Studies on the Population Biology of Colletotrichum coccodes Using AFLP and SCAR Markers

Black dot is a blemish disease of potato caused by the fungus Colletotrichum coccodes (Wallr.) Hughes. with worldwide distribution. It occurs in Africa, Asia, Australia, Europe, North America, South America, and Central America. C. coccodes has no known sexual cycle, but genetic exchange is possible through vegetative conjugation. The determination of VCG among fungal isolates is usually based on the complementation tests with nitrate nonutilizing (nit) mutants which enables researchers to compare strains of pathogens. Eight VCGs have been identified for the Europe/Israel population, seven for the North American population, and six for the Australian population. Variation in aggressiveness, morphological traits, and physiological traits have been detected among the different C. coccodes VCGs. AFLP markers have been used also to study relationships within and among North American VCGs. With this method, five VCGs were separated from C. coccodes isolates, coinciding almost completely with the six VCGs of nit mutants. Additionally, a relationship of specific AFLP bands to corresponding VCGs was reported using AFLP analysis. The objectives of this study were: to develop VCG-specific sequence characterized amplified regions (SCAR) markers, to study the population biology of C. coccodes of North America using the AFLP method, and to study genetic diversity of the global populations of C. coccodes. A total of 88 isolates representing the different C. coccodes VCGs were analyzed via the AFLP method to generate SCAR markers. A total of 47 primers were designed and evaluated in PCR reactions. Only one primer, AGb6F/R, with 156 bp amplification PCR product was found to be specific for NA-VCG6 and NA V CG 7 of C. coccodes. For the second objective, 210 loci were generated and used to cluster the isolates into their NA-VCGs and to test the genetic structure of the North American population of C. coccodes. C. coccodes isolates recovered from potato plants were assigned to fourNA-VCGs: NA-VCGl, NA-VCG2, NA-VCG4/5, and NA-VCG6/7. No isolates tested belonged to NA-VCG3. NA-VCG2 was the dominant group in the population (n=238) and was the most frequently detected NA-VCG among states, fields, farms, and plants. However, in several instances there was more than one NA-VCG recovered from the same plant, field, farm, and state, indicating variability within the C. coccodes population in United States. Genetic differentiation among the nine states was 0.331, and overall gene flow for the 366 isolates was (Nm =1.01). For the genetic diversity of the global C. coccodes population, 855 isolates were studied. Three primer pairs were used and generated 210 loci. Based on this study, the population of C. coccodes exists as one large population with four main groups (NA-VCGl/3; NA-VCG2; NA-VCG4/5; and NA-VCG6/7). NA-VCG5 was the most common VCG globally followed by NA-VCG2. Among the five regions studied, there was relatively low gene diversity (0.222). The overall gene flow (Nm) was 1.25, meaning that one or more individuals are exchanged among the five regions each generation and that the populations will gradually become similar. Most of the variation among the five geographic regions originated from within population differentiation. Among VCGs of C. coccodes, there was high VCG differentiation (GsT=0.463), meaning there is a differentiation among the different C. coccodes VCGs and a population structure exists. AFLP analysis proved to be valuable in differentiating and studying the global population of C. coccodes

Evaluation of aerial microbial pollutants in Al-Haram Al-Nabawi during pilgrimage of 2013

Al-Madinah Al-Munawwarah is the second holiest site in Islam. The possibility of new emerging microbes is valid due to the increased number of pilgrims. The objectives of the current study were to estimate the numbers of fungi and bacteria inside and outside Al-Haram Al-Nabawi and to find whether new bacterial and fungal species have emerged compared to previous studies. Air samples were collected twice a day from 12 spots and four directions during the pilgrim year of 2013 for four consecutive weeks by using the sedimentation method. Thirty five genera and fifty eight species were identified. The most recovered bacterial genera were Staphylococcus, Micrococcus, Bacillus, and Dermacoccus with 32.47%, 18.18%, 12.85%, and 11.23%, respectively. Fifty nine isolates of fungi were molecularly identified. Aspergillus species had the highest percentage (78%). The other fungal genera identified (Alternaria triticina, Emericella nidulans, Emericella striata, Mucor circinelloides, Penicillium chrysogenum, Penicillium minioluteum, Rhizopus arrhizus, Rhizopus oryzae, and Syncephalastrum racemosum) had less than 5% frequency. In places such as Al-Haram Al-Nabawi, a large and crowded public (millions) exist especially during pilgrimages and Ramadan, thus, exposure to microorganisms is high. On the other hand, microorganism infectivity depends on many factors including their virulence, landing site, and person’s immunity. For those reasons, many aspects should be considered to avoid aerosol contaminants

Arbuscular Mycorrhizal Fungi Inoculation Improves Flower Yield and Postharvest Quality Component of Gerbera Grown under Different Salinity Levels

High salinity levels of irrigated water and the accumulation of salt over time in the soil is a major concern worldwide, including in Jordan. The objective of this two-year study was to assess the influence of arbuscular mycorrhizal fungi (AMF) inoculation on the physiology, yield, and flower quality of gerbera (Gerbera jamesonii cvs. Beaudine and Palm Beach) under different salinity levels (0.0, 20.0 and 40.0 mM-NaCl). The study was arranged in a randomized complete block design with five replicates. During the experimental period (2018–2019), chlorophyll content index (SPAD), leaf gas exchange (photosynthesis, Pn; stomatal conductance, gs; transpiration, E), flower yield, flower quality (pedicel length and diameter, number of days to flowering, flower diameter, and vase life), root sporulation, and colonization were measured. Irrigation with saline water (20 and 40 mM-NaCl) significantly increased salt accumulation in soil. The mean soil electrical conductivity (EC) after two growing seasons for the 20 mM-NaCl treatment was 2.9 dS m−1 and 4.4 dS m−1 for the 40 mM. High salinity level (40 mM-NaCl) reduced root AMF sporulation by 53–62% and colonization by 12–25% across cultivars. Interestingly, root colonization was higher than 50% across salinity level and in both cultivars. Saline water at 40 mM-NaCl significantly reduced SPAD, Pn, gs, E, flower yield, and quality component, especially vase life. Interestingly, leaf chlorophyll content index from AMF-inoculated plants was significantly higher than uninoculated ones across cultivars at the second growing season. In addition, inoculation with AMF significantly increased yield in both ‘Beaudine’ (34–40%) and ‘Palm Beach’ (42–44%) cultivars and across the study period, 2018 to 2019. In addition, AMF increased vase life in ‘Beaudine’ by 19% to 28% and in ‘Palm Beach’ by 21% to 22%. Overall, our results revealed that gerbera growers can increase their flower yield and postharvest flower quality component (vase life) under saline conditions (soil EC < 4.4 dS m−1) by inoculating the seedlings with AMF

Soil Health and Sustainable Agriculture

A healthy soil acts as a dynamic living system that delivers multiple ecosystem services, such as sustaining water quality and plant productivity, controlling soil nutrient recycling decomposition, and removing greenhouse gases from the atmosphere. Soil health is closely associated with sustainable agriculture, because soil microorganism diversity and activity are the main components of soil health. Agricultural sustainability is defined as the ability of a crop production system to continuously produce food without environmental degradation. Arbuscular mycorrhizal fungi (AMF), cyanobacteria, and beneficial nematodes enhance water use efficiency and nutrient availability to plants, phytohormones production, soil nutrient cycling, and plant resistance to environmental stresses. Farming practices have shown that organic farming and tillage improve soil health by increasing the abundance, diversity, and activity of microorganisms. Conservation tillage can potentially increase grower’s profitability by reducing inputs and labor costs as compared to conventional tillage while organic farming might add extra management costs due to high labor demands for weeding and pest control, and for fertilizer inputs (particularly N-based), which typically have less consistent uniformity and stability than synthetic fertilizers. This review will discuss the external factors controlling the abundance of rhizosphere microbiota and the impact of crop management practices on soil health and their role in sustainable crop production

Effect of Using <i>Trichoderma</i> spp. on Turfgrass Quality under Different Levels of Salinity

Lawns achieve environmental, functional, and aesthetical roles in urban environments. The objectives of this research were to assess the effect of different salinity levels on Trichoderma isolates and to study the effect of Trichoderma spp. on perennial ryegrass under different levels of salinity. T. harzianum (ThLem2017-01) and T. atroviride (TaDP2019-01) isolates had a higher mycelium growth rate than T. atroviride (TaDP2019-02) when salinity levels were low. In contrast, the mycelium growth rate of T. atroviride (TaDP2019-02) isolate at high salinity levels had superior results. Turfgrass seeds that were inoculated with (TaDP2019-02) isolate maintained high radicle length, coleoptile length, and leaf length under high salinity levels. Increasing salinity level decreased clippings’ fresh weight (FW), dry weight (DW), and shoot and root dry weight of perennial ryegrass. Interestingly, perennial ryegrass pots that were treated with (TaDP2019-02) isolate had increased FW and DW by 16 to 114% and 24 to 76%, respectively. Soils that were inoculated with Trichoderma (TaDP2019-02) had higher CO2 respiration (75%) than the control. Therefore, using T. atroviride (TaDP2019-02) isolate revealed promising results in increasing plant biomass and as an environmentally friendly alternative factor to overcome salinity stress

Phomopsis Stem Canker: A Reemerging Threat to Sunflower (Helianthus annuus) in the United States

Phomopsis stem canker causes yield reductions on sunflower (Helianthus annuus L.) on several continents, including Australia, Europe, and North America. In the United States, Phomopsis stem canker incidence has increased 16-fold in the Northern Great Plains between 2001 and 2012. Although Diaporthe helianthi was assumed to be the sole causal agent in the United States, a newly described species, D. gulyae, was found to be the primary cause of Phomopsis stem canker in Australia. To determine the identity of Diaporthe spp. causing Phomopsis stem canker in the Northern Great Plains, 275 infected stems were collected between 2010 and 2012. Phylogenetic analyses of sequences of the ribosomal DNA internal transcribed spacer region, elongation factor subunit 1-α, and actin gene regions of representative isolates, in comparison with those of type specimens, confirmed two species (D. helianthi and D. gulyae) in the United States. Differences in aggressiveness between the two species were determined using the stem-wound method in the greenhouse; overall, D. helianthi and D. gulyae did not vary significantly (P ≤ 0.05) in their aggressiveness at 10 and 14 days after inoculation. These findings indicate that both Diaporthe spp. have emerged as sunflower pathogens in the United States, and have implications on the management of this disease

Identification of Diaporthe longicolla on Dry Edible Peas, Dry Edible Beans and Soybeans in North Dakota

North Dakota soybean production has expanded geographically, and possible short rotations with dry edible bean and pea raise concerns of pathogens (such as Diaporthe longicolla, cause of Phomopsis seed decay and stem disease of soybean) developing overlapping host ranges. To the best of our knowledge, this is the first report of D. longicolla causing stem disease on dry edible beans and dry edible peas, and stem disease on soybean in North Dakota. Its impact on dry edible beans and dry edible peas is uncertain