Insect-fungal ecology on selected new crops in South Africa

[摘要] English: This study investigates insect-fungal-plant interactions on three new crops (viz.cactus pear, pistachio and pigeonpea) in South Africa. Isolation of Drosophila.melanogaster and D. hydei flies from cactus pear (Opuntia ficus-indicay orchardsshowed that these two species harbour fungi. Inoculations of specific fungi obtainedfrom the two Drosophila species onto fruit and cladodes of cactus pear showed that someof the fungi had the ability to cause rot and may even be pathogenic. Scanning electronmicroscopy (SEM) confirmed the harbouring of fungi on the bodies by of the twoDrosophila species and it also showed that most of the fungal propagules were present onthe legs of the flies. An insect succession study showed that both Drosophilidae flies andNitidulidae beetles play a vital role in the degradation of the fruit by contributing to therate of fruit decomposition and by spreading yeasts and fungi that cause rot. Further tothis a dissemination potential experiment with Drosophilidae also showed that these fliesare capable of transmitting fungi, which are capable of causing rot on 0. ficus-indicafruit. Isolation of Nysius natalensis bugs collected in Pistacia vera (pistachio) orchardsshowed that this species harbours fungi. Additionally, isolation of the heads and faecesof Sparrmannia flava beetles collected in pistachio orchards showed that this species alsoharbours fungi. More specifically, both these species harbour fungi known to bepathogenic to P. vera. SEM of N. natalensis confirmed that they harbour fungi on theexoskeleton and that most of the fungal propagules were present on the legs of theinsects. It was also shown that N. natalensis cause feeding lesions on pistachio nuts,thereby providing access for fungal infection. Analysis of N. natalensis confirmed thattheir numbers are higher in late summer and that cover crops and surrounding vegetationhave an influence on their population dynamics. Analysis of S. flava showed that theyhave a peak season during summer and that their flight activity is influenced by acombination of temperature, rainfall, windspeed, soil type and lunar phases. Isolation ofClavigralla tomentosicollis bugs collected in a Cajanus cajan (pigeonpea) cultivationshowed that this speceis harbours fungi. Some of these fungi are known to be pathogenicto C. cajan. Scanning electron microscopy (SEM) confirmed the harbouring of fungalpropagules on the exoskeleton of C. tomentosicollis. It was also shown that fungalpropagules were present all over the body, most importantly the mouthparts. Adissemination potential experiment showed that this species is capable of transmittingfungal proapgules to pigeonpea plants. C. tomentosicollis prefers some pigeonpeacultivars above others.

[发布机构] University of the Free State