Honeydew Excretion Research Articles

Phenotypic evaluation of Ptb 33 introgressed rice lines for resistance to brown planthopper, Nilaparvata lugens (Stål)

Brown planthopper (BPH), Nilaparvata lugens (Stal) continues its dominantce as an important pest in rice and cause considerable yield loss. Ptb 33 is a well-known source of resistance to BPH. Introgressed lines from Ptb 33 were evaluated against BPH using various parameters of resistant mechanisms. Initial screening was done by protray and modified seedbox screening tests. Eight entries illustrate resistance to BPH in mass screening. Further experiments assessed the mechanisms viz., antibiosis, antixenosis and tolerance in selected resistant entries. Antibiosis studies revealed reduced honeydew excretion, lower nymphal survival rates and prolonged developmental periods in resistant lines compared to the susceptible check. Antixenosis was evaluated through nymphal settling preference tests, with resistant entries showing reduced BPH attraction over time. Tolerance parameters, including Functional Plant Loss Index (FPLI) and Plant Dry Weight Loss Index (PDWLI), indicated varying levels of resistance among the introgressed lines. Among the entries identified as resistant through screening, FSR-3 exhibited strong resistance across all three mechanisms, while X21302-145 showed excellent antibiosis but poor tolerance character. Correlation analysis revealed significant interrelation between various resistance parameters. The study identifies promising BPH-resistant rice lines and elucidates their underlying resistance mechanisms, contributing valuable insights for rice breeding programs in developing durable BPH-resistant cultivars.

Jasmonate-mediated polyamine oxidase 6 drives herbivore-induced polyamine catabolism in rice.

Polyamines (PAs) along with their conjugated forms, are important mediators of plant defense mechanisms against both biotic and abiotic stresses. Flavin-containing polyamine oxidases (PAOs) regulate PA levels through terminal oxidation. To date, the role of PAOs in plant-herbivore interaction remains poorly understood. We discovered that infestation by the brown planthopper (BPH) disrupts PA homeostasis within the leaf sheaths of rice plants, which co-occurs with the upregulation of OsPAO6, a tissue-specific inducible, apoplast-localized enzyme that regulates the terminal catabolism of spermidine (Spd) and spermine. Functional analysis using CRISPR-Cas9 genome-edited plants revealed that pao6 mutants accumulated significantly higher levels of Spd and phenylpropanoid-conjugated Spd in response to BPH infestation compared to wild-type controls. In addition, BPH feeding on pao6 mutants led to increased honeydew excretion and plant damage by female adults, consistent with in vitro experiments in which Spd enhanced BPH feeding. Furthermore, OsPAO6 transcription is regulated by jasmonate (JA) signaling, and it is dependent on MYC2, which directly binds to the G-box-like motif in the OsPAO6 promoter. Our findings reveal an important role of OsPAO6 in regulating polyamine catabolism in JA-induced responses triggered by herbivore attacks in rice.

Rice Brown Planthopper, Nilaparvata lugens (Stål) Feeding Behaviour in Resistant NAGINA22 Rice Mutants

Background: Rice (Oryza sativa L.), is an important staple food and an excellent source of calories in India. Of the different insect pests attacking rice, brown planthopper, BPH, Nilaparvata lugens (Stål) is an important sucking pest causing upto 100% yield losses. Host plant resistance is the most important method in keeping BPH under control and understanding the underlying mechanisms of resistance is necessary to breed the resistant varieties with desirable characters. Methods: Selected EMS mutant lines of Nagina22 (N22) variety, which were previously mass screened under controlled greenhouse conditions were assessed for their antixenosis mechanism to brown planthopper feeding by measuring probing marks and honeydew excretion area by following standard procedures and statistical analysis was done by using Statistix 8.1 software. Result: Both the brown planthopper nymphs and adults probed more in the resistant mutants compared to the susceptible mutants whereas the BPH adults probed more times (24.4) compared to the nymphs (22.2). The recorded honeydew excretion area by the resistant mutants was lower than that of susceptible mutants. In general, the BPH adults fed more and excreted more honeydew (79.5 mm2) compared to the nymphs (59.0 mm2). The damage score has a negative correlation with the probing marks of adults (-0.207) and nymphs (-0.411); and a positive correlation with honeydew excretion of adults (0.547) and nymphs (0.200). In this study, the EMS N22 mutants resistant to BPH, with a greater number of probing marks and less honeydew excretion area can serve as best donors in the breeding programmes to develop brown planthopper resistant varieties.

Genome-wide association study and genomic prediction for resistance to brown planthopper in rice.

The brown planthopper (BPH) is the most destructive insect pest that threatens rice production globally. Developing rice varieties incorporating BPH-resistant genes has proven to be an effective control measure against BPH. In this study, we assessed the resistance of a core collection consisting of 502 rice germplasms by evaluating resistance scores, weight gain rates and honeydew excretions. A total of 117 rice varieties (23.31%) exhibited resistance to BPH. Genome-wide association studies (GWAS) were performed on both the entire panel of 502 rice varieties and its subspecies, and 6 loci were significantly associated with resistance scores (P value < 1.0e-8). Within these loci, we identified eight candidate genes encoding receptor-like protein kinase (RLK), nucleotide-binding and leucine-rich repeat (NB-LRR), or LRR proteins. Two loci had not been detected in previous study and were entirely novel. Furthermore, we evaluated the predictive ability of genomic selection for resistance to BPH. The results revealed that the highest prediction accuracy for BPH resistance reached 0.633. As expected, the prediction accuracy increased progressively with an increasing number of SNPs, and a total of 6.7K SNPs displayed comparable accuracy to 268K SNPs. Among various statistical models tested, the random forest model exhibited superior predictive accuracy. Moreover, increasing the size of training population improved prediction accuracy; however, there was no significant difference in prediction accuracy between a training population size of 737 and 1179. Additionally, when there existed close genetic relatedness between the training and validation populations, higher prediction accuracies were observed compared to scenarios when they were genetically distant. These findings provide valuable resistance candidate genes and germplasm resources and are crucial for the application of genomic selection for breeding durable BPH-resistant rice varieties.

Genomic dissection of brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae) resistance in Indica rice genotypes

AbstractThe population growth and the regular breakout of Nilaparvata lugens pose a significant risk to rice cultivation. Four different N. lugens biotypes have been identified worldwide, with biotype 4 being the most destructive and prevalent throughout Asia, particularly in India. Therefore, a rice variety with multiple resistance genes/alleles is required for effective management of N. lugens. Hence, 191 rice genotypes collected from various parts of India were evaluated for resistance to N. lugens. Further, SSR markers representing 23 different N. lugens resistant (R) genes were assayed to identify genomic regions associated with resistance. The results of the genetic analysis showed that the average genetic diversity value of all markers was 0.165 and polymorphic information content of 0.145 for all the markers used. The population structure and cluster analysis divided the studied genotypes into three distinct groups, with resistant genotypes grouped separately. These findings were confirmed by the principal coordinate analysis, which categorized resistant genotypes, moderately resistant genotypes, and susceptible genotypes into distinct components. Additionally, 90% of the genetic variation was between individuals of populations and 10% between the populations. Marker‐trait association study through mixed linear model and generalized linear model identified six SSR markers such as RM6732 (Bph15), RM314 (Bph6), RM16999 (Bph6), RM7 (QBph3), RM401 (bph4), and RM7102 (Bph1), which were significantly associated with various phenotypic parameters, such as feeding mark, honeydew excretion, percent damage and nymphal survival. The resistant genes identified in these genotypes could help in the marker‐assisted rice variety development with durable resistance against N. lugens.

Rice brown planthopper, Nilaparvata lugens (Stål) feeding behavior in relation to elevated CO2 and temperature

Feeding behavior of brown planthopper, Nilaparvata lugens (Stål) populations collected from different geographical regions Ludhiana, Nalgonda and West Godavari at three generations 1, 5 and 10 fed on rice plants grown under different CO2 and temperature levels 1) Ambient CO2@ 380±25ppm + ambient temperature (aCO2+aT), 2) Elevated CO2@500±25ppm + ambient temperature (eCO2+aT) and 3) Elevated CO2@500±25ppm + elevated temperature (eCO2+eT) in closed CO2 chambers was studied. Elevated CO2 + elevated temperature increased feeding rate of BPH nymphs while BPH adults showed declined feeding rate. BPH nymphal feeding rate increased with progressive generations while it decreased in BPH adults. Ludhiana adult BPH population showed higher honeydew excretion compared to West Godavari and Nalgonda populations. CO2 + temperature levels at progressive generations have varying effects on adults and nymphs of three BPH populations. Biochemical composition of rice plants grown under different CO2 levels revealed increased rate of soluble sugars, phenols and decreased rate of reducing sugars, soluble proteins, free amino acids, nitrogen, potassium, phosphorous in elevated CO2 + elevated temperature levels compared to ambient conditions. Increased feeding rate of BPH under elevated CO2 levels may be to compensate changes in host plant quality i.e., high soluble sugars and low nitrogen.

Comprehensive comparative toxicity study on tomato (Solanum lycopersicum) and brinjal (Solanum melongena) using green labelled insecticides against Bemisia tabaci

Bemisia tabaci a serious sucking pest of tomato (Solanum lycopersicum L.) and brinjal (Solanum melongena L.), is mostly managed using high-dose conventional insecticides, which are harmful for end-users and the environment. Target-insect is also known to exhibit host-dependent variation in insecticidal toxicities; therefore an experiment was conducted during 2020–22 at ICAR-Indian Agricultural Research Institute, New Delhi, to study the host-specific toxicity relationships on tomato and brinjal using market-available safer insecticides with green labels in the Indian context. Bioefficacy evaluated on eggs, nymphs, and adults using leaf-dip bioassay (IRAC) recorded higher LC50 for candidate insecticides (clothianidin, spinetoram and cyantraniliprole), but lower toxicities for azadirachtin and novaluron for test-insects reared on brinjal. The possible role of test-leaf on LC50 was evaluated in a reciprocal way, i.e. test-populations grown in tomato were subjected to brinjal leaf bioassay and vice versa. This resulted to no significant change in LC50 and implies no effect of the test leaf. Feeding (honeydew excretion) and oviposition studies showed higher honeydew excretion (76.4 mm2) and egg-laying (43.6 eggs) per 20 adults on brinjal. Detoxification enzymatic activities in control showed the test enzymes, viz. carboxylesterase, glutathion S-transferase and cytochrome P450 monooxygenase, were at higher concentrations in the brinjal population, i.e. 1.75, 1.43 µ mol/min/mg, and 3.10 n mol/min/mg of protein. Results showed that brinjal is the preferred host for B. tabaci, on which it develops healthier and resulting in a higher insecticide dose to arrive at the desired lethal effect.

Sublethal concentrations of pymetrozine reduce Sogatella furcifera transmission of Southern rice black-streaked dwarf virus.

The transmission of plant viruses is closely associated with the specific probing behaviors of the vectors. Pymetrozine is a pyridine azomethine insecticide that interferes with nervous regulation of feeding behavior of piercing-sucking insects. This study aimed to evaluate the potential of sublethal concentrations of pymetrozine in reducing the transmission of Southern rice black-streaked dwarf virus (SRBSDV) by the planthopper Sogatella furcifera. Laboratory assays showed that both acquisition and inoculation rates of SRBSDV decreased significantly in the planthoppers feeding on plants treated with lethal concentrations 10% and 50% (LC10 and LC50 ) pymetrozine compared with the insects feeding on the control plants, for which significant effects of pymetrozine concentration and time post-treatment were detected. Honeydew excretion of the planthoppers showed significant reduction with increasing concentration of the insecticide but no significant association with time post-treatment. Electrical penetration graph recordings revealed that total durations of each waveform in both acquisition and inoculation were significantly affected by pymetrozine treatment, with total durations of non-probing (NP), penetration initiation (N1), and extracellular activity (N3) elongated whereas those of salivation (N2) and phloem-related activities (N4-a and N4-b) shortened. Additionally, both acquisition and inoculation rates were significantly lower at 168 h than at 6 h post-treatment. The results indicate that sublethal concentrations of pymetrozine reduce SRBSDV transmission, which is associated with reduction in feeding and alteration in probing behaviors characterized by the prolonged non-probing, penetration initiation and extracellular activity and shortened salivation and phloem-related activities. © 2023 Society of Chemical Industry.

The salivary chaperone protein NlDNAJB9 of Nilaparvata lugens activates plant immune responses.

The brown planthopper (BPH) Nilaparvata lugens (Stål) is a main pest on rice. It secretes saliva to regulate plant defense responses, when penetrating rice plant and sucking phloem sap through its stylet. However, the molecular mechanisms of BPH salivary proteins regulating plant defense responses remain poorly understood. A N. lugens DNAJ protein (NlDNAJB9) gene was highly expressed in salivary glands, and the knock down of NlDNAJB9 significantly enhanced honeydew excretion and fecundity of the BPH. NlDNAJB9 could induce plant cell death, and the overexpression of NlDNAJB9 gene in Nicotiana benthamiana induced calcium signaling, mitogen-activated protein kinase (MAPK) cascades, reactive oxygen species (ROS) accumulation, jasmonic acid (JA) hormone signaling and callose deposition. The results from different NlDNAJB9 deletion mutants indicated that the nuclear localization of NlDNAJB9 was not necessary to induce cell death. The DNAJ domain was the key region to induce cell death, and the overexpression of DNAJ domain in N. benthamiana significantly inhibited insect feeding and pathogenic infection. NlDNAJB9 might interact indirectly with NlHSC70-3 to regulate plant defense responses. NlDNAJB9 and its orthologs were highly conserved in three planthopper species, and could induce ROS burst and cell death in plants. Our study provides new insights into the molecular mechanisms of insect-plant interactions.

Reducing Expression of Salivary Protein Genes by Flonicamid Partially Contributed to Its Feeding Inhibition of the Brown Planthopper on Rice.

Flonicamid inhibits the feeding of piercing-sucking pests as a selective systemic insecticide. The brown planthopper (BPH), Nilaparvata lugens (Stål), is one of the most serious pests on rice. During feeding, it uses its stylet to collect sap by penetrating the phloem, and at the same time, it delivers saliva into the rice plant. Insect salivary proteins play important roles in feeding and interacting with plants. Whether flonicamid affects the expression of salivary protein genes and then inhibits the feeding of BPH is not clear. Here, from 20 functionally characterized salivary proteins, we screened five salivary proteins (NlShp, NlAnnix5, Nl16, Nl32, and NlSP7) whose gene expressions were significantly inhibited by flonicamid. We performed experimental analysis on two of them (Nl16 and Nl32). RNA interference of Nl32 significantly reduced the survival rate of BPH. Electrical penetration graph (EPG) experiments showed that both flonicamid treatment and knockdown of Nl16 and Nl32 genes significantly reduced the feeding activity of N. lugens in the phloem and also reduced the honeydew excretion and fecundity. These results suggested that the inhibition of flonicamid on the feeding behavior in N. lugens might be partially attributed to its effect on the expression of salivary protein genes. This study provides a new insight into the mechanism of action of flonicamid on insect pests.

Seed Priming of Rice Varieties with Decoyinine Improve Their Resistance against the Brown Planthopper Nilaparvata lugens

The brown planthopper (BPH), Nilaparvata lugens Stål (Hemiptera: Delphacidae) is one of the most destructive rice pests in Asia. The microbial metabolite decoyinine (DCY) has been extracted from Streptomyces hygroscopicus. Recent studies have suggested that treating rice seeds with DCY could improve the growth and yield of rice. To further assess the effects of priming the seeds of different rice varieties with DCY on rice seedling resistance against BPH, an age-stage, two-sex life table and choice test were applied to investigate the individual fitness, population parameters, and preference behavior of BPHs in this study. The results indicated that feeding on rice seedlings grown from seeds primed with DCY significantly affected BPHs’ adult longevity, oviposition period, fecundity, as well as the net reproductive rate (R0), intrinsic rate of increase (rm), finite rate of increase (λ), doubling time (DT), and population size in terms of BPH. The honeydew excretions and the weights of BPHs fed on DCY-pretreated rice plants were remarkably lowered. The two-way ANOVA results also showed that there were significant differences in the biological parameters, honeydew excretions, and of BPH weights owing to DCY treatment, rice variety, and the interactions between DCY treatment and rice variety. Additionally, the feeding and oviposition preferences of BPHs for the pretreated rice plants were reduced. Our results imply that the priming of seeds with DCY can improve rice resistance against BPH, which could facilitate the utilization of seed priming as a new avenue for effective crop protection.

Characterizing the Mechanism of Serotonin Alleviates Rice Resistance to Brown Planthopper Nilaparvata lugens (Homoptera: Delphacidae) Nymphs

Serotonin is a well-known secondary metabolite that plays an important role in many growth and developmental processes, as well as biotic and abiotic stress responses of plants. Yet, whether serotonin biosynthesis regulates the resistance of rice to the brown planthopper (BPH) Nilaparvata lugens and its underling mechanisms have not been entirely investigated. In this study, we found that expression levels of four serotonin biosynthesis gene, OsTDC1, OsTDC2, OsTDC3, and OsT5H, and the serotonin content were significantly induced by BPH nymph infestation. The rice seedlings pretreated with serotonin were more attractive to BPH nymphs and promoted their feeding behavior as indicated by increased honeydew excretion. In addition, serotonin application to artificial diets increased the survival rates of BPH nymphs in a dose-dependent manner compared to the controls. Moreover, the exogenous serotonin application to rice seedlings increased the average injury scale and functional plant loss indices caused by BPH nymph infestation. Moreover, supplemented serotonin enhanced soluble sugar and free amino acid contents, as well as the activities of SOD, POD, and PPO, but repressed the production of flavonoids. Our findings illustrated that serotonin plays a negative role in the regulation of rice resistance to BPH nymphs probably by modulating contents of soluble sugars, free amino acids, and flavonoids.

Management of whitefly, Bemisia tabaci (Gennadius) in bushy Lac host, Flemingia semialata at Thrissur, Kerala

Flemingia semialata is an established host plant of lac insects and is widely grown to promote lac cultivation in India. One of the most destructive pests that can cause significant yield loss in many crops is a sap sucking whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), which is also found to infest the Flemingia sp. They cause vast damage to the host plants during feeding by reducing the rate of photosynthesis through the excretion of honeydew and by transmitting a large number of plant pathogenic viruses. Although there are several methods to control whitefly infestation, the commonly adopted practice is the application of chemical pesticides, owing to their efficiency in whitefly control. This study focused to test the effectiveness of two chemical: Thiamethoxam 25% WG (Actara®) and Phosmet 70 % WP (Imidan®) and an organic pesticide: Neem Oil, in whitefly control on F. semialata. The experimental design consisted of two different concentrations of each pesticide i.e., Phosmet 0.5 ml/L, 1ml/L, Thiamethoxam 0.25g/L, 0.5 g/L, Neem oil 1ml/L, 2ml/L applied on 21 test plants in sets of three and also on three regions of the test plants i.e, upper, middle and lower. The number of whiteflies was counted after 6, 12 and 24 hours of pesticide application. The results revealed that, among all the treatments, Thiamethoxam 0.5mg/L was found to be the most effective with highest percentage of reduction over control in the number of whiteflies in all the time intervals. The leaves in the middle and lower regions of the test plants showed relatively higher loads of whiteflies than those in the upper region throughout the experiment. Although, Neem oil is an environment friendly natural pesticide, Thiamethoxan has negligible volatilization properties and high degradation rates in the soil and therefore could be successfully and safely applied on the lac insect host plants during the pre-inoculation stages to lessen the whitefly attack.

Volatiles from male honeydew excretions attract conspecific male spotted lanternflies, Lycorma delicatula (Hemiptera: Fulgoridae).

The spotted lanternfly (SLF), Lycorma delicatula (Hemiptera: Fulgoridae), is a generalist phloem feeder that produces copious amounts of honeydew, which in turn coats the understory. These insects form large aggregations covering the trunks of some trees, while similar trees nearby mysteriously seem unattractive. We investigated whether volatiles from SLF honeydew are attractive to conspecifics by collecting honeydew from the field and testing it for SLF attraction in a two-choice olfactometer. We found that honeydew excreted by adult male SLF was significantly attractive to male SLF, but not female SLF. Although the honeydew excreted by adult female SLF did not significantly attract male or female SLF, both sexes showed a positive trend towards attraction in response to female honeydew in the olfactometer. Analysis of the headspace volatiles of honeydew was conducted, and numerous semiochemicals were identified. Five of which, 2-heptanone, 2-octanone, 2-nonanone, benzyl acetate, and 1-nonanol, were tested in two-choice behavioral assays against a blank control. Benzyl acetate and 2-octanone were attractive to both sexes, whereas 2-heptanone was only attractive to males, and 2-nonanone only to females. The remaining compound, 1-nonanol, repelled females, but not males. Although honeydew has been reported as a source of kairomones for some natural enemies, this may be the first report of sex-specific attractants for conspecific insects found in the honeydew volatiles of a planthopper.

Apolygus lucorum effector Al6 promotes insect feeding performance on soybean plants: RNAi analysis and feeding behaviour study with electrical penetration graph.

The mirid bug Apolygus lucorum, a dominant mirid species in northern China, is a notorious polyphagous pest with more than 200 hosts, including several major crops such as cotton and soybean, resulting in massive economic loss. Studies of insect salivary effectors may provide a novel control strategy for A. lucorum. An A. lucorum effector, that is, Al6, that inhibits plant immunity by using glutathione peroxidase to repress reactive oxidase accumulation was previously identified. In this study, we further explored the molecular functions of Al6 associated with feeding behaviour and insect survival on soybean, a major host of A. lucorum, using RNA interference and electrical penetration graph (EPG) techniques. We initially observed the injury symptom of this mirid bug and characterized feeding behaviour on soybean leaves using EPG. Our results revealed that A. lucorum preferred to feed on young plant organs such as tender leaves, shoots and buds. This mirid bug used cell rupture as a feeding strategy to ingest cell contents from plant tissues. Subsequently, we silenced the Al6 gene using RNAi and investigated the feeding behaviour, honeydew excretion, body weight, and survival rates of A. lucorum on soybean after Al6 knockdown. Our results demonstrated that silencing of Al6 significantly reduced feeding duration, amount of honeydew secretion, body weight, and survival rates of A. lucorum. Thus, our findings provide a novel molecular target of plant-mediated RNAi for the control of A. lucorum.

Effect of nitrogen fertilizer on the resistance of rice near-isogenic lines with BPH resistance genes

BackgroundNitrogen is an essential macronutrient for plant growth and development. Crops with a high nitrogen input usually have high yields. However, outbreaks of brown planthoppers (Nilaparvata lugens; BPH) frequently occur on rice farms with excessive nitrogen inputs. Rice plants carrying BPH resistance genes are used for integrated pest management. Thus, the impact of nitrogen on the resistance of rice near-isogenic lines (NILs) with BPH resistance genes was investigated.ResultsWe tested these NILs using a standard seedbox screening test and a modified bulk seedling test under different nitrogen treatments. The amount of nitrogen applied had an impact on the resistance of some lines with BPH resistance genes. In addition, three NILs (NIL-BPH9, NIL-BPH17, and NIL-BPH32) were further examined for antibiosis and antixenosis under varying nitrogen regimes. The N. lugens nymph population growth rate, honeydew excretion, female fecundity, and nymph survival rate on the three NILs were not affected by different nitrogen treatments except the nymph survival rate on NIL-BPH9 and the nymph population growth rate on NIL-BPH17. Furthermore, in the settlement preference test, the preference of N. lugens nymphs for IR24 over NIL-BPH9 or NIL-BPH17 increased under the high-nitrogen regime, whereas the preference of N. lugens nymphs for IR24 over NIL-BPH32 was not affected by the nitrogen treatments.ConclusionsOur results indicated that the resistance of three tested NILs did not respond to different nitrogen regimes and that NIL-BPH17 exerted the most substantial inhibitory effect on N. lugens growth and development.

Wild Rice Species in Sri Lanka as Genetic Resources for Breeding for Brown Plant Hopper (&lt;em&gt;Nilaparvata lugens&lt;/em&gt; (Stål)) Resistance in Rice

Brown pl anthopper (BPH) Nilaparvata lugens (Stål.) is considered the most destructive rice pest in rice-growing countries including Sri Lanka. Resistance breeding considered the most e conomical management strategy, starts by identifying new genetic resources for BPH resistance and comparative analysis wi th existing donors. So far, scientists have identified 38 genes/QTLs responsible for BPH resistance. This study explored the BPH resistance in five wild rice species in Sri Lanka, inc luding the endemic species Oryza rhizomatis. One recommended rice variety; Bg 352, fourteen O. rhizomatis accessions, and one accession from Oryza nivara, Oryza rufipogon, Oryza granulata and Oryza eichingeri screened by the honeydew test. The experiment was arranged in a complete randomize d design with fifteen replicates with Bg 380 and Ptb 33 as susc eptible and resistant checks respectively. The lower amount of honeydew excretion recorded in all tested O. rhizomatis accessions, O. nivara, O. granulata, and O. eichingeri accessions suggested BPH resistance. Both Ptb 33 and O. rufipogon showed a similar level of resistance with low honeydew excretion. The varieties Bg 352 and Bg 380 showed a high amount of honeydew excretions confirming higher susceptibility to the BPH. Therefore, all fourteen accessions of O. rhizomatis and the selected accessions of O. nivara and O. eichingeri are potential donors for rice breeding programs. Further, th e coding sequences (CDS) of known BPH genes of O. sativa were used as queries to search similar genes in wild rice genomes. The CDS coverage and phylogenetic analysis suggest, of known BPH resistance genes, at least BPH6, BPH9, BPH14-1, and BPH18 are present in O. rhizomatis, O. eichingeri, O. nivara, and O. rufipogon genomes. This information will assist in marker-as sisted breeding attempts.

Genomic analysis and finding of candidate genes for Nilaparvata lugens (stål) resistance in Indian pigmented and other indigenous rice genotypes

Rice production is facing serious threats due to frequent outbreak of brown plant hopper, Nilaparvata lugens (Stål.) population. Globally, four biotypes of N. lugens has been recorded, of which biotype-4 is the utmost damaging one prevailing in Asian subcontinents particularly in India. Therefore, effective management of N. lugens requires durable resistant rice variety with multiple resistant traits and genes. Hence, in the present study 268 rice genotypes were screened against N. lugens. From initial screening results, 96 genotypes were selected for further genotyping using 93 molecular markers linked to 26 different N. lugens resistant (R) genes. Genetic analysis revealed the mean genetic diversity of 0.275 and polymorphic information content of 0.240 for all 93 markers. Genetic association through cluster and population structure analysis clearly differentiated the 96 genotypes into three major genetic groups with resistant genotypes grouped in a separate cluster. Likewise, Principal co-ordinate analysis supported the above claim with susceptible, moderately resistant and resistant genotypes accommodated in separate components. Further, genetic variation among population showed a 92% variation among individuals of the population and only 8% between populations. Marker trait association via generalized linear model (GLM) and multi linear model (MLM) picked out five markers for their significant association with different phenotypic parameters such as percent damage, nymphal survival, feeding mark and honeydew excretion. Three markers viz. RM19291 (Bph30), RM28472 (Bph18) and RM28449 (Bph17) were common for both GLM and MLM analysis. These identified resistant genes in rice landrace will serves as the source for development of durable resistant variety against N. lugens.

Local and systemic effect of azadirachtin on host choice and feeding activity of Macrosiphum rosae on rose plants

Many studies in the last decades addressed the antifeedant and repellent effects of neem (Azadirachta indica)-based pesticides on arthropod herbivores with azadirachtin as the leading active ingredient. However, results for aphids regarding repellence and feeding were often contradictory and mainly based on laboratory studies with self-made neem extracts in high concentrations. Moreover, no data are available on the presence of azadirachtin in the phloem of treated plants—the tissue that most aphids feed on. We investigated how the application of the commercial neem product NeemAzal-T/S onto only one plant half (upper or lower) affects nymphs of the aphid Macrosiphum rosae in clip cages on the untreated plant half. Results for aphid mortality indicate that active ingredients of NeemAzal-T/S are translocated both upwards and downwards in rose plants and that active ingredients are transported in the phloem. Furthermore, we investigated whether NeemAzal-T/S has a repellent or antifeedant effect on M. rosae. A choice test in the greenhouse as well as the quantification of honeydew excretion and electrical penetration graph analysis do not show differences in settling or feeding on untreated and NeemAzal-T/S-treated rose plants. Collectively, our data show that the effect of approved concentrations of NeemAzal-T/S on M. rosae is based on the toxicity after feeding on treated plants, not on starvation.

English

Rathu Heenati is a donor parent commonly used in the development of resistant rice varieties against brown planthopper (BPH), Nilaparvata lugens, which is a devastating insect pest of rice. The variety is reported to have a broad-spectrum resistance against BPH, through the action of multiple genes and quantitative trait loci (QTL) including Bph3, Qbph3, Qbph4 and Qbph10. The present study was carried out to validate the effectiveness of those genes against Malaysian BPH population. The study was conducted using an F2 segregating population which was obtained from a cross between Rathu Heenati and a Malaysian commercial variety, MR219. Plant damage score was used to estimate the degree of plant tolerance, while the amount of honeydew excretion was used to measure the level of antibiosis. The gene presence in an individual plant was determined based on the segregation pattern of the flanking microsatellite markers of the respective reported genes. Results confirmed the role of Bph3 and the three other QTLs in conferring resistance against the Malaysian biotype of BPH. Marker assisted breeding can facilitate the monitoring of the introgressed genes in the plants of a breeding population. © 2022 Friends Science Publishers