Browsing by Author "Bull, J"

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Effects of pachymetra root rot and nematodes on some elite sugarcane clones in Australia
(ASSCT, 2016) Bhuiyan, SA; Croft, BJ; Wong, E; Ogden-Brown, J; Turner, M; Parfitt, R; Magarey, RC; Bull, J; Cox, MC
PACHYMETRA ROOT ROT and nematodes are the two most important soil-borne pathogens of sugarcane in Australia. An experiment was established in Yandaran, Queensland in grey forest soil with high Pachymetra spore counts (>100 000 spores/kg). Fifteen elite varieties and one advanced clone, from pachymetra root rot susceptible, intermediate and resistant categories, were planted in the experiment. The experiment was maintained until the second ratoon crop and Pachymetra and nematode populations were assessed in each crop. In addition, the incidence of smut was recorded before harvesting. Cane yield (TCH), commercial cane sugar (CCS) and sugar yield (TSH) were also measured in each crop. Pachymetra spore counts remained significantly lower in resistant varieties compared to susceptible and intermediate varieties until the second ratoon. In intermediate and susceptible varieties Pachymetra spore counts increased substantially, in particular, in second ratoon. In intermediate varieties such as Q232A and Q208A Pachymetra spore counts increased more than three times from plant crop to second ratoon. Numbers of nematodes, in particular root-lesion nematode, more than doubled in the second ratoon crop compared to the plant and first ratoon crops. Only Q248A had significant levels of smut, with 25% and 30% infected plants in the first and second ratoon crops, respectively. Yield reduction was substantial in the second ratoon compared to the plant and first-ratoon crop. Sugar yield decreased by 45% in the second ratoon compared to the first ratoon. Mostly, poor or negative correlations were observed between both Pachymetra spore counts and nematode numbers and yield.
Plant-parasitic and free-living nematodes associated with sugarcane in North Queensland
(ASSCT, 2018) Bull, J; Stirling, GR; Magarey, R
SURVEYS OF NORTH Queensland sugarcane soils indicated that root-lesion nematode (Pratylenchus zeae) was the most important nematode pest because it occurred in most fields and was often present at high population densities. However, the presence of root knot nematode (Meloidogyne spp.) in sandy soils and the relatively widespread distribution of moderately pathogenic nematodes such as stunt nematode (Tylenchorhynchus annulatus), stubby root nematode (Paratrichodorus minor), ring nematode (various Criconematidae) and dagger nematode (Xiphinema elongatum) suggested that in most fields, several nematode species were feeding on roots and contributing to root health problems. With regard to the free-living nematode community, survey results showed that bacterial-feeding nematodes were much more common than fungal-feeding nematodes and numbers of omnivorous and predatory nematodes were relatively low. Collectively, these findings suggest that the biological status of many north Queensland sugarcane soils is relatively poor. In addition to having high numbers of plant-parasitic nematodes they have low numbers of fungal-feeding nematodes. This indicates that fungi are not an important component of the detritus food web and this has implications for the ecosystem services they provide: decomposition of recalcitrant forms of organic matter; aggregation of soil particles; enhancement of plant nutrient uptake; improvement of disease resistance in plants; and suppression of pests and pathogens. The lack of omnivorous and predatory nematodes also has implications for pest suppression, as these nematodes help regulate populations of plant-parasitic nematodes.