RESUMEN
Reproduction of the woolly apple aphid, Eriosoma lanigerum (Hausmann), can take place parthenogenetically or sexually when both host plants, apple (Malus domestica Borkh.) and elm (Ulmus americana L.) are available. Since elm is not commonly grown in New Zealand, E. lanigerum, a major pest of apple, is thought to reproduce only parthenogenetically here. During our studies between 1999 and 2003, different morphs of E. lanigerum have been observed on apple trees, which were studied in more detail in 2003 and 2004. In the laboratory, alates reproduced mainly sexual morphs with degenerated mouthparts. Oviparous females lived for 8.95 +/- 0.17 days (n = 20) and males lived for 7.1 +/- 0.12 days (n = 20). Both went through 4 moults, without feeding or changing body size. Oviparous female laid a single egg and died soon after oviposition. In addition to sexual morphs, shiny brown, oblong eggs were seen on apple leaves grown outside as well as in the glasshouse. As the numbers of eggs and sexual morphs on trees grown outside were less than on those grown in the glasshouse, we suggest that alates disperse into the natural environment searching for an apple or elm tree to continue the sexual reproduction while spreading the population.
Asunto(s)
Áfidos/fisiología , Animales , Femenino , Masculino , Nueva Zelanda , Dinámica Poblacional , Reproducción/fisiologíaRESUMEN
A detailed genetic map has been constructed in apple (Malus x domestica Borkh.) in the region of the v f gene. This gene confers resistance to the apple scab fungus Venturia inaequalis (Cooke) Wint. Linkage data on four RAPD (random amplified polymorphic DNA) markers and the isoenzyme marker PGM-1, previously reported to be linked to the v f gene, are integrated using two populations segregating for resistance to apple scab. Two new RAPD markers linked to v f (identified by bulked segregant analysis) and a third marker previously reported as being present in several cultivars containing v f are also placed on the map. The map around v f now contains eight genetic markers spread over approximately 28 cM, with markers on both sides of the resistance gene. The study indicates that RAPD markers in the region of crab apple DNA introgressed with resistance are often transportable between apple clones carrying resistance from the same source. Analysis of co-segregation of the resistance classes 3A (weakly resistant) and 3B (weakly susceptible) with the linked set of genetic markers demonstrates that progeny of both classes carry the resistance gene.