The species structure of plant parasitic nematode populations from the rhizosphere of winter
wheat grown with crop rotation or in 48-year-old monoculture was analyzed and compared.
Dominating species: Bitylenchus dubius, Merlinius microdorus, Paratylenchus neglectus
and Heterodera avenae, in monoculture plots, had higher populations than in crop
rotation plots. Heterodera avenae eggs and larvae were infected by pathogenic fungi in 68%
of the monoculture crops (vs. 65–66% of the cysts from crop rotation), 12–20% of Paratylenchus
sp. specimens were colonized by bacteria, mainly by Bacillus penetrans. This study
shows nematological changes occurring in long-term wheat breeding, thus providing additional
information necessary to fight dangerous viral vectors of the examined cereal.
Concerns about food quality and environmental protection have led to the search for effective
and safe insect control measures. This study was carried out to evaluate the efficacy
of some insecticides (malathion, alpha-cypermethrin, lambda-cyhalothrin) and clove oil,
alone and in combinations, to protect wheat grain against Rhyzopertha dominica. Adult
mortality, progeny emergence and weight loss of treated grain were examined. The results
revealed that the tested insecticides and clove oil alone showed high efficiency to
R. dominica with respect to mortality, progeny of the adults and weight loss of wheat grain.
The mixing of lambda-cyhalothrin and clove oil with the most effective insecticide (alphacypermethrin)
enhanced its efficacy to R. dominica. It was more efficient against R. dominica
than when used alone with respect to mortality and progeny of the adults. However,
mixing alpha-cypermethrin with malathion reduced the efficacy of alpha-cypermethrin
against R. dominica with respect to mortality and progeny of the adults. Combinations of
alpha-cypermethrin and clove oil reduced wheat grain loss more than using them alone.
Mixing lambda-cyhalothrin and clove oil with low concentrations of alpha-cypermethrin
improved its efficacy against R. dominica and therefore may reduce environmental pollution,
lower risks to human health, and delay insect resistance development.
Potato white mold caused by Sclerotinia sclerotiorum is an important plant disease occurring in many potato-producing areas throughout the world. In this study,
a specific diagnostic method was used to detect and quantify S. sclerotiorum ascospores, and its forecasting ability was assessed in potato fields during flowering
periods of 2011 to 2014 in Bahar County, Hamedan Province. Using GenEMBL database, a primer pair, HZSCREV and HZSCFOR, was designed and optimized
for the pathogen. After testing the sensitivity of primers, DNA was extracted from samples of outdoor Burkard traps from potato fields. A linear association was observed
between pathogen DNA and the number of ascospores using the quantitative PCR (qPCR) technique in the presence of SYBR dye. The qPCR could successfully
detect DNA amounts representing two S. sclerotiorum ascospores and was not sensitive to a variety of tested fungi such as Botrytis cinerea, Alternaria brassicae,
Fusarium solani. In contrast to the amount of rainfall, a direct relationship was found between ascospore numbers and the incidence of potato white mold from
2011 to 2014.
Quantitative resistance in barley to four Fusarium head blight (FHB) species was investigated in vitro. Nine components involved in three assays (detached leaf, modified Petridish
and seedling tests) were compared on two widely grown Syrian barley cultivars: Arabi Aswad (AS) and Arabi Abiad (AB). On AB, inoculation with FHB species resulted in
a significantly shorter latent period and larger lesion length of detached leaf inoculation, more standardized area under disease progress curve (AUDPCstandard) of modified Petridish
inoculation and a higher percentage of infected seedlings of pin-point inoculation than on AS. The latent period of AB was 14.89% less than AS, lesion length of AS was 6.01%
less than AB, AUDPCstandard of AS was 17.07% less than AB and the percentage of infected seedlings of AS was 4.87% less than AB. Inoculation with FHB species resulted in no significant
differences in the other five components measured: incubation period of detached leaf inoculation, germination rate reduction and coleoptile length reduction of modified Petridish
inoculation, percentage of infected seedlings of foliar-spraying inoculation and lesion length of clip-dipping inoculation. AS was more resistant to in vitro FHB infection than AB.
The latent period and AUDPCstandard recorded the highest values compared with the lowest values for lesion length and percentage of infected seedlings. It seems that measurement of
the latent period and AUDPCstandard may be useful in identifying barley cultivars which are highly susceptible or resistant to FHB at early stages.
The aim of the present work was to evaluate the selectivity of nicosulfuron, alone and in
combinations, applied in post-emergence (V4) of glyphosate and sulfonylurea tolerant
(RR/STS) soybean. The experiments were conducted in 2015/16 and 2016/17, in Piracicaba
– state of São Paulo (SP). In 2016/17, the experiment was also conducted in Palotina – state
of Paraná (PR). The experiment was a randomized block design, with four repetitions and
16 treatments, with combinations of nicosulfuron, glyphosate, chlorimuron, sulfometuron
and cloransulam, applied alone or in tank mixture. Crop injury and variables related to
agronomic performance were evaluated. Data were subjected to analysis of variance and
treatment means were compared by the Tukey test. The results obtained are significant
in the positioning of herbicides in RR/STS soybean, since in the five experiments, all the
treatments were selective, except for glyphosate + sulfometuron which reduced the yield of
a cultivar (CD 2630 RR/STS) in the 2015/16 season.
Control failure of pests and selectivity of insecticides to beneficial arthropods are key data
for the implementation of Integrated Pest Management (IPM) programs. Therefore, the aim
of this study was to assess the control failure likelihood of Plutella xylostella and the physiological
selectivity active ingredients to parasitoid Oomyzus sokolowskii (Hymenoptera:
Eulophidae) and to predators Polybia scutellaris (Hymenoptera: Vespidae) and Lasiochilus
sp. (Hemiptera: Anthocoridae). In bioassays, P. xylostella larvae and O. sokolowskii,
P. scutellaris and Lasiochilus sp. adults were used. Concentration-mortality curves of six
insecticides for P. xylostella were established. These curves were used to estimate the mortality
of P. xylostella at the recommended concentration, in order to check a control failure
of insecticides to this pest. Furthermore, the lethal concentration for 90% of populations
(LC90) and the half of LC90 were used in bioassays with the natural enemies to determine
the selectivity of these insects to insecticides. All tested insecticides showed control failure
to P. xylostella, indicated by high LC90 and low estimated mortalities (less than 80%). The
cartap insecticide was selective in half of LC90 to Lasiochilus sp. and moderately selective in
LC90 and the half of LC90, to Lasiochilus sp. and P. scutellaris, respectively. Deltamethrin was
moderately selective in the half of LC90 to predator Lasiochilus sp. Cartap, carbaryl, and deltamethrin
reduced the mortality of Lasiochilus sp. in the half LC90. The results also showed
that the insecticides methamidophos, carbaryl, parathion methyl and permethrin were not
selective to any of the tested natural enemies. The role of insecticides in IPM systems of
Brassica crops is discussed based on their control failures to P. xylostella and selectivity to
their natural enemies.
In August 2016, tomato plants grown during a hot, wet summer with heavy soil flooding, displaying symptoms of wilting, dead plant, root rot with crown and stem rot, at Beni Suef
and Fayoum governorates were examined. A number of 16 fungal isolates were isolated from tomato plants displaying the above symptoms. These isolates were classified as belonging
to six species, namely: Alternaria solani, Chaetomium globosum, Fusarium solani, Fusarium oxysporum, Pythium spp. and Rhizoctonia solani. Isolates of Pythium spp. were
prevalent and were found to be more pathogenic than the other fungal isolates. This species causes damping-off, root rot, sudden death, stem rot and fruit rot. The pathogen was
identified as Pythium aphanidermatum based on morphological, cultural, and molecular characteristics. Biogenic silver nanoparticles (AgNPs) were produced using the F. oxysporum
strain and characterized by transmission electron microscopy (TEM). The size of these spherical particles ranged from 10 to 30 nm. In vitro, biogenic AgNPs showed antifungal
activity against P. aphanidermatum. In greenhouse and field experiments, AgNPs treatment significantly reduced the incidence of dead tomato plants due to root rot caused by
P. aphanidermatum compared to the control. All of the investigated treatments were effective and the treatment of root dipping plus soil drenching was the most effective. To the
best of our knowledge, this study describes P. aphanidermatum on tomato in Egypt for the first time. Also, biogenic AgNPs could be used for controlling root rot disease caused by
this pathogen.
Severe leaf spot disease was observed on Aloe vera plants in the winters of 2011 and 2012
during a survey of various nurseries of Gwalior, India. Irregular, sunken, dark creamish
brown spots having reddish brown margin were noticed on both surfaces of the leaves. The
causal organism was consistently isolated from symptomatic leaves on potato dextrose agar
media (PDA). A total 59 isolates of fungi were recovered from diseased A. vera leaves, and
37 isolates were identified as belonging to the genus Fusarium. On the basis of morphological
characteristics and internal transcribed spacer (ITS) region of rDNA amplified using
the primers ITS4/ITS5 the pathogen was identified as Fusarium proliferatum (Matsushima)
Nirenberg and pathogenicity of the isolate was confirmed by using Koch’s postulates. To
the best of our knowledge, this is the first report of leaf spot disease caused by Fusarium
proliferatum on A. vera plants in India.
Water samples were collected from irrigation ditches and drainage canals surrounding
fields in southern Greater Poland. Initially, the samples were subjected to low and highspeed
centrifugation and obtained pellets were used to perform biological assays. Viral
identification involved biological, electron microscopic as well as molecular methods. The
occurrence of Tobacco mosaic virus (TMV) and Tomato mosaic virus (ToMV) was demonstrated
in 12 of the 17 examined water sources. The molecular analysis results showed TMV
and ToMV co-infections in the analysed water samples. To our knowledge, this is the first
report of tobamoviruses being found in environmental water in Poland.
Our research provides novel information concerning the insecticidal activity of Brassica alba mustard oil applied to the intestinal tract via insects’ diet against pests from the order
Lepidoptera: Cydia pomonella, Dendrolimus pini, and Spodoptera exigua. The LC50 value of
the oil against C. pomonella was 0.422 mg ⋅ ml–1. The LC50 of the plant oil against D. pini was
11.74 mg ⋅ ml–1. The LC50 of the botanical product against S. exigua was 11.66 mg ⋅ ml–1. The
plant substance was the most active against C. pomonella in comparison with D. pini and
S. exigua. The LC50 values of the oil against D. pini and S. exigua were similar. The plant oil
exhibited high insecticidal activity against pests from the order Lepidoptera and may prove
to be an effective biopesticide.
Potato virus Y (PVY) is one of the most destructive viruses infecting potato in Egypt and worldwide. Recent research has shown that a necrotic PVY-NTN strain is infecting potato
in Upper Egypt. Chemical control is not effective to control this viral pathogen. An alternative to control PVY infecting potato is using a mild PVY strain to elicit systemic cross
protection in potato plants against infection with a severe necrotic strain of PVY. Results of this study showed that a PVY necrotic strain produced a significant lesser number of local
lesions on diagnostic plants (Robinia pseudoacacia L.) when these plants were treated first with a mild PVY strain. Data obtained from greenhouse and field experiments indicated
that treatment of potato plants (variety Burna) with a mild PVY strain significantly protected potato from infection with a severe necrotic PVY strain, and resulted in a significant increase
in tuber yield compared with infected plants without prior treatment with a mild PVY strain. The highest increase in potato tuber yield was obtained when potato plants were
inoculated with a mild PVY strain 3 days before challenging with the severe necrotic PVY strain. This study proved that using a mild strain of PVY can significantly protect potato
plants from infection with a severe strain of this virus under both greenhouse and field conditions and can present a potential method to reduce losses due to infection of this virus
in Assiut governorate and Upper Egypt.
Biological control of plant diseases is strongly emerging as an effective alternative to the use
of chemical pesticides and fungicides. Stress tolerance is an important attribute in the selection
of bacteria for the development of microbial inoculants. Fourteen salt-tolerant bacteria
showing different morphological features isolated from the rhizosphere of maize were
evaluated for different plant growth-promoting activities. All isolates showed auxin production
ranging from 5 to 24 μg ⋅ ml–1 after 48 h incubation in tryptophan supplemented
media. Phosphate solubilization ranged from 15 to 419 μg ⋅ ml–1. 1-aminocycloproprane-
1-carboxylate (ACC) deaminase activity was shown by 6 isolates, ammonia production by
9 isolates, siderophore production by 8 isolates while HCN production by 4 isolates. Four
bacterial isolates with all plant growth-promoting properties also showed strong antagonistic
activities against Fusarium oxysporum, F. verticillioides, Curvularia lunata and Alternaria
alternata and abiotic stress tolerance against salinity, temperature, pH and calcium
salts. Two selected bacterial isolates significantly enhanced the growth of pea and maize test
plants under greenhouse conditions. The bacterial isolate M1B2, which showed the highest
growth promotion of test plants, was identified as Bacillus sp. based on phenotypic and 16S
rDNA gene sequencing. The results indicated that Bacillus sp. M1B2 is a potential candidate
for the development of microbial inoculants in stressful environments.
The response of the Mi-1 gene to different densities of Meloidogyne incognita race 2 was
investigated under controlled conditions. Susceptible and resistant tomato seedlings were
inoculated with 25, 50, 100, 200, 400, 1000, 2000, 5000 and 10000 second-stage juveniles
of M. incognita. Plants were uprooted 8 weeks after inoculation and the numbers of
egg masses and galls on the roots, and second-stage juveniles in 100 g soil per pot were
counted. In susceptible plants, there was a correlation between the number of egg masses
on roots until 2000 J2 inoculum densities. In resistant plants, when inoculum densities
increased, the number of egg masses and galls also increased. The reproduction factor
ratio was >1 in the susceptible plant and <1 in the resistant plant. The data showed that
the 5000 J2 inoculum was a critical limit, and 10000 J2s were above threshold for resistant
plants. The data indicate that densities of M. incognita can seriously affect the performance
of the Mi-1 gene.