Resistência mediada por aleloquímicos de genótipos de tomateiro à mosca-branca e ao ácaro-rajado

Abstract

O objetivo deste trabalho foi comparar os graus de resistência à mosca-branca (Bemisia argentifolii) e ao ácaro-rajado (Tetranychus urticae) de híbridos de tomateiro resultantes do cruzamento entre linhagens com alto teor de zingibereno (ZGB) e linhagens com alto teor de acilaçúcar (AA), em contraste com as linhagens parentais e testemunhas comerciais. Foram avaliadas linhagens com altos teores de AA, linhagens com alto teor de ZGB, híbridos duplos heterozigotos ZGB+AA, híbridos heterozigotos para ZGB e híbridos heterozigotos para AA. Os acessos selvagens PI-127826 e LA-716 foram utilizados como testemunhas para alto teor de ZGB e AA, respectivamente, e os genótipos Débora Max e TOM-684 foram utilizados como testemunhas para baixo teor de ambos os aleloquímicos. Os genótipos foram submetidos ao teste de resistência à mosca-branca e ao teste de repelência ao ácaro. Os genótipos duplos heterozigotos apresentaram graus de resistência à mosca-branca superiores aos das testemunhas comerciais e inferiores aos das linhagens com alto ZGB ou com alto AA. Os genótipos duplos heterozigotos apresentaram maior repelência ao ácaro, em relação às testemunhas comerciais, e repelência semelhante à das linhagens com alto ZGB ou com alto AA. Não foi observado efeito sinérgico entre ZGB e AA nos genótipos duplos heterozigotos quanto à resistência à mosca-branca e repelência ao ácaro.

Role of allelochemicals and trichome density in the resistance of tomato to whitefly

“…IV = type IV trichome; VI = type VI trichome ;Gland = glandular density. Analogous results with the allelochemicals AS and ZGB were found by Silva et al (2009), in which AS-rich (TOM-688 and TOM-689) and ZGB-rich (ZGB-703 and ZGB-704) lines exhibited greater resistance to the silverleaf whitefly. However, Silva et al (2009) observed that ZGB was significantly more efficient than AS in reducing number nymphs, indicating that ZGB may bestow a higher degree of antixenosis than AS.…”

“…For the purpose of infestation by B. tabaci biotype B, as previously identified and used by Silva et al (2009) and Maluf et al (2010), silverleaf whiteflies were grown in a protected greenhouse with a 12-m 2 domed protective structure covered by transparent plastic. Adult insects were randomly collected at several tomato cv.…”

“…This pest is usually managed by applying insecticides, which may cause damage to humans and the environment and may lead to the development of insecticide resistance (BACCI et al, 2007;SILVA et al, 2009).…”

“…Maluf et al (2010) assessed the AS-mediated resistance of the tomato plant to arthropod pests and found that hybrids with intermediate AS contents exhibited satisfactory resistance to Bemisia tabaci biotype B and Tuta absoluta (Lepidoptera: Gelechiidae), similar to homozygous lines with high AS contents. Silva et al (2009) compared the degrees of resistance to B. tabaci biotype B and Tetranychus urticae (Thysanoptera: Tetranychidae) exhibited by tomato plant hybrids resulting from the crossing of lines with high ZGB and AS contents with those of the parental lines and commercial controls. These authors found that both allelochemicals were effective in conferring pest resistance in both homozygotes and heterozygotes.…”

“…Alth ough correlat ions between the concentrations of foliar allelochemicals (2-TD, ZGB or AS) and the degree of pest resistance have been established (ARAGÃO; DANTAS; BENITES, 2000;MALUF et al, 2007;SILVA et al, 2009;GONÇALVES NETO et al, 2010;MALUF et al, 2010), few critical studies have compared the degree of pest resistance among lines rich in different allelochemicals.…”