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Author: search.filters.author.Croft, BJSubject: search.filters.subject.Pachymetra

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Now showing 1 - 5 of 5
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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.
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    Does rotating cultivars with intermediate resistance influence pachymetra root rot of sugarcane : ASSCT peer-reviewed paper
    (ASSCT, 2019) Jensen, AS; Croft, BJ; Parfitt, RC; Brown, PH
    Concerns have been raised by industry members over lower than expected cane yields associated with high oospore levels in sugarcane cultivars rated to have intermediate resistance to pachymetra root rot. This is a significant issue, as intermediate cultivars represent more than 70% of the sugarcane grown in Australia. It is possible that planting the same intermediate cultivar in successive crop cycles could lead to increased yield losses due to pachymetra root rot. This paper examines the residual soil-borne effect of the current major sugarcane cultivars on the following sugarcane crop in three field trials, located in the Herbert, Central and Southern growing regions. Levels of oospores of Pachymetra chaunorhiza and cane yields were assessed in ratoon crops of replicated cultivar-assessment trials and in subsequent crops of intermediate resistant Q208A (planted on the sites of previous cultivar trials). The relationships between Pachymetra oospore levels and cane yield in Q208A crops and pre-plant oospore levels were examined. High oospore levels occurred in plots planted to some intermediate cultivars, as well as susceptible cultivars. In the following crop of Q208A, which was planted into plots of the previous cultivar trial, Pachymetra oospore levels at harvest were related to oospore levels prior to re-planting at all trial sites. Cane yield (t/ha) of Q208A was significantly related to pre-plant oospore levels at a site near Bundaberg (P=0.0049). Yield losses of 21% were incurred at 120 oospores/g soil in Q208A. Cultivation of Q208A following a crop of Q208A did not result in higher Pachymetra oospore populations or yield losses compared with planting Q208A after other cultivars of similar resistance rating. In the Herbert and Central field trials, Pachymetra oospore levels were lower and there were no significant relationships between oospore levels and yield in Q208A planted at these sites. We demonstrate that significant yield losses in Q208A are associated with high Pachymetra oospore levels that occur under intermediate and susceptible cultivars in the previous crop. There was no evidence to support the hypothesis that repeatedly planting the same intermediate cultivar could lead to host-cultivar-specific virulence in P. chaunorhiza. Greater emphasis should be placed on breeding and selecting highly resistant cultivars that are suited to soil types conducive to Pachymetra
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    Inheritance of resistance to pachymetra root rot : SRDC final report BS27S
    (BSES, 1994) Croft, BJ; Berding, N
    Genetical resistance to root pathogens is a sensible strategy for disease control in a perennial crop such as sugarcane. Pachymetra root rot is a serious disease in Queensland and can cause losses of 30-40% in susceptible varieties. An understanding of the mode of inheritance of resistance is important in developing breeding strategies.
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    Bioassay for comparing levels of pythium graminicola in soils
    (BSES, 1987) Croft, BJ
    In the study of any soil borne pathogen it is essential to have some technique for determining the level of the pathogen in the soil. The levels of Pythium species in soil have been measured by soil dilution plating on selective media (Dick and Ali-Shtayeh 1986. Trans. Br. Mycol. Soc. 86(1):49-62). However species with lobulate sporangia are not frequently isolated on these media and bioassay techniques have been developed for these fungi (Stanghellini and Kronland 1985. Phytopathology 75:1242-1245). In Hawaii, pineapple roots have been used as baits in a bioassay for P. graminicola Subr. (Adair 1972. Hawaii. Plant. Rec. 58:213-240). However, considerable space is required to maintain pineapple plants and they are not always readily available. Poor Root Syndrome (PRS) of sugarcane in Queensland causes serious crop losses (Egan et al. 1984 ASSCT p 1-9). A Pachymetra sp. (formerly referred to as the root rot fungus) which rots the primary roots of the sugarcane plant, and P. graminicola which can restrict fine root development, are two pathogens consistently found in affected soils (Croft and Magarey, 1984 ASSCT Conf. p 55-61). The study of the role of P. graminicola in the sugarcane PRS in Queensland has been hampered by the lack of a means of quantifying the level of this species in soils. This paper outlines the development of a sorghum bioassay (SB) for P. graminicola using sorghum seedling roots.
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    Soil constraints to productivity improvement
    (1990) Croft, BJ; Magarey, RC; Hurney, AP; Reghenzani, JR
    Yields of most crops are known to decrease if that crop is grown continuously without fallowing or rotation with other crop species. Sugarcane has been grown continuously on many fields in Queensland for 50-100 years. As early as 1934 soil-borne factors which restricted root and shoot growth were identified in fields which had grown sugarcane for a number of years. During the 1970s nematodes were found to be causing serious losses in Bundaberg on certain soil types and a serious root disease complex known as poor root syndrome was identified in northern Queensland. During the 1980s intensive research into poor root syndrome identified the important new disease Pachymetra root rot and a number of minor fungal pathogens. Poor root syndrome has been identified in all regions of Queensland and general poor root health has been noted in all soils which have grown sugarcane for a number of years. Yield increases of 50-100% were obtained in areas severely affected by poor root syndrome in northern Queensland by soil fumigation with methyl bromide and metham sodium, and by soil solarisation. Recent experiments have recorded yield responses of 20-40% to methyl bromide fumigation in all major sugarcane regions. These experiments suggested that yield losses due to soil-borne factors may be greatly restricting yields throughout the sugar industry. Research to identify the causes of the yield losses has commenced and progress to date is summarised in this paper.