Domestication Impacts the Wheat-Associated Microbiota and the Rhizosphere Colonization by Seed- and Soil-Originated Microbiomes, Across Different Fields

The seed-transmitted microorganisms and the microbiome of the soil in which the plant grows are major drivers of the rhizosphere microbiome, a crucial component of the plant holobiont. The seed-borne microbiome can be even coevolved with the host plant as a result of adaptation and vertical transmission over generations. The reduced genome diversity and crossing events during domestication might have influenced plant traits that are important for root colonization by seed-borne microbes and also rhizosphere recruitment of microbes from the bulk soil. However, the impact of the breeding on seed-transmitted microbiome composition and the plant ability of microbiome selection from the soil remain unknown. Here, we analyzed both endorhiza and rhizosphere microbiome of two couples of genetically related wild and cultivated wheat species (Aegilops tauschii/Triticum aestivum and T. dicoccoides/T. durum) grown in three locations, using 16S rRNA gene and ITS2 metabarcoding, to assess the relative contribution of seed-borne and soil-derived microbes to the assemblage of the rhizosphere microbiome. We found that more bacterial and fungal ASVs are transmitted from seed to the endosphere of all species compared with the rhizosphere, and these transmitted ASVs were species-specific regardless of location. Only in one location, more microbial seed transmission occurred also in the rhizosphere of A. tauschii compared with other species. Concerning soil-derived microbiome, the most distinct microbial genera occurred in the rhizosphere of A. tauschii compared with other species in all locations. The rhizosphere of genetically connected wheat species was enriched with similar taxa, differently between locations. Our results demonstrate that host plant criteria for soil bank’s and seed-originated microbiome recruitment depend on both plants’ genotype and availability of microorganisms in a particular environment. This study also provides indications of coevolution between the host plant and its associated microbiome resulting from the vertical transmission of seed-originated taxa.

Impact of citrus species on the biological characteristics and life table parameters of Eutetranychus orientalis (Klein) (Acari: Tetranychidae)

Biological characteristics and life table parameters of Eutetranychus orientalis (Klein) were revealed on four different citrus species: grapefruit (Citrus paradisi Macf. cv. Star Ruby), lemon (C. limon (L.) Burm. f. cv. Meyer), mandarin (C. reticulata Blanco cv. Okitsu) and orange (C. sinensis L. cv. Washington Navel) under laboratory conditions. Results show that oviposition period, fecundity, and life table parameters varied significantly depending on the host plant species. Furthermore, host plant species had little effect on immature development, except for the teleiochrysalis and total developmental period, which was significantly shorter on lemon (13.77 days for females, 12.67 days for males). Total mean numbers of eggs laid by E. orientalis was 15.92 on mandarin and 29.78 on lemon. In addition, intrinsic rate of increase (rm), net reproductive rate (R0), finite rate of increase (λ) and doubling time (DT) are 0.12 day–1, 10.41 ♀/♀, 1.13 day–1 and 5.59 days for lemon, 0.17 day–1, 22.36 ♀/♀, 1.19 day–1 and 4.04 days for grapefruit, respectively. However, shortest and longest mean generation times (To) were obtained at 18.26 days on orange and 19.37 days on grapefruit. Our results demonstrate that intergeneric differences of Citrus should be considered when determining E. orientalis population abundance and dynamics in field conditions.

Chinese Cabbage Changes Its Release of Volatiles to Defend against Spodoptera litura

Plants respond to herbivorous insect attacks by releasing volatiles that directly harm the herbivore or that indirectly harm the herbivore by attracting its natural enemies. Although the larvae of Spodoptera litura (the tobacco cutworm) are known to induce the release of host plant volatiles, the effects of such volatiles on host location by S. litura and by the parasitoid Microplitis similis, a natural enemy of S. litura larvae, are poorly understood. Here, we found that both the regurgitate of S. litura larvae and S. litura-infested cabbage leaves attracted M. similis. S. litura had a reduced preference for cabbage plants that had been infested with S. litura for 24 or 48 h. M. similis selection of plants was positively correlated with the release of limonene; linalool and hexadecane, and was negatively correlated with the release of (E)-2-hexenal and 1-Butene, 4-isothiocyanato. S. litura selection of plants was positively correlated with the release of (E)-2-hexenal, 1-Butene, 4-isothiocyanato, and decanal, and was negatively correlated with the release of limonene, nonanal, hexadecane, heptadecane, and octadecane. Our results indicate that host plant volatiles can regulate the behavior of S. litura and M. similis.

Notes on tenuipalpid mites associated with Quercus pubescens in southern Italy

During a survey of the flat mites (Tenuipalpidae) on forest trees and agricultural crops in five different sites of the Apulian territories (Southern Italy) in 2019, Brevipalpus recki (Livschitz and Mitrofanov) and Cenopalpus longirostris (Livschitz and Mitrofanov) were collected on Quercus pubescens (Willdenow) (Fagaceae). The authors give an account of the new record of C. longirostris, which was not listed in the previous Italian fauna, and of the finding of B. recki in southern Italy, since it was only mentioned from the northern region of the country so far. In addition, the paper lists Q. pubescens as a new host plant for C. longirostris.

Xylosandrus crassiusculus (Motschulsky) (Coleoptera: Curculionidae) and Its Fungal Symbiont Ambrosiella roeperi Associated with Arecanut Kernel Decay in Karnataka, India

Xylosandrus crassiusculus (Coleoptera: Curculionidae: Scolytinae) is reported causing damage to areca palm plantations (Areca catechu L.—Arecaceae) in Karnataka (India). In particular, X. crassiusculus has been observed attacking and successfully reproducing on areca nuts; besides the new host plant record, the data provided here represent the first documented case of spermatophagy for this xyleborine beetle. All infestation symptoms of this polyphagous pest were documented and illustrated. The identity of the scolytid, besides morphologically, was confirmed by its DNA barcoding. Eggs, larvae and pupae were found within the galleries of infested kernels. All galleries of the infested kernels were characterized by the presence of whitish to greyish fungal growth. The fungus was identified as Ambrosiella roeperi, a known symbiont of Xylosandrus crassiusculus. Incidence of this symbiotic insect-fungus complex in the economic part of arecanut, i.e., the kernel, is of serious concern. In a climate change scenario, this beetle with fungal symbionts may pose a serious threat to arecanut production in India and elsewhere.

Two new species of Aulacaspis Cockerell, 1893 (Hemiptera: Coccomorpha: Diaspididae) from China

Two new armoured scale insects in the genus Aulacaspis (Hemiptera: Coccomorpha: Diaspididae) are described and illustrated from Guizhou Province, China. Aulacaspis paralonganae sp. n. was collected from the host-plant Schima superba (Theaceae) and A. guiyangensis sp. n. was collected from Cinnamomum camphora (Lauraceae). Aulacaspis longanae Chen, Wu & Su 1980 is redescribed and a new host-plant record is reported. The type specimens of the two new species and material of A. longanae are deposited in the Institute of Entomology, Guizhou University, Guiyang, China. An identification key based on adult females is provided to separate Chinese species of Aulacaspis.