Fecundity, fertility and reproductive recovery of irradiated Queensland fruit fly Bactrocera tryoni

Abstract

Pupae of the Queensland fruit fly or Q‐fly Bactrocera tryoni (Froggatt) are irradiated routinely to induce reproductive sterility in adults for use in sterile insect technique programmes. Previous studies suggest that adult sexual performance and survival under nutritional and crowding stress are compromised by the current target dose of radiation for sterilization (70–75 Gy), and that improved mating propensity and survival under stress by irradiated males may be achieved by reducing the target sterilization dose without reducing the level of induced sterility. This raises the question of the amount by which the irradiation dose can be reduced before residual fertility becomes unacceptable. The present study measures the levels of residual fertility in male and female irradiated Q‐flies at different irradiation doses (20, 30, 40, 50, 60 and 70 Gy), and investigates the possibility that fecundity and fertility increase between 10–15 and 30–35 days post emergence. Male flies require a higher dose than females to induce sterility, with no residual fertility found in females irradiated at doses of 50 Gy or above, and no residual fertility found in males irradiated at doses of 60 Gy or above. Irradiated females are more fecund at 30–35 days post emergence than at 10–15 days. However, fertility does not increase between 10 and 15 days post emergence and 30–35 days, even at doses below 50 Gy. The present study shows that there is scope to reduce the target sterilization dose for Q‐flies below that of the current dose range (70–75 Gy) at the same time as retaining an adequate safety margin above radiation doses at which residual fertility can be expected.

Evaluating Irradiation Dose for Sterility Induction and Quality Control of Mass-Produced Fruit Fly <I>Bactrocera tryoni</I> (Diptera: Tephritidae)

“…Furthermore, this study found that longevity under crowding stress (FAOÐ IAEAÐUSDA 2003) correlated negatively with irradiation dose, and that sexual competitiveness steadily decreased with increasing irradiation dose (Collins et al 2009). These results strongly suggest that reduced irradiation dose would be beneÞcial to ßy quality and would not sacriÞce adequate sterility (see also Collins and Taylor 2011).…”

Optimising irradiation dose in mass‐produced Queensland fruit fly, Bactrocera tryoni, for sterile insect release: the incorporation of residual effects on F1 progeny

“…On the other hand, several important caveats with using lower irradiation were not measured in this study and would need to be explored. Two such concerns are sterile male and sterile female matings and the problems with recovered fecundity and fertility (Collins & Taylor, 2011;Collins et al, 2012). As lower irradiation doses increase residual fertility in both sexes, matings between sterile males and sterile females in the field would have a higher probability of producing fertile offspring, though these sterile matings have been shown to have exceedingly low probability of egg hatch (Collins et al, 2008).…”

“…Also, irradiated Qflies can experience recovered fecundity and fertility at older ages (Collins & Taylor, 2011). Cellular repair mechanisms can repair damage caused by irradiation, resulting in recovered fertility (Siddiqui et al, 2013).…”

A role for copula duration in fertility of Queensland fruit fly females mated by irradiated and unirradiated males

“…Fertility of female Q-flies mated once by a normal male is typically 60-80% (Collins et al, 2009;Pérez-Staples et al, 2007a), but is reduced to <0.05% in females mated once by a sterile male (Collins et al, , 2009Collins and Taylor, 2011). But what happens if females remate?…”