Crop Protection Research Research Articles

Recent innovations in crop protection research.

As the world's population continues to grow and demand for food increases, the agricultural industry faces the challenge of producing higher yields while ensuring the safety and quality of harvests, operators, and consumers. The emergence of resistance, pest shifts, and stricter regulatory requirements also urgently calls for further advances in crop protection and the discovery of new innovative products for sustainable crop protection. This study reviews recent highlights in innovation as presented at the 15th IUPAC International Congress of Crop Protection Chemistry held in New Delhi, in 2023. The following new products are discussed: the insecticides Indazapyroxamet, Dimpropyridaz and Fenmezoditiaz, the fungicides Mefentrifluconazole and Pyridachlomethyl, the nematicide Cyclobutrifluram, the herbicides Rimisoxafen, Dimesulfazet, and Epyrifenacil as well as the abiotic stress management product Anisiflupurin. In addition, the latest innovative research areas and discovery highlights in all areas of crop protection will be presented, including insecticidal alkyl sulfones and 1,3,4-trisubstituted pyrazoles, fungicidal picolinamides, herbicidal ketoenols, and trifluoromethylpyrazoles, as well as the latest advances in crop enhancement and green pest control research. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

First Report of Powdery mildew Caused by Golovinomyces ambrosiae on Verbena × hybrida in the U.S.

Verbena × hybrida, also known as common garden verbena, has an important ornamental value for their wide range of flower colors and for attracting hummingbirds and butterflies. During the winter of 2021-2022 (December through February), more than 50% pot-grown verbena plants showed symptoms of powdery mildew in a field trial at a Syngenta Crop Protection research facility in Vero Beach, FL. Symptoms were characterized by the development of white, superficial mycelium on the adaxial side of leaves which, eventually, progressed to covering the whole surface of leaves, causing leaf discoloration, shoot distortion, and eventual plant death. Morphological characterization was carried out by observing powdery mildew colonies under the microscope. This powdery mildew forms dense patches of white mycelia, mainly on the adaxial leaf surfaces. The mycelium was a mat of hyphae with septa. Conidiophores were erect. The foot cells were straight, followed by one to three short cells bearing short chains of up to four conidia. The conidia were hyaline and ellipsoidal to doliiform in shape. Conidial germination is of the Eudoidium type. The conidia ranged from 25 to 32 μm long by 12 to 16 μm wide. The length to width ratio ranged between 1.6 and 2.3, but most were between 2.0 and 2.2. This is further verification of its identity as Golovinomyces ambrosiae and not Golovinomyces latisporus, because the length to width ratio of the latter species is consistently less than 2.0 (Qiu et al. 2020). Chasmothecia were not observed. Additionally, the ITS, GAPDH, and IGS regions were sequenced using the primer pairs ITS4/ITS5 (White et al. 1990), PMGAPDH1/PMGAPDH3R (Bradshaw et al. 2022a), and IGS-12a/NS1R (Carbone and Kohn 1999), respectively. The ITS region (GenBank number=PP924119) cannot distinguish between G. latisporus and G. ambrosiae and as such aligned 100% with both species on GenBank. However, the GAPDH and IGS regions can be used to distinguish G. ambrosiae from G. latisporus (Bradshaw et al. 2022b). The GAPDH (GenBank number=PP931995) and IGS (GenBank number=PP931996) regions aligned 100% with multiple G. ambrosiae sequences from GenBank including ON360708 and MK452567, respectively. The specimen was deposited in the Larry F. Grand Mycological Herbarium (NCSLG 24479). To confirm pathogenicity, 'Tuscany® Pink Picotee' and 'Quartz XP Violet with Eye' plugs were transplanted to 10-cm diameter pots containing ProMix potting mix and maintained in a greenhouse (± 26 °C). Inoculation was carried out 21 days after transplanting by touching infected leaves onto healthy leaves of 15 disease-free plants of each variety. Fifteen non-inoculated plants of each variety were used as controls. Typical powdery mildew symptoms and signs were first observed ten days after inoculation and the pathogen was more aggressive on 'Tuscany® Pink Picotee'. Symptoms were not observed on non-inoculated plants. The fungus was morphologically identical to the one originally recovered from infected plants in the field. There have been many reports of Golovinomyces spp. affecting Verbena spp. worldwide; however, this is the first report of G. ambrosiae causing powdery mildew on Verbena × hybrida in the U.S. (Braun and Cook, 2012, Choi et al., 2021; Bradshaw et al. 2024). Powdery mildews reduce plant quality and decreases the aesthetics value of infected plants, causing great losses to the ornamental industry. Correct identification of the causal agent is crucial to recommend appropriate control methods, as they may differ according to the pathogen species.

A Search for Biologically Active Compounds for Potential Pharmaceutic and Agronomic Applications.

Summarized here are some aspects of my research activities in Ciba-Geigy Central Research Laboratories (1985-1996), in Novartis and Syngenta Crop Protection Research (1997-2020). I have followed the chronological order of these research activities covering only published data.

Vulnerability of pear (Pyrus) genetic resources in the U.S.

AbstractPears (Pyrus) represent an important part of consumer diets, and have the fourth highest production of non-citrus fruits, measured by fresh weight, in the U.S. They are maintained clonally and grown as composite plants, consisting of a scion (fruit bearing) cultivar grafted onto a rootstock cultivar. Up to 98% of existing production relies on only a few scion and rootstock cultivars, leaving the standing crop vulnerable to threats. Pears are faced with a wide range of biotic and abiotic threats and production vulnerabilities, some of which can be limited by integrating resistance and horticultural traits from wild and cultivated materials from around the world. The National Clonal Germplasm Repository (NCGR Corvallis), part of the USDA-ARS National Plant Germplasm System, maintains a large Pyrus collection from across the globe, consisting of 2793 Pyrus accessions from 37 species. The collection represents an important resource for preservation, research, and breeding efforts for pears. The crop vulnerability status of pears in the U.S. is currently moderate to high, with increasing threats and challenges. Breeding and preservation efforts, along with genetic, crop protection and production research are, however, actively targeting these needs.

Importance of pathobiomes to the success of microbial weed biocontrol agents

The role of microbial communities in the establishment of plant pathogens introduced to new environments as weed biocontrol agents is relatively unexplored. Substantial evidence from crop protection research shows how bulk microbial communities influence the establishment, survival, and success of pathogens. Just as mismatches between biocontrol agents, host genotypes, and climate can lead to establishment failure, we propose that mismatches between microbial biocontrol agents and resident microbiomes may be a cause of apparent weed biocontrol failures. From this perspective, we discuss recent progress in research on plant-associated microbial communities whose interactions influence disease development, or “pathobiomes,” and consider the implications for biocontrol agent evaluation and release. Open questions about how weed pathobiomes develop and influence agent success rates provide ample opportunity for researchers to adapt new methods and analytical frameworks that will enhance biocontrol programs. We conclude by prioritizing the development of standard methods to include microbiomes as a component of release studies. Developing a pathobiome-aware agent selection and release process will improve agent establishment rates and biocontrol outcomes.

Towards dsRNA-integrated protection of medical Cannabis crops: considering human safety, recent- and developing RNAi methods, and research inroads.

Owing to the expanding industry of medical Cannabis, we discuss recent milestones in RNA interference (RNAi)-based crop protection research and development that are transferable to medical Cannabis cultivation. Recent and prospective increases in pest pressure in both indoor and outdoor Cannabis production systems, and the need for effective nonchemical pest control technologies (particularly crucial in the context of cultivating plants for medical purposes), are discussed. We support the idea that developing RNAi tactics towards protection of medical Cannabis could play a major role in maximizing success in this continuously expanding industry. However, there remain critical knowledge gaps, especially with regard to RNA pesticide biosafety from a human toxicological viewpoint, as a result of the medical context of Cannabis product use. Furthermore, efforts are needed to optimize transformation and micropropagation of Cannabis plants, examine cutting edge RNAi techniques for various Cannabis-pest scenarios, and investigate the combined application of RNAi- and biological control tactics in medical Cannabis cultivation. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Introduction to Bioisosteric Replacement and Scaffold Hopping in Crop Protection Research.

Introduction to Bioisosteric Replacement and Scaffold Hopping in Crop Protection Research.

Silicon-Containing Complex II Acaricides─Design, Synthesis, and Pharmacological Optimization.

Bioisosteric replacement has been proven to be a powerful strategy in life science research. In this review, general aspects of carbon-silicon bioisosteric substitution and its applications in pharmaceutical and crop protection research are described. Carbon and their silicon analogues possess similar intrinsic properties. Replacing carbon with silicon in pharmaceuticals and pesticides has shown to result in positive effects on efficacy and selectivity, physicochemical properties, and bioavailability and also to eliminate or improve human or environmental safety properties as well as to provide novelty and new intellectual property in many cases. Furthermore, the application of carbon-silicon substitution in the search for new complex II acaricides is highlighted. This research led to the discovery of sila-cyflumetofen 23a and other silicon-containing analogues of cyflumetofen that match or exceed the acaricidal activity of cyflumetofen. The molecular design strategy, synthetic aspects, biological activity, computational modeling work, and structure-activity relationships will be discussed.

Trifluoromethylpyridine: An Important Active Fragment for the Discovery of New Pesticides.

Trifluoromethylpyridine (TFMP) is a biologically active fragment formed by connecting trifluoromethyl and pyridine ring. As a result of its unique physical and chemical properties and outstanding biological activity, a variety of pesticide compounds with the TFMP fragment have been discovered and marketed and have played important roles in crop protection research. It is therefore a timely and valuable task to summarize the rationality on how to create new molecules containing TFMP fragments based on the structure-activity relationships, design mentality, and potential mechanism. This review gives a brief summary on the pesticides containing TFMP fragments in the past 5 years and introduces the latest progress of our group in this field. The aim is to provide readers with a convenient route to touch this topic and hopefully serve some educational purpose for graduate students as well.

Quinazolinone Alkaloid Febrifugine and Its Analogues To Control Phytopathogenic Diseases Caused by Oomycete Fungi

AbstractControlling phytopathogenic diseases caused by oomycete fungi is still a challenge in crop protection research. Studies on identifying new starting points to control phytopathogens revealed that the quinazolinone alkaloids febrifugine (1) and halofuginone (2) are efficiently inhibiting the growth of Phytophthora infestans in microtiter tests. However, despite the very good in vitro activity of 0.13 and 0.06 ppm in IC50, respectively, both compounds did not exhibit a good control of P. infestans on tomato plants. Creating a homology model of prolyl‐tRNA synthetase – the molecular target of halofuginone – helped to understand the interactions between 2 and the binding pocket and guided the synthesis of further derivatives. Ultimately, we found that deoxy‐febrifugine (14) and halofuginol (17) and its derivatives were able to control P. infestans also on the plant.

Soil Health: New Opportunities to Innovate in Crop Protection Research and Development

Soil health-based agricultural management practices are widely promoted to reduce erosion, increase nutrient use efficiency, improve soil structure, and sustain or increase yields. Pest and disease management are less frequently considered as components of a soil health management system. We present a framework for how the crop protection industry can advance soil health by developing systems of crop protection innovation that simultaneously target soil health outcomes, either through direct impact on soil or by enabling practices that promote soil health outcomes. Such an approach could lead to cross-sectoral, integrated agricultural solutions that achieve agronomic, environmental, and economic goals.

Tuber Minerals and Phenolic Compounds in Calcium Nitrate foliar-sprayed Dioscorea alata var. Agbodo and D. rotundata var. Amula.

Calcium Nitrate foliar spray for the management of anthracnose disease was assessed in Dioscorea alata variety Agbodo and D. rotundata var. Amula in two experiemental plots in COLPANT Farms, College of Plant Science and Crop Production, Federal University of Agriculture, Abeokuta, Ogun State in Nigeria. The design in each plot was randomized complete block (RCBD) with three replications. Mounds were 1 metre (m) by 1m and about 80cm high, with inter-replicate inter-row and intra-row spacing of 1m, 1m and 0.5m respectively. One metre (1m) clear border was maintained on each of the four sides of each plot. Each replicate had 18 plants. Calcium Nitrate foliar spray at the rates 0mgl-1, 5mgl-1 and 10mgl-1 was applied without surfactant at twelve weeks after planting (12 WAP). Anthracnose incidence and severity results are presented in another paper. But tubers in the plots were sampled at 24 WAP in order to determine, Calcium nitrate foliar spray of 5mgl-1 and 10mgl-1 without surfactant, effect on tuber minerals, namely Calcium (Ca), Magnesium (Mg), Nitrogen (N), Phosphorus (P), Potassium (K) and Sulphur (S), as well as Tuber Total Phenolic Compounds (TPC) and yield. The results of yield, TPC and the tuber minerals are presented in this paper. Statistical analysis was carried out separately for each plot. Tuber Number Per Plant (TNPP) and Tuber Weight Per Plant (TWPP) were similar across treatments for water Yam Agbodo and white guinea yam Amula. TNPP overall means are 4.43 and 3.16 for Agbodo and Amula respectively. TWPP overall means are 2.00kg (or 20.00 tonsha-1) and 1.91kg (or 19.10 tonsha-1) for Agobdo and Amula respectively. Yield (tuber fresh weight) is similar to that obtained in a report of Calcium nitrate foliar spray for anthracnose control in Dioscorea species (two improved and one local variety), but which had relatively higher spray concentrations of 0 to 12000 milligram per litre and with surfactant in the spray liquid. Tuber Ca, Mg, N and P were significantly higher in the treatments than the control in water yam Agbodo as follows: Ca in mg/100g dm is 21.48 (10mgl-1) > 19.16 (5mgl-1) > 16.31 (Control); Mg in mg/100gdm is 24.53 (10mgl-1) > 21.22 (5mgl-1) > 19.02 (control); N in percent (%) is 1.86 (10mgl-1) > 1.37 (5mgl-1) > 0.95 (control); P in mg/100g dm is 56.27 (10mgl-1) > 53.14 (5mgl-1) > 49.76 (control). K in mg/100g dm in Agbodo is 807.70 (10mgl-1) higher than 770.60 (control). S and Total Phenolic Compounds (TPC) of Agbodo were overall means 4.68% and 5.58mg Gallic Acid Equivalent per gram dry matter (5.58mgGAE/gdm) respectively. In white guinea Yam Amula, TPC and five of the minerals were higher significantly in the treatments than the control as follows: TPC in mgGAE/gdm is 5.92 (10mgl-1) > 5.39 (5mgl-1) > 4.82 (control); Ca in mg/100gdm is 18.22 (10mgl-1) > 16.45 (5mgl-1) > 14.49 (Control); N in % is 1.80 (10mgl-1) > 1.11 (5mgl-1) > 0.91 (control); P in mg/100gdm is 54.82 (10mgl-1) > 50.84 (5mgl-1) > 48.59 (control); K in mg/100gdm is 812.44 (10mgl-1) > 793.29 (5mgl-1) > 759.22 (control); S in % is 6.42 (10mgl-1) > 5.23 (5mgl-1) > 4.48 (control). Mg in white Yam Amula was overall mean of 20.19mg/100gdm, similar across treatments. A numerical comparison may be made of the two species (two varieties) because statistical analysis was carried out separately in the two experimental plots. Thus numerically (not statistically) overall means were higher in Agbodo in yield (TNPP and TWPP), TPC, Ca, Mg, N, P and K, than Amula. Amula was numerically higher in Sulphur only than Agbodo. Phenolic compounds reports of association with defence mechanisms in crop plants because they exhibit anti-fungal, anti-bacterial and anti-viral properties is discussed. Phenolic compounds reports of exhibition of antioxidant or free radical scavenging properties that boost immunity against diseases caused by free radical reactions such as cancer, diabetes, aging and cardio vascular diseases, as well as analgesic and anti-inflammatory properties  is also discussed. This is to draw attention to inputs during Crop Protection Research such as this study which will effect synthesis of, or increase phenolic compounds in the edible food yams for disease resistance as well as for health benefits. Increase in calcium in this study would enhance disease resistance due to calcium role in the enhancement of the integrity of intracellular cementing materials. Magnesium and phosphorus requirement in yams is reported to be low, thus the increase in this study will ensure yams receive the optimum of the two elements. Lastly, Nitrogen and Potassium increase is to be emphasized for recommendation of 5mgl-1 and 10mgl-1 calcium nitrate foliar spray in Dioscorea species as the two are the most important for optimum yield in yams.

New Food Crop Domestication in the Age of Gene Editing: Genetic, Agronomic and Cultural Change Remain Co-evolutionarily Entangled.

The classic domestication scenario for grains and fruits has been portrayed as the lucky fixation of major-effect “domestication genes.” Characterization of these genes plus recent improvements in generating novel alleles (e.g., by gene editing) have created great interest in de novo domestication of new crops from wild species. While new gene editing technologies may accelerate some genetic aspects of domestication, we caution that de novo domestication should be understood as an iterative process rather than a singular event. Changes in human social preferences and relationships and ongoing agronomic innovation, along with broad genetic changes, may be foundational. Allele frequency changes at many loci controlling quantitative traits not normally included in the domestication syndrome may be required to achieve sufficient yield, quality, defense, and broad adaptation. The environments, practices and tools developed and maintained by farmers and researchers over generations contribute to crop yield and success, yet those may not be appropriate for new crops without a history of agronomy. New crops must compete with crops that benefit from long-standing participation in human cultural evolution; adoption of new crops may require accelerating the evolution of new crops’ culinary and cultural significance, the emergence of markets and trade, and the formation and support of agricultural and scholarly institutions. We provide a practical framework that highlights and integrates these genetic, agronomic, and cultural drivers of change to conceptualize de novo domestication for communities of new crop domesticators, growers and consumers. Major gene-focused domestication may be valuable in creating allele variants that are critical to domestication but will not alone result in widespread and ongoing cultivation of new crops. Gene editing does not bypass or diminish the need for classical breeding, ethnobotanical and horticultural knowledge, local agronomy and crop protection research and extension, farmer participation, and social and cultural research and outreach. To realize the ecological and social benefits that a new era of de novo domestication could offer, we call on funding agencies, proposal reviewers and authors, and research communities to value and support these disciplines and approaches as essential to the success of the breakthroughs that are expected from gene editing techniques.

Design, synthesis and acaricidal activities of Cyflumetofen analogues based on carbon-silicon isosteric replacement

The application of a carbon-silicon bioisosteric replacement strategy to find new acaricides with improved properties led to the discovery of Sila-Cyflumetofen 6B, a novel and highly potent acaricide. The essential t-butyl group in the beta-ketonitrile acaricide Cyflumetofen 6A could be swapped with the bioisosteric trimethyl-silyl group with retention of high level acaricidal activity and favourable pharmacological properties. Sila-Cyflumetofen 6B was found to possess similar preferred energy-minimized conformation and electrostatic potential surface compare to Cyflumetofen 6A. Herein we also report the development and application of the first homology model of the spider mite mitochondrial electron transport complex II (succinate ubiquinone oxidoreductase; SQR) and demonstrated that the active metabolite AB-1 of Cyflumetofen 6A and its sila-analogue Sila-AB-1 bind to the Qp site in same binding pose and that both compounds form two H-bonds and a cation-π interaction with Trp 165, Tyr 433 and Arg 279, respectively. Furthermore, we also developed a new mode of action test for spider mite Complex II using cytochrome c as electron acceptor and blocking its re-oxidation by addition of KCN resulting in a sensitive and convenient colorimetric assay. This new method avoids the use of non-specific artificial electron acceptors and allows to measure SQR inhibition in crude extracts of Tetranychus urtice. In this assay Sila-AB-1, the intrinsically active metabolite of Sila-Cyflumetofen, 6A exhibited even a somewhat lower IC50 value than the metabolite of Cyflumetofen AB-1. Synthetic methodologies are described for the preparation of Sila-Cyflumetofen 6B and its active metabolite Sila-AB-1 which enable an efficient synthesis of these compounds in only 5 and 4 steps, respectively, from cheap commercial starting materials. Although the value of carbon-silicon bioisosteric replacements has already be demonstrated in the past it is to the best of our knowledge the first report of a successful application in crop protection research in the last two decades.

RNA-Based Biocontrols—A New Paradigm in Crop Protection

Modern agribusiness plays a vital role in safeguarding and improving the production, quality, and quantity of food, feed, fiber, and fuel. Growing concerns over the impact of chemical pesticides on health and the environment have stimulated the industry to search for alternative and greener solutions. Over the last years, the RNA interference (RNAi) process has been identified as a very promising new approach to complement the arsenal of foliar spray, soil, or seed treatments applied as chemical and biological pest control agents, and of plant-incorporated protectants (PIPs). RNA-based active ingredients (AIs) possess a unique mode of action and can be implemented via both genetic modification (GM) and biocontrol approaches. RNA-based AIs promise to deliver the selectivity and sustainability desired in future crop protection agents. This is due to their utilization of a natural process to exert control and their high level of selectivity, which leads to reduced risk for non-target organisms (NTOs). This review discusses the advantages and limitations of RNA-based solutions in crop protection and recent research progress toward RNA-based biocontrols against the Colorado potato beetle (CPB), corn rootworm (CRW), and soy stink bug (SSB). Many challenges still exist on the road to the implementation of a broad range of RNA-based products and their widespread use and application. Despite these challenges, it can be expected that RNA-based AIs will become valuable new tools complementing the current arsenal of crop-protection solutions.

Agrochemical lead optimization by scaffold hopping

Scaffold hopping, the exchange of a specific portion of a potential active ingredient with another substructure with the aim of finding isofunctional molecular structures with significantly different molecular backbones, often offers the chance in lead discovery or optimization to mitigate problems related to toxicity, intellectual property, and insufficient potency or stability. Scaffold hopping tools such as isosteric ring replacement including 1,3 nitrogen shift and cyclic imine-amide isosterism, but also ring opening and ring closure approaches, functional group isosterism, reversion of functional groups, chain shortening, chain lengthening, and scaffolds delivered by natural products, have become a permanent fixture of the innovation and optimization process in crop protection research. Their appropriate use will be explained through examples of success stories in the field of agrochemistry. Analogies to, but also differences from, the main categories of scaffold hopping in medicinal drug discovery are discussed. © 2017 Society of Chemical Industry.

PM 7/28 (2) Synchytrium endobioticum

Specific scopeThis Standard describes a diagnostic protocol for Synchytrium endobioticum.This Standard should be used in conjunction with PM 7/76 Use of EPPO diagnostic protocols.Specific approval and amendmentApproved in 2003‐09. Revision approved in 2017‐06.

Natural Products in the Discovery of Agrochemicals.

Natural products have a long history of being used as, or serving as inspiration for, novel crop protection agents. Many of the discoveries in agrochemical research in the last decades have their origin in a wide range of natural products from a variety of sources. In light of the continuing need for new tools to address an ever-changing array of fungal, weed and insect pests, new agricultural practices and evolving regulatory requirements, the needs for new agrochemical tools remains as critical as ever. In that respect, nature continues to be an important source for novel chemical structures and biological mechanisms to be applied for the development of pest control agents. Here we review several of the natural products and their derivatives which contributed to shape crop protection research in past and present.

First Report of Downy Mildew on Basil (Ocimum basilicum) in China

HomePlant DiseaseVol. 99, No. 11First Report of Downy Mildew on Basil (Ocimum basilicum) in China PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Downy Mildew on Basil (Ocimum basilicum) in ChinaX. Y. Kong, S. Wang, S. L. Wan, C. L. Xiao, F. Luo, and Y. LiuX. Y. KongSearch for more papers by this author, S. WangSearch for more papers by this author, S. L. WanSearch for more papers by this author, C. L. XiaoSearch for more papers by this author, F. LuoSearch for more papers by this author, and Y. LiuSearch for more papers by this authorAffiliationsAuthors and Affiliations X. Y. Kong S. Wang S. L. Wan C. L. Xiao F. Luo Y. Liu , Sanya Science & Technology Academy for Crop Winter Multiplication, Winter Multiplication Crop and Plant Protection Research Center, Sanya Key Laboratory for Pest Management of Winter Cucurbits and Vegetables, Sanya 57200, Hainan, China. Published Online:26 Aug 2015https://doi.org/10.1094/PDIS-01-15-0077-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat In December 2014, Sanya City (18°N) of Hainan Province, the southernmost city of China, suffered an onslaught of downy mildew over large basil-growing areas. According to our investigation, almost 40% of the plants in the region (70 km2) were infected by the disease, which spread very rapidly. Given favorable conditions, the disease rate could reach 100% three to five days after the attack, making prevention and control extremely difficult. The seedling and adult plant stages of basil are subject to infection by the disease. In the early stages of the disease, the infected parts of the green leaf blades turn yellow, and then brown spots develop at the leaf margins. In the later stages of the disease, the spots spread along the margins or main veins of the leaves into larger areas, amassing as irregular, brown, necrotic spots that can consequentially wither the blades, and more seriously, cover more than half of the leaves. Meanwhile, the leaf back can be completely covered with a grayish-black layer of mildew. In the final stages of the disease, all the leaves of the plant will be infected, whereupon they will turn brown. When examined under a microscope, large amounts of sporangiophores and sporangia were found in the samples of the mildew layer collected from the infected leaves. Sporangiophores were hyaline, 197.0 to 595.3 μm (average 370.6 μm) in length, branched two to seven times, and ending with two slightly curved branchlets having a single sporangium at the tip of each branchlet. The longer branchlets measured 14.3 to 38.3 μm in length (average 23.2 μm), while the shorter ones were 2.4 to 22.1 μm in length (average 8.1 μm). Sporangia were oval or circular, ranged from brown to dark brown, measured 19.8 to 33 μm in length (average 27.6 μm) and 15.1 to 29.3 μm in width (averaging 23.0 μm) (a length/width ratio of 1.2), and produced germ tubes by direct germination. Based on these morphological characteristics, the causal agent was identified as Peronospora belbahrii Thines (Belbahri et al. 2005; Thines et al. 2009). Furthermore, genomic DNA was extracted from infected plant tissue according to Dellaporta et al. (1983). The complete ITS rDNA region was amplified and sequenced using primers ITS5 and ITS4 (Nagy and Horvath 2011). The consensus sequences were deposited in GenBank (Accession No. KP657570), and a BLAST analysis in the NCBI database revealed 99% similarity to all of the P. belbahrii sequences previously reported in regard to basil (EU863410 and KJ960193). For the preparation of the inoculum, infected leaves were flooded with sterile distilled water to collect the sporangia. The sporangia were washed once with sterile distilled water and the suspension was diluted to 1 × 105 sporangia/ml. The sporangia suspension was sprayed onto 15 healthy leaves grown in the same period for inoculation, and sterilized distilled water was sprayed on 15 healthy leaves serving as controls. The experiment was repeated 10 times. Every replicate was placed in a separate petri dish under 12 h of light at 20°C, and 90 to 95% relative humidity. Five days after inoculation, the leaves inoculated with the suspension showed typical symptoms of the disease while the control leaves showed no symptoms. Infected leaves under the microscope showed large amounts of P. belbahrii fungi. Therefore, all of the results suggest that the downy mildew on basil was caused by the fungus P. belbahrii. To our knowledge, this is first report of downy mildew on basil in China.

Identifying and developing maize germplasm with resistance to accumulation of aflatoxins

Efforts to identify maize germplasm with resistance toAspergillus flavus infection and subsequent accumulation of aflatoxins were initiated by the US Department of Agriculture, Agricultural Research Service at several locations in the late 1970s and early 1980s. Research units at four locations in the south-eastern USA are currently engaged in identification and development of maize germplasm with resistance toA. flavus infection and accumulation of aflatoxins. The Corn Host Plant Resistance Research Unit, Mississippi State, MS, developed procedures for screening germplasm for resistance toA. flavus infection and accumulation of aflatoxins. Mp313E, released in 1990, was the first line released as a source of resistance toA. flavus infection. Subsequently, germplasm lines Mp420, Mp715, Mp717, Mp718, and Mp719 were released as additional sources of resistance. Quantitative trait loci associated with resistance have also been identified in four bi-parental populations. The Crop Protection and Management Research Unit and Crop Genetics and Breeding Research Unit, Tifton, GA, created a breeding population GT-MAS:gk. GT601, GT602, and GT603 were developed from GT-MAS:gk. The Food and Feed Safety Research Unit, New Orleans, LA, in collaboration with the International Institute for Tropical Agriculture used a kernel screening assay to screen germplasm and develop six germplasm lines with resistance to aflatoxins. The Plant Science Research Unit, Raleigh, NC, through the Germplasm Enhancement of Maize (GEM) Project provides to co-operators diverse germplasm that is a valuable source of resistance toA. flavus infection and accumulation of aflatoxins in maize.