Varieties, plant breeding and release

Permanent URI for this collectionhttp://elibrary2.sugarresearch.com.au/handle/11079/13841

Research outcomes: Comprehensive and efficient variety breeding, selection and release programs responding to yield expectations, environmental constraints, resource scarcity and regional preferences. Faster varietal adoption using advanced methods for bulking, distribution and planting.

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Overcoming constraints to high yield and CCS in large and lodged cane crops
(2001) Chapman, SC; Jackson, PA; Lawn, RJ
Past research indicates that large sugarcane crops (that usually also happen to be lodged) experience a slowdown in growth during winter, well before harvest (Muchow et al. 1996). The project examined factors affecting the growth of crops in both the dry (irrigated) and wet tropics and aimed to interpret and explain the effects of the identified factors on net growth and death processes as well as on the stalk and sucker dynamics, cane yield and CCS. Treatments included installation of bamboo scaffolding to prevent crop lodging, and a late ratooning of the crop so that a physiologically young crop would be growing into the winter ripening period. Experiments were conducted over two seasons (1997-1998 & 1998-1999) in commercial fields in areas where large crops may experience substantial lodging under different environmental conditions (Burdekin and Tully). Four or five sequential harvests were taken to determine if and when growth slowdown occurred and to separate the effects of crop age, season and lodging. By installing scaffolding to prevent lodging, we eliminated the growth ‘slowdown’ in three experiments to confirm that lodging and stalk death is part of the explanation. In both the wet and dry (irrigated) tropics, lodging of sugarcane significantly decreased both cane yield and fresh commercial cane sugar content (CCS). Prevention of lodging increased fresh cane yield by 11 - 15 %, CCS by 3 - 12 % and sugar yield by 15 - 35 % at the final harvest in August/September. The rate of increase in CCS in lodged cane was reduced following lodging, although CCS recovered by harvest to be similar to that of erect cane. While death of stalks was confirmed as a major component of the effect of lodging there was also a reduced weight and sugar content of live stalks. Dead and rat damaged stalks had CCS levels that were regularly less than 50% of sound live stalks. In the dry tropics, where cane is irrigated and grows under high radiation, sugar yield was 40 t/ha with scaffolding installed. The increased yield (compared to 35 t/ha in lodged cane) was due to both the survival of an extra 0.8 stalks/m2 and increased accumulation of sugar in live stalks. These experimental results have been published in two conference papers and in an upcoming issue of the Australian Journal of Agricultural Research (early 2003).
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.
The role of root growth and activity in determining sugarcane productivity : SRDC final report CLW002 (previously CSS02 & CSS2S)
(1999) Magarey, R; Nable, R; Reghenzani, J; Smith, J; Berthelsen, S; Grace, D; Robertson, M
Research conducted in this project aimed to better understand the relationship between root and shoot growth, in areas such as how the size of the root system affects shoot growth, do particular root parameters have a controlling influence on shoot growth, how do soil characteristics affect root penetration rates, and how the root system develops through the life of a sugarcane crop. This was achieved through the application of a wide range of experimental techniques in both the glasshouse and field situation. The study of root systems in sugarcane is difficult - due to the size of the crop and the length of the cropping period. As a result there have been few previous studies on sugarcane root systems in Australia, and indeed around the world. A number of techniques were either developed, or adapted, in this project research. A soilless aeroponic culture technique was installed and refined at Tully Sugar Experiment Station. This allowed sugarcane roots to be examined on a daily basis and root measurements made, or root pruning to occur. This overcame the difficulty of dealing with the bulky, opaque soil medium. A tall pot system was adapted for sugarcane where sugarcane could be grown for an extended period in controlled conditions. This enabled plant water relations to be studied in association with modification to root growing conditions. Root image analysis techniques were further refined for sugarcane, allowing measurement of both whole glasshouse-grown root systems, or the quantification of root lengths in material from soil cores obtained in the field. A technique for growing sugarcane with a split root system was also adapted enabling the direct and indirect effects of water stress and root pruning in a soil culture to be examined, and the likely presence of root signals as a mechanism for control of shoot growth. Studies using these techniques facilitated an examination of the relationship between roots and shoots under various experimental conditions - ranging from controlled conditions with no soil in the glasshouse, through other soil-based glasshouse trials, to the field situation. This gave depth to project results and a broader understanding of root-shoot relationships using a range of experimental observations.