Psyllid rearing and hybridization
The original Kyushu colonies were founded by individuals from
collections made in 2004 and 2015 within Kumamoto prefecture on the
Japanese island of Kyushu, while the source population of the Hokkaido
colony originated from individuals collected in 2007 from the Lake Toya
area on the island of Hokkaido (Grevstad et al., 2013). The A.
itadori populations at MSU were founded via shipments of 480 and 400
Kyushu (southern population) adults in April and June, respectively, and
600 Hokkaido (northern population) adults in June 2021 from colonies
maintained at Oregon State University. An additional 350 Kyushu
individuals were shipped from the Phillip Alampi Beneficial Insect
Rearing Laboratory (New Jersey Department of Agriculture) in August
2021.
We reared the Kyushu population on Japanese knotweed and the Hokkaido
population on giant knotweeds (Grevstad et al. 2013) by placing 100
adults into a 40 x 40 x 60 cm mesh cage (Restcloud, Chengdu, China)
containing a single potted knotweed plant for 14 days. The adults
emerging over the course of 4-5 weeks were kept for an additional 2
weeks in cages to mate and then the next generation was started as
described above. The rearing took place in a laboratory at room
temperature (22 °C ± 5, RH 40% ± 10, 16L: 8D); under these conditions,
psyllids developed from egg to adult in 35 days.
To create the reciprocal crosses knotweed plants infested by either
Kyushu or Hokkaido 5th-instar nymphs were cleared of all adults and
monitored every 24 hours. Newly-emerging adults were collected, sorted
by sex based on the identification of genitalia (Hall, 2008) and paired
with similarly collected virgin individuals of the opposite sex and
population. Both reciprocal hybrid crosses, the one using Kyushu females
paired with Hokkaido males (FemKYU), and the one using Hokkaido females
paired with Kyushu males (FemHOK) were reared on Bohemian knotweeds by
placing 100 psyllids (50♀ x 50♂) in a cage containing a potted knotweed
plant. Adults were kept in the cage for 2 weeks to mate and lay eggs and
then removed. Developing psyllids were kept together in the same cage
for 8 more weeks that allowed for adult emergence, sexual maturation,
and mating. These first-generation (F1) adults were used to start the
second generation (F2) without any additional crossing or back-crossing.