Molecular Characterization of Penicillium expansum Isolated from Grapes and its Management by Leaf Extract of Chenopodium murale

Penicillium expansum Link causes an economically important postharvest blue mold disease in a number of fruits and vegetables. In the present study, this fungus was isolated from rotted grapes and identified on morphological basis. Identification of the pathogen was further confirmed on molecular basis by using four different primer pairs namely ITS, β-tubulin, CMD and CF under accession numbers MN752155, MN787831, MN787832 and MN787833, respectively. Leaf extract of Chenopodium murale was assessed for its potential to control in vitro growth of P. expansum. For this purpose, leaves were extracted in methanol and after evaporation of the solvent, the resulting extract was successively partitioned with n-hexane, chloroform, ethyl acetate and n-butanol followed by antifungal bioassays with different concentrations (1.562 to 200 mg mL-1) each organic solvent fraction. Although all the fractions variably controlled the fungal pathogen, however, n-butanol fraction showed the highest antifungal activity causing 45–86% reduction in biomass of the pathogen. Ethyl acetate fraction was also highly antifungal and reduced fungal biomass by 44–81%. Chloroform and n-hexane fractions were comparatively less effective and reduced biomass of P. expansum by 30–72% and 11–44%, respectively. This study concludes that ethyl acetate and n-butanol fractions are highly antifungal in nature against P. expansum.

Cytological, Histological and Molecular Characterization of Two Isolates of Cucumber Mosaic Virus (CMV) in Egypt

Two isolates of Cucumber mosaic virus (CMV), CMV-wild tobacco (from Alexandria governorate) and CMV-cucumber (from Kafr El-Sheikh governorate) were investigated in this study. Cytological studies on epidermal strips of Nicotiana glutinosa leaves separately infected with each isolate revealed the presence of viral crystalline inclusion bodies within the infected cells. Electron microscopy of ultrathin sections of CMV infected N. glutinosa leaves showed significant alterations in the shape and internal structure of chloroplasts. The cell wall had serrated edges in infected cells but was more severe in cells infected with CMV-wild tobacco isolate compared to those infected with CMV-cucumber isolate. CMV-cucumber isolate was partially purified from systemically infected leaves of N. glutinosa. The ratio A260/ 280 was 1.0 and the concentration of the virus in the preparation was estimated using an extinction coefficient of E260nm0.1%, 1cm = 5. Yield of purified virus was about 2.8 mg/100 g fresh weight of infected N. glutinosa leaves. Electron microscopy of the purified preparation of CMV showed the presence of numerous spherical particles with a mean particle diameter of 28 nm. Amplified real-time reverse transcription-polymerase chain reaction (qRT-PCR) product of coat protein gene of each isolate was purified and sequenced. Sequences of both isolates had been submitted to GenBank Database and ware assigned accession number (LT669766) for CMV-cucumber isolate and (LT706517) for CMV-wild tobacco isolate. The sequences were edited using Chromas Pro. Version 1.34 software and compared with previously subgrouping of 27 isolates of the virus retrieved from the GenBank database. Both CMV-wild tobacco and CMV-cucumber isolates were closely related to the isolate with the accession number AJ585086 with a similarity of 97.07% and 98.54%, respectively, suggesting that the two isolates belong to subgroup II. According to the available literature, this is the first report in Egypt where CMV isolates belonging to subgroup II have been obtained

Botryosphaeria Tree Fungal Pathogens and Their Diversity

The genus Botryosphaeria identified in 1863 as saprophytes of dead tissue of woody plants have been described as pathogens of economically important plantation trees in agriculture and native forests. The genus is a species-rich, worldwide distributed occurring on diverse host ranges. Species of the Botryosphaeria are reported as the pathogens of many plantation trees, including species of Acacia, Eucalyptus, and Pinus causing canker and rapid dieback diseases which often end up in death. Botryosphaeria fungal pathogens have cross pathogenicity on different host tree species which enables them important and focus area of research. The taxonomy of Botryosphaeria spp. have been under research, identification of these fungi has generally been based on morphological features of the anamorph that usually seen under the microscope. Characters that are used to classify genera in the Botryosphaeria have mostly relied on the macroscopic features of the ascospores and the conidial features. Currently, molecular techniques such as DNA sequencing involving amplification of ITS region are important for exact identification of the genera to species level. Recent molecular, phylogenetic and morphological findings showed that order Botryosphaeriales is diverse consisting nine families and 33 genera with 23 genera only in the family Botryosphaeriaceae. Botryosphaeria spp. are naturally endophytes associated with tree plants known to cause monocyclic or polycyclic diseases resulting in polyetic epidemics. The factor that makes plants more prone to Botryosphaeria fungal species is assumed to be stress or wounding associated with the host plants. Global climate change driven drought is an important factor that initiate stress resulting in nutrient deficiencies. Botryosphaeria fungal tree diseases can be best managed by ensuring plants are in optimal health through appropriate integration of cultural, silvicultural and fungicidal applications to effectively prevent and control the diseases.

Optimization of Culture Conditions for Mycelial Growth and Sporulation of Myrothecium roridum

Culture and nutrition conditions of Myrothecium roridum Tode were optimized by conducting a series of interlined experiments on a growth medium, temperature, pH, and photoperiod. In contrast, relation of culture age with virulence was measured by fungal development on young leaves of bitter gourd. The physiological response was measured on colony radial growth and spore production. Among the six test growth media, i.e., nutrient agar (NA), potato dextrose agar (PDA), Czapek-Dox agar (CDA), glucose agar (GA), malt extract agar (MEA), and bitter gourd agar (BGA), the highest radial growth (77 mm) and the highest number of spores (239 × 106 spores/ml) were observed on PDA. Incubation temperature was evaluated between a range of 15-40 °C, and the highest colony growth (87 mm) was observed at 30 °C, whereas the highest spore production (315 × 106 spores/ml) was at 35 °C. Different pH levels, i.e., 5, 5.5, 6, 6.5, 7, and 7.5, were optimized, and the highest colony growth (87 mm) and spore production (504 × 106 spores/ml) was recorded at pH 5.0. Impact of photoperiod was studied, and the highest mycelial growth (88 mm) and maximum spore production (524 × 106 spores/ml) was observed at 16/8 h alternate light and dark period. It was concluded that the optimum conditions for mycelia growth and spore production was pH 5.0-6.0 and at 30 ± 2 °C in PDA with 16/8 h alternate light and dark photoperiod.

Combat Ug99-Current scenario

The yield potential of wheat crop is not achieved abundantly because of disease pressure. One of the most destructive of such diseases is stem rust (SR). SR caused by Puccinia graminis f. sp. tritici (Pgt), had been controlled successfully during three decades throughout the world with deployment of semi-dwarf resistant cultivars in the last half of previous century. During 1999 appearance and dispersion of stem rust race Ug-99 in Uganda (a virulent race against Sr31) created an alarming situation worldwide. Widespread germplasm was protected by gene Sr31 found susceptible to this terrible strain as the gene was protecting 80% wheat lines cultivated throughout planet. The emergence of the Ug99 race of stem rust in Africa and the Middle East together with the appearance of new strains in Europe catalyzed a main effort to recognize sources of stem rust resistance genes against new virulent strains and incorporate these genes into wheat lines. Scientific community addressed the dilemma in time and efforts did not go waste. Worldwide concern regarding the danger to global wheat production caused by Ug99 led to breeding wheat for durable resistance against disease and achieved considerably. This success is attributed to team work of experts and serves as an example for research workers in future. However, the continued emergence of stem rust variants that overcome new resistance genes, demands an amplified emphasis on pathogen evolution and virulence mechanisms. A major role for BGRI is to keep ‘the eye on the ball’ with regard to all these aspects. This article enables us to design strategy to tackle a situation which appears without alarm but in this case intellectuals coordinated each other and solution became possible. The same principle does not apply in plant pathology but in Human pathology and Veterinary pathology.

Brown Spot and Stalk Rot Diseases of Maize (Zea Mays) and Susceptibility of Two Varieties to Physoderma Maydis in Far North Cameroon

Corn (Zea mays L.) is one of the most widely grown cereals in the world. However, in Cameroon, particularly in the Far North Region, yields remain low because of diseases increasing due to farming practices and climate change. This work aimed to characterize Brown Spot and Stalk Rot of corn and evaluate the susceptibility of two maize varieties to Physoderma maydis in field conditions. Two maize varieties, CMS9015, and CMS8704 were evaluated in a randomized block design. Disease symptoms were observed and described using identification keys. Microscopic characteristics of pathogens were performed using a microscope. Incidence, severity, and areas under disease curve progress (AUIPC and AUSiPC) were calculated. Brown spot occurred 3 or 4 weeks after sowing (WAS) at the growing stage in CMS8704 variety first, and stalk rot 7 WAS. Brown spot appeared in leaves and is characterized by oval yellowish spots in the leaf blade and brownish spots in the midrid. Stalk rot infects stem nodes and is characterized by brownish spots, leading to the broken stem. The incidence of brown spot increased with time and environmental conditions (rainfall). The highest incidence of Physoderma Brown Spot was recorded with CMS8704 variety 53.06 % against 51.72 % with CMS9015. Severity was respectively 54.40 % and 47.12 % with CMS8704 and CMS9015. The incidence and severity of stalk rot were almost identical in both varieties. AUIPC of PBS and PSR was higher in CMS9015 than in CMS 8704, 63 DAS. PBS and PSR infect maize production, and both varieties are susceptible to P. maydis.

Screening of Okra Varieties for Resistance to Okra Yellow Vein Mosaic Disease under Field Conditions

Okra (Abelmoschus esculentus L.) can contract okra yellow vein mosaic disease (OYVMD) caused by Bhendi yellow vein mosaic virus (genus: Begomovirus and family: Geminiviridae), vectored by whitefly (Bemisia tabaci). This study was carried out to screen okra varieties for resistance to OYVMD and to determine the correlation of vector population with the severity of the disease. Six varieties namely, Tulsi, Durgah, Sabz Pari, Sarahariya, Ramaan Kirshna and Pooja were grown under field conditions at localities of Shahpur, Tando Adam and Peer Kathi during rabi (winter cropping) and kharif (summer cropping) seasons during 2016 and 2017, respectively. The first incidence percent of the disease was recorded in the 8th week during rabi and the 6th week during kharif growing season. The Tulsi variety remained disease-free during both growing seasons. A significantly lower disease incidence % was recorded in Sabz Pari (29.32%) and Sarahariya (30.09%) varieties than Durgah, Ramaan Kirshna and Pooja during the rabi growing season. Both varieties were disease-free during the kharif season. There was remarkable variation in disease severity recorded in okra varieties at different trials during rabi and kharif seasons using a 0-6 rating scale (i.e., 0 = The disease-free plants, 1 = 1-10 % vein clearing, 2 = 11-25 % vein yellowing of small leaves , 3 = 26-50 % yellow network on some leaves, 4 = 51-60 % yellow network on all leaves, 5 = 60-70 % complete leaves turn yellow or cream color and 6 = 70 % plant stunted, deformed and small fruit and whole plants becomes colorless). Whitefly appeared in the 5th week during the rabi and 4th week during the kharif growing seasons. Vector population during the rabi growing season was significantly higher than in the kharif season. There was a nonsignificant relationship between disease severity and whitefly population in Ramaan Kirshna, Sarahariya, and Sabz Pari varieties. The disease severity in the Pooja variety showed a significant relationship with vector population, but only in the Tando Adam trial (R2= 0.7455, P= 0.0084), whereas the Durgah variety showed a significant relationship between disease severity and vector population in Shahpur (R2= 0.6615, P= 0.0267) and Tando Adam trials (R2= 0.8235, P= 0.0018). The same variety showed a nonsignificant relationship between disease severity and vector population in the Peer Kathi trial. It is concluded that Sabz Pari and Tulsi varieties are resistant to the disease

Impact of Farm Management Practices on Downy Mildew Disease of Cucumber in High Tunnels

Downy mildew of cucumber caused by Pseudoperonospora cubensisis is a serious threat to the cucurbits production in high tunnels. In this study, the disease incidence and severity were recorded from nine high tunnel farms, located at Vehari District, Pakistan. The results revealed that downy mildew incidence was ranged from 24 to 80%. The disease development was correlated with plant genotype, sowing time, commonly used fungicides, and plant growth stages. "Kaan" was the most resistant while "Yayla" was the highly susceptible plant genotype against the disease. Cucumber sowing at mid-November showed significantly less disease over early and late sowing. Flowering was the most vulnerable stage of plants for disease development. ‘Champion’ (Copper hydroxide) followed by ‘Score’ (Difenoconazole) fungicides reduced the disease to 55% and 43%, respectively, which increased the yield 8-15 %. We conclude that the use of resistant genotype “Kaan”, protectant fungicide ‘Champion’ and appropriate sowing time Mid-November may reduce the disease incidence appreciably in high tunnels.

Bacterial Leaf Blight (BLB) Disease Incidence and Severity in Basmati and Non-Basmati Rice Growing Areas of Punjab, Pakistan

Bacterial leaf blight (BLB) is one of the most damaging diseases of rice in Asia and annually incurring significant yield loss to rice production in Pakistan. Management of disease required the information of BLB incidence and severity in basmati and non-basmati rice areas. The current study presented the observation of BLB disease incidence and severity in 19 major rice growing districts of Punjab. In this study, 9 Basmati growing and 10 non-basmati rice growing districts were surveyed from September to October in 2009, 2010, 2012, and 2013. Rice fields near to roadside, research stations and adjoining farmer fields were preferred for the survey. Each halt was after 10 km on the route depending upon the crop intensity. The general appearance of the field was observed for the absence or presence of BLB disease symptoms. The incidence of BLB was recorded as a percentage of plants infected in a field on a visual basis. For each field, 4 plants were observed at 5 points/hill along the diagonal transect for disease symptoms. The data of severity was recorded as the percentage of leaf area infected out of the total leaf area. Among the districts with basmati rice, the mean incidence of BLB was maximum in Gujranwala, Sheikhupura and Hafizabad followed by Mandi Bahauddin and Gujrat. A similar pattern of disease severity was observed in the basmati rice belt with maximum BLB mean severity in Gujranwala, Sheikhupura and Hafizabad having most of the field with a severity scale of 9. Overall, the disease trend showed that both the incidence and the severity were higher in 2010, 2012 and 2013 in the basmati rice belt. The ten districts, comprising of mostly non-basmati rice varieties showed relatively less BLB incidence and severity compared to basmati rice districts. The maximum mean incidence of 20-25% was observed in Faisalabad, Chiniot and Sahiwal in at least one year of the rice season. None of the field with BLB disease symptoms was observed in districts Okara, Khanewal and Bahawalpur during the 2012 and 2013 rice season. Maximum disease severity of mean value 3 was observed in Sahiwal during 2009 while the rest of the districts showed less than 2 mean severity during all rice growing season. Overall, in non-basmati rice districts, no specific trend of disease incidence and severity was apparent, however, the disease was present in very low magnitude or absent during the surveyed years. The information from this study is helpful in the selection of variety for basmati and non-basmati districts of Punjab and the adoption of appropriate disease management strategies.

Phytonematodes Associating Wheat in North Eastern Egypt and Pathogenicity of Heterodera avenae on Certain Cereal Cultivars

A survey of plant-parasitic nematodes (PPNs) associating wheat in Ismailia governorate, northeastern Egypt was carried-out during 2016/2017 and 2017/2018 growing seasons. Results showed that seven PPNs genera and/or species were found associating wheat roots. These genera and/or species, in descending order of frequency, were: Tylenchorhynchus spp. (14%), Helicotylenchus spp. (10%), Heterodera avenae (8%), Ditylenchus spp. (5%), Meloidogyne javanica (4%), Pratylenchus spp. and Xiphinema spp. (3%, each). Two screening pot experiments, in two consecutive growing seasons (2017/17 and 2017/18) were carried out to determine the host suitability of 15 Egyptian cereal cultivars including bread wheat (Triticum aestivum), barley (Hordeum vulgare) and oat (Avena sativa) to the cereal cyst nematode, Heterodera avenae, under greenhouse conditions. Results of both experiments were very similar and showed that oat cv. Baladi and wheat cv. Giza 171 were highly susceptible, while wheat cvs. Masr 1, Masr 2, Masr 3, Sakha 95, Seds 1, Seds 12, and Shandawel 1 were susceptible. However, barley cvs. Giza 135, Giza 123, Giza 124, and Giza 125 were found to be moderately resistant to the tested nematode. H. avenae suppressed (P ≤ 0.05) the dry weights of roots, shoots and spikes of the inoculated plants, compared to the non-inoculated checks. Another greenhouse pot experiment was carried out during the wheat-growing season 2018/2019 to determine the effect of different initial population densities (Pi) of H. avenae on the growth parameters of wheat cv. Giza 171 and on nematode reproduction. Results showed that as the nematode Pi increased, both the wheat growth parameters and the nematode reproduction factor (Rf) were decreased (P ≤ 0.05).