Levels Of Antibiosis Research Articles

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

Evaluation of A3 cytoplasmic male sterile forage sorghum lines for resistance to sugarcane aphid.

Three known sugarcane aphid-resistant pollinator parents were sterilized in A3 cytoplasmic male sterility and were confirmed in this study to be resistant to sugarcane aphid allowing for the development of sugarcane aphid-resistant forage hybrids. We utilized A3 cytoplasmic male sterility and converted known sugarcane aphid-resistant sorghum TX 2783, and newly released R. LBK1 (Reg. No. GP-865, PI 687244) and R. LBK2 (Reg. No. GP-866, PI 687245) into A3 sterility to determine if the sterile counterparts would also equally express tolerance and or antibiosis to sugarcane aphid. Free-choice flat screen trials and life-table demographic studies were utilized and compared to know susceptible/fertile entries KS 585, and TX 7000, and known resistant/fertile entries TX 2783 and DKS 37-07. The R. LBK1 fertile entry was more tolerant than the known susceptible entries KS 585 and TX 7000, but was not as resistant as the other resistant entries, sustaining a damage rating of 6.0 across two different screen trials. The sterile A3 R. LBK2 showed a greater tolerance and expressed higher levels of antibiosis during aphid reproductive studies when compared to the known resistant and fertile TX 2783. All other fertile (R. LBK2, TX2783) and the A3 male sterile counterparts (A3 R. LBK2, A3 TX2783) were very similar in expression of high levels of tolerance and exhibited statistically similar damage ratings of 3.3-4.3 when exposed to sugarcane aphids. No entry, either fertile or sterile, was as tolerant as DKS 37-07, a known resistant commercial hybrid. Other plant measurements including percent loss in chlorophyll content, difference in plant height, and number of true leaves for sugarcane aphid infested versus non-infested were very consistent and highly correlated with damage ratings. Antibiosis was also exhibited in both fertile and sterile versions of the resistant lines. There was a 2 × reduction in fecundity between the R. LBK1 fertile and its sterile A3 R. LBK1 when compared to the susceptible KS 585 and TX 7000; however, the remaining fertile and sterile entries had 3.8 × to 5.8 × decrease in fecundity when compared to the susceptible KS 585 and TX 7000. Other measurements in life-table statistics such as nymphs produced/female/d, and the intrinsic rates of increased were significantly lower for all fertile and sterile lines, showing that antibiosis significantly affected sugarcane aphid reproduction. In conclusion, the A3 cytoplasmic male sterility shows consistency for maintaining the single dominant trait SCA-resistant trait of TX 2783 for expressing both antibiosis and tolerance, and great utility in the development of sugarcane aphid-resistant forage sorghums.

Determination of the Antagonistic Effects of Some Rhizospheric Bacteria against Macrophomina phaseolina under In Vitro Conditions

Macrophomina phaseolina (Tassi) Goid. is a fungal pathogen causes charcoal rot disease (Sin: Rhizoctonia bataticola) and is responsible for significant yield losses in many plants. In our study, we aimed to evaluate the antagonistic ability of 39 different bacteria, isolated from the fields of sugar beet in 2019, against the pathogen Macrophomina phaseolina isolated from sugar beet, beans and chickpeas. Approximately 31% of the bacteria showed antibiosis effect against the pathogen. It was determined that the effectiveness level of Lelliottia amnigena, Bacillus atrophaeus, B.pumilus and B. cereus (7 isolates) was moderate to high against Macrophomina phaseolina. Bacillus atrophaeus (PTo15-1a) showed the highest efficacy of 80%, 72.94% and 82.35% against Macrophomina phaseolina of chickpea, bean and sugar beet respectively. Lelliottia amnigena (Pto 14-1b) was moderately effective (57.78%) against the chickpea isolate of the pathogen. It was observed that of the seven Bacillus cereus isolates used in the experiment, three isolates (Pto14-1a, Pto12-1b, Pto17-1b) were highly effective against the chickpea pathogen, two (Pto12-1b, Pto14-2b) against bean pathogen, and one (Pto15-1b) against sugar beet isolate. Results have shown varied level of antagonism by different test bacterial against different Macrophomina phaseolina isolates, while the highest level of antibiosis shown by Bacillus atrophaeus against all pathogenic isolates indicated that it can be a potential future bioagent in managing the disease.

Assessment of antixenosis and antibiosis levels in rice genotypes against Sogatella furcifera (Hemiptera: Delphacidae)

White-backed planthopper, Sogatella furcifera Horváth (Hemiptera: Delphacidae) is a migratory and serious pest of rice crop worldwide including Pakistan. The current experiment was carried out to assess the antixenosis and antibiosis level of fifteen rice genotypes against S. furcifera under greenhouse conditions. In antixenosis studies, proportion of nymphs and adults settled was recorded in relation to control. Less preferred varieties by nymphs were RPP49 (3.80), N22 (5.60), IR 64 (6.20), IR 72 (6.60), Basmati Pak (6129) (5.40), and Super Basmati (5.00) as compared to TN1 (12.00). Lower number of eggs were laid on RPP49, N22, IR 64, Super Basmati and PKBB 8. Based on feeding marks the genotypes ranked from highest to lowest as RPP49, N22, IR 64, IR 72 and Basmati Pak. In antibiosis tests, RPP49, N22, IR64, IR 72, Super Basmati and Basmati Pak varieties performed well as compared to TN1. Minimum feeding rate (47.8 mm2) was recorded on RPP49 followed by N22, IR 64, IR74, Basmati Pak, Super Basmati, PKBB 8, PK 10684 and PK 10436 as compared to TN1(470.8 mm2). The results revealed that RPP49 emerged as the new resistant source against S. furcifera. Super Basmati, Basmati Pak have shown a moderate level of resistance while PKBB 8, PK 10684 and PK 10436 are new varieties with a moderate level of resistance to S. furcifera which can be used as resistance source in breeding programs against S. furcifera.

Maize Resistance to Stem Borers Can Be Modulated by Systemic Maize Responses to Long-Term Stem Tunneling.

Limited attention has been paid to maize (Zea mays L.) resistance induced by corn borer damage, although evidence shows that induced defenses have lower resource allocation costs than constitutive defenses. Maize responses to short- and long-term feeding by the Mediterranean corn borer (MCB, Sesamia nionagrioides) have been previously studied, but the suggested differences between responses could be due to experimental differences. Therefore, in the current study, a direct comparison between short- and long-term responses has been made. The objectives were (i) to determine changes in the level of antibiosis of the stems induced by feeding of S. nonagrioides larvae for 2days (short-term feeding) and 9days (long-term feeding), (ii) to characterize the metabolome of the stems’ short- and long-term responses to borer feeding, and (iii) to look for metabolic pathways that could modulate plant resistance to MCB. Defenses were progressively induced in the resistant inbred, and constitutive defenses were broken down in the susceptible inbred. Results suggest that the different resistance levels of the two inbreds to stem tunneling by MCB could depend on their ability to establish a systemic response. Based on these results, a high throughput look for specific metabolites implicated in systemic induced resistance to maize stem borers is recommended; the current focus on constitutive defense metabolites has not been successful in finding molecules that would be valuable tools for pest control.

First sources of resistance in faba bean (Vicia faba L.) to the stem borer weevil, Lixus algirus L. (Coleoptera: Curculionidae)

Faba bean (Vicia faba L.) is a grain legume widely cultivated in many countries for food and animal feed. The faba bean stem borer (Lixus algirus L.) (Coleoptera: Curculionidae) is considered one of the major biotic stresses of faba bean in some Mediterranean areas, including Morocco. The use of genetic resistance is the most economical and environmentally friendly control method of insect pests. Therefore, a set of 233 faba bean genotypes from two ICARDA sets (GCP Ref.Set-2015 and AYT-2015) was evaluated for resistance to L. algirus under open field and net cage conditions at Douyet and Marchouch Stations in Morocco. Twelve genotypes (11 from the GCP Ref.Set-2015 and one from AYT-2015) showed a low level of infestation by the stem borer in the field and under cages. The results of free-choice screening showed a significant egg-laying preference of stem borer for the susceptible cultivars Defes and Alfia, compared with the two germplasm accessions IG 11561 and IG 72498. The accession IG 72498 expressed the highest level of antibiosis; with 100% mortality of first or second instars, with no adult exit holes on any of the plants checked. These two accessions are being used in the ICARDA crossing program to develop recombinant inbred lines to study the genetics of resistance to faba bean stem borer. This is the first report of resistance to stem borer in faba bean with antixenotic and antibiotic categories of resistance.

Leaf structural traits rather than drought resistance determine aphid performance on spring wheat

Drought represents one of the most severe constraints to agricultural production; therefore, resistance to drought has the highest priority in the development of new cultivars. How insect pests respond to drought-resistant cultivars is poorly understood. In this study, by using the rose-grain aphid, Metopolophium dirhodum (Walker), in controlled laboratory conditions, we investigated the level of antibiosis of six commercially available cultivars of spring wheat (Triticum aestivum L.), which differed in their resistance to drought (drought-resistant cultivars: Septima, Jarissa and Seance; drought-sensitive cultivars: Quintus, Kabot and SW Kadrilj). Leaf morphological and structural traits were also measured for each cultivar to determine which leaf traits may be responsible for the observed differences. We used an age-stage, two-sex life table approach for comprehensive quantification of the aphid response to a particular cultivar and for projecting population growth. Although we found significant differences in all the life table and population growth parameters between the cultivars (SW Kadrilj was the most resistant to the aphids and Septima and Quintus were the most susceptible to the aphids), resistance to drought alone did not explain the observed variation. The cultivars also varied in most of the morphological and structural leaf traits measured. An increase in cuticle thickness at the cell junction above the major vein hampered the development of the aphid nymphs, which resulted in slower rates of population increase. Trichome density seemed to reduce the survival of the aphid nymphs. These two traits support not only drought resistance in general but also resistance to aphids and are potentially useful for selection in the future breeding of cereals.

Characterization and potential mechanisms of resistance of cucumber genotypes to Bemisia tabaci (Hemiptera: Aleyrodidae)

Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) is a major pest of several agricultural crops, being vector of an extreme number of viruses. The broad variety of host plants, high adaptability and evolution of resistance to insecticides evidence the difficult in the management of B. tabaci in the agriculture system. Host plant resistance is a valuable and sustainable method of insect management. To date, few studies have characterized the resistance of cucumber (Cucumis sativus L.) genotypes to B. tabaci, although this plant is one of the most preferred host of this hemipteran. The objective of this study was to assess the resistance of 60 cucumber genotypes against B. tabaci in greenhouse and laboratory conditions and to characterize the mechanisms of resistance involved based on morphological and physical plant parameters. Initially, 12 genotypes were selected in a screening bioassay. In general, ‘IAC-1214’ expressed high levels of antixenosis to the insect, causing low attractiveness to adults and non-preference for oviposition and colonization. 'Wellington' prolonged the development of the insect and provoked low levels of adult emergence, expressing levels of antibiosis. Antibiosis and/or antixenosis were detected in ‘IAC-1201’, ‘Campeiro’, ‘Japones’, and ‘IAC-1311’, while antixenosis was detected in ‘Kyria’ and ‘IAC-1175’. The density of the trichomes and the color of the leaves are described and discussed here. The selected genotypes present potential application in integrated programs that focus on reducing populations of B. tabaci in the agricultural system and in breeding programs aiming to explore resistant genotypes against the insect.

Silverleaf whitefly-resistant common beans: an investigation of antibiosis and/or antixenosis

ABSTRACT The silverleaf whitefly Bemisia tabaci biotype B is one of the most important sucking pests of common bean, which causes severe damages and requires frequently synthetic insecticides spraying to protect crop productivity. The use of common bean cultivars resistant to whitefly attack is an important strategy within an integrated pest management (IPM) program. The biological development of B. tabaci confined to 17 bean genotypes was evaluated in greenhouse trials to verify the occurrence of antibiosis. Whitefly adults were released on plants of these genotypes to oviposit, afterward the incubation period of eggs, nymphal period, complete development period (egg–adult), and viability of the silverleaf whitefly nymphs were recorded. As main results, genotype CHIP 300 prolonged the developmental period from egg to adult (~10 days) and BRS Estilo, Arcelina 4, IPR Garca, Tybata, CHIP 300, IPR Eldorado, H96A102-1-1-1-52, SCS-202-Guara and CHIB 06 caused nymphal mortality, suggesting high levels of antibiosis and/or antixenosis. These genotypes may be helpful in common bean breeding programs aimed at developing commercial cultivars resistant to B. tabaci biotype B.

Antibiosis in soybean genotypes to Spodoptera cosmioides (Lepidoptera: Noctuidae)

Abstract The occurrence of the black caterpillar Spodoptera cosmioides (Lepidoptera: Noctuidae) has been increasing in soybean crops in Brazil leading to yield losses. The objective of this study was to evaluate antibiosis in soybean genotypes to S. cosmioides. The following parameters were evaluated: duration, viability and larval weight; duration and viability of the pre-pupal; duration, weight and viability of pupa; total cycle and sex ratio. The design was completely randomized with 18 treatments (genotypes) and 30 replicates. The genotypes PI 227687, PI227682, IAC 100 and BRS 7270 IPRO showed significant levels of antibiosis against S. cosmioides. These results will be useful for soybean producer or in breeding programs focusing on host plant resistance.

Category of Resistance, Antixenosis, Antibiosis, and Tolerance to Acyrthosiphon pisum (H.) (Hemiptera: Aphididae) in Selected Lentil Genotypes ( Lens Culinaris M.)

The pea aphid (Acyrthosiphon pisum Harris) is an economically important insect pest of lentil in Ethiopia. The development of pea aphid resistant lentil genotypes with known resistance mechanism is an economical and effective way to manage this pest. Hence, the current study was conducted to determine the mechanisms (antibiosis, antixenosis, and tolerance) of resistance in six lentil (Lens culinaris Medikus.) genotypes to pea aphid. Three released varieties (Alemaya, Chalew, and R-186), three accessions (ILL-2595 and ILL-4422, and ILL-7664) and one susceptible accession were included in this study. A no-choice study was conducted to determine the categories of antibiosis and tolerance while free choice studies were conducted to determine antixenosis resistance mechanism. In the antibiosis test, there were significant differences in life table characteristics and demographic statistics among the resistant and susceptible lentil genotypes. ILL-7664 had high levels of an antibiotic effect than the others. Alemaya had high levels of tolerance to pea aphid. Choice studies indicated the presence of antixenosis resistance in the lentil genotype, Chalew, ILL-2595 and ILL-4422. The evaluated lentil genotypes exhibited different types of resistance mechanism and level of expression. Chalew showed a three mode of resistance, i.e., antibiosis, antixenosis, and tolerance. Further research should concentrate on levels of antibiosis, i.e., toxins and growth inhibitors to A. pisum.

Quantification of antibiosis levels in nine different rice genotypes against Nilaparvata lugens (Homoptera: Delphacidae)

AbstractStudies on different parameters of antibiosis to simultaneously compare diverse genotypes with different resistance levels are lacking. Such studies are necessary to identify the genetic variability among resistant genotypes, which, ultimately, can lead to the identification of resistance genes with diverse mechanisms. The current study was undertaken to quantify antibiosis levels in nine rice genotypes against the brown planthopper (BPH), Nilaparvata lugens (Stål), under glasshouse conditions using nine parameters. Among these genotypes, RP2068-18-3-5 and Ptb33 displayed significantly better performance as compared to other genotypes in most of the parameters studied and did not differ from each other. Rathu Heenati was the best in unfertilised eggs laid and similar to the above two genotypes regarding percent of nymphal survival. All the test genotypes performed significantly better than the susceptible check TN1, though INRC3021 did not differentiate from the former in some tests. The overall damage score was positively and significantly correlated with the amount of honeydew excretion, percent nymphal survival and emergence, the proportion of brachypterous females, female population, and growth index, and were negatively and significantly correlated with percent unfertilised eggs laid and nymphal development period. Regression analysis revealed a significant linear relationship between damage score and nymphal emergence, nymphal survival percentage, and proportion of brachypterous females. RP2068-18-3-5 is the new source of BPH resistance identified through this study, which breeders can further use in resistance breeding.

English

Cowpea (Vigna unguiculata L. Walp.) is an important cash, food and nutritional security grain legume crop in the semi-arid regions of sub-Saharan Africa. However, its productivity is hampered by several biotic stress factors including numerous insect pests that infest and damage the crop at all its development stages in the field as well as during storage. This study sought to identify new sources of resistance to cowpea aphids. Ten lines were infested with three strains of aphids and their resistance was evaluated. Results revealed that among the cowpea genotypes, line IT97K-556-6 was found to be the most resistant to all the three strains of aphids. Line N ° 2300 was the most susceptible to all the three strains of aphids. KN-1 considered as a susceptible control was found to be resistant. Prior to lines classification based on their resistance to aphids, the analysis of the Area Under the Infestation Progress Curve (AUIPC) showed that IT97K-556-6 has exhibited the higher level of antibiosis. It was the least favorable to the development of aphids and NS-1 was the most favorable. Promising lines have been identified for further evaluation and utilization for improvement in cowpea. Key words: Vigna unguiculata, Aphis craccivora, antibiosis, genetic resistance, area under the infestation progress curve (AUIPC), control.

Antixenosis and antibiosis mechanisms of resistance to pod borer, Helicoverpa armigera in wild relatives of chickpea, Cicer arietinum

The noctuid pod borer, Helicoverpa armigera is one of the most damaging pests of chickpea, Cicer arietinum. The levels of resistance to H. armigera in the cultivated chickpea are low to moderate, but the wild relatives of chickpea have exhibited high levels of resistance to this pest. To develop insect-resistant cultivars with durable resistance, it is important to understand the contribution of different components of resistance, and therefore, we studied antixenosis and antibiosis mechanisms of resistance to H. armigera in a diverse array of wild relatives of chickpea. The genotypes IG 70012, PI 599046, IG 70022, PI 599066, IG 70006, IG 70018 (C. bijugum), ICC 506EB, ICCL 86111 (cultivated chickpea), IG 72933, IG 72953 (C. reticulatum), IG 69979 (C. cuneatum) and IG 599076 (C. chrossanicum) exhibited non preference for oviposition by the females of H. armigera under multi-choice, dual-choice and no-choice cage conditions. Based on detached leaf assay, the genotypes IG 70012, IG 70022, IG 70018, IG 70006, PI 599046, PI 599066 (C. bijugum), IG 69979 (C. cuneatum), PI 568217, PI 599077 (C. judaicum) and ICCW 17148 (C. microphyllum) suffered significantly lower leaf damage, and lower larval weights indicating high levels of antibiosis than on the cultivated chickpea. Glandular and non-glandular trichomes showed negative correlation with oviposition, while the glandular trichomes showed a significant and negative correlation with leaf damage rating. Density of non-glandular trichomes was negatively correlated with larval survival. High performance liquid chromatography (HPLC) fingerprints of leaf surface exudates showed a negative correlation of oxalic acid with oviposition, but positive correlation with malic acid. Both oxalic acid and malic acid showed a significant negative correlation with larval survival. The wild relatives exhibiting low preference for oviposition and high levels of antibiosis can be used as sources of resistance to increase the levels and diversify the basis of resistance to H. armigera in cultivated chickpea.

Development of 25 near-isogenic lines (NILs) with ten BPH resistance genes in rice (Oryza sativa L.): production, resistance spectrum, and molecular analysis

A first set of 25 NILs carrying ten BPH resistance genes and their pyramids was developed in the background of indica variety IR24 for insect resistance breeding in rice. Brown planthopper (Nilaparvata lugens Stal.) is one of the most destructive insect pests in rice. Development of near-isogenic lines (NILs) is an important strategy for genetic analysis of brown planthopper (BPH) resistance (R) genes and their deployment against diverse BPH populations. A set of 25 NILs with 9 single R genes and 16 multiple R gene combinations consisting of 11 two-gene pyramids and 5 three-gene pyramids in the genetic background of the susceptible indica rice cultivar IR24 was developed through marker-assisted selection. The linked DNA markers for each of the R genes were used for foreground selection and confirming the introgressed regions of the BPH R genes. Modified seed box screening and feeding rate of BPH were used to evaluate the spectrum of resistance. BPH reaction of each of the NILs carrying different single genes was variable at the antibiosis level with the four BPH populations of the Philippines. The NILs with two- to three-pyramided genes showed a stronger level of antibiosis (49.3-99.0%) against BPH populations compared with NILs with a single R gene NILs (42.0-83.5%) and IR24 (10.0%). Background genotyping by high-density SNPs markers revealed that most of the chromosome regions of the NILs (BC3F5) had IR24 genome recovery of 82.0-94.2%. Six major agronomic data of the NILs showed a phenotypically comparable agronomic performance with IR24. These newly developed NILs will be useful as new genetic resources for BPH resistance breeding and are valuable sources of genes in monitoring against the emerging BPH biotypes in different rice-growing countries.

Assessing Common Bean Cultivars for Resistance to the Soybean Looper Chrysodeixis includens (Lepidoptera: Noctuidae).

The soybean looper Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae) is known as an important pest of leguminous plants worldwide. In Brazil, this pest species is gaining importance to producers of the common bean Phaseolus vulgaris L. (Fabaceae) because it limits field production of the crop. Chemical control is still the primary method of insect control. However, due to the possible harmful effects of pesticides to humans and the environment, alternative and less aggressive practices are being investigated. For this reason, the use of resistant plant genotypes represents a valuable tool in insect control. This study evaluated the biological aspects of larvae of C. includens confined to 14 bean genotypes under laboratory conditions (26±2°C; 65±10% RH; photoperiod of 14h L:10h D). The duration of the instars, total duration of the larval phase, consumption while in the larval phase, weight of the fifth instar larvae, larval viability, duration of the pre-pupal and pupal phases, pupal weight, pupal viability, pupal deformity, caterpillar-to-adult cycle, duration of the pre-oviposition and oviposition periods, and total number of viable eggs per female were evaluated. The genotypes "IAC Boreal," "IAC Harmonia," and "IAC Formoso" expressed antibiosis, prolonging the caterpillar-to-adult cycle and reducing the larval viability; however, each of these genotypes also experienced high leaf consumption. "IAC Jabola" expressed moderate levels of antibiosis and/or antixenosis (feeding), while the genotype "BRS Horizonte" expressed antixenosis (feeding). The data obtained with IAC Boreal, IAC Harmonia, IAC Formoso, IAC Jabola, and BRS Horizonte are promising and may help with the improvement of programs aimed at managing C. includens damage to this leguminous agricultural crop.

Antibiosis resistance against larval cabbage root fly, Delia radicum, in wild Brassica-species

AbstractCabbage root flies (Delia radicum) are a major threat to cabbage production in Western Europe and North America. Host plant resistance is the most promising option in controlling cabbage root fly damage. In a no-choice field test, we evaluated 94 accessions belonging to 16 Brassica-species for antibiosis resistance against the larvae. Thirteen accessions were selected as putatively resistant, which were subsequently re-tested in the greenhouse. The proportion of eclosed flies was introduced as the main parameter to assess antibiosis in the greenhouse, together with other insect and plant parameters. High levels of antibiosis resistance were identified in B. fruticulosa PI663081 and B. spinescens BRA2994, with significantly lower proportions of eclosed flies (1 % of the number of eggs used for infestation) compared to other accessions. Both species are difficult to cross with B. oleracea. Plants with a high level of antibiosis and medium to high tolerance were found in several accessions of other Brassica species (B. villosa BRA2922, B. montana BRA2950, B. hilarionis HRIGU12483, B. macrocarpa BRA2944) which are more amenable for crossing with B. oleracea. Selection of the most resistant plants belonging to these accessions may yield promising candidates for breeding cabbages resistant to Delia radicum.

Antibiosis levels of common bean genotypes toward Zabrotes subfasciatus (Boheman) (Coleoptera: Bruchidae) and its correlation with flavonoids

Expression of the antibiosis-resistance category to weevils has been evaluated in several bean genotypes with very promising results. Among the several causes responsible for this resistance category the arcelin protein and trypsin inhibitors stand out. Other mechanisms may be associated with plant resistance to the attack of weevils; however, few studies seek to discover these possible causes. Thus, our research aimed at identifying bean genotypes resistant to Zabrotes subfasciatus, classify them into resistance levels, quantify the content of flavonoids, and correlate it with data obtained from the genotypes. An antibiosis test was performed with beans of 43 genotypes and 40 replications (bean grains) under a completely randomized design. The biological parameters recorded from Z. subfasciatus were the periods from egg to larvae, larvae to adult, egg to adult, longevity and life cycle, in addition to egg viability, adults emerged, susceptibility relative index, adult weight, sex ratio, and the dry mass consumed by larvae. The chemical profile of flavonoids from each genotype was assessed by means of LC-MS. Based on the results of the weevil biological parameters and dry mass consumed provided by univariate and multivariate statistical analyses, the bean genotypes were classified into four levels of resistance (antibiosis): highly resistant, moderately resistant, susceptible and highly susceptible. Among the evaluated flavonoids, we could identify isoquercitrin; however, it has no correlation with the expression of resistance. From the results obtained in this work, more studies will be conducted with the genotypes that stood out as resistant, evaluating other resistance categories and defense mechanisms of these materials against the attack of Z. subfasciatus and other pests, as well as studies of other important agronomic characteristics aiming at future commercialization of the bean genotypes.

Ethylene Contributes to maize insect resistance1-Mediated Maize Defense against the Phloem Sap-Sucking Corn Leaf Aphid.

Signaling networks among multiple phytohormones fine-tune plant defense responses to insect herbivore attack. Previously, it was reported that the synergistic combination of ethylene (ET) and jasmonic acid (JA) was required for accumulation of the maize insect resistance1 (mir1) gene product, a cysteine (Cys) proteinase that is a key defensive protein against chewing insect pests in maize (Zea mays). However, this study suggests that mir1-mediated resistance to corn leaf aphid (CLA; Rhopalosiphum maidis), a phloem sap-sucking insect pest, is independent of JA but regulated by the ET-signaling pathway. Feeding by CLA triggers the rapid accumulation of mir1 transcripts in the resistant maize genotype, Mp708. Furthermore, Mp708 provided elevated levels of antibiosis (limits aphid population)- and antixenosis (deters aphid settling)-mediated resistance to CLA compared with B73 and Tx601 maize susceptible inbred lines. Synthetic diet aphid feeding trial bioassays with recombinant Mir1-Cys Protease demonstrates that Mir1-Cys Protease provides direct toxicity to CLA. Furthermore, foliar feeding by CLA rapidly sends defensive signal(s) to the roots that trigger belowground accumulation of the mir1, signifying a potential role of long-distance signaling in maize defense against the phloem-feeding insects. Collectively, our data indicate that ET-regulated mir1 transcript accumulation, uncoupled from JA, contributed to heightened resistance to CLA in maize. In addition, our results underscore the significance of ET acting as a central node in regulating mir1 expression to different feeding guilds of insect herbivores.

Differing effects of cabbage and pepper on B and Q putative species of Bemisia tabaci

B and Q putative species of Bemisia tabaci are two of the most invasive pests in the world. In China, Q is displacing B, but the underlying mechanism has been poorly explored. The difference in tolerance to host plants between B and Q may shed some light on the displacement. In the present study, two types of resistance (antixenosis or antibiosis) of cabbage and pepper against B and Q putative species were characterized based on demographic parameters (host selection, fecundity, etc.) and feeding behavior [as determined by electrical penetration graph (EPG)]. Female longevity, fecundity, and nymph survival were substantially higher on cabbage than on pepper for B, but were similar on the two hosts for Q. B nymphs suffered high mortality on pepper, suggesting a high level of antibiosis against B in pepper. Both B and Q preferred to settle and oviposit on cabbage rather than on pepper, indicating a high level of antixenosis against B and Q in pepper. With regard to feeding behavior, EPG data indicated that both B and Q whiteflies fed more efficiently on cabbage than on pepper. Overall, both B and Q preferred cabbage to pepper, and both performed better on cabbage than on pepper, but the negative effects of pepper were greater on B than on Q. Our results demonstrate that Q is more tolerant of a low suitability host than B, which may partially explain why Q has displaced B in China.