Bracon brevicornis Genome Showcases the Potential of Linked-Read Sequencing in Identifying a Putative Complementary Sex Determiner Gene

Bracon brevicornis is an ectoparasitoid of a wide range of larval-stage Lepidopterans, including several pests of important crops, such as the corn borer, Ostrinia nubilalis. It is also one of the earliest documented cases of complementary sex determination in Hymenoptera. Here, we present the linked-read-based genome of B. brevicornis, complete with an ab initio-derived annotation and protein comparisons with fellow braconids, Fopius arisanus and Diachasma alloeum. We demonstrate the potential of linked-read assemblies in exploring regions of heterozygosity and search for structural and homology-derived evidence of the complementary sex determiner gene (csd).

Braconidae revisited: Bracon brevicornis genome showcases the potential of linked-read sequencing in identifying a putative complementary sex determiner gene

ABSTRACTBracon brevicornis is an ectoparasitoid of a wide range of larval-stage Lepidopterans, including several pests of important crops, such as the corn borer, Ostrinia nubilalis. It is also one of the earliest documented cases of complementary sex determination in Hymenoptera. Here, we present the linked-read genome of B. brevicornis, complete with an ab initio-derived annotation and protein comparisons with fellow braconids, Fopius arisanus and Diachasma alloem. We demonstrate the potential of linked-read assemblies in exploring regions of heterozygosity and search for structural and homology-derived evidence of the complementary sex determiner gene (csd).

Chemical Cues Induced from Fly-Oviposition Mediate the Host-Seeking Behaviour of Fopius arisanus (Hymenoptera: Braconidae), an Effective Egg Parasitoid of Bactrocera dorsalis (Diptera: Tephritidae), within a Tritrophic Context

Fopius arisanus is a solitary endoparasitoid that parasitizes a variety of tephritid species. Native to the Indo-Australian region, it is currently exploited worldwide as a biological control agent due to its exceptional efficiency in reducing pest populations. The efficiency of any biological control program is affected by the host location ability of the parasitoids. The present study used a Y-tube olfactometer to test the behavioural responses of female F. arisanus to four fruit species which had undergone different types of damages: undamaged, damaged through Bactrocera dorsalis ovipositioning (i.e., infested), or different levels of mechanical damage. Our results suggest that F. arisanus females were significantly attracted to mangoes and pears (vs. purified air), regardless of their condition; however, whilst infested mangoes did not attract more female parasitoids compared to healthy or mechanically damaged fruits, infested pears attracted significantly more. For citrus fruits and peaches, oviposition damage caused them to be more attractive to parasitoid females. In terms of the longevity of the effects, infested mango fruits remained attractive for up to 5 days after infestation, whereas for infested peaches, pears, and citrus fruits, the attractiveness tended to decrease as time passed. Regarding mechanical damage, mango fruits that had undergone any intensity of damage were equally attractive to parasitoid females; however, peach and citrus fruits with high levels of mechanical damage were more attractive, and pears were found to be most attractive with slight mechanical damage. Additional to the above, we also tested the effect of insecticides on behavioural responses using mangoes. We found that the treatment of infested fruits with lambda-cyhalothrin and cypermethrin remained attractive to F. arisanus females, albeit to different extents, which is in contrast to spinosad, cyantraniliprole, and acetamiprid. Finally, we suggest that the host-searching behaviour of F. arisanus females is mainly mediated by oviposition-induced volatiles, either emitted from the fruit or left by the fruit fly.

Asosiasi Lalat Buah (Bactrocera spp.) (Diptera : Tephritidae) dan Parasitoidnya pada Tanaman Jambu Biji Kristal (Psidium guajava L.) yang Dibudidayakan di Bali

Association of Fruit Flies (Bactrocera spp.) (Diptera: Tephritidae) and Their Parasitoid on Guava (Psidium guajava L.) Cultivated in Bali. The study on the association of fruit flies (Bactrocera spp.) (Diptera: Tephritidae) and their parasitoid on guava (Psidium guajava L.) cultivated in Bali was conduted in order to know the abundance, attacks percentage and the species of parasitoid associated on guava, cultivated in Bali. The sampling was done intentionally by taking attacked fruit in Musi Village, Buleleng Regency; Pelaga Village, Badung Regency; and Tiga Village, Bangli Regency. The results showed that 3 species of fruit flies were found, namely B. carambolae, B. papayae and B. albistrigata. The percentage and number of adult insect emergence in Musi Village were B. papayae (50.87% ; 2772 imago), B. carambolae (35.18% ; 1803 imago) and B. albistrigata (13.94% ; 741 imago). In Pelaga Village B. carambolae (61.31% ; 2864 imago) dominates and B. papayae only 38.69% and 1801 imago. B. carambolae is also found dominant in Tiga Village (59.08% ; 2303 imago) and B. papayae only 40.92% and 1603 imago. Percentage of damage to guava is 24.27% on average. There are three species of parasitoids found that are associated with fruit flies on guava in Bali, namely Fopius arisanus, Diachasmimorpha sp. and Opius sp. The average parasitic rate is 6.76%. The highest parasitic rate is in Musi Village, Buleleng while the lowest is in Tiga Village, Bangli.

Fruit Preference, Parasitism, and Offspring Fitness of Fopius arisanus (Hymenoptera: Braconidae) Exposed to Bactrocera dorsalis' (Diptera: Tephritidae) Infested Fruit Species

Fopius arisanus (Sonan) (Hymenoptera: Braconidae) is a koinobiont solitary parasitoid of various fruit flies, particularly those in the genus Bactrocera. Researchers introduced F. arisanus into Africa for the biological control of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), a pest of a wide range of fruit trees and vegetables. However, the suitability of host fruit species as egg-laying substrates for parasitoid development remains poorly investigated in tropical Africa. The present study examines the preference and performance of F. arisanus on B. dorsalis reared on eleven fruit species through laboratory choice-test trials. We assessed the oviposition activity, parasitism rate, developmental time, and offspring fitness of F. arisanus on nine cultivated and two wild host fruits species. Oviposition attempts were higher on Psidium guajava (L.) (Myrtales: Myrtaceae) and Mangifera indica (L.) (Sapindales: Anacardiaceae) than on the other host fruits tested. The wasp parasitized host eggs in P. guajava in no-choice experiments. Psidium guajava, Irvingia wombulu (Vermoesen) (Malpighiales: Irvingiaceae), and Irvingia gabonensis (Aubry_Lecomte) Baill (Malpighiales: Irvingiaceae) were suitable for parasitism in choice tests. Of all host fruits tested, the body and hind tibia lengths of both parasitoid sexes emerging from M. indica were longer than on the others. The female ovipositor was long on Annona squamosa (L.) (Magnoliales: annonaceae) and short on Eribotrya japonica ([Thunb.] Lindl.; Rosales: Rosaceae). We obtained the longest preimaginal developmental time for both sexes on E. japonica and the shortest for females and males on Carica papaya (L.) (Brassicales: Caricaceae). These results demonstrate the ability of some tested fruit species to serve for the permanent establishment of F. arisanus in the field.