Resistant Cultivars Research Articles

Genome wide association study reveals new genes for resistance to striped stem borer in rice (Oryza sativa L.).

Rice is one of the most important food crops in the world and is important for global food security. However, damage caused by striped stem borer (SSB) seriously threatens rice production and can cause significant yield losses. The development and use of resistant rice varieties or genes is currently the most effective strategy for controlling SSB. We genotyped 201 rice samples using 2849855 high-confidence single nucleotide polymorphisms (SNPs). We conducted a genome-wide association study (GWAS) based on observed variation data of 201 rice cultivars resistant to SSB. We obtained a quantitative trait locus (QTL)-qRSSB4 that confers resistance to SSB. Through annotation and analysis of genes within the qRSSB4 locus, as well as qRT-PCR detection in resistant rice cultivars, we ultimately selected the candidate gene LOC_Os04g34140 (named OsRSSB4) for further analysis. Next, we overexpressed the candidate gene OsRSSB4 in Nipponbare through transgenic methods, resulting in OsRSSB4 overexpressing lines (OsRSSB4OE). In addition, we evaluated the insect resistance of OsRSSB4OE lines using wild type (Nipponbare) as a control. The bioassay experiment results of live plants showed that after 20 days of inoculation with SSB, the withering heart rate of OsRSSB4OE-34 and OsRSSB4OE-39 lines was only 8.3% and 0%, with resistance levels of 1 and 0, respectively; however, the withering heart rate of the wild-type reached 100%, with a resistance level of 9. The results of the in vitro stem bioassay showed that, compared with the wild-type, the average corrected mortality rate of the SSB fed on the OsRSSB4OE line reached 94.3%, and the resistance reached a high level. In summary, we preliminarily confirmed that OsRSSB4 positively regulates the defense of rice against SSB. This research findings reveal new SSB resistance gene resources, providing an important genetic basis for SSB resistance breeding in rice crops.

Dual-RNA-sequencing to elucidate the interactions between sorghum and Colletotrichum sublineola.

In warm and humid regions, the productivity of sorghum is significantly limited by the fungal hemibiotrophic pathogen Colletotrichum sublineola, the causal agent of anthracnose, a problematic disease of sorghum (Sorghum bicolor (L.) Moench) that can result in grain and biomass yield losses of up to 50%. Despite available genomic resources of both the host and fungal pathogen, the molecular basis of sorghum-C. sublineola interactions are poorly understood. By employing a dual-RNA sequencing approach, the molecular crosstalk between sorghum and C. sublineola can be elucidated. In this study, we examined the transcriptomes of four resistant sorghum accessions from the sorghum association panel (SAP) at varying time points post-infection with C. sublineola. Approximately 0.3% and 93% of the reads mapped to the genomes of C. sublineola and Sorghum bicolor, respectively. Expression profiling of in vitro versus in planta C. sublineola at 1-, 3-, and 5-days post-infection (dpi) indicated that genes encoding secreted candidate effectors, carbohydrate-active enzymes (CAZymes), and membrane transporters increased in expression during the transition from the biotrophic to the necrotrophic phase (3 dpi). The hallmark of the pathogen-associated molecular pattern (PAMP)-triggered immunity in sorghum includes the production of reactive oxygen species (ROS) and phytoalexins. The majority of effector candidates secreted by C. sublineola were predicted to be localized in the host apoplast, where they could interfere with the PAMP-triggered immunity response, specifically in the host ROS signaling pathway. The genes encoding critical molecular factors influencing pathogenicity identified in this study are a useful resource for subsequent genetic experiments aimed at validating their contributions to pathogen virulence. This comprehensive study not only provides a better understanding of the biology of C. sublineola but also supports the long-term goal of developing resistant sorghum cultivars.

Unveiling mungbean yellow mosaic virus: molecular insights and infectivity validation in mung bean (Vigna radiata) via infectious clones.

Yellow mosaic disease (YMD) with typical symptoms of alternating bright yellow to green patches associated with stunting, downward cupping, and wrinkling has been observed in mung bean on agricultural farms in Coimbatore, Tamil Nadu, India. PCR using gene-specific primers indicated the presence of the yellow mosaic virus in symptomatic plants. Rolling circle amplification (RCA) followed by restriction digestion detected ~2.7 kb of DNA-A and DNA-B, allowing the identification of a bipartite genome. The full-length genome sequences were deposited in NCBI GenBank with the accession numbers MK317961 (DNA-A) and MK317962 (DNA-B). Sequence analysis of DNA-A showed the highest sequence identity of 98.39% to the DNA-A of mungbean yellow mosaic virus (MYMV)-Vigna radiata (MW736047), while DNA-B exhibited the highest level of identity (98.21%) to the MYMV-Vigna aconitifolia isolate (DQ865203) reported from Tamil Nadu. Recombinant analysis revealed distinct evidence of recombinant breakpoints of DNA-A within the region encoding the open reading frame (ORF) AC2 (transcription activation protein), with the major parent identified as MYMV-PA1 (KC9111717) and the potential minor parent as MYMV-Namakkal (DQ86520.1). Interestingly, a recombination event in the common region (CR) of DNA-B, which encodes the nuclear shuttle protein and the movement protein, was detected. MYMIV-M120 (FM202447) and MYMV-Vigna (AJ132574) were identified as the event's major and minor parents, respectively. This large variation in DNA-B led us to suspect a recombination in DNA-B. Dimeric MYMV infectious clones were constructed, and the infectivity was confirmed through agroinoculation. In future prospects, unless relying on screening using whiteflies, breeders and plant pathologists can readily use this agroinoculation procedure to identify resistant and susceptible cultivars to YMD.

Effect of postharvest treatments on physiological disorders of ‘Galant’: a new scab resistant apple cultivar

Effect of postharvest treatments on physiological disorders of ‘Galant’: a new scab resistant apple cultivar

Correlação entre resistência à brusone em cultivares de trigo e taxa de esporulação de conídios de Pyricularia oryzae Triticum

ABSTRACT: The use of resistant wheat cultivars is a fundamental strategy to minimize the damages caused by blast, a disease caused by the fungus Pyricularia oryzae Triticum (PoT). The objetive of this stydy was to (a) evaluate the reaction to blast of Brazilian wheat cultivars and (b) determine whether there is correlation between severity of symptoms on wheat spikes and “sporulation rate of PoT conidia per gram of wheat spike rachis” (Rscon). Plants of 16 wheat cultivars were grown in greenhouse until flowering (Zadoks stage 65), when their spikes were inoculated with a suspension formed by mixing the conidia of three PoT isolates. The evaluated variables were blast severity on spikes at 5, 7 and 11 days after inoculation (dai) and Rscon. Rachis were evaluated individually to determine the Rscon. Correlation analyzes were carried out between blast severity means on spikes of cultivars at 5, 7 and 11 dai and Rscon. The cultivars TBIO Mestre, TBIO Aton, ORS 1401, ORS 1403, ORS Destak, ORS Feroz, and CD 116 stood out for being classified in the statistical groups with the highest resistance to blast for the four variables considered in the study. The correlation between blast severity on spikes at 5, 7 and 11 dai and Rscon is at most moderate.

A novel Leifsonia xyli subsp. xyli quantitative LAMP-based diagnostic correlated with sugarcane ratoon stunting disease rating

Context Ratoon stunting disease (RSD), caused by Leifsonia xyli subsp. xyli (Lxx), poses a significant economic threat to sugarcane (Saccharum hybrid) worldwide. RSD is hard to manage due to its elusive visible symptomology and disease rating of cultivars is subjective. Aims We aimed to develop a sensitive, rapid, and quantitative Lxx diagnostic method able to correlate Lxx titre and disease resistance rating of sugarcane cultivars. Methods A Lxx diagnostic method was developed using heat lysis-based reagent-free DNA isolation from xylem sap followed by loop-mediated isothermal amplification (LAMP)-based colorimetric and fluorescence quantification within a single microcentrifuge tube. Bacterial titre was then statistically correlated with industry-agreed disease resistance ratings for key sugarcane cultivars. Key results The diagnostic was highly sensitive (1 cell/μL) and reproducible (%s.d. = <5%, for n = 3), and showed excellent linear dynamic range (i.e. 10 pM−1 aM or 107−100 copies/μL, r = 0.99) for quantitative Lxx detection. LAMP quantifications were completely concordant with quantitative polymerase chain reaction quantification from the same samples. Additionally, a strong correlation was determined between the detected quantitative bacterial titres and known cultivar disease resistance ratings (r = 0.82, n = 10, P < 0.001). Conclusion The novel LAMP-based Lxx diagnostic was validated as a fast, simple, and relatively cost-effective means of RSD resistance rating, making it a reliable contribution towards RSD management. Implications The development of this diagnostic tool provides a practical solution for accurately measuring Lxx titre and assessing disease resistance in sugarcane plants, aiding in effective risk management of RSD spread, and mitigating its economic impact on sugarcane crops worldwide.

Differential expression of microRNAs in response to Papaya ringspot virus infection in differentially responding genotypes of papaya (Carica papaya L.) and its wild relative.

Papaya ringspot virus (PRSV) is one of the most devastating viruses of papaya that has significantly hampered papaya production across the globe. Although PRSV resistance is known in some of its wild relatives, such as Vasconcellea cauliflora and in some of the improved papaya genotypes, the molecular basis of this resistance mechanism has not been studied and understood. Plant microRNAs are an important class of small RNAs that regulate the gene expression in several plant species against the invading plant pathogens. These miRNAs are known to manifest the expression of genes involved in resistance against plant pathogens, through modulation of the plant's biochemistry and physiology. In this study we made an attempt to study the overall expression pattern of small RNAs and more specifically the miRNAs in different papaya genotypes from India, that exhibit varying levels of tolerance or resistance to PRSV. Our study found that the expression of some of the miRNAs was differentially regulated in these papaya genotypes and they had entirely different miRNA expression profile in healthy and PRSV infected symptomatic plants. This data may help in improvement of papaya cultivars for resistance against PRSV through new breeding initiatives or biotechnological approaches such as genome editing.

Densidade inicial de inóculo, época de avaliação e reprodução de Meloidogyne enterolobii em goiabeira 'Paluma'

ABSTRACT Guava decline is a complex disease caused by the interaction between Meloidogyne enterolobii and Neocosmospora falciformis (Syn.: Fusarium solani). Thus, selecting M. enterolobii-resistant genotypes within the genus Psidium is essential for controlling this disease, and developing a resistant cultivar of Psidium guajava could significantly impact this issue. Thus, the objective of this study was to assess the response of the guava plants of the cultivar Paluma to different densities of M. enterolobii inoculum. Guava seedlings were inoculated with 500, 1,000, 5,000, 10,000, and 20,000 eggs + second-stage juveniles (J2) of M. enterolobii per plant. Root and shoot fresh weights, shoot dry weight, root length, plant height, and stem base diameter were evaluated at 70 and 135 days after inoculation (DAI). Total number of M. enterolobii eggs + J2 in the root system and nematode reproduction factor nematode were assessed. Nematode multiplication in roots was not proportional to increases in initial inoculum density; thus, the best plant responses to nematode multiplication in the evaluated cultivar were found for the lowest tested densities. The reproduction factor decreased as the inoculum density was increased, at both evaluations (70 and 135 DAI).

Characterization of the Bipolaris maydis: symptoms and pathogenicity in popcorn genotypes (Zea mays L.).

Southern corn leaf blight (SCLB) is one of the most important corn leaf diseases. Appropriate management strategies and the use of resistant cultivars allow disease control. Therefore, knowing the aspects related to the pathogen and the response of hosts makes it possible to design efficient strategies for selecting genotypes resistant to this disease. In this sense, the objective was to carry out the Bipolaris maydis isolate characterization, evaluating the pathogenicity in different popcorn lines and the symptoms generated in the host after inoculation. The isolate characterization consisted of the macromorphological evaluation of the colonies and the micromorphological evaluation of the conidia in the PDA medium. An experiment was carried out in a greenhouse to evaluate the pathogenicity of the isolate, using 20 inbred lines of popcorn in a randomized block design with four replicates. Inoculation was carried out by spraying leaves, with a suspension containing 1.0 x 104 conidia.ml-1 of the CF/UENF 501 isolate of B. maydis. An incidence assessment and three assessments of disease symptom severity were performed, with seven days intervals between evaluations. The morphological characterization data of the isolate were analyzed using descriptive statistics, and for disease severity, the linear regression model was applied the first-degree model. The variance analysis was performed for the linear and angular coefficients obtained for each treatment. When a difference was found, the Scott-Knott clustering algorithm at 5% significance was applied. The isolate had gray-green colonies, a cottony appearance, and an irregular shape. The lines L353, L354, and L624 show more resistance at the beginning and throughout the evaluations. The high virulence of the CF/UENF 501 isolate made it possible to differentiate the lines in terms of disease intensity and the pattern of symptoms presented.

Discovery of a resistance gene cluster associated with smut resistance in peanut

Peanut smut, caused by Thecaphora frezzii Carranza & J.C. Lindq., is an emerging threat for the global peanut industry. The disease’s destructive potential can be exemplified by pod incidence values as high as 70% and yield losses reaching 30%. Because fungicides have shown moderate but highly variable levels of control levels, development and deployment of smut resistant cultivars are the best strategies for disease management. Screening for smut-resistant germplasm requires years of field trials and is currently the only option for breeders because genetic markers for resistance have not yet been developed. The objectives of this study were to perform whole genome sequencing (WGS) on populations developed for smut resistance mapping and subsequently fine map discovered QTL associated with smut resistance. An expedited strategy was employed by phenotyping in the F3 generation. We phenotyped 200 families with 3 plants per family for smut resistance in infested fields during the 2019/2020 season in General Deheza (32°45′23″S 63°47′20″W), Argentina. Each individual was sequenced using iGenomXRipTide library preparation and Illumina NovaSeq sequencing to yield approximately 1 times genome coverage. Analysis of the phenotype and genotype data using Khufu resulted in the identification of a single major smut resistance QTL on chromosome 12 (B02). Chromosome level genome sequences were assembled for the resistant parent (Ascasubi) and susceptible parent (Granoleico) using PacBio HIFI sequencing. A validation population was sequenced using Khufu to validate the QTL region and analysis confirmed the major locus on chromosome 12. The identified variation will be used to develop smut resistant varieties quickly using molecular assisted breeding strategies.

Analysis of Germin-like protein genes family in Vitis vinifera (VvGLPs) using various in silico approaches.

Germin-like proteins (GLPs) play an important role against various stresses. Vitis vinifera L. genome contains 7 GLPs; many of them are functionally unexplored. However, the computational analysis may provide important new insight into their function. Currently, physicochemical properties, subcellular localization, domain architectures, 3D structures, N-glycosylation & phosphorylation sites, and phylogeney of the VvGLPs were investigated using the latest computational tools. Their functions were predicted using the Search tool for the retrieval of interacting genes/proteins (STRING) and Blast2Go servers. Most of the VvGLPs were extracellular (43%) in nature but also showed periplasmic (29%), plasma membrane (14%), and mitochondrial- or chloroplast-specific (14%) expression. The functional analysis predicted unique enzymatic activities for these proteins including terpene synthase, isoprenoid synthase, lipoxygenase, phosphate permease, receptor kinase, and hydrolases generally mediated by Mn+ cation. VvGLPs showed similarity in the overall structure, shape, and position of the cupin domain. Functionally, VvGLPs control and regulate the production of secondary metabolites to cope with various stresses. Phylogenetically VvGLP1, -3, -4, -5, and VvGLP7 showed greater similarity due to duplication while VvGLP2 and VvGLP6 revealed a distant relationship. Promoter analysis revealed the presence of diverse cis-regulatory elements among which CAAT box, MYB, MYC, unnamed-4 were common to all of them. The analysis will help to utilize VvGLPs and their promoters in future food programs by developing resistant cultivars against various biotic (Erysiphe necator and in Powdery Mildew etc.) and abiotic (Salt, drought, heat, dehydration, etc.) stresses.

Pathotype Characterization of Fusarium oxysporum f. sp. lentis (Fol) Isolates in North America

Fusarium wilt caused by Fusarium oxysporum f. sp. lentis ( Fol) is a devastating disease of lentils impacting yield in the Northern Great Plains. Characterizing the different pathotypes of Fol and their distribution is an essential part of breeding for resistant cultivars. To date, there has been no characterization of Fol pathotypes in North America. Using a lentil differential set from the International Center for Agriculture Research in Dry Areas, 51 pathogenic isolates of Fol from Canada, Montana, Washington, and North Dakota were characterized based on virulence assessed on foliar wilt symptoms using a disease index. Nine pathotypes were identified; pathotype 7 was highly virulent on all the differential sets and the most predominant at 55%. Pathotypes 1 and 6 were the second most predominant at 10 and 11%, respectively. This study identified for the first time Fol pathotypes present in North America. These findings will help in future efforts for Fusarium wilt management in lentils.

Methylglyoxal metabolism is altered during defence response in pigeonpea (Cajanus cajan (L.) Millsp.) against the spotted pod borer (Maruca vitrata).

Pigeonpea (Cajanus cajan ) production can be affected by the spotted pod borer (Maruca vitrata ). Here, we identified biochemical changes in plant parts of pigeonpea after M. vitrata infestation. Two pigeonpea genotypes (AL 1747, moderately resistant; and MN 1, susceptible) were compared for glyoxalase and non-glyoxalase enzyme systems responsible for methylglyoxal (MG) detoxification, γ-glutamylcysteine synthetase (γ-GCS), glutathione-S-transferase (GST) and glutathione content in leaves, flowers and pods under control and insect-infested conditions. MN 1 had major damage due to M. vitrata infestation compared to AL 1747. Lower accumulation of MG in AL 1747 was due to higher activities of enzymes of GSH-dependent (glyoxylase I, glyoxylase II), GSH-independent (glyoxalase III) pathway, and enzyme of non-glyoxalase pathway (methylglyoxal reductase, MGR), which convert MG to lactate. Decreased glyoxylase enzymes and MGR activities in MN 1 resulted in higher accumulation of MG. Higher lactate dehydrogenase (LDH) activity in AL 1747 indicates utilisation of MG detoxification pathway. Higher glutathione content in AL 1747 genotype might be responsible for efficient working of MG detoxification pathway under insect infestation. Higher activity of γ-GCS in AL 1747 maintains the glutathione pool, necessary for the functioning of glyoxylase pathway to carry out the detoxification of MG. Higher activities of GST and GPX in AL 1747 might be responsible for detoxification of toxic products that accumulates following insect infestation, and elevated activities of glyoxylase and non-glyoxylase enzyme systems in AL 1747 after infestation might be responsible for reducing reactive cabanoyl stress. Our investigation will help the future development of resistant cultivars.

Results Regarding the Re-Emergence of Early Blight (Alternaria spp.) and Risk Management in Potato Growing Areas

Early blight caused by Alternaria spp. is a problem in many potato and tomato growing areas. Since some years, more and more countries report an increasing occurrence of early blight in the fields. Attacks of early blight was not see in potato fields from Barsa country, Romania, in the last years. But 2019 was an year with reemergence of early blight attack to different potato varieties. Application of fungicides is commonly used to effectively control the disease, although they are undesirable due to environmental consequences. Use of resistant cultivars would be the most optimal solution, but there are no cultivars with high level of resistance available on the market. Potato trials were carried out between 2019-2020 to the NIRDPSB Brasov on chernozeum soil with a randomised complete block design and four replicates with five Romanian varieties: Brasovia, Cezarina, Asinaria, Sevastia and Castrum. At the time of the disease, observations were made regarding the level of the attack. The determinations were performed on the lower, middle and upper level of the foliage of the tested plants (10 plants x 2 rows x 4 repetitions). Area under the disease progress curve (AUDPC) was calculated based on visual assessment of foliar disease during the growing season each year. AUDPC ranged from 3143 to 170.5 in 2019 and from 1681.6 to 54 in 2020, respectively. The obtained productions varied between 27.17 t/ha (Castrum variety) and 43.03 t/ha (Cezarina variety) in 2019 and between 37.06 t/ha (Castrum variety) and 61.12 t/ha (Sevastia variety) in 2020.

Genome-wide association analysis identifies a consistent QTL for powdery mildew resistance on chromosome 3A in Nordic and Baltic spring wheat

Key messageQPm.NOBAL-3A is an important QTL providing robust adult plant powdery mildew resistance in Nordic and Baltic spring wheat, aiding sustainable crop protection and breeding.Powdery mildew, caused by the biotrophic fungal pathogen Blumeria graminis f. sp. tritici, poses a significant threat to bread wheat (Triticum aestivum L.), one of the world’s most crucial cereal crops. Enhancing cultivar resistance against this devastating disease requires a comprehensive understanding of the genetic basis of powdery mildew resistance. In this study, we performed a genome-wide association study (GWAS) using extensive field trial data from multiple environments across Estonia, Latvia, Lithuania, and Norway. The study involved a diverse panel of recent wheat cultivars and breeding lines sourced from the Baltic region and Norway. We identified a major quantitative trait locus (QTL) on chromosome 3A, designated as QPm.NOBAL-3A, which consistently conferred high resistance to powdery mildew across various environments and countries. Furthermore, the consistency of the QTL haplotype effect was validated using an independent Norwegian spring wheat panel. Subsequent greenhouse seedling inoculations with 15 representative powdery mildew isolates on a subset of the GWAS panel indicated that this QTL provides adult plant resistance and is likely of race non-specific nature. Moreover, we developed and validated KASP markers for QPm.NOBAL-3A tailored for use in breeding. These findings provide a critical foundation for marker-assisted selection in breeding programs aimed at pyramiding resistance QTL/genes to achieve durable and broad-spectrum resistance against powdery mildew.

Characterization of QoI-Fungicide Resistance in Cercospora Isolates Associated with Cercospora Leaf Blight of Soybean from the Southern United States.

Cercospora leaf blight (CLB) of soybean, caused by Cercospora cf. flagellaris, C. kikuchii, and C. cf. sigesbeckiae, is an economically important disease in the southern United States. Cultivar resistance to CLB is inconsistent; therefore, fungicides in the quinone outside inhibitor (QoI) class have been relied on to manage the disease. Approximately 620 isolates from plants exhibiting CLB were collected between 2018 and 2021 from 19 locations in eight southern states. A novel polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay based on two genes, calmodulin and histone h3, was developed to differentiate between the dominant species of Cercospora, C. cf. flagellaris, and C. cf. sigesbeckiae. A multilocus phylogenetic analysis of actin, calmodulin, histone h3, ITS rDNA, and transcription elongation factor 1-α was used to confirm PCR-RFLP results and identify remaining isolates. Approximately 80% of the isolates collected were identified as C. cf. flagellaris, while 15% classified as C. cf. sigesbeckiae, 2% as C. kikuchii, and 3% as previously unreported Cercospora species associated with CLB in the United States. PCR-RFLP of cytochrome b (cytb) identified QoI-resistance conferred by the G143A substitution. Approximately 64 to 83% of isolates were determined to be QoI-resistant, and all contained the G143A substitution. Results of discriminatory dose assays using azoxystrobin (1 ppm) were 100% consistent with PCR-RFLP results. To our knowledge, this constitutes the first report of QoI resistance in CLB pathogen populations from Alabama, Arkansas, Kentucky, Mississippi, Missouri, Tennessee, and Texas. In areas where high frequencies of resistance have been identified, QoI fungicides should be avoided, and fungicide products with alternative modes-of-action should be utilized in the absence of CLB-resistant soybean cultivars.

Adaptation of Fusarium Species causing Head Blight to Quantitative Resistance in Wheat: Field Evidence for Increased Aggressiveness in a New Pathogen Population

The use of quantitatively resistant wheat cultivars is an essential component of a sustainable management strategy of Fusarium head blight (FHB), caused by several Fusarium species. However, little information is available on the variation of aggressiveness of the newly emerging FHB collection compared to old one. It is therefore important to determine to what extent FHB populations can be selected for increased aggressiveness by wheat cultivars with several levels of quantitative resistance. To this end, FHB populations were sampled in 2005 (old population) and in 2015 (new population) from one of the major Syrian wheat production regions, chosen as a location where head blight occurs regularly. New and old FHB isolates were characterized for aggressiveness by single-floret inoculation under controlled conditions on eight durum and bread wheat cultivars of contrasting susceptibility to FHB, and molecularly distinguished using DNA markers. Results showed the new population caused a higher disease severity (ranging from 55% to 67%) than the old population. Thus, their aggressiveness increased between early and late samplings, suggesting that wheat plants cultivated over 10 years selected for increased aggressiveness during epidemics. Our comparative population genetic analyses with analyzed markers showed that the new population had more polymorphic loci compared with the old one. The information obtained in this study indicated that FHB populations adapt to prevailing wheat cultivars, irrespective of their resistance levels, and can therefore overcome polygenic, quantitative resistance. Adaptation to wheat resulting in increased pathogen aggressiveness that was not specific may render quantitative resistance nondurable if not properly managed

ASSESSMENT OF DIFFERENT TOMATO VARIETIES AND CHEMOTHERAPEUTIC COMPOUNDS FOR CONTROLLING ROOT ROT DISEASE CAUSED BY RHIZOCTONIA SOLANI

Solanum lycopersicum L., commonly known as tomato, is a vital vegetable crop with significant nutritional value but is susceptible to various pathogens causing diseases. Among all of these, Rhizoctonia solani-induced root rot is a highly destructive disease affecting tomato production and quality. This study aimed to identify resistant tomato varieties and effective chemical strategies for root rot management. Ten tomato varieties and advanced lines were evaluated under field conditions, and disease incidence was recorded. Nadir (11.80%) and Sundar (18.43%) exhibited resistance with the lowest disease incidence, while To-1057 f1 (25.87%), Ahmar (32.13%), and Litth-879-2 f3 (36.77%) showed moderate resistance. Moderately susceptible varieties included Rio-grandi (40.67%), Salar (47.90%), and Naqeeb (52.83%), while FS-2187 (75.90%) and Litth-861-4-17 (80.93%) were susceptible and highly susceptible, respectively. Additionally, six fungicides were tested under in-vitro and greenhouse conditions, with Dolomite, Nativo, and Evicine exhibiting the best performance. Further evaluation of these fungicides in field conditions confirmed Evicine effectiveness in reducing disease incidence. These findings emphasize the need for future research and development of resistant tomato cultivars and recommend the use of Evicine as an effective treatment against Rhizoctonia solani for disease management.

Infestation of White Waxy Scale on Coffea arabica in Southwestern Ethiopia

Over 49 coffee insect species reported in Ethiopia. However, mealybugs and whitefly are the pests currently recorded in Ethiopia. Ceroplastes brevicauda (Hemiptera: Coccidae) is one of potentially important coffee pest. From assessed coffee trees around 96% and 27% mean infestation of bearing branch and dried branch due to the insect recorded, respectively from coffee hybrids. Coffee berry disease resistant cultivars were exhibit cross-susceptibility against white waxy scale. The white waxy scale although affecting Acacia abyssinica shade tree. Cultural pest management such as pruning infested coffee branches and rubbing the waxy scale by using alcohol is best fits in integrated pest management which usually recommended for coffee producers. Therefore, future research works should be focused on characterizing and identifying the natural enemies and screening insecticides as one management of pest management options.

Development and assessment of biotic stress tolerant cucumber hybrids using land races and commercial varieties

Cucumber growers suffer significant economic losses due to yield reductions caused by pest such as fruit fly and diseases like powdery mildew, and downy mildew. Therefore, one of the greatest ways to reduce losses caused by these pressures is to grow resistant cultivars. The objective of this study was to estimate important genetic parameters to approximate inbred line performance in the F1 generation, and to identify appropriate F1 cross combinations resistant to these biotic stresses. Thirty F1 hybrid combinations were screened, along with 13 parents (ten diverse stable lines and three testers), and a standard check. The genotypes UHF-CUC-11, UHF-CUC-13, UHF-CUC-6, UHF-CUC-15, UHF-CUC-8, Solan Srijan and F1 cross-combinations UHF-CUC-11 × Solan Srijan, UHF-CUC-13 × Solan Srijan, UHF-CUC-6 × K-75, UHF-CUC-15 × Solan Srijan and UHF-CUC-8 × Solan Srijan were found superior for these biotic stresses in the experimental results. Additionally, the predominance of non-additive gene activity due to genetic complementation between parents suggests that heterosis breeding could be helpful in enhancing these features in cucumber. Therefore, the present study's identification of resistant parents and hybrid combinations can be used to introduce the resistance genes into the necessary elite backgrounds of cucumber for the generation of biotic stress resistant varieties/hybrids.