Nonpreference For Oviposition Research Articles

Categorization of resistance against the fall armyworm, Spodoptera frugiperda (J.E. Smith) in select maize inbred lines

Seven maize inbred lines were evaluated for resistance against fall armyworm, Spodoptera frugiperda (J.E. Smith). Non-preference for oviposition in no- and multi-choice tests and feeding non-preference of neonates in multi-choice test was observed in lines CML 338, CM 500 and CML 72. Antibiosis was observed in CML 338, CML 72 and CML 71, in terms of significantly prolonged larval period (18.22–19.56 days), lower larval (111.52–131.80 mg) and pupal weights (105.65–127.67 mg), shorter adult longevity and lower fecundity as compared to susceptible inbred lines, BML 6 and LM 24. Larvae fed on CML 338 and CML 71 had significantly higher mortality and lower nutritional indices. Significantly higher foliar damage rating was observed on younger plants (10 days old) in all test inbred lines, as compared to older plants (20 and 30 days old) during 2020 and 2021. The mean foliar damage rating by fall armyworm larvae varied significantly among the test inbred lines being significantly lower in CML 338 and CML 71 compared to BML 6 and CM 500 that had higher damage at all crop stages when recorded at 7, 14 and 21 days after release. Functional Plant Loss Index (FPLI) was significantly lower in CML 338 and CML 71 (12.18–18.58%) followed by CML 72 (24.87%). Regression of FPLI on fall armyworm larval dry weight indicated presence of antibiosis and tolerance in CML 338, CML 71 and CML 72 towards fall armyworm. Overall, maize inbred lines CML 338, CML 71 and CML 72 with moderate resistance may be used for resistance breeding programme against this insect pest.

Nonpreference for Oviposition of Sugarcane Borer (Lepidoptera: Crambidae) in Sugarcane Seedlings Is Influenced by Ripening Group and Plant Age.

The sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae) is considered the main sugarcane pest in many countries. The use of plant genotypes less preferred by insects are among the alternative methods to control this species which can be used alone or associated with other control methods such as biological control in Integrated Pest Management (IPM) programs. We assessed if the nonpreference for oviposition of D. saccharalis in sugarcane genotypes established by seedlings is different according to ripening group and plant age. For that purpose, four experiments were performed: 1) seedlings of early-ripening genotypes, 2) seedlings of late-ripening genotypes, 3) and mix of early- and late-ripening genotypes, seedlings, and 4) plants. There were least preferred genotypes for oviposition by D. saccharalis among seedlings of early-ripening (RB965902 and RB966928) and late-ripening (RB987935) genotypes. It was also observed when the groups were mixed as seedlings (RB965902) or plants (RB925345). The nonpreference for egg deposition in different ripening groups and plant age might be useful to integrate with other strategies for the management of D. saccharalis. Moreover, results of egg distribution might indicate the likely position of resistance factors on leaves, whether morphological or chemical.

Oviposition behavior of Helicoverpa armigera in soybean

ABSTRACT The objective of this study was to evaluate the oviposition behavior of Helicoverpa armigera confined in different adult pair density and growth stages of soybean plants, and the resistance of soybean genotypes to H. armigera in the category nonpreference for oviposition. The oviposition behavior of H. armigera was assessed using one, two, and four adult pairs per soybean plant of the cultivar BR-16 at the growth stages: vegetative V8 (eighth unrolled trifoliate leaf), reproductive R2 (full bloom) and reproductive R5.2 (beginning seed). The nonpreference for oviposition was evaluated using eight soybean genotypes and an oviposition preference index was calculated. The number of trichomes in leaflets was quantified for being correlated to H. armigera oviposition. One adult pair and soybean plants stage at pod-set affected and showed the best results oviposition preference on soybean plants. The genotypes M8230-RR and W711-RR presented resistance characteristics, and PI-227687 was preferred for oviposition. The trichome density positively affects the female oviposition behavior.

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.

Oviposition Preferences of Pickleworm (Lepidoptera: Crambidae) in Relation to a Potential Push-Pull Cropping Management Approach.

Pickleworm, Diaphania nitidalis Cramer (Lepidoptera: Crambidae), is a major pest of cucurbits. The current management approach for this pest is weekly insecticide applications. A push-pull cropping approach may be an alternative management practice and could reduce reliance on pesticides. One potential push-pull scenario is the use of squash (Cucurbita pepo L.) as a trap crop and watermelon (Citrullus lanatus [Thunb.] Matsum. & Nakai) as a deterrent intercrop to manage pickleworm on cantaloupe (Cucumis melo L.). This study investigated if the underlying mechanism required for the success of this management approach (a female oviposition preference or nonpreference among squash, cantaloupe, and watermelon) is present. A series of oviposition preference experiments was conducted to see how individual females responded when presented with different host plants for oviposition. Under laboratory conditions, when females had the choice of a leaf from squash, cantaloupe, and watermelon, they laid a higher proportion of their eggs on the cantaloupe leaf. However, under greenhouse conditions, when females were presented with whole plants of the three different species, they laid a higher percent of their eggs on the squash plant. Females laid a similar number of eggs on watermelon as compared with cantaloupe under greenhouse conditions, and appeared to not be averse to laying their eggs on watermelon. However, when presented with a noncucurbit, such as bean, females laid a low number of total eggs. Overall, it appears that squash may be more preferred as an oviposition substrate than cantaloupe or watermelon and may be a useful trap crop or pull. Further study to determine a suitable deterrent intercrop or push and evaluation of the proposed system under field conditions are needed.

Glycaspis brimblecombei Moore, 1964 (Hemiptera: Psyllidae) on eucalyptus: oviposition non-preference and antibiosis

Forest plantations with Eucalyptus spp. (L’ Her) in Brazil are highly yielding. However, this activity is more and more threatened due to interactions with phytophagous insects, especially by exotic species, such as the red gum lerp psyllid Glycaspis brimblecombei Moore (Hemiptera: Psyllidae). This study aimed to evaluate the resistance in eucalyptus against the psyllid in oviposition and biological development assays, attempting to identify potential genotypes resistant to the pest for forest plantations. In addition, we tested the hypothesis of that concentration of total phenolics and lignin, and amount of epicuticular wax were associated with the expression of resistance. Results showed that there was variation in the levels of resistance among the genotypes assessed. Oviposition non-preference was observed on Eucalyptus citriodora (Hook) in free-choice and no-choice tests, and Clone FP10 was least preferred in the no-choice test. The genotypes E. citriodora and Clone FP6 provided 100 % nymphal mortality, and Clones FP7 and FP9 also affected negatively the G. brimblecombei development by lengthening the duration of the nymphal stage and reducing adult emergence. Clone FP6 had higher concentration of total phenolics and larger contact angle formed between the water droplet and leaf surface, which may be associated with thicker layer of epicuticular wax on the leaves, and one of the causes of high nymphal mortality. Thus, the use of the resistant genotypes of eucalyptus screened against G. brimblecombei is a promising and viable alternative for forest plantations infested with this pest.

Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in cotton: vertical distribution of egg masses, effects of adult density and plant age on oviposition behavior

The objective of this work was to determine the most suitable density of adults per plant, ideal plant age, and vertical distribution of eggs in different parts of the plant in a greenhouse investigation for future resistance studies and improvement of S. frugiperda management practices in cotton. The experiments of Spodotera frugiperda oviposition in relation to adult density, relationship between cotton plant age and Spodoptera frugiperda oviposition, Spodoptera frugiperda non-preference for oviposition on cotton varieties were conducted with plants of cotton variety BRS Ita 90. The experiments were conducted with plants of cotton variety BRS Ita 90. Non-preference (antixenosis) for oviposition was studied in FiberMax 966, FiberMax 977, DeltaOpal, DeltaPenta, Acala 90, Coodetec 408, Coodetec 409, Coodetec 410, BRS Cedro, BRS Ipê, BRS Aroeira, IPR 96, IPR 20, BRS Araçá, IAC 24, and BRS Ita 90 varieties. We concluded that the fall armyworm S. frugiperda prefers to oviposit on plants with approximately 60 days of age, on the lower surface of leaves located in the upper third of the plant tests under greenhouse conditions. A density of at least three pairs of S. frugiperda adults per plant was sufficient to conduct non-preference-for-oviposition tests under greenhouse conditions. Coodetec 408, BRS Aroeira, BRS Araçá, BRS Ita 90 and DeltaPenta varieties showed non-preference-for-oviposition resistance to S. frugiperda. In regions with high infestations of S. frugiperda, it would be prudent for the cultivation the use of BRS Ita 90 cotton variety.

Não preferência para oviposição e alimentação por Tuta absoluta (Meyrick) em genótipos de tomateiro

Este trabalho buscou selecionar genótipos de tomateiro resistentes a Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), dos tipos não preferência para oviposição e alimentação, em testes com e sem chance de escolha. As espécies utilizadas foram Solanum lycopersicum L. (cv. Santa Clara, os híbridos: Saladete Italiano Ty Tyna, Santa Cruz Débora Ty, Salada Lumi, Saladete Italiano Andrea Victory e Santa Cruz Ty Carina Ty), S. habrochaites S. Knapp & D.M Spooner (linhagens PI 134417 e PI 134418) e S. pimpinellifolium L. (linhagens NAV 1062 e PI 126931). Nos testes de não preferência para oviposição, foram contados o número de ovos por planta às 24, 48 e 72 horas, após a liberação dos adultos. Para os testes de não preferência para alimentação, foram avaliados a atratividade das larvas pelos genótipos em cada repetição a 1, 3, 5, 10, 30, 60, 120, 360, 720 e 1440 minutos, após a liberação das larvas e massa consumida pelas larvas. Constatou-se que os genótipos de tomateiro avaliados não apresentam resistência dos tipos não preferência para oviposição. Já o genótipo PI 134417 apresenta resistência do tipo não preferência para alimentação.

Resistência de variedades de algodão ao curuquerê do algodoeiro Alabama argillacea Hubner (lepidoptera: noctuidae)

Este trabalho teve como objetivo verificar a ocorrência das formas de resistência, tais como: a não preferência para oviposição, a não preferência para alimentação e a antibiose, em variedades de algodoeiro (Gossypium hirsutum L.), à Alabama argillacea (Hubner, 1818), em experimentos de laboratório (27 ± 2 ºC, 70 ± 10% de U.R. e fotofase de 14 horas). Para avaliar a não preferência para oviposição e para a alimentação em teste com chance de escolha, adotou-se o delineamento em blocos casualizados e, no teste sem chance, o inteiramente casualizado. Para avaliar a antibiose, foram fornecidas às larvas, diariamente, folhas das variedades DeltaOpal, NuOpal, FMT 701, FMX 910 e 20 FMX 996. Durante este processo, verificou-se a duração de cada fase do inseto, avaliando-se a massa de larvas aos dez dias de idade, massa de pupas com 24 horas, período larval, pré-pupal e pupal, longevidade de adultos, viabilidade total e fecundidade. As variedades NuOpal e FMT 701 apresentam resistência do tipo não preferência para alimentação. As variedades NuOpal, FMT 701 e FMX 910 apresentam resistência do tipo antibiose em relação a A. argillacea.

Tomato plant inheritance of antixenotic resistance to tomato leafminer

The objective of this work was to determine the inheritance of resistance by antixenosis in tomato plants (Lycopersicon esculentum) to tomato leafminer [Tuta absoluta (Lepidoptera: Gelechiidae)]. Evaluations were performed for tomato plants of the generations P1, P2, F1, F2, RC1 and RC2. The measured characteristic in the parents, BGH-1497 (P2 male) and 'Santa Clara' (P1 female), and in the F1, F2, RC1 and RC2 generations was the number of eggs per plant. This number was converted to the oviposition nonpreference index. The inheritance of antixenosis resistance of genotype BGH-1497 is ruled by a gene of greater effect and polygenes in epistatic interactions, with a phenotypic proportion of 13:3 between susceptible and resistant genotypes, respectively.

Influence of trichomes on attractiveness and ovipositional preference of Bemisia tabaci (Genn.) B biotype (Hemiptera: Aleyrodidae) on tomato genotypes

Brazil is one of the world's largest tomato producer, but considerable part of the production is lost due to the attack of Bemisia tabaci (Genn.) B biotype. Resistant germoplasm plants can be an important method for B. tabaci control in integrated pest management approaches. The attractiveness and ovipositional preference of B. tabaci for 17 tomato genotypes were evaluated in a free-choice test. Trials were set up in a randomized block design with ten replicates. Each replicate (one tomato plant per pot) was placed in a cage (80 x 50 x 50 cm) and infested with 1,000 adults during four days. Linear correlation tests were applied between the number of insects and eggs and number of trichomes in each tomato genotype. LA716, LA444-1 and PI134418 genotypes were the least attractive, while the 'Santa Clara' was the most attractive; PI134417 trapped the largest number of adults. LA716 genotype (4.1 eggs/leaflet and 2.1 cm²/eggs per leaflet) was the least preferred for whitefly oviposition; NAV1062, 'Fanny', LA1335, 'Santa Clara' and IAC294 were the most preferred genotypes. The glandular trichomes density was negatively correlated with whitefly's attractiveness and oviposition per leaflet and per leaf, and positively with the number of trapped insects. The non-glandular trichomes density was negatively correlated with the number of trapped insects and positively with whitefly's oviposition per cm²/leaflet andper cm²/leaf. LA716 had high antixenosis level (ovipositional nonpreference) toward B. tabaci B biotype related with type IV glandular trichome.

Characterization of antibiosis and antixenosis to the whitefly silverleaf Bemisia tabaci B biotype (Hemiptera: Aleyrodidae) in several squash varieties

The objective of this study was to investigate the potential resistance mechanisms to Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) B biotype, in eight Cucurbita pepo varieties. Attractivity, oviposition preference, and nymphal development were evaluated under greenhouse and laboratory conditions. Variety Bianca was the least attractive to adult whiteflies in multi-choice tests. The whiteflies showed oviposition nonpreference (antixenosis) for Novita Plus, Bianca and Sandy in multi-choice test, and similar results were observed in no-choice tests with varieties Bianca, Novita, Caserta Cac and Sandy. Sandy expressed high antibiosis levels against whitefly nymphs, leading to 63.9% mortality. The high level of resistance in variety Sandy can serve as base for genetic improvement of C. pepo focusing on the development of resistant varieties to B. tabaci B biotype.

Morphological and chemical components of resistance to pod borer, Helicoverpa armigera in wild relatives of pigeonpea

Host plant resistance is an important component for minimizing the losses due to the pod borer, Helicoverpa armigera, which is the most devastating pest of pigeonpea. An understanding of different morphological and biochemical components of resistance is essential for developing strategies to breed for resistance to insect pests. Therefore, we studied the morphological and biochemical components associated with expression of resistance to H. armigera in wild relatives of pigeonpea to identify accessions with a diverse combination of characteristics associated with resistance to this pest. Among the wild relatives, oviposition non-preference was an important component of resistance in Cajanus scarabaeoides, while heavy egg-laying was recorded on C. cajanifolius (ICPW 28) and Rhynchosia bracteata (ICPW 214). Accessions belonging to R. aurea, C. scarabaeoides, C. sericeus, C. acutifolius, and Flemingia bracteata showed high levels of resistance to H. armigera, while C. cajanifolius was as susceptible as the susceptible check, ICPL 87. Glandular trichomes (type A) on the calyxes and pods were associated with susceptibility to H. armigera, while the non-glandular trichomes (trichome type C and D) were associated with resistance to this insect. Expression of resistance to H. armigera was also associated with low amounts of sugars and high amounts of tannins and polyphenols. Accessions of wild relatives of pigeonpea with non-glandular trichomes (type C and D) or low densities of glandular trichomes (type A), and high amounts of polyphenols and tannins may be used in wide hybridization to develop pigeonpea cultivars with resistance to H. armigera.

Leafminer Resistance in Spinach

Leafminer (Liriomyza spp.) is a major insect pest of many important agricultural crops, including spinach (Spinacia oleracea). Genetic variability in leafminer resistance has not been studied for spinach. The purposes of the present experiments were to evaluate differences in leafminer damage among spinach genotypes, to compare results obtained from insect cage and field experiments, and to study the association among different resistant traits. We screened 345 accessions of the U.S. spinach collection for leafminer resistance in an outdoor insect cage and putative resistant genotypes were further tested in the cage and in the field over 2 years. Although no genotype was immune to leafminers, significant genotypic differences were found for leafminer stings per unit leaf area, mines per plant, and mines per 100 g plant weight. PI 274065 had the lowest sting density, whereas PI 174385 showed the fewest mines per unit plant weight among genotypes in the field. Rank order of stings per square centimeter leaf area did not significantly change for the genotypes in the cage and field tests, and the sting results from different tests were also highly correlated, suggesting that a cage test could be used to screen germplasm for fewer leafminer stings, and sting density is a reliable trait for the selection of leafminer feeding nonpreference. Stings per unit leaf area were not correlated with mines per plant or per 100 g plant weight, which suggests that feeding nonpreference does not necessarily mean oviposition–nonpreference for a spinach genotype and these two traits can be improved independently. Stings per square centimeter leaf and mines per 100 g plant weight had little correlation with plant weight in cage and field tests, suggesting that leafminer sting and mine densities are not associated with plant biomass, and it is possible to improve and combine the leafminer resistance and yield traits in a spinach cultivar. From these findings, the genetic improvement of spinach for leafminer resistance seems feasible.

Mechanisms of resistance to Helicoverpa armigera and introgression of resistance genes into F1 hybrids in chickpea

The noctuid pod borer, Helicoverpa armigera is a major pest of chickpea, and host plant resistance is an important component for managing this pest. We evaluated a set of diverse chickpea genotypes with different levels of resistance to H. armigera, and their F1 hybrids for oviposition non-preference, antibiosis, and tolerance components of resistance under uniform insect infestation under greenhouse/laboratory conditions. The genotypes ICC 12476, ICC 12477, ICC 12478, ICC 12479, and ICC 506EB were non-preferred for oviposition under no-choice, dual-choice, and multi-choice conditions, and also suffered lower leaf damage in no-choice tests as compared to the susceptible check, ICCC 37. Antibiosis expressed in terms of low larval weights was observed in insects reared on ICC 12476, ICC 12478, and ICC 506EB. Weight gain by the third-instars was also low on ICC 12476, ICC 12477, ICC 12478, ICC 12479, and ICC 506EB at the podding stage. Non-preference for oviposition and antibiosis (poor larval growth) were also expressed in hybrids based on ICC 12477, ICC 12476, ICC 12478, ICC 12479, and ICC 506EB as compared to the hybrids based on the susceptible check, ICCC 37, indicating that oviposition non-preference and antibiosis in the F1 hybrids is influenced by the parent genotype. Loss in grain yield was lower in ICC 12477, ICC 12478, ICC 12479, and ICC 506EB compared to that on ICCC 37. The genotypes ICC 12477, ICC 12478, ICC 12479, and ICC 506EB showing antixenosis, antibiosis, and tolerance mechanism of resistance to H. armigera can be used for developing chickpea cultivars for resistance to this pest.

Desenvolvimento de Zabrotes subfasciatus (Boh.) (Coleoptera: Chrysomelidae, Bruchinae) em genótipos de Phaseolus vulgaris L. (Fabaceae) cultivados no Estado do Paraná e contendo arcelina

This research intended to evaluate the development of Zabrotes subfasciatus (Boh.), a stored-grain pest, on bean genotypes (Phaseolus vulgaris L.) commonly cultivated in the State of Parana and containing arcelin, and the possible resistance of these genotypes to the bruchine. Tests were performed under laboratory conditions (27 masculineC, fotophase 12h, 50 +/- 10 % RH) with the genotypes TPS-Bionobre, IAC-Una, IPR-Uirapuru, IAPAR 44, IPR Juriti, IAPAR 81, Pérola, Carioca, Bolinha, and two others containing arcelin, Arc 1 and Arc 2. The genotypes with Arc 1 and 2 alleles caused higher mortality of immature stages; in Arc 1 developmental period was prolonged and the male and female dry weights were the lowest, suggesting an antibiosis mechanism of resistance. Non-preference for oviposition was not observed for these two genotypes. Among varieties without arcelin, IAPAR 44 was the most resistant to the bruchid, being the least preferred for oviposition, and promoting low percentage of viable eggs, long developmental period and reduced male and female adult dry weight. Perola, IPR Juriti and Bolinha with high number of eggs and viable eggs, low mortality of immature stages, were the most susceptible.

Biologia e não-preferência para oviposição por Bemisia tabaci (Gennadius) biótipo B (Hemiptera: Aleyrodidae) em cultivares de algodoeiro

The purposes of this work were to evaluate some biological aspects of Bemisia tabaci (Gennadius) biotype B at egg and nymphal stages and to evaluate the non-preference for oviposition and its correlation with the number and type of trichomes on the cotton cultivars BRS Ipê, BRS 186-Precoce 3, BRS Acala, BRS Verde, BRS-200 Marrom, BRS Cedro, BRS Ita 90-2 and BRS Aroeira. The experiments were conducted in climatic chambers at 28 +/- 2 degrees C, 70% RH and photophase of 14h, and in greenhouse. Egg fertility was not affected by the cotton cultivars but survival in egg-adult period was influenced by the host plant. There was no influence of cultivars neither on the duration of egg stage, nymphs at 2nd, 3rd and 4th instars nor on the duration from egg to adult, but nymphs reared on the cultivar BRS Ipê had their 1st instar extended. Low number of eggs was detected on the cultivars BRS Aroeira, BRS Verde and BRS Ita 90-2 in both experiments with and without oviposition choice, indicating a possible mechanism of resistance, but no correlation could be established between trichome densisty and oviposition non-preference.

Atratividade e preferência para oviposição de Trialeurodes vaporariorum em genótipos de aboboreira

O comportamento de 13 genótipos de aboboreira foi avaliado em relação à atratividade para adultos e à preferência para oviposição da mosca-branca Trialeurodes vaporariorum (West.) (Hemiptera: Aleyrodidae) em testes com e sem chance de escolha, em campo e em casa de vegetação. Os experimentos foram conduzidos com plantas de aboboreira em fase vegetativa, infestadas naturalmente no campo (atratividade para adultos e oviposição com chance de escolha) e artificialmente em casa de vegetação (oviposição sem chance de escolha). Dentre as aboboreiras tipo moita, o híbrido Arlika apresentou a menor atratividade para adultos e, entre os genótipos de crescimento rasteiro, não houve diferença em relação à atratividade. Quanto à preferência para oviposição em teste de livre escolha, 'Arlika', no grupo de moita, e 'Atlas', 'Sandy', 'Bárbara', 'Baianinha' e 'Caravela', no grupo das rasteiras, apresentaram os menores índices de oviposição, que se confirmaram no teste sem chance de escolha, indicando que a menor preferência para oviposição de T. vaporariorum nesses genótipos é estável.

Inheritance of Resistance to Sorghum Shoot Fly, Atherigona soccata

ABSTRACTThe sorghum shoot fly, Atherigona soccata Rond. (Diptera: Muscidae), is one of the most important pests of sorghum [Sorghum bicolor (L.) Moench], and host plant resistance is an important component for the management of this pest. Most of the sorghum hybrids currently under cultivation are based on cytoplasmic male‐sterility (CMS). To develop a strategy to develop sorghum hybrids with resistance to shoot fly, we studied the nature of gene action for resistance to this pest in F1 hybrids derived from shoot fly‐resistant and ‐susceptible CMS and restorer lines. The hybrids based on shoot fly‐resistant CMS and restorer lines were glossy and trichomed and had lower proportion of plants with eggs (78.5% vs. 88.4 to 93.3%) and deadhearts (40.8% vs. 60.8 to 75.3%) than the hybrids based on other cross combinations, suggesting that resistance is required in both CMS and restorer lines for obtaining shoot fly‐resistant hybrids. Proportional contributions of CMS lines for oviposition, deadhearts, leaf glossiness, and recovery resistance were greater than those of the restorer lines. The general (GCA) and specific combining ability (SCA) estimates suggested that inheritance for oviposition nonpreference, deadhearts, recovery resistance, and the morphological traits associated with resistance or susceptibility to A. soccata were governed by additive‐type of gene action. The SCA effects and heterosis estimates indicated that heterosis breeding would not be rewarding in breeding for resistance to shoot fly.

Atratividade e não-preferência para oviposição de Bemisia tabaci (Genn.) biótipo B (Hemiptera: Aleyrodidae) em genótipos de feijoeiro

A mosca-branca e um dos insetos mais prejudiciais a cultura do feijoeiro, devido principalmente a intensa succao de seiva elaborada e a transmissao do virus do mosaico dourado. O uso de cultivares resistentes a esse inseto e uma ferramenta importante no seu controle. Foi testada a preferencia para oviposicao de Bemisia tabaci (Genn.) biotipo B em 20 genotipos de feijoeiro. Nos ensaios com chance de escolha, os materiais foram divididos em dois lotes de 10 genotipos, com 10 repeticoes de uma planta/vaso, dispostas em gaiolas de 80 x 50 x 50 cm, cobertas com voil e infestadas com 1.000 moscas-brancas durante quatro dias. Nos ensaios sem chance de escolha, realizaram-se 20 repeticoes de um foliolo (genotipos em melhoramento e cultivares) ou de um trifoliolo (genotipos selvagens) recem-expandido por gaiola e infestados com 25 casais de moscas-brancas durante 48h. Nos ensaios com chance de escolha, verificou-se que os genotipos G13028, Arc 5s, Arc 1s, G11056, Arc 3s apresentaram as menores oviposicoes e os menores indices de preferencia, variando de -91,9 a -78,6, enquanto Arc 1 (+33,0) teve o maior indice. Nos ensaios sem chance de escolha, os menores numeros de ovos/folha foram observados nos genotipos G13028 (28,2), Arc 3s (37,6) e G23425E (39,0), enquanto que o genotipo mais preferido teve 105,0 ovos/folha (Bolinha). O genotipo selvagem G13028 foi altamente resistente (nao-preferencia para oviposicao) a B. tabaci biotipo B. Destacaram-se tambem como resistentes, os genotipos Arc 3s, Arc 5s e G11056; ja Bolinha, Arc 1 e Arc 4 mostraram-se altamente suscetiveis a mosca-branca.