Browsing by Author "Bull, JI"

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    Chlorotic streak resistance screening in the Tully district
    (ASSCT, 2016) Magarey, RC; Sevntek, K; Bull, JI; Stringer, JK; Zamora, R
    CHLOROTIC STREAK DISEASE (CSD) was first recognised more than 85 years ago and is present in most cane-growing countries around the world. An important management strategy is the use of resistant varieties; past research has shown there is significant variability in resistance in the Australian sugarcane germplasm. Data are reported from a variety resistance screening trial conducted in the Tully district (2013–2015 period) that was subjected to at least five flooding events over a two-year period. Maximum ‘% stools diseased’ infection levels were over 60% in the most susceptible variety. Several current commercial varieties appear very susceptible, including Q241A and Q251A. The data show that a much higher disease incidence is evident when data on ‘% stools diseased’ are recorded rather than ‘% stalks diseased’. Recording data on a stools basis therefore may provide a shorter time frame for assessing varietal susceptibility. Crop inspections are also significantly easier using this parameter, especially in mature crops where symptom expression is often higher (and therefore desirable to undertake at this time). Major flooding events provide optimum conditions for disease transmission in field trials, as long as shoot survival is not unduly affected.
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    Chlorotic streak transmission and crop dynamics research
    (ASSCT, 2016) Magarey, RC; Sventek, K; Bull, JI; Braithwaite, KS
    CHLOROTIC STREAK DISEASE (CSD) is transmitted in water, specifically drainage, flood or irrigation water. Research showed that transmission in water was increased by the addition of oxytetracyline (Terramycin). A two-hour inoculation period, where roots were dipped in infected hydroponic solution containing the antibiotic, was sufficient to lead to significant disease levels in test plants grown in a hydroponic system. A hydroponic system incorporating no water circulation (still-hydroponics) was found more effective than one where the solution was regularly circulated. Monitoring of the disease at field sites showed that disease levels build up over time and that different lengths of inundation associated with flooding events may lead to uneven distribution of the disease in a commercial crop.