High Concentrations of Very Long Chain Leaf Wax Alkanes of Thrips Susceptible Pepper Accessions (Capsicum spp)

The cuticular wax layer can be important for plant resistance to insects. Thrips (Frankliniella occidentalis) damage was assessed on 11 pepper accessions of Capsicum annuum and C. chinense in leaf disc and whole plant assays. Thrips damage differed among the accessions. We analyzed the composition of leaf cuticular waxes of these accessions by GC-MS. The leaf wax composition was different between the two Capsicum species. In C. annuum, 1-octacosanol (C28 alcohol) was the most abundant component, whereas in C. chinense 1-triacotanol (C30 alcohol) was the prominent. Thrips susceptible accessions had significantly higher concentrations of C25-C29n-alkanes and iso-alkanes compared to relatively resistant pepper accessions. The triterpenoids α- and ß-amyrin tended to be more abundant in resistant accessions. Our study suggests a role for very long chain wax alkanes in thrips susceptibility of pepper.

Organic management promotes natural pest control through enhanced plant resistance to insects

Lower insect pest populations found on long-term organic farms have largely been attributed to increased biodiversity and abundance of beneficial predators. However, potential induction of plant defenses has largely been ignored. This study aims to determine whether host plant resistance mediates decreased pest populations in organic systems, and to identify the underpinning mechanisms. We demonstrate that greater numbers of leafhoppers (Circulifer tenellus) settle on tomatoes (Solanum lycopersicum) grown using conventional management as compared to organic. Soil microbiome sequencing, chemical analysis, and transgenic approaches, coupled with multi-model inference, suggest that changes in leafhopper settling between organically and conventionally-grown tomatoes are dependent on salicylic acid accumulation in the plant, likely mediated by rhizosphere microbial communities. These results suggest that organically-managed soils and microbial communities may play an unappreciated role in reducing plant attractiveness to pests by increasing plant resistance.

Preferência do Pulgão-Preto, Aphis Craccivora Koch, a Dois Diferentes Genótipos de Feijão-Caupi, Vigna Unguiculata (L.) Walp.

O feijão-caupi (Vigna unguiculata (L.) Walp.) destaca-se por sua importância socioeconômica para as famílias das regiões Norte e Nordeste do Brasil. O pulgão preto (Aphis craccivora Koch, 1854) destaca-se na cultura do feijão-caupi por ser considerado como uma das principais pragas que afetam negativamente a sua produção. O objetivo deste estudo foi verificar a preferência de A. craccivora por dois diferentes genótipos de feijão-caupi (Cauamé e Tapaihum) em condições de campo. O experimento contou com 5 populações diferentes para cada genótipo. As coletas dos dados foram realizadas nos dias 17/05, 29/05 e 07/06 do ano de 2013. Nesses dias foi realizada a contagem do número de pulgões que infestavam o pecíolo e o trifólio mais jovem de oito plantas ao acaso, em cada parcela o delineamento estatístico experimental utilizado foi o de blocos casualizados, com dez tratamentos (5 populações do genótipo Cauamé e 5 populações do genótipo Tapaihum) e quatro repetições. Os dados foram submetidos à ANOVA e as médias comparadas e transformadas em √x+1 pelo teste de Tukey a 5% no software ESTAT. Os pulgões observados nos genótipos de Feijão-caupi variaram de zero para Cauamé 12 a 6,88 no genótipo Tapaihum 6, nas observações do dia 29/05/2013, sendo a maior média do número de pulgões entre todas as populações dos genótipos (4,79) no dia 17/05/2013 e a menor (0,17). O pulgão A. craccivora não tem preferência entre os genótipos Cauamé e Tapaihum.Palavras-chave: Antixenose. Feijão de Corda. Resistência de Planta a Insetos.AbstractCowpea (Vigna unguiculata (L.) Walp.) stands out for its socioeconomic importance for the families of the North and Northeast regions of Brazil. Black aphid (Aphis craccivora Koch, 1854) stands out in the cowpea culture because it is considered one of the main pests that negatively affect its production. The aim of this study was to verify the preference of A. craccivora for cowpea genotypes under field conditions. The preference of black aphid to two different genotypes (Cauamé and Tapaihum) of Cowpea was evaluated. The experiment consisted of 5 different populations for each genotype. The data were collected on 05/17, 05/29 and 06/07 of the year 2013. In those days, the number of aphids that infested the petiole and the young trifolium of eight plants at random were counted, in each plot a randomized block design was performed with 10 treatments (5 populations of the Cauamé genotype and 5 populations of the Tapaihum genotype) and four replications. Data were subjected to ANOVA and the means compared and transformed in √x + 1 by the Tukey test (5%) in ESTAT software. The aphids observed in the cowpea genotypes ranged from zero to Cauamé 12 to 6.88 in the Tapaihum 6 genotype, the observations of may/29th/2013 were the highest mean of aphids among all populations of the genotypes (4.79) and on may/17th/2013 the lowest (0.17). The A. craccivora aphid has no preference between the Cauamé and Tapaihum Genotypes.Keywords: Antixenosis. Feijão de Corda. Plant Resistance to Insects.

Dampak Tanaman Transgenik Bt terhadap Populasi Serangga Pengendali Hayati

<p class="p1">An alternative technique to improve plant resistance to insect pests is plant transformation using the genetic engineering technology. Several transgenic plants resistant to insect have been produced and commercially released to environment in some industrial and developing countries. Before release, transgenic plants need to be assessed for their potential risks to human health and environment. One of the environmental risk assessments is the potential risk to non-target insects, including the biocontrol insects. Laboratories, glasshouse, and field experiments have been conducting the study of the impact of transgenic plant resistance to insect, especially transgenic Bt plants to the population of predators and parasitoids. However the results were controversial. The objective of this review is to inform some of controversial results, and to suggest serial experiments need to be done to solve the problem. The impact of the transgenic plant resistance to insects depends on several factors, such as genes that are used to transform the plants, the kind of plant pests, and the kind and stages of the insect natural enemies. Results of the experiments were influenced by sites of the experiments (laboratory, glasshouse, or field) and contact of the natural enemies to the toxin. Some experiments showed that the transgenic Bt plants have no impact to the natural enemies population, and otherwise. Due to the controversial results, the experiment and assessment should be done in depth and carefully studied. A sequential experiments need to be adopted to avoid the misleading interpretation, and the assessment need to be based on a case by case study.</p>