<b>Morphological and chemical characteristics of onion plants (<i>Allium cepa</i> L.) associated with resistance to onion thrips

Abstract

Thrips tabaci Lindeman is the main pest of onion crops, and chemical control is the main method adopted by farmers. Alternative control methods should be prioritised to reduce the amount of insecticides used. Resistant cultivars are one efficient way to control thrips in the field. Our aim was to assess the influence of morphological and chemical characteristics of seven onion cultivars and their resistance to T. tabaci. The number of thrips and the morphological and chemical characteristics of the plants were assessed. Among the evaluated cultivars, Alfa São Francisco RT, BR 29 and Sirius showed resistance to T. tabaci, as indicated by the lower number of thrips observed during the cycle (64, 87, and 74 thrips, respectively). Morphological and chemical characteristics were associated with onion's resistance to T. tabaci. For the cultivar Alfa São Francisco RT, a wider central angle (16.4°), a thinner cuticle, a larger amount of epicuticular waxes, and stomata on the surface of leaves accounted for resistance. For the cultivars BR 29 and Sirius, the resistance was likely due to the presence of resistance-conferring substances or high amounts of some component in the chemical composition of plants.Características morfológicas e químicas de plantas de cebola (Allium cepa L.) associadas à resistência ao tripes da cebola RESUMO. Thrips tabaci Lindeman é a principal praga da cultura da cebola e o controle químico é o principal método adotado pelos agricultores. Métodos alternativos de controle devem ser priorizados, visando diminuir a quantidade de inseticidas utilizada. Cultivares resistentes representam um método eficiente de controle de tripes no campo. Nosso objetivo foi verificar a influencia de características morfológicas e químicas de sete cultivares de cebola conferindo resistência a T. tabaci. O número de tripes, características morfológicas e químicas das plantas foram avaliadas. Dentre as cultivares avaliadas, Alfa São Francisco RT, BR 29 e Sirius mostraram-se resistentes a T. tabaci, uma vez que apresentaram um baixo número de tripes observados durante o ciclo (64, 87 e 74 tripes respectivamente). Características morfológicas e químicas estão associadas à resistência de plantas de cebola a T. tabaci. Para a cultivar Alfa São Francisco RT, um maior ângulo central (16,4˚), uma menor espessura de cutícula, e uma maior concentração de ceras epicuticulares e estômatos na superfície das folhas conferem resistência. Para as cultivares BR 29 e Sirius, a resistência provavelmente esta relacionada à presença de substâncias ou de quantidades elevadas de algum componente na composição química das plantas.Palavras-chave: Thrips tabaci, Thysanoptera, Thripidae, cebola, resistência de plantas a insetos.

Thrips (Thysanoptera) associated with onion (Allium cepa L.) and Welsh onion (Allium fistulosum L.)

“…The differences in thrips infestation of the studied cultivars are caused by a number of factors, and clarifying them requires further research. Presumably, factors affecting the colonisation of cultivars by T. tabaci were their biochemical and morphological features, influencing the vision, taste and smell senses of thrips, and could be responsible for antixenosis and antibiosis (Smith, 2005;Trdan et al, 2008b;Diaz-Montano et al, 2012;Silva et al, 2014).…”

Biological parameters of onion thrips, Thrips tabaci Lindeman on onion cultivars

“…Th e OW and NR cultivars were more susceptible to thrips infestation than NR-53 and ODK-301 as the result of their short development time, fecundity, and increased FLT parameters. Th e variation in resistance between the cultivars may be due to morphological characteristics and/or chemical and nutritional composition of the plants (Silva et al 2015). The morphological characteristics might involve thickness and rigidity of the cellular walls, the amount of epicuticular waxes, and the wider central angle between the leaves.…”

“…The morphological characteristics might involve thickness and rigidity of the cellular walls, the amount of epicuticular waxes, and the wider central angle between the leaves. Th ese features increase the diffi culty of attack by onion thrips on onion plants (Martin and Workman 2006;Mo et al 2008;Morsello et al 2008;Diaz-Montano et al 2010;Silva et al 2015). Chemical substances and the nutritional composition of onion plants infl uence the feeding rate, the development and reproduction of T. tabaci, resulting in plant resistance by antibiosis and antixenosis (Riefl er and Koschier 2009).…”

Dwarf‐cashew resistance to whitefly (Aleurodicus cocois) linked to morphological and histochemical characteristics of leaves

“…Cuticle and cell wall thicknesses, as well as epicuticular wax deposition, act as physical barriers by hindering movement, feeding, and oviposition of herbivores that feed directly from the epidermal cells. In onion plants, these structural characteristics were associated with resistance of different cultivars to Thrips tabaci . Populations of the whitefly B. tabaci have been positively correlated with the thickness of leaf lamina in cotton, black gram ( Vigna mungo ), and eggplant .…”