Resistance to silverleaf whitefly, Bemisia argentifolii (Hem., Aleyrodidae), in Gossypium thurberi, a wild cotton species

Abstract

Gossypium thurberi Todaro is a wild cotton species native to Mexico and parts of the southwestern USA. Four years of field studies in California's Imperial Valley revealed consistent very high levels of resistance in G. thurberi against silverleaf whitefly, Bemisia argentifolii Bellows and Perring, an important pest of cotton in many regions of the world. Naturally developing field infestations in plots of G. thurberi were significantly lower than in plots of the commercial cotton cultivars DP 5415, Siokra L23, and Stoneville 474. Gossypium thurberi has two morphological traits that, in past research, have been associated with lower levels of whitefly susceptibility: smooth-and okra-leaf; however, the levels of resistance observed in G. thurberi were significantly greater than in the cotton cultivar DP 5415, which is a smooth-leaf cotton, and Siokra L23 which, like G. thurberi, has both smooth-and okra-leaf traits. Therefore, the high level of resistance in G. thurberi seems to be due to factors above and beyond smooth-and okra-leaf. Siokra L23, which is among the least whitefly-susceptible cotton cultivars, developed whitefly populations over 30 times those on G. thurberi in all 3 years that Siokra L23 was tested. The difference in whitefly population development between G. thurberi and the other two cotton cultivars was even more striking, up to a 475-fold difference. In contrast to the clear results on naturally developing field infestations, experiments comparing nymphal survival among G. thurberi and commercial cotton cultivars did not detect antibiosis, and both choice and no-choice oviposition experiments did not detect antixenosis. Thus, the mechanisms of resistance in G. thurberi remain unknown.

Host Plant Resistance for the Management of Bemisia tabaci: A Multi-crop Survey with Emphasis on Tomato

“…In another screening for cotton resistance against B-biotype of B. tabaci, adults, eggs and nymphs were significantly corelated to leaf hairiness, with seasonal variability due to leaf color, shape, and hairiness types (Alexander et al 2004). A brief review by Walker and Natwick (2006) pointed out the mixed and sometimes contradictory results presented in these and other previous studies which associate the two different traits in cotton (smooth-leaf and okra-leaf) with reduced whitefly susceptibility, while in other studies, a slight effect, no effect, or even the opposite effect occurred. All these results together indicate that many morphological plant traits cumulatively contribute to whitefly population fluctuation (Sial et al 2003).…”

“…Recent field studies in California's Imperial Valley revealed consistent very high levels of resistance against the silverleaf whitefly in Gossypium thurberi Todaro, a wild cotton species native to Mexico and parts of the southwestern USA (Walker and Natwick 2006). However, the mechanisms of this resistance remains an enigma because both choice and no-choice experiments comparing oviposition and nymphal survival among G. thurberi and commercial cotton cultivars did not detect antibiosis or antixenosis (Walker and Natwick 2008).…”

“…However, the mechanisms of this resistance remains an enigma because both choice and no-choice experiments comparing oviposition and nymphal survival among G. thurberi and commercial cotton cultivars did not detect antibiosis or antixenosis (Walker and Natwick 2008).…”

Elucidating resistance in cotton genotypes to whitefly, Bemisia tabaci, by population buildup studies

“…The potential of whiteflies to colonize on a whole plant under no-choice conditions was not fully exploited. However, Walker and Natwick (2006) reported that the wild cotton species Gossypium thurberi showed a high level of resistance in field conditions, with no significant preference for oviposition being detected in no-choice experiments, in which whole plants were covered. Moreover, the plant age/stage used to identify resistant sources and biology studies by different workers is quite variable: e.g.…”

“…The cotton genotypes resistant to whitefly were identified by several workers under free choice conditions (Khan et al 2003;Puri et al 1998;Rao et al 1991) with the aim to identify an antixenosis mechanism of resistance among the three listed by Painter (Painter 1951). Under no-choice conditions, considerable attention has been given to detect antibiosis or antixenosis by confining whiteflies on a single leaf (Butter and Vir 1991;Walker and Natwick 2006;Zang et al 2006). The potential of whiteflies to colonize on a whole plant under no-choice conditions was not fully exploited.…”