Reproductive Modes in Onion Thrips (Thysanoptera: Thripidae) Populations from New York Onion Fields

Abstract

Thrips exhibit different reproductive modes including thelytoky (females produced from unfertilized eggs), arrhenotoky (males produced from unfertilized eggs and females produced from fertilized eggs) and deuterotoky (females and males produced from unfertilized eggs). We investigated patterns of reproductive modes in onion thrips, Thrips tabaci Lindeman, populations and potential effects of the bacterium Wolbachia and temperature on these modes. We also examined the possibility that male-producing T. tabaci populations were resistant to the frequently used insecticides, lambda-cyhalothrin and methomyl. In New York during 2002Ð2004, T. tabaci populations were sampled from 20 onion Þelds and reproductive mode was determined by identifying sex of progeny from virgins. Half of the populations were thelytokous and half were a mix of thelytokous, arrhenotokous and deuterotokous individuals, which we refer to as a male-producing population. In two of four cases, the reproductive mode of a population from the same onion Þeld changed across years, suggesting that populations either mix or an external factor caused the change. To address the latter, we speculated that Wolbachia or high temperature mediated reproductive modes. Samples of T. tabaci representing each reproductive mode were examined for Wolbachia using diagnostic polymerase chain reaction (PCR), but it was not detected. Cytological examination of ovaries from two additional thelytokous lines also showed no evidence of Wolbachia. Similarly, high temperature did not affect sex allocation ratios in either thelytokous or male-producing populations. Male-producing T. tabaci populations were not positively correlated with resistance to lambda-cyhalothrin, or tolerance to methomyl. The role of the different reproductive modes in T. tabaci populations in onion Þelds remains unclear.

Temporal Dynamics of Iris Yellow Spot Virus and Its Vector,Thrips tabaci(Thysanoptera: Thripidae), in Seeded and Transplanted Onion Fields

“…T. tabaci in onion Þelds have multiple reproductive modes in New York: thelytoky, the production of unfertilized females by females; arrhenotoky, the production of males from unfertilized eggs and females from fertilized eggs; and deuterotoky, the production of males and females by unfertilized eggs (Nault et al 2006). In general, NY populations of T. tabaci in June and July are primarily thelytokous, with very few males produced.…”

“…In general, NY populations of T. tabaci in June and July are primarily thelytokous, with very few males produced. By August, the populations shift to primarily arrhenotokous and/or deuterotokous (Nault et al 2006). Chatzivassiliou et al (2002) showed that arrhenotokous populations of T. tabaci collected from leeks were able to transmit TSWV, while thrips from thelytokous populations collected from leek were nonvectors.…”

Weed Hosts for Onion Thrips (Thysanoptera: Thripidae) and Their Potential Role in the Epidemiology of <I>Iris Yellow Spot Virus</I> in an Onion Ecosystem

“…Because identiÞ-cation keys do not exist for T. tabaci larvae, thrips larvae were removed from plant samples and reared to the adult stage. Using a Þne paintbrush, up to 30 larvae per composite weed sample were transferred to ventilated petri dishes containing sterilized leaf disks of cabbage, Brassica oleracea L. (Capitata group), and reared to adulthood following the procedure described in Nault et al (2006). Based on experience rearing T. tabaci larvae, those larvae that were clearly not T. tabaci were not collected nor counted.…”

Onion Thrips,Thrips tabaci, Have Gut Bacteria That are Closely Related to the Symbionts of the Western Flower Thrips,Frankliniella occidentalis

“…It is haplodiploid and arrhenotokous like most Thripidae, which implies that haploid, unfertilised eggs become males and diploid, fertilised eggs females. However, thelytoky (unfertilised diploid eggs, becoming females) was found in some T. tabaci populations (Murai 1990; Nault et al 2006; Zawirska 1976). …”