A soybean trypsin inhibitor reduces the resistance to transgenic maize in a population of Spodoptera frugiperda (Lepidoptera: Noctuidae).

Lepidopteran pests have been successfully managed by the adoption of insect resistant transgenic plants expressing Cry and/or Vip insecticidal proteins derived from Bacillus thuringiensis (Bt plants). Among such pests, Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) is highlighted for its destructive potential in maize crops and for cases of field-evolved resistance to Bt plants. Cry insecticidal proteins expressed in Bt plants are known for their interaction with insect midgut receptors and subsequent midgut cell disruption that leads to target pest death. In the midgut of lepidopteran larval pests such as S. frugiperda, serine proteases are important in dietary protein digestion and activation or degradation of insecticidal proteins. This work was conducted to evaluate if the use of a soybean trypsin inhibitor (SBTI) could disrupt the development of a Bt-susceptible and a Bt-resistant population of S. frugiperda ingesting Bt (expressing Cry1F, Cry1A.105, and Cry2Ab2 Cry proteins) and non-Bt maize plants. The SBTI was produced and purified using recombinant expression in E. coli followed by purification in Ni-Sepharose. Bioassays using non-Bt maize leaves indicated that the development of susceptible and resistant populations of S. frugiperda was not influenced by the ingestion of SBTI. However, when the resistant population consumed Bt maize plants amended with SBTI, high mortality along with a reduction in larval weight and reduced activity of digestive trypsins were observed. Although the mode of action was not elucidated, it is possible that the consumption of SBTI increased susceptibility to Bt maize in the resistant population of S. frugiperda.

First Report of Meloidogyne incognita Infecting Stachys byzantina in Brazil.

Stachys byzantina C. Koch (Lamiaceae alt. Labiatae), commonly known as lamb's ear, is an important medicinal plant with anti-inflammatory, antitumor, anticancer, antispasmodic, sedative and diuretic properties (Asnaashari et al. 2010). This plant is widely consumed in Europe and Asia as aromatic teas. In Brazil, it is an unconventional food plant, nonetheless, its medicinal properties have been recognized as well as its production. In May 2019, in a Sao Paulo State municipality, Jaboticabal, (21°14'38.7"S 48°17'10.6"W), S. byzantina plants presented reduced growth and chlorotic leaves associated with root galls. In the phytopathological clinic, 7,983 eggs and juveniles of Meloidogyne sp. were counted in 10 g of the plant roots. In 100 cm³ of soil surrounding the plant, 532 second-stage Meloidogyne sp. juveniles (J2) were found. Morphological, enzymatic and molecular identification of the nematode species found were performed (Fig. S1). For morphological analysis, perineal pattern of females (n = 10) and labial region of males (n = 10) were analyzed. In the perineal region of females, a high and trapezoidal dorsal arch with thick striations was observed, whereas the males presented the trapezoidal labial region with the prominent labial disc in relation to the sub-median lips and transverse streaks in the head region, typical characteristics of M. incognita (Kofoid and White, 1919) Chitwood 1949. (Netscher and Taylor 1974; Eisenback and Hirschmann 1981). The esterase enzyme profile, obtained individually from 8 females, was compatible with phenotype I1 [Rm (x100) = 46.25], also associated with M. incognita (Esbenshade and Triantaphyllou 1985). Molecular analysis was realized (n = 3) by applying the primers Finc/Rinc (Zijlstra et al. 2000) in the DNA of individual females, which resulted in the amplification of an amplicon of 1200 bp specific for M. incognita. Pathogenicity testing was conducted in a greenhouse by inoculation of 5,000 eggs and juveniles from the original population into S. byzantina seedlings (n = 4). After 90 days, the inoculated plants, unlike the non-inoculated ones, exhibited symptoms similar to those initially observed in the field. The nematodes were extracted from the roots of the inoculated plants, quantified, and the identity of M. incognita was confirmed. The average reproductive factor obtained was 136.6, confirming the pathogenicity of M. incognita to S. byzantina. Thus, this is the first report of M. incognita associated with S. byzantina in Brazil and in the world. Lamb's ear is a horticultural plant, and its high reproductive factor to M. incognita can also result in damage to the subsequent crops. In addition, Lamb's ear is propagated vegetatively and this favors the spread of nematodes to other areas. This new report is important in order to alert producers to realize the proper management of this nematode in S. byzantina.

Immune response and susceptibility to Cotesia flavipes parasitizing Diatraea saccharalis larvae exposed to and surviving an LC25 dosage of Bacillus thuringiensis.

Biological control using entomopathogens and natural enemies is an ecofriendly method for pest management in agriculture. Biological control agents often can be simultaneously employed and compatibility between agents may improve pest suppression. We investigated the influence of the entomopathogen Bacillus thuringiensis (Bt) on the immune system of the sugarcane borer Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) to determine if such changes impact parasitization by Cotesia flavipes Cameron, 1891 (Hymenoptera: Braconidae). The immune response of surviving D. saccharalis larvae fed with an LC25 dosage of a Bt-based biopesticide (Dipel®) was analyzed (total hemocyte count, hemocyte adhesion, and activities of phenoloxidase and lysozyme). Furthermore, the suitability of surviving Bt-fed larvae as hosts for C. flavipes was assessed by measuring parasitoid attributes such as number and size of teratocytes, weight of pupae, length of adult female tibia and number of emerged adults. Total hemocyte count, but not hemocyte adhesion, total protein content and phenoloxidase activity increased in the hemolymph of non-parasitized Bt-fed larvae (Bt-NP) compared to control larvae (NBt-NP). Lysozyme activity increased only after parasitization without Bt exposure (NBt-P). After parasitization, the immunological parameters activated in Bt-NP larvae decreased to levels at or below those observed in control larvae, showing that C. flavipes can regulate the activated immune response of Bt-fed larvae. The development of C. flavipes was not impaired in Bt-fed larval hosts (Bt-P); no changes were observed for teratocyte size, weight of pupal mass, length of hind tibia and number of adults emerged.