Ciência e Agrotecnologia, 44:e006920, 2020 Agricultural Science http://dx.doi.org/10.1590/1413-7054202044006920 eISSN 1981-1829 Strawberry genotypes with resistance to Tetranychus urticae mediated by leaf trichomes Resistência de genótipos de morangueiro ao Tetranychus urticae mediada por tricomas foliares Juliano Tadeu Vilela de Resende¹* , Renato Barros de Lima Filho2 , Luana Karolline Ribeiro² , Jéssica Vanessa Wosniak Corrêa² , Cleber Daniel de Goes Maciel2 , Khamis Youssef³ ¹Universidade Estadual de Londrina/UEL , Departamento de Agronomia, Londrina, PR, Brasil ²Universidade Estadual do Centro-Oeste/UNICENTRO, Departamento de Agronomia, Guarapuava, PR, Brasil ³Agricultural Researcher Center, Plant Pathology Research Institute, Giza, Egypt *Corresponding author: [email protected] Received in March 23, 2020 and approved in June 26, 2020 ABSTRACT The two-spotted spider mite (Tetranychus urticae) is the main pest encountered in strawberry cultivation in protected environments, causing damage and increasing the cost of production associated with chemical control. Breeding programs are essential for obtaining new cultivars that are more tolerant to two-spotted spider mites. The objective was to evaluate whether the leaf trichomes mediatethe resistance of intraspecific strawberry hybrids to two-spotted spider mites. Preselected hybrids were subjected to infestation by two-spotted spider mites and evaluated via the no-choice assay and the travel test. Resistance was correlated with the density of trichomes, both glandular and non-glandular, present on the surface of the leaflets of strawberry genotypes. The results indicated that there is an influence of hybrids and cultivars on the behavior of the pest, allowing the verification of the existence of resistant genotypes (RVDA#16, RVCS#44 and Camino Real). These treatments resulted in low numbers of eggs deposited and hatched compared with the other treatments and shorter distances traveled by two-spotted spider mites on the surface of leaflets. It was also verified that the glandular trichomes presented a significant negative correlation with the average distance traveled by two-spotted spider mites on the surface of the leaf discs, indicating that these structures alter the behavior of these arthropods. Genotype resistance was associated with the presence of glandular trichomes. In addition to the superiority of the agronomic and postharvest attributes of the preselected hybrids (RVDA#16 and RVCS#44) identified in the previous selection efforts, they proved to be promising materials for achieving resistance to the spider mite, revealing important genotypes for use as cultivars and particularly as parents in breeding programs. Index terms: Fragaria x ananassa; intraspecific hybridization; antibiosis; antixenosis. RESUMO O ácaro rajado (Tetranychus urticae) é a principal praga do morangueiro em ambiente protegido, causando danos e aumentando os custos de produção com o controle químico. Em programas de melhoramento, é essecial que as novas cultivares sejam tolerantes ao ácaro. Assim, objetivou-se avaliar a resistência ao ácaro rajado de híbridos intraespecíficos, pré-selecionados, mediada por tricomas foliares. Híbridos pré-selecionados foram submetidos a presença do ácaro rajado e avaliados por meio do teste sem chance de escolha e caminhamento, na superfície do folíolo. A resistência ao ácaro foi correlacionada de forma significativa e com a densidade de tricomas glandularese não glandulares,na superfície abaxial dos folíolos dos genótipos.Os resultados evidenciam que há influência dos híbridos pré-selecionados e cultivares, no comportamento do ácaro rajado, permitindo, constatar a resistência dos genótipos RVDA#16, RVCS#44 e Camino Real. Esses tratamentos obtiveram menor número de ovos depositados e eclodidos, quando comparados aos demais e, também menores distâncias percorridas pelo ácaro rajado. Verificou-se ainda que os tricomas glandulares foram correlacionados significativa e negativamente com a distância média percorrida pelo ácaro rajado, na superfície dos discos foliares dos genótipos RVDA#16, RVCS#44 e Camino Real, indicando que essas estruturas alteram o comportamento do artrópode-praga. A resistência dos genótipos está associada a presença dos tricomas gladulares. Os híbridos pré-selecionados (RVDA#16 e RVCS#44), além da superioridade dos atributos agronômicos e de pós-colheita, identificados na seleção anterior, foram promissores para resistência ao ácaro rajado, consistindo em importante genótipo para ser utilizado como cultivar e, principalmente, como parental em programas de melhoramento genético. Termos para indexação: Fragaria x ananassa; hibridação intraespecífica; antibiose; antixenose. 2020 | Lavras | Editora UFLA | www.editora.ufla.br | www.scielo.br/cagro All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License attribuition-type BY. 2 RESENDE, J. T. V. de et al. INTRODUCTION The identification of plants with greater resistance to pest arthropods is extremely important for plant breeding Strawberry (Fragaria x ananassa Duch.) shows high programs; therefore, evaluating and understanding their profitability and plays an important socioeconomic role in behavior is essential (Gong et al., 2018). However, the countries such as the United States, Mexico, Turkey, and resistance of different genotypes is not normally evaluated, Latin American countries such as Brazil and Chile (Biasio and in the main strawberry breeding programs, productive et al., 2015). However, pests and diseases are problems that aspects are the key parameters for the selection of plants. limit the yield potential of cultivars, as they significantly Reconciling these aspects makes it possible to select impair the development of fruits (Van Leeuwen et al., 2015; resistant or pest-tolerant plants, facilitating management Zhang et al., 2018). Among the pests attacking this crop, the in the production field. two-spotted spider mite, Tetranychus urticae Koch (Acari: Thus, the objective of this study was to evaluate Tetranychidae), stands out as the main pest in protected preselected strawberry genotypes regarding their resistance environments and can reduce fruit production by up to to spider mites associated with the presence of leaf 80% (Çobanoğlu; Güldali, 2017). The damage is caused by trichomes. the form of feeding, since the mites break the cells of the epidermis through the introduction of their chelicera on the MATERIAL AND METHODS underside of the leaves to feed on the intracellular contents, thereby causing the death of the attacked cells (Bernardi et Experimental material al., 2015; Gong et al., 2018). The application of acaricides is the most widely Twelve hybrid populations were obtained from used method for controlling spider mites (Van Leeuwen crosses between the Aromas, Camarosa, Dover, Festival, et al., 2010; Attia et al., 2013). However, the excessive Oso Grande, Sweet Charlie and Milsei Tudla cultivars. application of these products is responsible for causing the The seedlings obtained from each population were divided development of populations that are resistant to acaricides and evaluated under the climatic conditions of the south (Grbić et al., 2011), reductions in natural enemies, the of the state of Minas Gerais and the south-central state appearance of secondary pests and high levels of residues of Paraná. Genotypes selected based on agronomic and of phytosanitary products in fruits (Csányi et al., 2019). postharvest characteristics at both locations were used Thus, as an alternative to reduce the need for pesticides, to design the composition of treatments. The preselected varietal resistance is an important strategy within an strawberry hybrids used in the trial, RVFS#07 (Festival integrated pest management (IPM) program. In addition Florida x Sweet Charlie), RVDA#16 (Camarosa x Aromas) to influencing the behavior of the arthropod pest through and RVCS#44 (Camarosa x Sweet Charlie), came from the plant characteristics, this tool can be used in parallel with UNICENTRO/UEL/UFLA breeding program (Galvão et other control methods without any restrictions (Fahim; al., 2017; Barth et al., 2019; Barth et al., 2020), maintained Momen; Saiedy, 2020). at the Germplasm Bank of UEL/UNICENTRO. In addition In strawberry plants, both constitutive and to the hybrids, the commercial cultivars Camarosa, Camino inductive defense mechanisms protect plants against pest Real (short photoperiod cultivars), Albion, and Monterey attack (Karlec et al., 2017). In constitutive defense, the (neutral photoperiod cultivars) served as check treatments. plant does not depend on the presence or action of pests, The research was carried out at the Entomology and its resistance is expressed continuously. In contrast, Laboratory of Midwestern Parana State University, located the plant only expresses induced defense when injury in Guarapuava, PR (25° 38′ S and 51° 48′ W, with an occurs, and this type of resistance directly affect herbivores altitude of 1100 meters), from September to November or natural enemies (Smith; Clement, 2012; Moreira et 2019. al., 2018). Trichomes are important constitutive defense The plants were grown in a greenhouse in pots of mechanisms; there are two types of trichomes described in 5 dm3 containing subsurface soil corrected to 70% of base strawberry plants: glandular and non-glandular trichomes saturation. Forty-five days before the transplantation of (Benatto; Penteado; Zawadneak, 2019; Hata et al., 2020). the