Natural Infection In Field Research Articles

Screening of soybean [Glycine max (L.) merrill] lines for reaction to natural field infection and resistant against bacteria foliar diseases

The production of Soybean in Nigeria is still inadequate due to the menace of pests and diseases. The current study was conducted to screen the performance of nineteen newly developed soybean lines that were infected naturally with bacterial diseases, identify promising line(s) with high yield potential and resistance against the diseases. Symptoms of soybean foliar diseases were accessed from the 4-12 week after planting, the resistance level of selected lines was also determined and bacteria isolate were culture and identify through morphological and biochemical tests. Four Bacteria species (Pseudomonas syringae, Xanthomonas spp, Clavibacter michiganensis and Bacillus subtilis) were isolated and identified from disease soybean leaf in this study. Whereas based on the pathogenicity test only two were pathogenic and cause soybean foliar disease (P. syringae and X. spp). Identified soybean lines differed significantly [p ≤ 0.05] in disease incidence and severity for both diseases. TGx 1990-57F, TGx 1990-55F were moderately resistant to bacterial blight and bacterial pustules. The study confirms that bacteria blight and pustule were present in the study area. It is therefore, recommended that the lines identified as moderately resistant to both diseases may help in future studies and evaluation in local hotspots.

Worldwide transmission and infection risk of mosquito vectors of West Nile, St. Louis encephalitis, Usutu and Japanese encephalitis viruses: a systematic review

The increasing trend of mosquito-borne pathogens demands more accurate global estimations of infection and transmission risks between mosquitoes. Here, we systematically review field and laboratory studies to assess the natural field infection and experimental laboratory transmission risk in Culex mosquitoes. We studied four worldwide flaviviruses: West Nile, Usutu, Japanese encephalitis, and St. Louis encephalitis, belonging to the Japanese encephalitis Serocomplex (JES). The PRISMA statement was carried out for both approaches. The Transmission-Infection Risk of the diverse mosquito species for the different viruses was estimated through seven variables. We considered 130 and 95 articles for field and experimental approach, respectively. We identified 30 species naturally infected, and 23 species capable to transmit some of the four flaviviruses. For the JES, the highest Transmission-Infection Risk estimate was recorded in Culex quinquefasciatus (North America). The maximum Infection-Transmission Risk values for West Nile was Culex restuans, for Usutu it was Culex pipiens (Europe), for St. Louis encephalitis Culex quinquefasciatus (North America), and for Japanese encephalitis Culex gelidus (Oceania). We conclude that on a worldwide scale, a combination of field and experimental data offers a better way of understanding natural infection and transmission risks between mosquito populations.

The response to crop health and productivity of field pea (Pisum sativum L.) at different growing conditions

ABSTRACT With increasing the area of legumes one of the most possible risks for productivity limitation is diseases. The research on the response to diseases and productivity of field peas was carried out during 2018–2020. The six cultivars and breeding lines were grown at two different infection levels: at natural field infection and under disease control using seed treatment and foliar fungicides. The main disease in field peas during the research year was Ascochyta blight at different intensites depending on year, cultivar/breeding line and disease control efficacy. Dominating pathogenic fungus D. pisi on harvested grains prevailed. Pea grain yield was significantly affected by cultivar/breeding line, experiments year and growing conditions. The highest yield difference between growing conditions (natural field infection and under disease control) was recorded in 2020 when Ascochyta blight and Grey mould gave the most severe attack. This finding illustrates the importance to eliminate one of the most important limiting factors for productivity – severe diseases. Future research on the forecast system of Ascochyta blight and other field pea diseases infection risk is needed. The response of cultivar/breeding line to weather conditions was established in this research as well. Tested breeding lines showed higher drought stress tolerance compared with commercial cultivars. More focus on environment stress-resistant cultivars is needed.

Impact of humic acid, vigamax and potassium phosphate on control of cercospora leaf spot disease

Foliar spray with commercial nutrients, humic acid, vigamax, and potassium phosphate dibasic of sugar beet plants, was evaluated against leaf spot disease incited by Cercospora beticola. Significant reduction of Cercospora leaf spot (CLS) disease severity was reported under natural field infection. Spraying with humic acid (at 20.0 g/l) and mix treatments resulted in the lowest values of disease severity during the two seasons (2018/2019 and 2019/2020) and the highest efficiency against the disease (76.41-89.36%). Retarding of CLS and the reduction of disease severity due to nutrient applications correlated to yield increment. PR1 (SA responsive gene) and LOX2 (JA biosynthesis) genes expression levels were induced and increased in the sugar beet leaves after treatment applications. The nutrients have positive impacts on both sugar beet yield and health. In conclusion, humic acid, vigamax, and potassium phosphate dibasic could be involved in management strategies against Cercospora leaf spot.

Assessment of Cherry Cultivars for Resistance to Leaf Spot Caused by Passalora circumscissa

Cherry leaf spot (CLS), caused by Passalora circumscissa, is a fungal disease that can cause decreased fruit quality and yield via inconsistent ripening or premature defoliation. Germplasm resource screening is the most reliable approach to disease control for economically important crops. However, information is limited in China about the resistance of cherry cultivars to leaf spot caused by P. circumscissa. The aim of this study was to identify the resistance levels of cherry cultivars. Fifty-two cherry cultivars, including 40 Prunus avium, four Prunus pseudocerasus, and eight Prunus cerasus cultivars were collected for resistance level characterization. These specimens were then used to screen for P. circumscissa resistance through both detached leaf assays and natural field infection. Significant differences in the disease index (DI) value among test cultivars, ranging from 5.7 (resistant) to 53.7 (highly susceptible) and 6.5 (resistant) to 53.2 (highly susceptible), were observed under the controlled and field conditions respectively. Correlation coefficients between DI in pairs of years were highly significant (0.77–0.86). Although resistance rankings for cherry cultivars between screening methods were variable, the resistance levels of 52 cultivars evaluated under controlled and field condition were comparable with a correlation coefficient of 0.70 (P < 0.01). The results indicated that, across cherry cultivars, responses to CLS in the detached leaf assay corresponded well to responses under field conditions. A detached leaf assay was developed as a complementary method to facilitate the screening of cherry cultivars for resistance to leaf spot caused by P. circumscissa. Our study provides a theoretical basis for cherry disease resistance breeding and rational cultivar utilization.

The effectiveness of H9N2 vaccination in commercial broilers flocks under natural field infection

The effectiveness of H9N2 vaccination in commercial broilers flocks under natural field infection

The effectiveness of H9N2 vaccination in commercial broilers flocks under natural field infection

The effectiveness of H9N2 vaccination in commercial broilers flocks under natural field infection

The effectiveness of H9N2 vaccination in commercial broilers flocks under natural field infection

The effectiveness of H9N2 vaccination in commercial broilers flocks under natural field infection

Assessment of Resistance to Cereal Cyst Nematode, Stripe Rust, and Powdery Mildew in Wheat-Thinopyrum intermedium Derivatives and Their Chromosome Composition.

Wide hybridization between wheat and wild relatives such as Thinopyrum intermedium is important for broadening genetic diversity and improving disease resistance in wheat. We developed 30 wheat-Th. intermedium derivatives. Here, we report assessments of their resistance to different pathogens including cereal cyst nematode (CCN; Heterodera spp.), Puccinia striiformis f. tritici Erikss. causing stripe rust, and Blumeria graminis f. tritici (DC.) Speer inciting powdery mildew. Under natural field infection, all the wheat-Th. intermedium lines were resistant to at least one of the pathogens, and four lines were resistant to multiple pathogens. Twenty-nine of 30 tested lines exhibited resistance to H. avenae, a dominant CCN species in wheat fields. Twenty-four lines were resistant to H. filipjevi, an emerging threat to wheat production. Tests of phenotypic responses in the naturally infected field nurseries identified six stripe rust-resistant lines and 13 powdery mildew-resistant lines. Mitotic observation demonstrated that these newly developed wheat-Th. intermedium derivatives included not only octoploid but also chromosome addition, substitution, and translocation lines. Chromosome compositions of the four lines resistant to multiple pathogens were analyzed by genomic in situ hybridization and fluorescence in situ hybridization. The octoploid lines Zhong 10-68 and Zhong 10-117 carried both intact Th. intermedium chromosomes and translocated chromosomes. Line Zhong 10-149 had 42 wheat chromosomes and two wheat ditelosomes plus a pair of T3BS·J translocated chromosomes. Line Zhong 10-160 carried 41 wheat chromosomes plus one pair of the J genome chromosomes of Th. intermedium. The multiple disease-resistant wheat-Th. intermedium derivatives, especially lines with chromosome counts close to that of common wheat, provide valuable materials for wheat resistance breeding programs.

Screening Luffa germplasm and advanced breeding lines for resistance to Tomato leaf curl New Delhi virus

The two cultivated Luffa species can be severely infected by Tomato leaf curl New Delhi virus (ToLCNDV) with up to 100% yield loss. Here, 52 Luffa genotypes were screened for ToLCNDV resistance after natural field infection. Mean vulnerability index (VI) ranged from 0.00 to 75.33; genotypes IIHR-137 and IIHR-138 had no symptoms (VI 0), 16 genotypes were resistant (VI 0–25), 15 were moderately resistant (VI 26–50), and 19 were moderate to susceptible (VI > 50). Ten of the most resistant genotypes and five susceptible checks were then challenge-inoculated using whiteflies or sap in an insect-proof net house; only IIHR-137 [L. cylindrica (L.) Roem.] was symptomless (VI 0.00), and 3–5% of plants of IIHR-138 [L. cylindrica (L.) Roem.] and IIHR-Sel-1 [L. acutangula (L.) Roxb.] had only mild symptoms; genotype Arka Prasan was most susceptible (VI 80.96). Asymptomatic plants were confirmed as infected using polymerase chain reaction. Susceptible genotypes rapidly developed leaf curling, then a severe mosaic 10 days post-inoculation. The resistant inbred lines identified are good candidates for a breeding program for ToLCNDV-resistant cultivars.

Potential Adoption of the F2 Generation of Some TYLCV-Resistant Tomato Hybrids in Commercial Production under Natural Field Infection

The economic feasibility of using the tomato yellow leaf curl virus (TYLCV) resistant F1 tomato hybrids (Solanum lycopersicum L.) may be improved with the possibility of using their F2 generation in commercial production. Hence, this study was performed to evaluate the F1 and F2 generations of 15 TYLCV resistant/tolerant commercial tomato hybrids during the 2018 and 2019 fall season to identify the best hybrids and F2 populations for commercial production. Both F1 and F2 populations were evaluated separately for TYLCV resistance, yield, and fruit quality traits. Broad sense heritability (H2b) values of TYLCV-resistance were high, being > 60% in hybrids 186, Goldstone, Rabha, SV0922 and SV8320 in both seasons. F1 and F2 populations of ‘186’, ‘Dania’, ‘PS550’, ‘Rozalina’, ‘SV0922’, ‘SV8320’, and ‘Tyrmes’ had the highest total yield (TY)/plant, low TYLCV disease (TYLCVD) mean scores, acceptable fruit quality traits, and average fruit weight > 80 g. Desirable inbreeding depression (ID) values were observed for TYLCVD-mean score in F2 populations of most evaluated hybrids; for TY/plant in F2 populations of ‘SV3773’ in both seasons, and in populations of ‘186’, ‘448’, ‘Goldstone’, ‘Rabha’, ‘SV8320’ and ‘SV0922’ in the second season. Most hybrids had desirable significant ID values for fruit quality traits. Accordingly, it is concluded that the F2 populations of hybrids 186, SV0922 and SV8320 may be used in commercial tomato production under TYLCV-infection in fall season, as these populations recorded high h2b values for TYLCV-resistance trait and desirable ID for TYLCV-resistance, yield, and fruit quality traits.

INHERITANCE OF ADULT PLANT RESISTANCE TO POWDERY MILDEWIN SOME CROSSES OF BREAD WHEAT

Eight F2 populations of crosses carried out between the resistant cultivar Amigo and 8 susceptible bread wheat cultivars were evaluated to study the inheritance of resistance to powdery mildew (Pm) caused byBlumeria. graminis f.sp . tritici and also to estimate the number and action of genes related to adult plant resistance. The response to powdery mildew disease was studied in a conditioned glasshouse and natural infection in the open field. Individual plants were scored and classified as resistant or susceptible according to a specific scale. The tested local wheat cultivars showed susceptible responses at both seedling and adult stages, while the Amigo cultivar was susceptible at seedling stage and resistant at adult stage. The F2 plants of all tested crosses were susceptible at seedling stage and resistant at the adult stage. Obtained results revealed that the inheritance of resistance is ruled by a single gene in the crosses Amigo/Sids12 and Amigo/Misr2; and by two recessive genes in Amigo/Gemmeiza11 cross. The inheritance of resistance in F2 populations of Amigo/Sakha95, and Amigo/Giza171 crosses is controlled by two dominant genes, while in Amigo/Gemmeiza12, Amigo/Sakha94 and Amigo/Misr1 crosses is conditioned by two incompatible dominant genes. Sakha 95 and Giza171 wheat cultivars were the best and suitable for transferring the adult plant resistance gene Pm17.

Potato plants transformed with the Arabidopsis EF-Tu receptor (EFR) show restricted pathogen colonization and enhanced bacterial wilt resistance under conditions resembling natural field infections

Potato is considered a staple food in the world and its production is limited by the presence of bacterial wilt (bw) disease caused by Ralstonia solanacearum. Host resistance is the most sustainable and cost-effective strategy to manage bw, although resistant commercial potato cultivars are not yet available. Our group incorporated the efr receptor of Arabidopsis thaliana (atefr), which recognizes the elongation factor Tu, preserved in bacteria, triggering an immune response. atefr was tested in two genetic backgrounds: a susceptible commercial cultivar (inia Iporá) and a breeding clone with partial resistance introgressed from Solanum commersonii. In this work, the effect of the atefr receptor on bw resistance was evaluated for the first time, using conditions resembling natural field infection. In addition, the colonization patterns of wild-type and transgenic lines were compared by using luminescent and fluorescent R. solanacearum reporter strains. Both approaches showed a delay and a decrease in the severity of wilting symptoms in the atefr-transformed genotypes. Differential colonization patterns were observed, revealing a higher bacterial development in the non-transformed plants. This atefr effect seems more pronounced in the interspecific breeding line, possibly leading to a more effective activation of the plant immune system.

Incidence and management of <i>Colletotrichum gloeosporioides</i> canker on <i>Jatropha curcas</i> L. in Ibadan, southwestern Nigeria

The Impact of fungal pathogens on man is enormous, stretching from infecting humans to destroying a third of all food crops annually thereby causing economic losses and impacting global poverty. As a result, fungal disease incidence was assessed under natural field infection and data were collected randomly from 12 months old jatropha seedlings with cankers. Colletotrichum spp. isolated from the diseased sampled were interacted with known fungi and bacteria biocontrol agents. The experiment was carried out on completely randomized design (CRD) in the laboratory. Data were analyzed using ANOVA and statistically different means were separated using LSD (p≤0.05). The dual culture interaction proved that all the BCA used, possessed antagonistic potential, and could serve best for prophylactic protection. Plant diseases may be suppressed by the activities of one or more plant-associated microbes hence keeping them in check below threshold levels. This will help to maintain the quality and abundance of food, thereby mitigating hunger. Negative environmental consequences caused by excessive use and misuse of agrochemicals, requires that healthier and costeffective approaches to disease management should be adopted.
 Keywords: Biodiesel; Agrochemicals; Biocontrol agent; Dual culture; Pathogens

Improvement of a RD6 Rice Variety for Blast Resistance and Salt Tolerance through Marker-Assisted Backcrossing

RD6 is one of the most favorable glutinous rice varieties consumed throughout the north and northeast of Thailand because of its aroma and softness. However, blast disease and salt stress cause decreases in both yield quantity and quality during cultivation. Here, gene pyramiding via marker-assisted backcrossing (MAB) using combined blast resistance QTLs (qBl 1, 2, 11, and 12) and Saltol QTL was employed in solving the problem. To pursue our goal, the RD6 introgression line (RGD07005-12-165-1), containing four blast-resistant QTLs, were crossed with the Pokkali salt tolerant variety. Blast resistance evaluation was thoroughly carried out in the fields, from BC2F2:3 to BC4F4, using the upland short-row and natural field infection methods. Additionally, salt tolerance was validated in both greenhouse and field conditions. We found that the RD6 “BC4F4 132-12-61” resulting from our breeding programme successfully resisted blast disease and tolerated salt stress, while it maintained the desirable agronomic traits of the original RD6 variety. This finding may provide a new improved rice variety to overcome blast disease and salt stress in Northeast Thailand.

Characterization of Partial Resistance to Bean Rust Disease caused by Uromyces appendiculatus in Seven Common bean Varieties

Partial resistance (PR) to bean rust (Uromyces appendiculatus) in seven bean varieties was determined through three epidemiological parameters, final rust severity (FRS %), area under disease progress curve (AUDPC) and rate of disease increase (r-value) at adult plant stage under natural infection in open field, and four components of resistance (incubation period, latent periods, infection frequency and Pustule size under artificial inoculation in greenhouse) at seedling stage under artificial inoculation in greenhouse. Resistance parameters under both field and greenhouse conditions were varied significantly among bean varieties tested in different years. Montcalm, Nebraska and Bronco were classified partially resistant varieties with decreasing the amount of rust infection and disease development, whereas Karnak, Giza 6, Paulista and Contender were exhibited fast-rusting varieties based on both open field and greenhouse experiments. The partially resistant varieties had higher amounts of three enzymes catalase (CAT), peroxidase (POX) and polyphenoloxidase (PPO) compared with fast-rusting varieties. High significant correlations (r2) were observed among resistance parameters in both field and greenhouse experiments. Correlation matrix suggests that AUDPC and LP50 were good and more reliable parameters for evaluation and selection for resistance to bean rust.

Molecular and pathological investigation of a natural outbreak of Newcastle disease caused by genotype XVII in White Leghorn chickens

ABSTRACT Newcastle disease (ND) is an infectious viral poultry disease with great economic consequences. In developing countries, outbreaks of ND caused by virulent Newcastle disease virus (NDV) have been identified as a limiting factor to the growth of the poultry industry. Limited reports exist on the pathology of natural field infection caused by NDV genotype XVII in chickens. Here, we present clinical, pathological and molecular investigation of confirmed ND in a 24-week-old layer-type, semi-intensive poultry flock with recorded mortality of over 50%. During PM examination, tissues were harvested for virus isolation, histopathology and immunohistochemistry. Virus isolation was performed in 10-day-old embryonated chicken eggs, and a haemagglutinating agent thereof identified by one-step reverse transcription-polymerase chain reaction (RT–PCR). For the genotyping of the isolate, the full fusion gene was sequenced. Clinical signs observed included general body lethargy, inappetence and greenish diarrhoeic faeces from the cloaca before death with daily mortality exceeding 100 chickens. The pathology was characteristic of a viral haemorrhagic infection, with serosal haemorrhages, mucosal surface erosion and ulceration. In most of the carcasses, the main lesions seen included airsacculitis, meningeal congestion, haemorrhagic oophoritis, pancreatic necrosis, enteritis and faecal matting of the vent. Virus isolation and RT–PCR made a confirmatory diagnosis of ND. Based on the cleavage site motif sequence (112RRQKR/F117), the isolate was identified as a virulent strain with phylogenetic analysis showing clustering in genotype XVII viruses. To the best of the authors’ knowledge, this is the first report describing the pathological findings of a natural outbreak caused by NDV involving viruses of genotype XVII. RESEARCH HIGHLIGHTS First report of a natural outbreak of Newcastle disease in White Yarkon Leghorns. The outbreak was caused by virulent NDV belonging to genotype XVII. Pathology differed slightly from those in experimental studies using SPF and other unvaccinated chickens.

Effects of Treatment with Electrolyzed Oxidizing Water on Postharvest Diseases of Avocado

The present study comprised five trials to investigate the efficacy of postharvest treatment with electrolyzed oxidizing (EO) water on postharvest disease development in avocado. Mature (dry matter 24–34%), hard green fruit cv. Hass (four trials), and cv. Wurtz (one trial) from orchards receiving minimal fungicide sprays were sourced, and subsequently dipped for 30 s in treatment solutions. Fruit were ripened at 23 °C and 65% relative humidity to encourage postharvest disease development, and assessed when ripe for anthracnose and stem end rot (SER), arising from natural field infections and/or the size of lesions resulting from post-treatment inoculation with Colletotrichum siamense. In the case of natural infection, EO water treatment reduced severity of SER disease by 30–75% compared with water treated control fruit in all four trials where it was assessed. Reduction in severity of SER after Graduate A+ fungicide or hypochlorite (NaOCl) bleach treatment ranged from 60–88% or 25–50%, respectively, compared with water controls. Under extremely high anthracnose disease pressure, 20% v/v EO water, NaOCl, as well as Graduate A+ fungicide treatments were mostly ineffective. Treatments in the final trial were applied as overhead sprays in an experimental-scale packing line to simulate commercial conditions. This was the only trial where anthracnose (as well as SER) was significantly reduced in fruit by 20% v/v EO water (12–35%) and Graduate A+ (34%) compared with water control. In two trials with C. siamense-inoculated fruit, anthracnose lesion size was reduced by 68–85%, and 90–100% by 20% v/v EO water and Graduate A+, respectively, compared with water-treated fruit. Fruit firmness and the number of days to ripen were mostly not affected by the treatments. This study demonstrates the potential for electrolyzed oxidizing water to be incorporated into integrated management programs for postharvest diseases of avocado, and possibly other fresh produce.

Evaluation of soybean genotypes for reaction to natural field infection by Cercospora species causing purple seed stain.

Purple seed stain (PSS) of soybean (Glycine max (L.) Merr.) is a prevalent seed disease. It results in poor seed quality and reduced seed lot market grade, and thus undermines value of soybean worldwide. The objectives of this research were to evaluate the reaction of selected soybean genotypes collected from 15 countries representing maturity groups (MGs) III, IV, and V to PSS, and to identify new sources of resistance to PSS based on three years of evaluation of natural field infection by Cercospora spp. in the Mississippi Delta of the U. S. In this study, 42 soybean genotypes were evaluated in 2010, 2011, and 2012. Seventeen lines including six MG III (PI 88490, PI 504488, PI 417361, PI 548298, PI 437482, and PI 578486), seven MG IV (PI 404173, PI 346308, PI 355070, PI 416779, PI 80479, PI 346307, and PI 264555), and four MG V (PI 417567, PI 417420, PI 381659, and PI 407749) genotypes had significantly lower percent seed infection by Cercospora spp. than the susceptible checks and other genotypes evaluated (P ≤ 0.05). These genotypes of soybean can be used in developing soybean cultivars or germplasm lines with resistance to PSS and for genetic mapping of PSS resistance genes. In addition, among these 17 lines with different levels of resistance to PSS, nine soybean genotypes (PI 417361, PI 504488, PI 88490, PI 346308, PI 416779, PI 417567, PI 381659, PI 417567, and PI 407749) were previously reported as resistant to Phomopsis seed decay. Therefore, they could be useful in breeding programs to develop soybean cultivars with improved resistance to both seed diseases.

Identification of Resistance to Citrus Black Spot Using a Novel In-field Inoculation Assay

Citrus black spot is an important fungal disease of citrus resulting in fruit drop and rind blemish in tropical and subtropical production areas. The disease is incited by the fungus Phyllosticta citricarpa (McAlpine) van der Aa (synonym: Guignardia citricarpa Kiely), with control currently relying on the application of fungicides. Because the presence and expression of resistance is poorly understood, we sought to develop a method for inoculating fruit in the field that gives reproducible symptoms of citrus black spot consistent with natural field infection. We subsequently validated this method by screening 49 citrus accessions and characterized their qualitative expression of citrus black spot symptoms. Challenge inoculations were undertaken with a known isolate of P. citricarpa, and control fruit were inoculated with water or the endophyte P. paracapitalensis Guarnaccia & Crous. Our results showed that all mandarin, sweet orange, lemon and papeda types were susceptible; pummelo, lime, and sour orange types expressed immunity; while various hybrids were susceptible, resistant and immune. Hybrid progeny from crosses using pummelo [Citrus maxima (Burm.) Merr.] as a parent showed preliminary evidence of segregation for citrus black spot immunity. The implications of these results to achieve genetic improvement for citrus black spot resistance in citrus breeding programs are discussed.