 differs from P. teres and is identical to P. tritici-repentis, the causal agent of tan spot in wheat. The rest of the cyt b gene and other analyzed genes from mitochondrial and chromosomal DNA are identical to P. teres. In genes which differed between net type and spot type, the ISO-2210 sequences were identical to those of net type. ISO-2210 morphologically resembles P. teres and is pathogenic on barley, where it produces typical net blotch symptoms. An analysis of European isolates from 2019 and field samples from 2019 and 2020 did not indicate additional findings of such “hybrid”-isolates.

Plum pox potyvirus (PPV) is one of the most important viral pathogens of stone fruit trees. PPV-T (Turkey) is important, unique and dominated strain in Turkish PPV pool. Due to the virus in internal quarantine pathogen in Turkey, the rapid detection of virus is too important for preventing the spread of the disease to new areas. In this study, a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay from Varga and James was adapted for the rapid detection of PPV-T isolates in Turkey. RT-LAMP assay did not show cross-reaction with other viruses commonly infects Prunus spp. or natural hosts of PPV-T. Assay could be completed with the help of a water bath under isothermal conditions (60 °C) in 35 min. Sensitivity analysis showed that RT-LAMP detected viral RNA concentrations up to 0.01 ng/µL and it was 10 times more sensitive than reverse transcription-polymerase chain reaction (RT-PCR). The optimal Mg+2 and dNTP concentration for RT-LAMP of PPV-T were 6 mM and 0.4 mM, respectively. Furthermore, assessment with the naked eye after staining of in-tube RT-LAMP products with SYBR Green I facilitated the interpretation of positive LAMP reactions. These results reveal that the method is more sensitive, faster, cheaper and gene-specific test for the detection of PPV-T than RT-PCR. This adaptation study may help in preventing epidemic spread of this destructive strain of virus in Turkey. This is the first study for the use of RT-LAMP application of the assay for plant viruses in Turkey.

Chilli pepper or hot pepper (Capsicum annuum L.,) is an important spice and vegetable crop of family Solanaceae. Chilli is susceptible to various pathogens involving viruses, which cause heavy production losses. So far 65 viruses have been reported throughout the world including begomoviruses causing chilli leaf curl virus disease (ChiLCVD). ChiLCVD is the most destructive virus disease in terms of incidence and yield loss. The disease can be identified by typical upward leaf curling, crinkling, puckering and reduction in leaf area along with stunting of whole plants. It is transmitted by the whitefly Bemisia tabaci in persistent manner. Conventional plant breeding techniques remain the major antiviral strategy so far for the development of resistant chilli varieties. Recently, the concern about viral DNA methylation, activation of gene silencing machinery and ubiquitination-mediated defence against begomoviruses has been reported. Although a number of insecticides had been effectively used to manage this pest in the past, it is able to develop resistance very rapidly. This review provides an overview of ChiLCVD, virus vector relationship, its genome organization, replication, resistant sources, present status of its spread in different regions of India and strategies employed for controlling it.

Essential oils and their constituents are presently known to interfere with herbivorous insects’ behavioral and physiological activities. The effects of Ajwain (Carum copticum, L.) (Apiaceae) essential oil (AEO) and its main components were studied on Chilo suppressalis Walker (Lepidoptera: Crambidae), a serious pest of rice cropping in several parts of the world. The study included the toxicity of each component of AEO and the estimation of their synergistic or antagonistic effect on C. suppressalis larvae. The bioassay data showed the high insecticidal activity of AEO and thymol against the C. suppressalis larvae with LD50 values of 13.10 and 17.11 μg/larvae, respectively. The insecticidal activity was increased by binary mixtures of thymol + γ-terpinene or p-cymene, while the composition of p-cymene + γ-terpinene showed an antagonistic effect on the insects. The biochemical experiments demonstrated that treatment of AEO and its components enhanced the activities of detoxifying and antioxidant enzymes, and inhibited acetylcholinesterase. Among these compounds, thymol may be recommended as a potent biopesticide in controlling C. suppressalis populations, both insecticidal and compatible with other components with high AChE inhibition properties.

A study was carried out for identification and detection of Phytophthora spp. from soil and plant samples, collected from Solanaceous crops in Egypt and Italy. The samples were screened with specific and universal primers of Phytophthora 18S, ITS1–ITS2 and 28S regions, followed by PCR product sequencing. The Phytophthora spp. detected were P. infestans (Egypt) and P. parasitica (Italy). A molecular beacon probe was also developed based on the avr3a gene of P. infestans to detect a variant associated with virulence traits. The probe was suitable for avr3a allele identification from P. infestans and also from P. parasitica PCR products.

Chinese kale black spot disease is caused by the fungus Alternaria brassicicola (Schw.), which is one of the most significant destructive pathogens that attacks vegetable crops, especially Chinese kale. Currently, the pathogen management is achieved by using synthetic fungicides, but these are harmful to human health and tend to be expensive. Consequently, there is an urgent need to find alternative management options. The objective of this study was to evaluate the antagonistic activity of Talaromyces flavus (Klöcker) Stolk and Samson Bodhi001, Talaromyces trachyspermus (Shear) Stolk and Samson Bodhi002, Talaromyces flavus (Klöcker) Stolk and Samson Bodhi003, Neosartorya fischeri (Wehmer) Malloch and Cain, Bodhi004, Eupenicillium sp., and Gongronella butleri (Lendn.) Peyronel and Dal Vesco in in vitro tests for the control of A. brassicicola causing Chinese kale black spot disease under greenhouse conditions. The in vitro tests showed that among the tested pathogens, T. flavus Bodhi001 inhibited the mycelial growth of A. brassicicola by 65% in a dual culture method and formed an inhibition zone 0.8–0.9 cm wide. Under greenhouse conditions, spore suspensions of 106 spores mL−1 of Eupenicillium sp., T. flavus Bodhi001, T. trachyspermus Bodhi002, N. fischeri Bodhi004, G. butleri, and T. flavus Bodhi003 effectively reduced and suppressed the incidence of black spots caused by A. brassicicola at 30 days after transplanting (DAT). However, the greatest suppression of the development of black spots in terms of disease incidence was 32.56% and occurred when plants were treated with the spore suspension of T. flavus Bodhi001 once at 30 DAT and again at 40 DAT compared to a water control. The results of this study indicated that T. flavus Bodhi001 could provide protection for Chinese kale, and is a promising biological control agent against A. brassicicola.

Fusarium oxysporum f. sp. capsici (Foc) induces wilt disease in chilli and affects its yield. Implementing microorganisms and plant extracts for plant disease management has recently gained momentum as chemical measures pose a serious threat to the environment. Field experiments were conducted over two consecutive years to evaluate the effectiveness of Trichoderma harzianum (either as seed treatment or as soil application) and neem (Azadirachta indica; as seed treatment with leaf extract) alone or in combination, in managing chilli wilt. Untreated plots served as control. Chilli plants were grown in field plots of 2 × 2 m2 size, and experiments were organised in complete randomised block design with three replications. In the absence of Foc, T. harzianum (sa) + A. indica (st) increased growth and yield of chilli. In Foc-inoculated plots, both, T. harzianum and A. indica, showed a reduction in disease severity. Disease severity and chlorophyll content were negatively correlated (P ≤ 0.05). During both years, T. harzianum (sa) + A. indica (st) caused the strongest reduction in wilt severity and the highest increase in chlorophyll content, number of fruit/plant, fresh yield/plant, fresh and dry weight as well as plant length. Soil population of T. harzianum increased significantly during crop growth and was higher in plots inoculated with the pathogen. Highest concentrations (4.52 × 104 and 4.87 × 104 cfu/g soil) were found in plot soil where T. harzianum was applied in the soil, whilst maximum increase of Foc (3.02 × 104 and 3.05 × 104 cfu/g soil) was observed in plots that lacked any treatment.

Ceratitis capitata (Wiedemann, 1824) (Diptera: Tephritidae) is a polyphagous, holometabolous and multivoltine insect that has spread from its supposed origin in sub-Saharan Africa to regions between 45° north and 45° south geographic latitude. It is considered an important economic pest worldwide, due to the direct damage caused to fruit, the high cost of its management and the restriction of the export of fruit from infested countries to markets in countries exempt from infestation. If no control measures are applied against this pest, C. capitata can destroy 50% of total production or 100% in “preferred” hosts. Currently, chemical insecticides are commonly applied to control medflies due to their rapid and satisfactory action; however, this method has many problems, including the destruction of non-target organisms, residues on agricultural products, environmental pollution and the development of insect resistance to insecticides. These negative effects have led scientists to search for more sustainable and ecological new control methods. Recently, great attention has been given to biological control, which has become a practical option for the ecological control of pests. Among biological control, entomopathogenic nematodes (EPNs) have great potential as control agents for soil-borne pests, like C. capitata. This review focuses particularly on the control of C. capitata, specifically emphasizing the use of EPNs as biological control agents and their integration into integrated pest management. It is apparent from this study that species of Steinernema sp. and Heterorhabditis sp. are highly virulent against the late instars larvae and adults of C. capitata under controlled laboratory conditions, as well as these EPNs significantly reduce the population of this pest in semi-field and field trials. The pathogenicity of entomopathogenic nematodes against C. capitata was influenced by natural physicochemical and anthropogenic factors. The most effective EPNs were found to be compatible with certain mineral, chemical and biological products with insecticidal activity, indicating that these products can be combined with EPNs in the context of integrated control. Based on this, EPNs have a promising future as an alternative to conventional chemicals against Mediterranean fruit fly.