Soybean leaf age and plant stage influence expression of resistance to velvetbean caterpillar and fall armyworm

Abstract

Numerous species of herbivorous insects are associated with soybeans, including the specialist velvetbean caterpillar (VBC), Anticarsia gemmatalis, and the generalist fall armyworm (FAW), Spodoptera frugiperda. Expression of plant resistance is in uenced by factors intrinsic to host plants, such as leaf age and plant stage, which can differentially affect specialist and generalist insects due to varying levels of plant defense and corresponding insect adaptation. In this study four experiments were carried out to test the hypotheses that levels of antibiosisresistance to VBC and FAW in the resistant genotype PI 227687 and susceptible genotype IGRA RA 626 RR are related to leaf age and plant stage of soybean. Furthermore, the concentrations of nutrients and selected avonoids were quanti ed to give insights on possible chemical mechanisms underlying the resistance. As results, development of VBC and FAW were negatively affected when larvae fed leaves of the resistant genotype, older leaves from the lower part of plants, or leaves from reproductive-stage soybeans. The effects were partly different for each insect species, and the generalist FAW was more affected by higher resistance levels in the older leaves of soybean than the specialist VBC. Distribution and concentrations of nutrients and avonoids in soybean in function of leaf age and plant stage may explain the varying levels of antibiosis-resistance to VBC and FAW. These results can bene t developments of speci c protocols for screening resistant soybean genotypes and pest management strategies focused in plant parts and growth stages that insect-resistance levels are lowest. Key MessageLeaf age and plant stage are factors that in uence expression of resistance to insects. These factors were investigated in soybean genotypes on VBC and FAW development.Development of VBC and FAW were negatively affected on the resistant genotype, older leaves, and leaves from reproductive-stage soybeans, and the varying levels of resistance may be explained by avonoids and nutrients concentrations.The results can bene t developments of speci c protocols for screening soybean resistant genotypes and pest management strategies.

Evaluation of Rearing Factors Affecting Clanis bilineata tsingtauica Mell Larvae Fed by Susceptible Soybean Variety NN89-29 in Spring and Autumn Sowing

“…The development of the velvetbean caterpillar, Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae) and the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), was negatively affected when larvae fed on leaves of the resistant genotype, older leaves from the lower part of plants or leaves from reproductive-stage soybeans [ 32 ]. Distribution and concentrations of nutrients and flavonoids of leaf age and plant stage in soybeans may explain the varying levels of antibiosis to the velvetbean caterpillar and the fall armyworm [ 32 ].…”

Effects of fast and slow-wilting soybean genotypes on fall armyworm ( Spodoptera frugiperda ) growth and development

“…We speculate that these effects are also due to the possible partitioning of chemical defenses that may have individual compounds expressed more in early and mid-stages. It has been suggested that there are higher levels of rutin, a type of secondary metabolite, in the early stages of soybean plants, which has been shown to retard the development of FAW at every stage and decrease pupal viability [ 49 , 50 ]. Further investigation is needed, as differential effects are shown in the literature, such as Souza et al [ 50 ] specifically finding that older leaves were more detrimental to FAW and another Lepidopteran pest, velvetbean caterpillar – Anticarsia gemmatalis .…”

“…It has been suggested that there are higher levels of rutin, a type of secondary metabolite, in the early stages of soybean plants, which has been shown to retard the development of FAW at every stage and decrease pupal viability [ 49 , 50 ]. Further investigation is needed, as differential effects are shown in the literature, such as Souza et al [ 50 ] specifically finding that older leaves were more detrimental to FAW and another Lepidopteran pest, velvetbean caterpillar – Anticarsia gemmatalis . Studies by Mai et al [ 51 ] support our findings that earlier-stage soybeans were also detrimental to FAW.…”

Cut off Behavior of Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) in Soybean (Glycine max (L.) Merrill) Seedlings

“…Another important factor that we must point out is the possibility of the presence of phenolic substances in the leaves of soybean plants, which act as defense against herbivores that cause leaf injury [27], thus giving rise to another alternative, which in turn may explain the unusual behavior of this arthropod.…”