Plant Resistance Studies Research Articles

Integrated Approach for Screening Groundnut Genotypes and Unveiling Morphological and Biochemical Factors Associated with Resistance to Thrips, Scirtothrips dorsalis Hood

Thrips is an important sucking insect pest and are the major problem in the groundnut. The pressure from thrips is higher in the summer. One species of thrips i.e., Scirtothrips dorsalis Hood was reported in the present investigation. To minimize crop losses, it is important to efficiently manage thrips, Scirtothrips dorsalis Hood. Finding the source of resistance is one strategy to reduce yield losses. In the summers of 2020 and 2021, forty-four groundnut varieties were screened in the field to determine their resistance to thrips occurrence. Nineteen genotypes were chosen for additional research, including host preference and oviposition preference tests in greenhouse conditions and host plant resistance studies, based on preliminary screening studies conducted at the field level in 2020 and 2021. None of the genotypes were totally free from thrips damage. Nonetheless, three genotypes (Dh-256, RST-1-2020-12, and INS-1-2020-11) were classified as resistant. Ten genotypes were very vulnerable, 14 were susceptible, and 17 were somewhat resistant. The biochemical and morphological examination results showed that resistance against thrips was conferred by increased levels of phenols, tannins, trichome density, and leaf colour.

Genome‐wide association study of adult plant resistance to spot blotch in an elite Canadian two‐row barley germplasm collection

AbstractSpot blotch, caused by Bipolaris sorokiniana, is a growing concern for barley (Hordeum vulgare) production in most humid, temperate growing regions of the world. Under epidemic conditions, this disease can reduce yields significantly. Reduction of kernel plumpness is associated with lower malt extract and consequently grain quality. Enhanced resistance to this disease is a major goal of western Canadian two‐row barley breeding programmes; however, two‐row barley is considered to be more susceptible than six‐row barley. Plant–pathogen interactions observed for Canadian germplasm are polygenic, where quantitative breeding methods could be beneficial for the development of resistant germplasm. A germplasm panel consisting of 200 two‐row, spring barley genotypes with differential reaction to spot blotch was evaluated at Brandon, Manitoba (MB), and Melfort, Saskatchewan (SK), over eight site years. Genome‐wide association study was conducted using a 50k single‐nucleotide polymorphism (SNP) Illumina iSelect genotyping array. The most‐resistant germplasm was found to carry Midwest Six‐rowed Durable Resistant Haplotype (MSDRH) alleles at the loci located on chromosomes 1H (Rcs‐qtl‐1H‐11_10764), 3H (Rcs‐qtl‐3H‐11_10565) and 7H (Rcs‐qtl‐7H‐11_20162, Rcs5 locus), where the 3H locus was found to be the most under‐represented in Canadian germplasm. Additional marker‐trait associations within nurseries were identified on chromosomes 1H, 2H and 4H. Several of the SNP markers identified were found to be polymorphic within the Canadian two‐row germplasm panel and thus could be useful for enhancing spot blotch resistance in two‐row barley for development of resistant cultivars.

Use of effective sources of winter wheat resistance in breeding for immunity

Winter wheat is one of the most important crops in Ukraine, and modern varieties have the potential to produce high yields under favourable conditions. The realisation of the genetic yield potential of a variety is the result of a complex interaction of genotype and environmental variables. In order to find effective sources of resistance, a collection of winter wheat accessions of different ecological and geographical origin was studied. The research was conducted in 2017-2019 in the Right-Bank Forest-Steppe, and the analysis of plant resistance of the winter wheat collection of the National Centre of Plant Genetic Resources of Ukraine was tested against a synthetic infectious background of septoria, brown rust and smut as opposed to the natural background of powdery mildew, leaf yellowing (pyrenophorosis) and other root rot. The collection of 32 varieties was represented by 9 countries, most of them of Ukrainian origin. In the field, on artificial and natural infectious backgrounds, we identified varieties characterised by group resistance to pathogens of major diseases. The studies of adult plant resistance under conditions of infectious natural background and the use of the method of artificial complex infectious background have established that it is possible to investigate and identify sources of resistance to both individual pathogens and a complex of pathogens. As a result, no accessions were found to possess group resistance against the six pathogens presented. The selected varieties, Zdoba Kyivska, Vykhovanka Odeska and Feonia, can be used as sources of group resistance, which allows for excellent breeding efforts leading to the development of resistant wheat varieties. The selected sources are suitable for inclusion in breeding programmes as starting material for the development of modern high-yielding winter durum wheat varieties resistant to diseases and other environmental factors

Evaluating global Vaccinium germplasm for resistance against invasive Drosophila suzukii (Diptera: Drosophilidae).

Control of spotted-wing Drosophila, Drosophila suzukii, in small fruits emphasizes biological, cultural, and chemical approaches, whereas studies of host plant resistance as a form of genetic control are just getting underway. The identification of resistance patterns among genotypes of host plants whose fruit, leaves, roots, stems, or seeds are specifically targeted by an invasive pest is the first step in the development of an effective genetic control. Therefore, a detached fruit bioassay was developed to screen for D. suzukii oviposition and larval infestation within berries from 25 representative species and hybrids of wild and cultivated Vaccinium. Ten Vaccinium species showed strong resistance; among them, two wild diploids originating from within the fly's native range: V. myrtoides and V. bracteatum. Other resistant species came from the sections Pyxothamnus and Conchophyllum. They included New World V. consanguineum and V. floribundum. Large-cluster blueberry, V. amoenum, and three Floridian genotypes of related rabbiteye blueberry, V. virgatum, were the only hexaploids expressing strong resistance against D. suzukii. Most screened blueberry genotypes from managed lowbush and cultivated highbush types were susceptible to the flies' attacks (i.e., oviposition). Tetraploid blueberries tended to host the most eggs, whereas diploids and hexaploids harbored 50%-60% fewer eggs, on average. D. suzukii cannot lay eggs or complete development in the smallest, sweetest, and firmest diploid fruits. Likewise, certain genotypes of large-fruited tetraploid and hexaploid blueberry strongly curbed D. suzukii egg-laying and larval growth, indicating the possibility of heritable resistance operating against this invasive fly species.

Aluminum tolerance and micronutrient content in the grain of oat cultivars with different levels of breeding improvement from the VIR collection

Background. Soil toxicity of Al is associated with severe changes in plant root morphology that limit the uptake of water and mineral nutrients. Long-term exposure to Al results in deficiencies in some important nutrients, such as phosphorus, calcium, magnesium, potassium, and iron. Thus, the joint study of plant resistance to the effects of Al and the accumulation of micronutrients in the oat grain is relevant.Materials and methods. Thirty oat accessions of Russian and French origin from the VIR collection served as the research material. They were represented by cultivars with different levels of breeding improvement: landraces (early 1920s), cultivars developed by primitive breeding (1920–1930s), and modern improved cultivars.Results. Oat cultivars with different breeding improvement levels demonstrated significant differences in the content of micronutrients and aluminum tolerance. Among the studied accessions, landraces and modern improved cultivars showed a tendency towards medium or high Al tolerance, the group of primitive cultivars from Russia had the lowest Al tolerance, while primitive cultivars from France demonstrated the highest average resistance (0.5–1.9).Conclusion. The content of Fe and Zn was influenced by the geographic origin of genotypes. The concentrations of different micronutrients positively correlated with each other. Strong correlations were recorded between the contents of Zn and Fe (r = 0.81), and between Zn and Mg (r = 0.75). There was a positive correlation between the content of micronutrients and the resistance to crown rust (0.38 to 0.50). High content of the studied set of micronutrients was registered in such improved cultivars from France as the naked ‘Avoine Nue Renne’, ‘Chantilly’, ‘Negrita’ and ‘Noire de Michamps’, plus the Russian improved naked cultivar ‘Gavrosh’. Among them, ‘Chantilly’ was distinguished for its yield, and the naked ‘Gavrosh ‘for its high tolerance to aluminum.

Comparative studies on biophysical and biochemical basis of resistance in Brinjal and chilli against aphid (Aphis gossypii)

Investigations on studies of aphid on brinjal and chilli and host plant resistance studies were carried out during 2020 in vallampadugai village, Tamil Nādu, India. Significant difference was observed between the brinjal and chilli local variety in length, thickness, breath was positive correlated and trichome density and trichome length and types were negatively correlated. Biochemical component of resistant plants is sugar, nitrogen was positively correlated, and phenol, potash and silica were negatively correlated with aphid feeding preference.

Hydrogen Sulfide Alleviates Manganese Stress in Arabidopsis.

Hydrogen sulfide (H2S) has been shown to participate in various stress responses in plants, including drought, salinity, extreme temperatures, osmotic stress, and heavy metal stress. Manganese (Mn), as a necessary nutrient for plant growth, plays an important role in photosynthesis, growth, development, and enzymatic activation of plants. However, excessive Mn2+ in the soil can critically affect plant growth, particularly in acidic soil. In this study, the model plant Arabidopsis thaliana was used to explore the mechanism of H2S participation and alleviation of Mn stress. First, using wild-type Arabidopsis with excessive Mn2+ treatment, the following factors were increased: H2S content, the main H2S synthetase L-cysteine desulfhydrase enzyme (AtLCD) activity, and the expression level of the AtLCD gene. Further, using the wild-type, AtLCD deletion mutant (lcd) and overexpression lines (OE5 and OE32) as materials, the phenotype of Arabidopsis seedlings was observed by exogenous application of hydrogen sulfide donor sodium hydrosulfide (NaHS) and scavenger hypotaurine (HT) under excessive Mn2+ treatment. The results showed that NaHS can significantly alleviate the stress caused by Mn2+, whereas HT aggravates this stress. The lcd mutant is more sensitive to Mn stress than the wild type, and the overexpression lines are more resistant. Moreover, the mechanism of H2S alleviating Mn stress was determined. The Mn2+ content and the expression of the Mn transporter gene in the mutant were significantly higher than those of the wild-type and overexpression lines. The accumulation of reactive oxygen species was significantly reduced in NaHS-treated Arabidopsis seedlings and AtLCD overexpression lines, and the activities of various antioxidant enzymes (SOD, POD, CAT, APX) also significantly increased. In summary, H2S is involved in the response of Arabidopsis to Mn stress and may alleviate the inhibition of Mn stress on Arabidopsis seedling growth by reducing Mn2+ content, reducing reactive oxygen species content, and enhancing antioxidant enzyme activity. This study provides an important basis for further study of plant resistance to heavy metal stress.

Metabolomics as an emerging tool to study plant-microbe interactions.

In natural environments, interaction between plant roots and microorganisms are common. These interactions between microbial species and plants inhabited by them are being studied using various techniques. Metabolomics research based on mass spectrometric techniques is one of the crucial approaches that underpins system biology and relies on precision instrument analysis. In the last decade, this emerging field has received extensive attention. It provides a qualitative and quantitative approach for determining the mechanisms of symbiosis of bacteria and fungi with plants and also helps to elucidate the tolerance mechanisms of host plants against various abiotic stresses. However, this -omics application and its tools in plant–microbe interaction studies is still underutilized compared with genomic and transcriptomic methods. Therefore, it is crucial to bring this field forward to bear on the study of plant resistance and susceptibility. This review describes the current status of methods and progress in metabolomics applications for plant–microbe interaction studies discussing current challenges and future prospects.

Feeding behavior of Brevicoryne brassicae in resistant and susceptible collard greens genotypes: interactions among morphological and chemical factors

AbstractThe cabbage aphid, Brevicoryne brassicae (L.) (Hemiptera: Aphididae), is distributed throughout the tropical and subtropical areas of the world. The main crops attacked by B. brassicae are cabbage, collard greens, broccoli, Brussels sprouts, and cauliflower. To survive the attack of pest insects, plants have evolved various resistance mechanisms that may affect pest feeding behavior. The use of electronic monitoring through EPG (electrical penetration graph) can help characterize and distinguish the resistance mechanisms involved. This study evaluated the feeding behavior of B. brassicae in eight genotypes of collard greens, Brassica oleraceae L. var. acephala (Brassicaceae), exhibiting antixenosis and/or antibiosis resistance to this insect. Possible correlations were established between the glucosinolate levels, the hardness, and the epicuticular wax on the leaves vs. aphid feeding behavior. On the genotypes 22V, 5E, and 27VA, for which many ‘potential drop’ waves were performed, aphid development was slower, indicating antixenosis as resistance type. Aphids on the genotypes 22V and 24X required more time until accessing the phloem, also suggesting antixenosis as resistance category. Genotypes 22V and PE had hard leaves, which also points at antixenosis. Genotypes 20T and HS had higher total wax and wax mg−1. Feeding parameters on ARI and 24X were similar to those observed on HS; antibiosis is likely to be the predominant resistance category of this germplasm. Because HS was considered as a susceptible standard genotype in this study, a higher gluconapin amount indicates that this compound does not influence cabbage aphid feeding behavior. The present study confirms that analysis of the physical and chemical aspects of collard greens genotypes by the EPG technique can provide a useful approach for the study of plant resistance to cabbage aphids.

Phytochemicals Involved in Plant Resistance to Leporids and Cervids: a Systematic Review.

Non-nutritive phytochemicals (secondary metabolites and fibre) can influence plant resistance to herbivores and have ecological impacts on animal and plant population dynamics. A major hindrance to the ecological study of these phytochemicals is the uncertainty in the compounds one should measure, especially when limited by cost and expertise. With the underlying goal of identifying proxies of plant resistance to herbivores, we performed a systematic review of the effects of non-nutritive phytochemicals on consumption by leporids (rabbits and hares) and cervids (deer family). We identified 133 out of 1790 articles that fit our selection criteria (leporids = 33, cervids = 97, both herbivore types = 3). These articles cover 18 species of herbivores, on four continents. The most prevalent group of phytochemicals in the selected articles was phenolics, followed by terpenes for leporids and by fibre for cervids. In general, the results were variable but phenolic concentration seems linked with high resistance to both types of herbivores. Terpene concentration is also linked to high plant resistance; this relationship seems driven by total terpene content for cervids and specific terpenes for leporids. Tannins and fibre did not have a consistent positive effect on plant resistance. Because of the high variability in results reported and the synergistic effects of phytochemicals, we propose that the choice of chemical analyses must be tightly tailored to research objectives. While researchers pursuing ecological or evolutionary objectives should consider multiple specific analyses, researchers in applied studies could focus on a fewer number of specific analyses. An improved consideration of plant defence, based on meaningful chemical analyses, could improve studies of plant resistance and allow us to predict novel or changing plant-herbivore interactions.

Progress in physiological and genetic research concerning forest tree response to low temperature

Abstract Forest trees are a great model for physiological and genetic studies of plant resistance to unfavourable environmental conditions, since the same species can successfully acclimate at different latitudes. Modern biology, such as genomics, transcriptomics, proteomics, etc., significantly facilitates these studies and accelerates the acquisition of new knowledge. This allows for a more effective implementation of conservation measures and the renewal of forest ecosystems. This review contains information on the latest scientific achievements in the field of acclimatization and tolerance to abiotic stresses, such as cold and frost, of forest trees. There is no doubt that in the course of evolution forest trees developed a complex and dynamic mechanism for controlling the entry into the winter dormancy stage, which allows woody plants to successfully survive in cold and freezing conditions and is initiated long before the beginning of winter. Studying the function of individual genes in forest tree species, however, remains an incredibly difficult task due to large genomes, specific development as well as the lack of standard techniques and routine procedures. In recent years, similarities between the well-studied genetic response to low temperatures of the model plant Arabidopsis thaliana and forest trees have been identified, which produced meaningful analogies and allows for issues of functional genetics to be addressed more effectively. The main goal of this work was to show that findings from forest tree genomics can be effectively used as a tool for the reproduction and protection of important tree species through the identification of the predisposition of specific populations to climate change and their adaptive capacity.

Assessing the Individual and Combined Effects of QTL for Adult Plant Stripe Rust Resistance Derived from Cappelle-Desprez

The release of commercial wheat cultivars resistant to stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), remains one of the primary objectives in many breeding programs. Previous studies of adult plant resistance derived from the winter wheat cultivar Cappelle-Desprez identified the quantitative trait loci (QTL) QYr.ufs-2A, QYr.ufs-2D, QYr.ufs-5B and QYr.ufs-6D to affect stripe rust under South African conditions. Phenotypic field assessment, fluorescence microscopy and molecular analysis were used to characterise recombinant inbred lines differing in number and combinations of these QTL. Besides the confirmation of enhanced resistance through co-occurring resistance loci, varying levels of defence, conditioned by different QTL combinations were observed. Carriers of QYr.ufs-2A or QYr.ufs-2D, accompanied by at least one other QTL, exhibited higher resistance levels than lines with a single QTL. The knowledge gained in this study will help wheat breeders to develop cultivars with more diverse combinations and potentially more durable sources of stripe rust resistance.

In Silico Characterization of Meloidogyne Genus Nematode Cellulose Binding Proteins

Abstract Root-knot nematodes are a group of endoparasites species that induce the formation of giant cells in the hosts, by which they guarantee their feeding and development. Meloidogyne species infect over 2000 plant species, and are highly destructive, causing damage to many crops around the world. M. enterolobii is considered the most aggressive species in tropical regions, such as Africa and South America. Phytonematodes are able to penetrate and migrate within plant tissues, establishing a sophisticated interaction with their hosts through parasitism factors, which include a series of cell wall degradation enzymes and plant cell modification. Among the parasitism factors documented in the M. enterolobii species, cellulose binding protein (CBP), a nematode excretion protein that appears to be associated with the breakdown of cellulose present in the plant cell wall. In silico analysis can be of great importance for the identification, structural and functional characterization of genomic sequences, besides making possible the prediction of structures and functions of proteins. The present work characterized 12 sequences of the CBP protein of nematodes of the genus Meloidogyne present in genomic databases. The results showed that all CBP sequences had signal peptide and that, after their removal, they had an isoelectric point that characterized them as unstable in an acid medium. The values of the average hydrophilicity demonstrated the hydrophilic character of the analyzed sequences. Phylogenetic analyzes were also consistent with the taxonomic classification of the nematode species of this study. Five motifs were identified, which are present in all sequences analyzed. These results may provide theoretical grounds for future studies of plant resistance to nematode infection.

Metabolite-Centric Reporter Pathway and Tripartite Network Analysis of Arabidopsis Under Cold Stress.

The study of plant resistance to cold stress and the metabolic processes underlying its molecular mechanisms benefit crop improvement programs. Here we investigate the effects of cold stress on the metabolic pathways of Arabidopsis when directly inferred at system level from transcriptome data. A metabolite-centric reporter pathway analysis approach enabled the computation of metabolites associated with transcripts at four time points of cold treatment. Tripartite networks of gene-metabolite-pathway connectivity outlined the response of metabolites and pathways to cold stress. Our metabolome-independent analysis revealed stress-associated metabolites in pathway routes of the cold stress response, including amino acid, carbohydrate, lipid, hormone, energy, photosynthesis, and signaling pathways. Cold stress first triggered the mobilization of energy from glycolysis and ethanol degradation to enhance TCA cycle activity via acetyl-CoA. Interestingly, tripartite networks lacked power law behavior and scale free connectivity, favoring modularity. Network rewiring explicitly involved energetics, signal, carbon and redox metabolisms and membrane remodeling.

Comparative Genome-Wide-Association Mapping Identifies Common Loci Controlling Root System Architecture and Resistance to Aphanomyces euteiches in Pea.

Combining plant genetic resistance with architectural traits that are unfavorable to disease development is a promising strategy for reducing epidemics. However, few studies have identified root system architecture (RSA) traits with the potential to limit root disease development. Pea is a major cultivated legume worldwide and has a wide level of natural genetic variability for plant architecture. The root pathogen Aphanomyces euteiches is a major limiting factor of pea crop yield. This study aimed to increase the knowledge on the diversity of loci and candidate genes controlling RSA traits in pea and identify RSA genetic loci associated with resistance to A. euteiches which could be combined with resistance QTL in breeding. A comparative genome wide association (GWA) study of plant architecture and resistance to A. euteiches was conducted at the young plant stage in a collection of 266 pea lines contrasted for both traits. The collection was genotyped using 14,157 SNP markers from recent pea genomic resources. It was phenotyped for ten root, shoot and overall plant architecture traits, as well as three disease resistance traits in controlled conditions, using image analysis. We identified a total of 75 short-size genomic intervals significantly associated with plant architecture and overlapping with 46 previously detected QTL. The major consistent intervals included plant shoot architecture or flowering genes (PsLE, PsTFL1) with putative pleiotropic effects on root architecture. A total of 11 genomic intervals were significantly associated with resistance to A. euteiches confirming several consistent previously identified major QTL. One significant SNP, mapped to the major QTL Ae-Ps7.6, was associated with both resistance and RSA traits. At this marker, the resistance-enhancing allele was associated with an increased total root projected area, in accordance with the correlation observed between resistance and larger root systems in the collection. Seven additional intervals associated with plant architecture overlapped with GWA intervals previously identified for resistance to A. euteiches. This study provides innovative results about genetic interdependency of root disease resistance and RSA inheritance. It identifies pea lines, QTL, closely-linked markers and candidate genes for marker-assisted-selection of RSA loci to reduce Aphanomyces root rot severity in future pea varieties.

In silico modeling and characterization of phytoparasitic nematodes translationally-controlled tumor proteins.

Plant parasitic nematodes infect a wide range of hosts representing the largest source of biotic stress experienced by plants. Meloidogyne genus comprises the most important parasitic nematodes, also known as root-knot nematodes. These parasitic organisms obtain nutrients to support their development through complex interactions with their hosts. The translationally-controlled tumor protein (TCTP) is widely expressed in eukaryotic organisms, and is related to a great diversity of biological processes such as calcium binding, cell proliferation and growth, pluripotency, regulation of apoptosis, microtubules stabilization, and histamine release. TCTP has been identified in the secretions of plant-parasitic nematodes, and may play a role in suppressing the plant immunity and programmed cell, hence promoting nematode parasitism. Our results revealed a high conservation of the evaluated protein sequences and little variation in their physico-chemical characteristics, such as isoelectric points and hidropathicity. Phylogenetic analysis also revealed the presence of three main groups of TCTPs, corresponding to plant parasitic, animal parasitic and free-living nematodes. Six plant parasitic TCTPs tertiary structure models were generated by homology modeling. The constructed models were highly similar and most of the structural variations occurred outside the characterized functional domains. To our knowledge, these are the first theoretical models of plant parasitic nematodes TCTPs and these results may provide a theoretical basis for future studies of host plant resistance to nematode infection.

Resistance to Melanaphis sacchari (Hemiptera: Aphididae) in Forage and Grain Sorghums.

The sugarcane aphid, Melanaphis sacchari (Zehntner), has established itself as a perennial pest of grain and forage sorghums in the United States since the summer of 2013. We conducted traditional plant resistance studies that determine tolerance, antibiosis, and antixenosis in 32 sorghum genotypes when challenged with sugarcane aphids. The genotypes included one exotic plant introduction and 31 seed and pollinator parental lines that are used to produce grain, sudangrass, and forage sorghum hybrids. One seed parent (B11055) and one grain pollinator parent (R13219) expressed significant degrees of tolerance, antibiosis, and antixenosis and were top performers in all three resistance type experiments. An additional group of seed parents (B13045 and B1057) and grain pollinator parents (R11159, R13422, and RTx2908) and the plant introduction (PI 550610) resulted in an intermediate range of phenotypic resistance (i.e., 4.0 < 6.0) indicative of antibiosis from reduced fecundity, increased intrinsic rate of increase, and increased generation times. The forms of resistance expressed in these lines, especially B11055 and R13219, have great potential in breeding programs that can be integrated into useable forms of resistant sorghums.

Novel insights into the molecular mechanisms underlying the resistance of Camellia sinensis to Ectropis oblique provided by strategic transcriptomic comparisons

The tea plant (Camellia sinensis (L.) O. Kuntze) is vulnerable to Ectropis oblique (Prout) (tea geometrids) in warm and humid climates. Therefore, tea plants have generated a series of mechanisms in response to the two stimuli related to E. oblique feeding: mechanical damage and oral secretion stimuli. To elucidate the molecular mechanisms underlying the responses to these distinct inducers, we employed RNA-sequencing (RNA-Seq) to compare three genome-wide expression profiles of a mechanically damaged plant, geometrid-damaged plant and undamaged control.Using the Illumina sequencing platform, we obtained approximately 304.54 million reads in total. These reads were assembled into 65,548 unigenes with an average length of 602bp and an N50 of 860bp. By comparing the profiles between the mechanically damaged plant and undamaged control, geometrid-damaged plant and undamaged control and geometrid-damaged plant and mechanically damaged plant, 33,418, 27,029 and 28,260 differentially expressed unigenes were identified, respectively. A comparison of the transcriptomes of the geometrid-damaged and mechanically damaged plants showed that 2995 unigenes were induced only by oral secretion stimuli. These unigenes exhibited significant differences in expression for the jasmonate/ethylene signaling and brassinosteroid pathways, terpenoid synthesis and phenylpropanoid biosynthesis, which are involved in defense against insect pests. Finally, reverse transcription PCR (RT-PCR) was used to verify the expression of preferentially expressed unigenes in the geometrid-damaged plant compared with that of the mechanically damaged plant as predicted by RNA-Seq.Our research yielded novel insights into the molecular mechanisms of pest resistance in tea plants and determined numerous genes and pathways that are involved in these processes. In addition, the expressed sequences were compiled to provide a valuable resource for the study of tea plant resistance to pests.

Overview and Application of QTL for Adult Plant Resistance to Leaf Rust and Powdery Mildew in Wheat

ABSTRACTLeaf rust and powdery mildew, caused by Puccinia triticina and Blumeria graminis f. sp. tritici, respectively, are widespread fungal diseases of wheat (Triticum aestivum L.). Development of cultivars with durable resistance is crucially important for global wheat production. This paper reviews the progress of genetic study and application of adult plant resistance (APR) to wheat leaf rust and powdery mildew. Eighty leaf rust and 119 powdery mildew APR quantitative trait loci (QTL) have been reported on 16 and 21 chromosomes, respectively, in over 50 publications during the last 15 yr. More important, we found 11 loci located on chromosomes 1BS, 1BL, 2AL, 2BS (2), 2DL, 4DL, 5BL, 6AL, 7BL, and 7DS showing pleiotropic effects on resistance to leaf rust, stripe rust, and powdery mildew. Among these, QTL on chromosomes 1BL, 4DL, and 7DS also correlate with leaf tip necrosis. Fine mapping and cloning of these QTL will be achieved with the advent of cheaper high‐throughput genotyping technologies. Germplasm carrying these potential resistance genes will be useful for developing cultivars with durable multidisease resistance. In addition to its non‐NBS–LRR (nucleotide binding site–leucine rich repeat) structure, the senescence‐like processes induced by Lr34 could be the reason for durability of resistance; however, more information is needed for a full understanding of the molecular mechanism related to durability. Adult plant resistance genes have been used by CIMMYT for more than 30 yr and have also been transferred to many Chinese wheat varieties through shuttle breeding.

A method for estimating the number of eggs in egg masses of yellow stem borer

Egg masses of yellow stem borer (YSB), Scirpophaga incertulas (Walker), are multilayered and densely covered with hair. Consequently, it is not possible to count the number of eggs in an egg mass, either before or after the eggs have hatched. This results in difficulties in many studies of YSB behavior and host plant resistance in which plants or plots are artificially infested with egg masses, and where interpretation of results would be more powerful if the number of larvae hatching from the egg mass was known. This study demonstrates the accuracy of a method of egg number estimation that we have developed, based on comparison of test egg masses with a “reference collection.”