Browsing by Author "McRae, TA"

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Alternative selection strategies for the Burdekin sugarcane improvement program : SRDC final report BS4S
(1994) McRae, TA; Hogarth, DM
An automated cane billet sampler for research trials : SRDC final report BS118S
(1998) McRae, TA
The Australian sugar industry invests millions of dollars annually on sugarcane breeding programs and associated research. Improved selection efficiency as a result of more accurate estimates of commercial cane sugar (ccs) will greatly enhance returns on this investment. Sugarcane breeding and research programs use hand cut sound whole-stalk samples for determination of ccs and other quality components. Whole-stalk provide a biased sample of the material harvested for milling from experimental plots as they are free from extraneous matter and inferior quality cane. The small mill has low efficiency of juice extraction from whole-stalks, extracting only 26-50% of the absolute juice, and this also leads to bias. The bias in processing billet and whole-stalk samples through a small laboratory roller mill and a hydraulic press with higher levels of juice extraction was quantified in experiments at Tully, Burdekin, Bundaberg and Broadwater. The use of sound whole-stalk samples processed through a small laboratory roller mill with low levels of juice extraction seriously biases the accuracy of estimation of sugar content of sugarcane. Bias for whole-stalk samples was quantified and compared with samples of commercially harvested cane in selection experiments at Broadwater and Tully. A bias of more than seven units of ccs was measured in badly lodged, heavily suckered and deteriorated cane harvested green at Tully. A bias of three units of ccs was less serious in burnt cane at Broadwater. Despite these biases and the inaccurate over-estimation of sugar content of harvested cane from experimental plots, sound whole-stalk samples are usually adequate for ranking of clones for selection purposes. However, billet samples provide a far more accurate estimate of commercial ccs and are preferable for predicting the true responses of commercial varieties to various agronomic treatments. There is a need for an automated method of sampling harvested cane from experimental plots for the unbiased collection of samples. The use of unbiased samples should greatly improve the accuracy of ccs assessment and provide a direct measure of the commercial value of the harvested material. Automated sampling of billets should be more efficient than the manual collection of whole-stalk samples and, with appropriate strategies, will result in greater genetic gain for sugar content. The acquisition of an automated billet sampler will greatly improve labour use efficiency and workplace safety. Information collected in project BS118S has resulted in SRDC funding project BS156S and the construction of an automated sampler.
Genotype X environment interaction and selection of sugarcane families for the Burdekin River irrigation area : SRDC final report BS57S
(1995) McRae, TA; Jackson, PA
The arable lands being developed for sugarcane production in the Burdekin River Irrigation Area (BRIA) are on markedly different soil types and, as a consequence, may present environmental challenges different to those influencing sugarcane production on the more established alluvial soils of the Burdekin delta and levee areas.
Optimal plot size and replication for testing clones in early stages of selection : SRDC final report CSR017
(1998) Jackson, P; McRae, TA
The aim of CSRO 17 was to identifY optimal plot design, replication and selection criteria for testing and selecting clones in small plots in early stages of selection in sugarcane breeding programs. Problems associated with the use of small plots are well known in field experimentation. This is particularly so in variety selection trials where measurements in small plots are subject to possible bias due to competition effects when there are significant differences in height between genotypes being compared. In sugarcane breeding programs, small, single row or two row plots are usually used extensively for the first two stages of selection within seedling populations. The reasons for this include the desire to screen large populations of clones within available resource constraints to identifY rare, elite recombinants, and the necessity to bulk up planting material from original seedlings before planting to larger plots. Given the level of resources usually devoted to early stage selection trials, it is important that optimal procedures are used so that selection is effective and efficient. The overall approach used in the project was to obtain estimates of key genetic parameters from field experimentation and then to use these to predict gains from selection among relatively unselected clonal populations in sugarcane breeding programs using different selection options. The clones used in this study were representative of those directly derived from hybridisation in two different sugarcane breeding programs, and were unbiased by any previous selection. As such, the genetic parameters are useful for other studies that may simulate and assess different options for selection from the first stages of selection in sugarcane breeding programs.
Optimum selection strategies in original seedlings particularly for heavily lodged crops : SRDC final report BS46S
(1999) Kimbeng, CA; McRae, TA
The objectives for this project were: to evaluate the effectiveness of family selection in the plant crop of original seedlings of sugarcane grown to full crop potential in the Burdekin region. The crop will probably be heavily lodged; to evaluate the effectiveness of visual (mass) selection in the young first ratoon crop; to determine the level of family performance in seedling populations required for a family to be selected. Information derived from this study would enable the breeder to design the most cost effective and efficient selection scheme for this stage of the breeding program for the Burdekin region