Differential levels of soybean resistance to the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) under controlled and uncontrolled environments are associated with plant age, damage intensity, and trichome density

Whiteflies are a severe threat to soybean production in the tropics. This study aimed to evaluate the soybean resistance level of the whitefly Bemisia tabaci in controlled and uncontrolled environments that is associated with plant age, damage intensity, and trichome density. The research was conducted under two conditions: non-sprayed (NS) and sprayed (SP). This study used 50 soybean genotypes arranged in a randomized block design with three replicates. The whitefly population was derived from natural infestations. The results showed that the highest wild population of B. tabaci occurred at 40 days after planting (DAP), i.e., 126.08 adults/plant in the NS environment and 22.57 adults/plant in the SP environment. The peak damage intensity occurred at 50 DAP, 20.71% in the NS environment, and 17.15% in the SP environment. In the NS environment, there were six resistant genotypes (including the resistant control G100H), 25 moderate, and 19 susceptible genotypes. In the SP environment, 19 genotypes were resistant, 22 genotypes were moderate, and nine genotypes were susceptible, respectively. Six soybean genotypes showed consistent resistance to B. tabaci in NS and SP environments. The low density of leaf trichomes in soybean may influence the high resistance to B. tabaci. The resistant genotypes identified in this study could be utilized in breeding programs for B. tabaci resistance.

Os tricomas de Capsicum spp. interferem nos aspectos biológicos do ácaro-branco, Polyphagotarsonemus latus Banks (Acari: Tarsonemidae)? / Do Capsicum spp. trichomes Influence the biological aspects of the broad mite, Polyphagotarsonemus latus Banks (Acari: Tarsonemidae)?

Variações nas características morfológicas das plantas podem ter efeito imediato sobre a preferência alimentar, escolha de sítios de oviposição e vulnerabilidade de herbívoros a inimigos naturais. A longo prazo, podem ter consequências sobre a dinâmica populacional desses organismos, já que atuam sobre seu desenvolvimento, sobrevivência e reprodução. Neste trabalho, avaliou-se o desenvolvimento de Polyphagotarsonemus latus (Banks) em cinco espécies de Capsicum com diferentes densidades de tricomas. Testou-se a hipótese de que o crescimento populacional de P. latus nessas plantas apresenta relação negativa com o aumento da densidade de tricomas nas folhas. Observou-se um padrão decrescente na taxa intrínseca de crescimento (r m) de P. latus com o aumento da densidade de tricomas nas folhas. O menor r m foi obtido em folhas de C. praetermissum (r m = 0,46), que apresenta a maior densidade de tricomas entre as espécies de Capsicum avaliadas. Os maiores valores de r m foram observados em espécies de Capsicum com densidade intermediária de tricomas nas folhas, Capsicum frutescens (r m = 0,77) e Capsicum chinense (r m = 0,76). Os tricomas de Capsicum spp. atuaram como fator limitante ao desenvolvimento de P. latus à medida que se apresentaram em maiores densidades e mais bem distribuídos na superfície foliar. Foi discutido ainda o papel da defesa morfológica e química de plantas de Capsicum sobre o desenvolvimento de P. latus.

Plant morphology traits can affect the feeding preference, oviposition choice and the vulnerability of herbivores to natural enemies. At long term, these plant variations may influence herbivore population dynamics due to the interference on their development, survival and reproduction. In this paper, the development of the broad mite Polyphagotarsonemus latus (Banks) was evaluated on five species of Capsicum with different density of trichomes. We tested the hypothesis that P. latus population growth has a negative relationship with the increase trichome density on leaves. It was assessed a decrease in the intrinsic growth rate (r m) of P. latus with the increase of trichome density on the leaves tested. The lower r m was measured in leaves of C. praetermissum (r m = 0.46), which has the highest trichome density among the assessed Capsicum species. The highest values of r m were observed on Capsicum species with intermediate densities of trichomes on leaves such as Capsicum frutescens (r m = 0.77) and Capsicum chinense (r m = 0.76). Capsicum spp. trichomes acted as a limiting plant trait for the development of P. latus when they were in higher densities and better distributed on the leaf surface. We also discuss the role of morphologic and chemical plant defenses on P. latus development.