PLANT RESISTANCE Impact of Melon Accessions Resistant to Aphids on the Demographic Potential of Silverleaf Whitefly NICOLAS SAUVION, 1 VALE ´ RIE MAURIELLO, BENJAMIN RENARD, AND NATHALIE BOISSOT Unite ´ de Recherche en Productions Ve ´ ge ´ tales, Centre Antilles-Guyane, Institut National de la Recherche Agronomique, Petit-Bourg, Guadeloupe, 97170, France J. Econ. Entomol. 98(2): 557Ð567 (2005) ABSTRACT Bemisia tabaci (Gennadius) and Aphis gossypii Glover are devastating melon, Cucumis melo L., pests. The geographic areas where they occur overlap, and the same chemicals are used to control both of them. Therefore, to reduce pesticide use, it would be necessary to breed melon lines that simultaneously express a resistance to both insects. Female survival; the time when reproduction starts, peaks, and ends; the number of female offspring at the reproductive peak; and total reproduction (S) were determined under semicontrolled conditions for B. tabaci kept in clip-cages on a susceptible melon genotype Vedrantais, and 12 potential resistant accessions, particularly genotypes expressing the Vat gene controlling resistance to A. gossypii. By using the Lewontin triangular reproductive function and Bootstrapping, the intrinsic rate of increase (r) and its variance were calculated. Statistical analysis showed that the parameter S was as relevant as r for discriminating between the melon accessions. Three genotypes were potential genitors of resistance to the whiteßy: PI 161375, PI 414723, and PI 532841. Those possessing the Vat gene were either resistant (PI 161375 and PI 414723) or susceptible (Margot, IsoVat R, and AR 5). This demonstrated the ineffectiveness of Vat against B. tabaci. In this article, we propose a strategy to breed lines that express resistance to aphids and whiteßies on the short term. KEY WORDS Cucumis melo, Bemisia tabaci, host plant resistance, population dynamics, Va gene SWEET POTATO WHITEFLY, Bemisia tabaci (Gennadius), and the cotton (melon) aphid, Aphis gossypii Glover, are devastating melon pests, Cucumis melo L., found in major melon production areas (United States, Mexico, Central America and South America, southern France, and Spain), where they cause major economic losses either as herbivores (Slosser et al. 1989, Gerling and Mayer 1996) or as virus vectors (Lecoq et al. 1998). The losses due to B. tabaci have increased over the past 20 yr because of the appearance of new biotypes and the emergence of their associated viruses (Jones 2003). Integrated pest management programs to control these two pests consist of a combination of chemicals (in particular, imidacloprid and pymetrozin) and cul- tivation practices to maintain insect populations be- low an economic threshold level (McCreight 1998). But the development of resistance against the chem- icals (Devonshire 1989, Prabhaker et al. 1998) makes it necessary to Þnd alternative strategies such as the use of resistant breeding lines. In melon, resistant cultivars have shown evidence of their effectiveness in controlling A. gossypii in France, where 80% of the registered varieties are resistant to this aphid. Never- theless, these varieties are susceptible to B. tabaci and because the same chemicals are used to control pierc- ing-sucking insects, the extension of the whiteßy casts doubts on the advantage of using these commercial varieties as a means of limiting pesticide use. It would therefore be advantageous for the breeding lines to simultaneously express resistance to the aphid and the whiteßy to limit the use of chemicals. Presently, no study has been done on this subject. Research into melon genotypes resistant to B. tabaci is recent and has revealed material that could be useful for breeding because screening was essentially based on tolerance (i.e., loss of biomass) in the Þeld (Moreno et al. 1993, Simmons and McCreight 1996). Riley and Palumbo (1995a, b) estimated losses in the Þeld on the basis of the density of whiteßy popula- tions. They evoked the possibility of the glabrous char- acter of leaves as a resistance factor, but it has not yet been applied to breeding. In Þeld trials, Boissot et al. (2003) observed partial resistance to B. tabaci (i.e., reduction of the density of adults and larval insects on leaves) in PI 161375, PI 414723, PI 164723, and 90625, but the study did not allow an assertion that these genotypes were suitable candidates to retain for a genetic analysis of resistance. Under free-choice and no-choice conditions, Soria et al. (1999)) quantiÞed 1 Current address: UMR BGPI INRAÐCIRADÐENSAM, Equipe Epi- de ´ miologie-virus/vecteurs, CIRAD TA 41/K, Campus International de Baillarguet, Montpellier Cedex 5, 34398, France. 0022-0493/05/0557Ð0567$04.00/0  2005 Entomological Society of America Downloaded from https://academic.oup.com/jee/article/98/2/557/2218274 by guest on 13 February 2023