Genetics of Resistance to Phosphine in <I>Rhyzopertha dominica</I> (Coleoptera: Bostrichidae)

Abstract

The inheritance of resistance to phosphine was studied in two strains of the lesser grain borer, Rhyzopertha dominica (F.), labeled 'Weak-R' and 'Strong-R'. These strains were purified versions of field-selected populations collected in Queensland, Australia. Weak-R and Strong-R were, respectively, 23.4 times (20-h exposure) and 600 times (48-h exposure) resistant to phosphine compared with a reference susceptible strain (S-strain). Each -R strain was crossed with the S-strain and the response to phosphine was measured in their respective F1, F2, and F1-backcross (F1-BC) progenies. Data from testing of reciprocal F1 progeny indicated that resistance in Weak-R was autosomal and incompletely recessive with a degree of dominance -0.96. Modified chi-square analysis and contingency analysis of the observed response to phosphine of F1-BC and F2 progenies rejected the hypothesis of single gene inheritance of resistance. Analysis of the response of the F1, F2, and F1-BC progeny from the Strong-R x S-strain cross also rejected the null hypothesis for single gene resistance. Resistance in the Strong-R strain was autosomal and incompletely recessive with a degree of dominance of -0.64. The Weak-R and Strong-R strains were then crossed. Analysis ofthe F1 and F2 progenies of this reciprocal cross revealed that the strong resistance phenotype was coded by a combination of the genes already present in the Weak-R genotype plus an extra major, incompletely recessive gene. There was also evidence of a minor dominant gene present in approximately 5% of Strong-R individuals.

Resistance of stored-product insects to phosphine

“…(Benhalima et al, 2004;Wang et al, 2006). Also, due to poor fumigation standards (Lorini et al, 2007), phosphine concentration does not reach the level required for selection of resistance at immature stages (Bengston et al, 1999;Collins et al, 2002Collins et al, , 2005Benhalima et al, 2004). The phosphine resistance detected among the populations may be the result of previous selection pressure caused by inadequate fumigations in the storage units, from where the samples were taken.…”

“…These advantages have contributed to increased dependence on this fumigant (Chaudhry, 2000;Hasan & Reichmuth, 2004;Wang et al, 2006). However, long-term use of a single fumigant also increases the risk of appearance of resistant pest populations (Bengston et al, 1999;Collins et al, 2002;Daglish, 2004).…”

“…In addition, the lack of ideal airtight conditions for fumigation, in most storage units, increases the frequency of control failures and, consequently, increases the frequency of applications Chaudhry, 2000;Benhalima et al, 2004;Lorini et al, 2007). These factors combine to result in higher selection pressure for phosphine resistance (Bengston et al, 1999;Collins et al, 2002).…”

“…Monitoring changes in the susceptibility of insects are essential to manage phosphine resistance (Collins et al, 2002(Collins et al, , 2005. Through such monitoring, it is possible to evaluate the efficiency of commonly used management strategies to delay resistance development.…”

Developing effective fumigation protocols to manage strongly phosphine‐resistant Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae)

“…However, this overreliance on a single fumigant has resulted in the development of high levels of resistance to phosphine in key storage pest species across the globe. 6 -16 In Australia, a high level of resistance to phosphine has been reported in a strongly resistant strain of Rhyzopertha dominica (F.) (600×) over a 48 h fumigation, 6 Tribolium castaneum (Herbst) (431×) over a 20 h fumigation 17 and Cryptolestes ferrugineus (Stephens) (1450×) over a 72 h fumigation, calculated on the basis of the LC 50 of each strain relative to their respective susceptible counterparts. The level of resistance in C. ferrugineus is the highest ever detected in any stored-product insect species 10 and needs special attention.…”