نشریه مهار زیستی در گیاه پزشکی
سال ششم شماره 2 (پاییز و زمستان 1397)

Pochonia chlamydosporia and Purpureocillium lilacinum are important biocontrol agents of root-knot and cyst nematodes. Both fungi were first reported from sugar beet cyst nematode from Khorasan province and have shown promising potential as biocontrol agents of Heterodera schachtii, Globodera rostochiensis and Meloidogyne spp. In this study, sporulation and shelf life of fungi were evaluated on solid substrates for 2 months. The fungi were grown on cereals, their spore production and stability at 10 °C and 25 °C were evaluated. Based on media, storage duration and temperature regime, spore production of fungi differed. Pochonia produced spores on wheat grain, barley grain, wheat and rice bran after 30 days, and on rice husk after 60 days. P. lilacinum colonized all the substrates and yield of spore was highest on barley grain and rice husk. Viability of both fungi was slightly decreased after 60 days storage at 25 ºC, but at 10 ºC with some discrepancy did not change significantly. After 60 days, Pochonia produced average 1.5 × 108 and 7 × 107 spores / g of wheat and rice bran, and other cereals, respectively. Meanwhile, P. lilacinum produced 2.7 × 108 and 1.5 × 108 spores /g wheat and barley bran, respectively. Chlamydospores are resting spores of P. chlamydosporia var. chlamydosporia and one of the most common sources of inoculation in soil. On barley 1.1× 105 and on wheat and rice bran average 5 × 103 chlamydospores were produced.

This study was conducted to investigate the expression pattern of chitinase in mutant strains of the fungus Trichoderma harizanum, to the wildisolate.For this purpose, the strains of T. harizanum were subjected to mutation with optimum doses of 250 Gy of gamma radiation. Both the anti-mutant and wild strains were studiedwith the dual culture on the plant pathogen Sclerotinia sclerotiorum..All statistical analyzes were performed with SAS software and test least significant difference (LSD). The profile protein of produced enzymes by all strains using SDS-PAGE electrophoresis and proteome pattern of wildisolate with Th M8 mutant strains by colloidal chitin substrate was investigated using two-dimensional electrophoresis techniques and software ImageMaster 2D Platinum.The results showed that the majority of mutant strains compared to wild strains in the production of extracellular enzyme chitinase, were significantly different in the 1% and 5%. The results of the test antagonist showed that the potential control mutant strains compared to wild strains of the fungus S. sclerotiorum cope with significantly increased. The highest and lowest inhibition is related to strain ThM8 to 72% and ThM3 to 43%, respectively. On the other hand,the proteome pattern based on, two- dimensional electrophoresis technique showed that the protein spots of mutant strains compared to wild type isolates different both quantitatively and qualitatively.This suggests that mutations can lead to a change in the pattern of expression of the protein is secreted. The results of this study showed that gamma irradiation techniques can be effective in the production of enzymes in maycoparasitism and improvement biological control potential of plant diseases to be effective in management.

The tomato leafminer, Tuta absoluta (Meyrick) (Lep., Gelechiidae) is a devastating key pest of tomato, and its damage may reach up to 100%. Here, the potential of the infective juveniles (IJs) of the entomopathogenic nematode Steinernema feltiae Filipjev species on different larval stadia of T. absoluta was studied under laboratory conditions and the ability of most effective nematode concentration when applied in the greenhouse conditions. In the in vitro, the six concentrations of third-infective juveniles S. feltiae (0, 125, 200, 355, 632 and 1124 IJs/ml) were tested against the three larval instars, L2, L3 and L4 of T. absoluta. Forty eight hours after infection, the entomopathogenic nematode was able to infect all instars of the pest. With increasing density of S. feltiae, the pest larva mortality also increased with a significant difference at 1% probability level. The percentage mortality of L2, L3 and L4 at the highest concentration of nematodes (1124 IJs) were 31.5, 75.6 and 85.9%, respectively. These values at the lowest concentration of nematodes (125 IJs) were 16.8, 26.7, and 30.3%. In the greenhouse test, three treatments included; S. feltiae (1124 IJs/ml), Bacillus thuringiensis (0.25%, Belthirul 32% WP, Probelte Co.) and control in a completely randomized design with six replicates were conducted. The percentage mortality of different T. absoluta larval stages by S. feltiae and B. thuringiensis treatments were 77.5%±2.9 and 40%±13.7 with a significant difference at 1% probability level. The results indicate the potential of S. feltiae as a native entomopathogenic nematode could be used in an integrated management measure in controlling of the T. absoluta.

Trichoderma species are dominant organisms in most of soil microflora due to metabolic diversity and competitiveness and found approximately in all diverse habitats. In this study, four selected Trichoderma strains were evaluated to better control of cucumber stem and root rot disease caused by Fusarium solani. Cucumber germinated seeds were sown into inoculated soil with Trichoderma strains. Cucumber seedlings at forth leaf stages were inoculated with Fusarium. One month after inoculation by Fusarium, biocontrol effect of Trichoderma strains were evaluated by measuring the disease severity and cucumber growth factors. The results showed that Trichoderma strains were reduced disease severity and increased the growth factors in which both strains T189-4 (T. aureoviride) and T127-12 (T. harzianum) had the greatest impact on reducing infection with 91.67% in compare to untreated plants. The effect of Trichoderma strains on plant growth factors including root and stem length, dry and wet weight of root and stem, stem diameter and relative chlorophyll resulted that different Trichoderma strains have a posetive effects on increasing plant growth factors in which the strains T189-4 and T127-12 had the greatest effect on root dry weight in the presence of the pathogen, with 97% and 82%, respectively. These results indicated that the use of these Trichoderma native strains could be recommended for the control of Fusarium stem and root rot in the integrated management program of disease.

Fusarium wilt caused by Fusarium oxysporum f.sp. phaseoli is an important worldwide disease of beans. The pathogenicity of two isolates from the southwest of Iran was tested on cowpea, red bean, and kidney bean. To find the appropriate method for biological control of the disease, the inhibition of mycelial growth of fungal isolates by silver nanoparticle extract of Trichoderma harzianum was investigated in vitro. The extract of superior isolate of T. harzianum was converted into nanoparticles by mixing with silver-nitrate solution, and the formation of nanoparticles was proved by ultraviolet light spectroscopy. The maximum absorption was at 440 nm in a concentration of 5 Mm of silver-nitrate. The inhibitory effect of 10 concentrations of this nanoparticle on the mycelial growth of hyper-virulent isolate of the pathogen examined and the concentration of EC50 = 650 ppm was determined. The effect of EC30, EC50, EC70 concentrations of this synthesized nanoparticles solution, pure T. harzianum extract and silver-nitrate solution on the severity of the disease in kidney and red beans was tested in greenhouse conditions. All treatments significantly reduced the severity of the disease in beans, but their efficacy was lower than those of silver-nitrate and pure extract of T. harzianum. The biological control potential of Fusarium wilt by silver nanoparticle extract of T. harzianum is being reported for the first time.

Foraging parasitoids often adjust their foraging behavior according to the conditions they encounter. In this study the effects of age and experience on foraging and oviposition behaviors of Fopius carpomyiae Silvestri, was studied on ber fruit fly, Carpomyia vesuviana Costa. For this purpose, synchronous cohorts of F. carpomyiae were established in two age groups (7-8, and 12-13 days old). Then, the mated females (naïve females) in both ages were released individually into Petri dishes containing a ber fruit with a batch of eggs of ber fruit fly. Each female (n= 20) was observed continuously under a stereomicroscope while all distinguishable behavioral events of its foraging (the time of onset and duration) were recorded in the patch. In another experiment, the female wasps (7-8 days old), were exposed individually to a batch of host eggs on ber fruit flies, in the experimental patch for 24 h (experienced females). Results revealed that older females spent longer time in patches (5.48 min) compared with that of younger females (5.13 min). However, the average time of oviposition behavior (144.7±9.3 versus 146.4±8.9 s / female, respectively; P= 0.636) and percent parasitism (38.5±3.5 versus 39.2±3.2%, respectively; P= 0.84) were not significantly different between two age groups of female wasps. There was no significant difference in patch staying times of naïve and experienced females, nevertheless, the later allocated more time to ovipositing behavior and had significantly higher frequency and ratio of this behavior compared with those of former. In general, experienced females parasitized more host eggs compared to that of naïve females (46.5±2.8 versus 39.2±3.2%, parasitized eggs / female, respectively; P= 0.045)

Biocontrol of nematodes is now a priority in order to reduce the harmful effects of chemicals, including human health and environmental pollution. A lot of research suggest effective performance of Trichoderma spp. in reducing the damage and inhibition of various diseases. In this study, we investigated the effect of Trichoderma harzianum Iran2375c culture extracts on second stage juvenile mortality and egg hatching at 24, 48 and 72 hours using the concentrations of 1: 1, 1:10 and 1:100. In greenhouse studies, four leaf seedlings were inoculated with a concentration of 106 spores/g and after 10 days of inoculation of the soil, 3000 eggs and juvenile (stage two) of Meloidogyne incognita nematode per Kilogram were inoculated to the root of seedling. Experiment was carried out in greenhouse conditions in completely randomized design with four treatments in ten replications. Two month after inoculation of nematode, plant growth indices and indices related to nematode were measured. The concentration of 1:1 was the most effective in second stage juvenile mortality and egg hatching. Based on the results of greenhouse studies, the growth and nematode indices of treatments showed a significant difference. The results of this study indicates the potential of T. harzianum Iran2375cin biological control of M. incognita and promotion of plant growth.

Reproduction strategy of biological control agents can be affected by host deprivation. This effect was investigated on Trichogramma pintoi at laboratory condition (25±1 ºC, 65±5% RH, 16:8 LD). Treatments of 0 to 4 days of host deprived wasps in 10 replications were prepared. The wasps were then provided by daily supplies of Sitotroga cerealella eggs for the rest of their life. Female longevity, number of parasitized eggs and rate of progeny emergence were calculated. Results showed that wasps with 4 days host deprivation had greater longevity (14.16 days) but it was not significantly different compared with other treatments. As deprivation time increased, the total number of parasitized host decreased without significant differences. It was averagely 116.5 egg/wasp in 0 day host deprived treatment (control) and 70.6 egg/wasp in 4 days host deprived wasps. Moreover, host deprivation had no effect on emergence rate. In general, host deprivation for a few days may not seriously affect the biological characteristics of T. pintoi