Resistência de genótipos de aboboreira a Bemisia tabaci (Genn.) biótipo B (Hemiptera: Aleyrodidae)

Abstract

-Whitefly control using resistant cultivars can be considered the ideal option in integrated pest management programs. Squash cultivars and lines with different genealogies have been developed and released by private and public research institutions. However, little information is available about the resistance or susceptibility of those genotypes to insects. The main squash (Cucurbita spp.) cultivars available in the Brazilian market were evaluated as to Bemisia tabaci biotype B resistance, under greenhouse conditions. The cultivar 'Golden Delight' was the most attractive to adults, while 'Menina Brasileira', 'Bárbara' and 'Atlas' presented the lowest numbers of adults on the abaxial leaf surfaces. Oviposition was evaluated in free-choice and no-choice tests. 'Novita', 'Exposição' and 'Caserta' behaved as resistant and showed oviposition nonpreference as the resistance mechanism. The cycle from egg to adult emergence was determined in six genotypes. In 'Golden Delight', the duration of this cycle was the shortest one (24.9 days), and the percentage of adult emergence, the highest one (93.8%), thus indicating that this cultivar is suitable to the insect. On the other hand, 'Exposição' and 'Menina Brasileira' prolonged this cycle (35.8 and 33.5 days, respectively) and reduced the adult emergence (46.3 and 58.1%), showing to be resistant.

Development of leaf silvering in squash cultivars infested by silverleaf whitefly

“…This genotype also provides the shortest development time from egg to adult and the highest adult emergence of B. tabaci biotype B (Alves et al, 2005). In agreement with these data, in the present research we found that 'Golden Delight' is also, among the most sensitive genotypes to the leafsilvering.…”

“…It should be mentioned that 'novita' and 'Atlas' are among the cultivars less attractive and less oviposited by B. tabaci biotype B while 'Atlanta GA-303' is one of the cultivars with the greatest oviposition by this insect (Alves et al, 2005). Thus, the factors which determine the sensitivity to the leafsilvering may be different from the ones which determine the resistance against the insect.…”

“…Besides being highly oviposited, 'Golden Delight' is one of the most attractive varieties to adults (Alves et al, 2005). This genotype also provides the shortest development time from egg to adult and the highest adult emergence of B. tabaci biotype B (Alves et al, 2005).…”

“…Each pot, presenting on average eight leaflets with about 300 adults per leaflet was transplanted equally spaced from the plots, one for four pits. The leaf-silvering evolution was evaluated in each cultivar through a graded scale varying from 1 to 5 (Alves, 2005), adapted from the scale proposed by Paris et al (1987). The grade 1 means absence of symptoms on leaves and the others indicate the gradual development of the symptoms, it means, the silvering intensity, up to the grade 5, which refers to the totally silver leaf.…”

Atratividade para adultos e preferência para oviposição de Bemisia tabaci (Genn.) biótipo B (Hemiptera: Aleyrodidae) em genótipos de Cucurbita spp

“…geralmente está associada ao prateamento-dasfolhas (LOURENÇÃO; NAGAI, 1994; FRANÇA; VILLAS-BÔAS; BRANCO, 1996;SUMMERS;STAPLETON, 2002;MELO, 2005). Essa anomalia, também reportada como desordem fisiológica, ocorre devido à alimentação de ninfas e adultos dessa mosca-branca, que durante o processo de alimentação injetam toxinas OSBORNE, 1990aOSBORNE, , 1990bYOKOMI, 1990YOKOMI, , 1991DE BARRO et al, 2011), provocando queda na produtividade e deixando os frutos descoloridos em relação aos normais (NAGAI et al, 1992).…”