Investigating the use of sweet sorghum as a model for sugar accumulation in sugarcane

This paper outlines a current investigation of sugar accumulation in sweet sorghum to assist in understanding and simplifying this complex trait in sugarcane. A recombinant inbred line (RIL) sorghum population, between a sweet and a grain sorghum, has been developed and phenotyped for various morphological and agronomic traits related to grain yield, biomass and stem sugar content. A genetic linkage map will be constructed for the sweet sorghum population with the objective of identifying genomic regions associated with sucrose accumulation in sweet sorghum. This will lead to further work, including comparative mapping in sugarcane, to identify the extent to which sweet sorghum can be used as a model for investigating sugar accumulation in sugarcane.

Soil exploration by sorghum root systems in wide row cropping systems

Wide and ‘skip row’ row configurations have been used as a means to improve yield reliability in grain sorghum production. However, there has been little effort put to design of these systems in relation to optimal combinations of root system characteristics and row configuration, largely because little is known about root system characteristics. The studies reported here aimed to determine the potential extent of root system exploration in skip row systems. Field experiments were conducted under rain-out shelters and the extent of water extraction and root system growth measured. One experiment was conducted using widely-spaced twin rows grown in the soil. The other experiment involved the use of specially constructed large root observation chambers for single plants. It was found that the potential extent of root system exploration in sorghum was beyond 2m from the planted rows using conventional hybrids and that root exploration continued during grain filling. Preliminary data suggested that the extent of water extraction throughout this region depended on root length density and the balance between demand for, and supply of, water. The results to date suggest that simultaneous genetic and management manipulation of wide row production systems might lead to more effective and reliable production in specific environments. Further study of variation in root-shoot dynamics and root system characteristics is required to exploit possible opportunities.

Present and future potential of pineapple biotechnology

Pineapple is an important crop for many countries in Central and South America as well as the Asia-Pacific region. Even though the history of the crop dates to pre-Colombian times there is a remarkable lack of commercial varieties with a single cultivar ‘Smooth Cayenne’ dominating the whole industry. Variety improvement is a very difficult task for pineapple breeders and very little progress has been made in this respect when compared to other crops more suitable to classical breeding approaches. This special characteristic makes pineapple specially suited for genetic engineering approaches that can transfer specific traits from other species into pineapple. In this presentation past and present efforts to use biotechnological methods for the improvement of pineapple will be reviewed. On-going biotechnology projects include control of flowering and control of ‘blackheart’ disease. The development of pineapple biotechnology, as with any other crop, is dependent on the availability of a number of molecular tools, which will also be discussed. For pineapple, these tools can be roughly classified into three different categories: (1) availability of useful genes (2) availability of suitable promoters and (3) availability of an efficient transformation method.