Varieties, plant breeding and release

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Environmental stimuli for sugarcane suckering in the wet tropics : SRDC final report BSS221
(2003) Berding, N; Hurney, AP; Bonnett, GD; Joseph, F
The northern section of the industry has been in crisis for most of the years in the decade up to 2002 because of declining CCS. This decline has been due to increased extraneous matter levels due largely to increased sucker culm content of the crop. These have developed because of marked wet episodes during the harvest period in the majority of years in this period. This resulted in open canopy situations, because of sprawling and lodging, increased light penetration, and initiation and development of sucker culm populations.A hypothesis was proposed that excessive mature-crop moisture, combined with continued excessive nitrogen use, particularly early in the decade were initiating variables for the problem. Observations suggested that light, via an open canopy situation, also was a driver.The project tackled the problem with a preliminary series of experiments that allowed optimisation of management and data collection techniques for use in a main experiment proposed. The main experiment sought to establish the importance of levels of three environmental variables, light, nitrogen and moisture, on sucker initiation, and their interaction with each other and with two cultivars of known suckering propensity under commercial conditions.The preliminary experiments allowed us to make the following recommendations for the design and methods for the main experiment:1. The late nitrogen application of 70 kg N will be in late April early May if the weather is suitable and as soon as possible thereafter if the weather is too wet to allow the application at the desired time.2. That spectroradiometry measurements will be made in the core plots at a height of 10 cm and 1 m to determine the effect of plant spacing on the spectral composition received. Photosynthetically active radiation measurements will also be made.3. A similar soil sampling and nitrate measurement regime will be made in the main experiment as that in the preliminary experiment with the exception that more frequent smaller diameter cores will be taken to speed up sampling.4. Sucker counting and other trial management will continue as originally proposed.5. Applications of late N will be made in separate experiments on different cultivars and if possible to soils with low basal nitrate levels.
Maximising whole-of-industry benefits from the Australian sugarcane improvement program through an optimal genetic evaluation system
(2007) Wei, X; Stringer, J; Jackson, P; Cox, MC
An optimal genetic evaluation system (GES) is the backbone of any breeding program because maximising genetic gains is primarily a matter of efficient selection. A GES provides information to breeders about which individuals should be selected as parents for crossing and which ones should be selected for commercial production.At the commencement of this project, selection of both parents and clones for commercial production was principally based on the index knows as net merit grade (NMG). NMG is based on the performance of a test clone (or a cross) relative to the average of a number of commercial varieties (or corsses) for the traits of commercial cane sugar (CCS), tonnes of cane per hectare (TCH), appearance grade and fibre content. NMG was used to generate a breeding code for selecting parental clones for crossing. Cross ratio, a measure of each cross's performance relative to the whole population at each selection stage, was used to determine priority of crosses. For selecting elite clones to be retained for further testing, NMG was used in all three selection stages to determine which clones would be advanced to next stage.
Pathways to exploiting enhanced photosynthetic efficiency for higher sucrose and biomass yield
(2011) Inman-Bamber, NG
Australia has one of the highest commercial cane sugar (CCS) levels in the world but unfortunately CCS appears to have plateaud at about 14% of fresh cane weight over the past 20 years. Up to now in breeding programs, increased fibre has been considered to have negative economic impacts because of adverse effects on sugar extraction and milling rate. It is possible that high fibre genotypes can produce higher biomass yields than high sucrose types because high sucrose content in the stalk may feedback negatively on photosynthesis either through end-product suppression or through sugar signalling compounds. This is now an assumption which is gaining acceptance through recent publications. Prior to this project this assumption had not been tested using high fibre and high sucrose clones. Feedback inhibition is also suspected to be the cause of the ‘reduced growth phenomenon’, a term applied to lower than expected biomass accumulation after a certain stage in crop development. This project aimed to establish the role of cane stalk sucrose in feedback inhibition of photosynthesis in order to reveal existing limitations to increasing sucrose content and biomass yield.

Varieties, plant breeding and release

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