BIOCHEMICAL RESISTANCE OF CITRUS TO FRUIT FLIES. DEMONSTRATION AND ELUCIDATION OF RESISTANCE TO THE CARIBBEAN FRUIT FLY, ANASTREPHA SUSPENSA

Abstract

Resistance of citrus fruit to attack by the Caribbean fruit fly, Anastrepha suspensa (Loew), was attributed to allelopathic essential oils in the flavedo region of the peel. Hatchability of eggs laid between peel oil glands was significantly greater than that of eggs laid into glands. Mortality occurred principally in the 1st larval instar, and most larvae died before reaching the albedo (the non‐oily region of the peel). Grapefruit were more susceptible to larval development than oranges, and lemons were virtually immune to successful attack by this fly. Fruit that were allowed to remain on the tree until overripe were somewhat more susceptible than early‐season fruit. Fruit resistance was correlated with (1) flavedo thickness, (2) a high concentration of linalool in relation to limonene in the peel oil, and (3) the absolute amount of oil per unit area of peel. Volatile components of the peel oil rather than high boiling fractions appear to account for oil toxicity. Possible applications of these findings are discussed. RÉSUMÉ Résistance biochimique des agrumes aux mouches des fruits. Démonstration et étude de la résistance à Anastrepha suspensa Nous avons trouvé que la résistance des fruits de Citrus aux attaques d'Anastrepha suspensa Loew est due aux huiles essentielles allélopathiques de la zone flavedo du zeste. Le taux d'éclosion des œufs pondus entre les glandes essentielles du zeste était significativement plus élevé que celui des œufs pondus dans les zones glandulaires. La mortalité se produisait essentiellement au premier stade larvaire, et beaucoup de larves mouraient avant d'atteindre l'albédo (la zone sans huile essentielle du zeste). Les pamplemousses sont plus sensibles au développement larvaire que les oranges, et les citrons ne portent virtuellement pas d'attaques réussies de cette mouche. Les fruits qui étaient laissés sur l'arbre après la maturation étaient un peu plus sensibles que les fruits de début de saison. La résistance du fruit était liée à 1) l'épaisseur dur flavedo 2) une forte concentration de linalool en relation avec le limonène dans les essences du zeste et 3) la valeur absolue d'essences par unité de surface de zeste. Les composés volatiles de l'essence de zeste plutǒt que les fractions à point d'ébullition élevé paraissent ětre responsables de la toxicité des essences. Les citrons, qui sont indemnes d'attaques de cette espèce et d'autres de Tephritidae, avaient un flavedo sifnificativement plus épais et avait deux foi plus d'essences par unité de surface de zeste que les oranges et les pamplemousses; l'essence de citron est connue aussi pour ětre riche en terpénoïdes oxygénés, comme le linalool. La discussion porte sur les applications possibles de ces phénomènes dans l'amélioration de la résistance des agrumes aux Téphritidae.

Oviposition of fruit flies (Diptera: Tephritidae) and its relation with the pericarp of citrus fruits

“…According to Branco et al (2000), in addition to reduction on essential oil contents, peel firmness decreases allowing higher larval survival due to lower difficulty of the larva to migrate from peel to pulp. The results of this study corroborate the work performed by Greany et al (1983) that found tangerines more susceptible to the attack of Anastrepha suspensa (Loew) than orange and lemon.…”

“…The flavedo constitution is cited by several authors as the most critical resistance mechanism to fruit flies infestation in citrus (Back and Pemberton, 1915;Greany et al, 1983;Salvatore et al, 2004;Ioannou et al, 2012). Possibly, when oil glands in the flavedo are broken, they release toxic compounds that, in contact with eggs and first instar larvae, can cause death before the larvae reach the albedo region (non-oily region of the peel) (Greany, 1989).…”

“…Susceptibility of citrus to fruit flies varies according to the fly species, fruit maturity, fruit species and cultivar, oviposition behavior of the insect and consistency of the fruit peel are factors possibly involved in this process (Greany et al, 1983). Females of fruit flies consider qualitative and quantitative aspects of the citrus fruit composition in the selection process for an oviposition site.…”

Danos de moscas-das-frutas (Diptera, Tephritidae) em citros, manejados no sistema orgânico de produção

“…A mudança de coloração coincide com as mudanças físico-químicas da polpa do fruto e condicionam a preferência para oviposição e dano. Destaque deve ser dado para a presença de glândulas com óleos essenciais alelopáticos, na casca de ambos os cultivares de citros, apontadas como responsáveis pela inviabilidade de ovos e mortalidade de larvas de Anastrepha suspensa (Loew, 1862) (Greany et al, 1983). Isto impediria o desenvolvimento larval e o consequente dano no início da maturação, por causa das elevadas concentrações dessa substância, nos frutos, nesse estádio fenológico.…”

Performance de Ceratitis capitata Wiedemann (Diptera: Tephritidae) em frutos: comparação de duas populações criadas em laboratório

“…Os dados deste trabalho para a laranja como hospedeiro corroboram os obtidos por Greany et al (1982), que demonstraram e elucidaram a resistência bioquímica de laranjas e pomelos a Anastrepha suspensa (Loew). Os resultados indicaram ser o mamão o fruto mais adequado para o desenvolvimento das fases imaturas, concordando com os dados obtidos por Zucoloto (1993).…”