Selection Of Resistant Varieties Research Articles

Sugarcane borers: species, distribution, damage and management options

AbstractLepidopteran borers stand out as the most destructive pests in sugarcane, leading to reductions in stalk weight, juice quality and sugar recovery. Presently, integrated pest management (IPM) systems are utilized for sugarcane borer management, employing diverse methods encompassing cropping system, chemical pesticides, behavioral manipulation, biological agents and the selection of resistant varieties. However, the effectiveness of this strategy remains controversial due to concerns about harmful residues, formulation limitations, environmental variability, labor shortages and increased input costs. Currently, multiple lines of transgenic sugarcane expressing insecticidal genes from the bacterium Bacillus thuringiensis (Bt) have been developed globally, offering the prospect of increases production with reduced pesticides application, thereby eliminating the negative effect of IPM. In Brazil, the first genetically modified sugarcane cultivars resistant to the sugarcane borer have been approved and released for commercial cultivation, shedding a bright light on a viable solution for sugarcane borers. This paper reviews borer species and distribution, the significant damage caused by sugarcane borers, current control approaches and the future effective control strategies. Additionally, this work provides comprehensive understanding on Bt sugarcane, serving as an additional tool to complement conventional sugarcane borers control resistance programs.

Resistance of cayenne pepper varieties (Capsicum frutescens) to anthracnose disease (Colletotrichum gloeosporioides) isolates from swampy areas

Anthracnose, a primary disease in chili plants caused by the pathogen fungus Colletotrichum sp., has proven significant losses by affecting harvests and inducing fruit decay. Control measures using synthetic pesticides have been implemented but yielded unsatisfactory results. The utilization of resistant varieties stands as a pertinent approach in early control efforts to minimize harvest losses. Additionally, the use of resistant varieties is a crucial component of integrated disease control implementation. This study aims to investigate the resistance levels of ten chili varieties commonly grown in swampy areas against specific isolates of Colletotrichum sp. present in swampy locations. The research, conducted in a randomized complete design in a greenhouse, tested ten varieties of cayenne pepper typically cultivated in swampy areas. The results revealed that the Hiyung variety is Susceptible, while Bara, Dewata 43 F1, Tiung Tanjung, Genie, Sekar, and CR-9 varieties exhibit moderate resistance. Conversely, Tiung Ulin, Alip, and Sret varieties are classified as resistant. The incubation period for tested cayenne pepper varieties varied, ranging from 3.5 to 5.3 days. A longer incubation period indicates greater resistance to anthracnose in chili varieties. The selection of resistant varieties is a pivotal step in anthracnose management, not only to minimize harvest losses but also to support an effective integrated control approach.

The Evaluation of Implementation of Integrated Pest and Disease Control by Farmers of Food and Holticultural Corps in Banyuasin and Ogan Komering Ulu Timur

Reducing crop cultivation is providing ecological biota for plants through Integrated Pest Management (IPM). Farmers' problems regarding pests and diseases in Banyuasin and OKU Timur, especially for food crops and horticulture farmers. The purpose of this research is to evaluate the compliance of food crops and horticulture farmers in implementing safe and environmentally friendly IPM. Study on various fields of food and horticulture farmers in Banyuasin and Ogan Komering Ulu. The research method used is purposive sampling. Observation of Plant Pests and Diseases was completed directly in the field. Then determine the disease score in each sample plant. The parameters observed in this study are the behavior of farmers towards the decision-making process of using pesticides. Pest and disease intensity, and disease attack percentage were analyzed descriptively in the form of tables and graphs, as well as correlation analysis. The highest value of diversity of pests and diseases of food and horticultural crops based on the entire area of the observed land was found in a land area of 0.25 ha, which is the area that is often found in land for crop cultivation. The average age percentage of farmers in Banyuasin and OKU East is 40 to 50 years old. The average education of farmers in Banyuasin and OKU Timur is 24 farmers. The percentage and intensity of both horticultural and food crops in Banyuasin are good because only a few farmers get a score of 2 or 1. Cultivation techniques are land preparation, land sanitation, selection of resistant varieties, spacing, irrigation, crop rotation, intercropping, mulching, natural enemies of insects, and weeding.

Plectosphaerella melonis (Syn. Acremonium cucurbitacearum) — Plant Pathogenic Organism

Fungal diseases cause signifi cant damage to agriculture. Plectosphaerella melonis (syn. Acremonium cucurbitacearum and Nodulisporium melonis) is a pathogen of cultivated plant diseases in Spain, Italy, Japan, USA, Egypt, and Ukraine. This review discusses the main results of research related to this phytopathogen. By morphological and cultural features, P. melonis is a morphologically intermediate species between A. strictum and A. charticola, however, 5.8S-ITS regionbased phylogenetic analysis showed that P. melonis is a monophyletic taxon more closely related to Plectosphaerella than to other species of the genus Acremonium. The most susceptible plants are at the stage of germination; however, the development of the disease is manifested in the fruiting period. For a comprehensive assessment of virulence, real leaf area (RLA) of the first two leaves, lesion of hypocotyl (RH), root collar (RSR), primary (R1R) and secondary roots (R2R) are measured. P. melonis affects the root system, in particular the root collar and hypocotyl, and colonizes the epidermis and cortex of the root centrographically towards the stem. The range of host plants includes Cucurbitaceae, however, peppers, tomatoes, basil, and parsley are infected as well. Plants vary in susceptibility depending on the species and even variety. The pathogenic response of plants differs depending on the growing conditions (protected and open soil), the interaction between the pathogen and competing microorganisms, and other ecological and trophic relationships. The main means of control are the use of long-term crop rotations and the selection of resistant varieties. In Ukraine, a strain of the antagonist fungus Trichoderma viride was selected, which is an effective means for controlling P. melonis 502. The aim of our work was to establish the role of P. melonis in the development of diseases of cultivated plants.

Stem-end rot in major tropical and sub-tropical fruit species

Stem-end rot (SER) is one of the most destructive postharvest diseases affecting some tropical and sub-tropical fruits. The disease is caused by several fungal pathogens, including Botryosphaeriaceae species. In mango, Dothiorella dominicana, D. mangiferae, Lasiodiplodia theobromae, Phomopsis mangiferae, Cytosphaera mangiferae, Pestalotiopsis sp. endophytically colonize the inflorescence in the orchard or field. Fungi may occur endophytically in the stem tissue of the trees prior to inflorescence emergence. During the endophytic stage, the fungi colonize the phloem and xylem at stem-end and, after fruit ripening, some fungi become necrotrophic and colonize the fruit pulp causing SER. The SER pathogens in other fruit species, including ripe avocado or papaya, are not known to undergo an endophytic phase. Stem-end rot is a disease that is difficult to control. Preharvest cultural practices and selection of resistant varieties are beneficial to reduce field infections. Studies have shown that numerous control options, involving cultural, chemical (fungicides, essential oils) and biological approaches, are available to manage SER through either direct inhibition of fungi or induction of host defenses. These may be used individually or integrated manner. The most common and effective practice for controlling the SER is pre- and postharvest application of synthetic fungicides. With the new tools that are currently available, and expected to emerge, there is a possibility of a better understanding the host–pathogen or host-microbiota interactions within the stem-end region, leading to newer technologies as alternatives to toxic synthetic fungicides for the management of SER in fruits.

Variability of Alternaria Leaf Spot Resistance in Jerusalem Artichoke (Helianthus Tuberosus L.) Accessions Grown in a Humid Tropical Region

Alternaria leaf spot is an emerging disease of Jerusalem artichoke (Helianthus tuberosus L.) in tropical regions. The lack of known resistant germplasm sources is an important constraint to development of Jerusalem artichoke varieties with resistance to Alternaria leaf spot. The objectives of this study were to identify variability of Jerusalem artichoke genotypes for resistance to Alternaria leaf spot under field conditions and to investigate the relationships among resistance characters, yield, and yield components for selection of resistant varieties. Ninety six accessions of Jerusalem artichoke were evaluated in replicated trials under field conditions in early rainy and late rainy seasons in Khon Kaen, Thailand during 2014. Parameters evaluated included disease incidence, disease score, disease severity index, area under disease progress curve of disease incidence, area under disease progress curve of disease severity index, number of tubers/plants, tuber size, and fresh tuber yield. The genotypes HEL 335, HEL 256, HEL 317, HEL 308, and JA 86 were identified as sources of leaf spot resistance in both seasons. These genotypes can be used as sources of leaf spot resistance for Jerusalem artichoke breeding programs. HEL 293 and HEL 246 showed susceptibility to leaf spot disease in both seasons and should be used as standard susceptible checks.

Pre-harvest measures against Fusarium spp. infection and related mycotoxins implemented by Dutch wheat farmers

Fusarium spp. are one of the most widespread mycotoxin-producing fungi in small-grain cereals like wheat. Their rate of infection and production of mycotoxins is mainly influenced by weather and pre-harvest agronomic measures. Consequently, farmers' prevention and control of mycotoxins are imperative since it is difficult to remove mycotoxins further down the cereal supply chain. This study aimed to (i) identify which pre-harvest preventive and control measures Dutch wheat farmers currently apply against Fusarium spp. infection and mycotoxin contamination and to (ii) examine which farm and farmer characteristics explain the implementation of these measures. Field data on pre-harvest measures, like the selection of resistant varieties, fungicide use, and crop rotation, along with farm and farmer characteristics were collected from Dutch wheat farmers via an online questionnaire. Probit models were applied to examine farm and farmer characteristics that explain the implementation of pre-harvest measures. Results showed that most farmers applied six or more different measures against Fusarium spp. infection and mycotoxin contamination in wheat and that the use of pre-harvest measures is related to at least one other measure. However, results indicated that about 44% of farmers could become more effective if they implemented a benchmark approach consisting of a combination of fungicide use during flowering, selection of a Fusarium resistant wheat variety, and plowing or crop rotation. Five out of the ten evaluated farm and farmer characteristics significantly (p < 0.05) explained the implementation of at least one of the eight pre-harvest control measures. These five farm and farmer characteristics include wheat as main income crop, the use of a decision support system, the education level of the farmer, the farmer's knowledge about mycotoxins, and the farmer's level of risk aversion. Insight into relevant characteristics can be used by farmer cooperatives, processing industries and government agencies to improve the overall mycotoxin management of wheat farmers.

Agricultura familiar e proteção das culturas: abordagens tradicionais e proximidade com práticas de agricultura biológica

For almost a century, crop protection on family farms has combined traditional practices with curative methods against pests, diseases and weeds, in particular the use of pesticides. These farmers have great territorial, economic and social relevance in Portugal, and the society seeks for their products in local markets, since they associate them with agricultural practices with lower impacts on health and the environment and close to the organic farming concept. Thus, we aim to identify the agricultural practices adopted by family farmers, in the crop protection component, which may have negative impacts on the environment and human health, and which are distant from organic farming. Using a questionnaire (cheklist), applied to 125 family farmers with farms located in Portugal (Viseu, Braga and Barcelos) and Spain (Pontevedra and Padron), the agricultural practices related to crop protection were identified. Some common practices with organic farming were identified: cultural diversity, consociations, crop rotation, and selection of resistant varieties. Others, such as fallow, green interventions or biotechnology protection methods, are only used by some family farmers. On the other hand, chemical control is used by most family farmers.

Molecular characterization and phylogenetic analysis of betasatellite molecules associated with okra yellow vein mosaic disease in Sri Lanka

Okra production in Sri Lanka has been severely affected by okra yellow vein mosaic disease (OYVMD), which is caused by begomoviruses and associated betasatellites. These betasatellite molecules commonly determine the development and severity of the disease. Therefore, knowledge about the genetic variability of betasatellites associated with OYVMD could assist okra breeding programs in the selection of resistant varieties. The present study aimed to characterize the betasatellite DNA sequences associated with OYVMD in Sri Lanka and to determine their phylogenetic relationships. Betasatellite DNA of six virus isolates from widely separated geographical locations were sequenced and compared with already reported begomovirus betasatellites. The betasatellite molecules have features common to other betasatellite DNAs: a conserved nonanucleotide TAATATTAC, a coding sequence for the protein βC1, an adenine rich region and a satellite conserved region. Nucleotide diversity among the isolates was relatively low (π = 0.034). A recombination event was detected at a specific region in the genome of all isolates. The isolates shared >96% sequence identity with bhendi yellow vein betasatellites reported from India and phylogenetic analysis confirmed their genetic relationship.

Advances and Prospects in Wheat Eyespot Research: Contributions from Genetics and Molecular Tools

AbstractEyespot disease caused by the soil‐borne facultative fungi Oculimacula yallundae and O. acuformis is the major component of the stem‐base disease complex of wheat in temperate regions of the world with a cool and wet climate. In this review, we focus on results of genetic studies concerning both partners of the host–pathogen interaction. This comprises analyses of genetic diversity of the pathogen and identification of particular genes within it, evaluation and screening methods for host resistance, resistance sources and genetics of these resistances, breeding of resistant cultivars in wheat, and application of genetic markers in tagging and tracking of eyespot resistance genes. We also attempt to foresee some of the key issues and developments that may occur in future. The identification of markers tightly linked to eyespot resistance genes is the important research focus opening the door to marker‐assisted selection of resistant varieties.

Variabilidade genética de Xanthomonas axonopodis pv. passiflorae

A mancha bacteriana, causada por Xanthomonas axonopodis pv. passiflorae, é uma das mais importantes doenças do maracujazeiro, podendo limitar a produção dessa frutífera em algumas regiões do País. O uso de resistência genética e controle químico, juntamente com o emprego de medidas de exclusão, são as práticas de controle da doença mais recomendadas. Para o desenvolvimento de variedades resistentes é necessário conhecer tanto a variabilidade genética do hospedeiro quanto do patógeno. Nesse trabalho foi estudada a variabilidade de cinqüenta isolados patogênicos de Xanthomonas axonopodis pv. passiflorae, coletados em quatro diferentes locais no estado de São Paulo. No estudo da variabilidade genética foram usados dados de marcadores moleculares RAPD (Random Amplified Polymorphic DNA), os quais foram usados para o cálculo do coeficiente de similaridade de Dice entre os isolados, análise de variância molecular (AMOVA) entre e dentro das populações e agrupamento dos isolados pelo método UPGMA. Para análise da agressividade foram usados cinco isolados, mais divergentes, baseado no dendrograma. O coeficiente de similaridade variou entre 0,6887 e 0,9688. Na análise de agrupamento, os isolados foram separados em sete grupos e não houve relação evidente entre local de coleta com a composição dos grupos. Na análise da variância molecular (AMOVA) verificou-se que a maior parte da variabilidade genética está dentro das populações (89,4%) e apenas 10,6%, entre populações. Os resultados da análise de agrupamento e da AMOVA indicam que existe grande fluxo gênico entre isolados bacterianos nas regiões analisadas. No teste de patogenicidade verificou-se diferença significativa de agressividade entre os isolados. Os resultados demonstram a importância do conhecimento da variabilidade genética e da agressividade na seleção dos isolados para serem utilizados em testes de resistência genética no desenvolvimento de variedades resistentes.

DNA amplification fingerprinting in coconut: protocol optimization and analysis of resistance to root (wilt) disease

Root (wilt) disease is a serious malady in coconut causing a loss of approximately 968 million nuts a year in India. Integrated management practices are the only suggested methods to reduce its effect to some extent, while the development of resistant varieties will offer a permanent solution for which concrete breeding efforts are required. Considering the long life cycle of coconut, selection of resistant varieties through conventional methods will be time consuming and laborious. Molecular markers offer numerous advantages over markers traditionally used in plant mapping and selective breeding. Here, we present the optimization of PCR conditions for DNA amplification fingerprinting (DAF) of coconut using arbitrary oligonucleotide primers. Three of the primers could detect variations between root (wilt) resistant and susceptible coconut palms. This study constitutes the basis for future efforts to tag the root (wilt) resistant gene(s) in coconut.

A PECULIARITIES OF PRINCIPAL DISEASES MANIFESTATION ON STRAWBERRY

Data on the resistance of the strawberry varieties to the above diseases are presented in the article. Many modern strawberry varieties having a high level of commercial characters are susceptible to diseases. White and brown leaf spots are the most harmful diseases in the conditions of Orelregion. With mass infection of strawberry plants, pathogens can affect up to 90% of the leaf mass. The aim of the studies was to evaluate the strawberry varieties for resistance to white and brown leaf spots and identify the most promising varieties for the further breeding. 41 domestic and foreign strawberry varieties have been studied. Currently, the main preventive measures against diseases are the selection of resistant varieties, the use of healthy planting material, as well as the control of leaf infections with fungicides before and after harvest. As a result of the studies, the most resistant varieties to white and brown leaf spots have been identified: Bogema, Bereginya, Rosinka and Krymskaya Rannia which are mostly promising for cultivation in the Central Chernozem region. The strawberry varieties Jonsok, NF 311, Sara, Marmolada, Sonata, Civ 64, Rubin and Frida were susceptible to white and brown leaf spots during three years with the degree of damage 3 points.