BREEDING FOR A BETTER INDUSTRY: CONVENTIONAL BREEDING

摘要

A continuing supply of improved cultivars satisfying the requirements of sugarcane industries worldwide has underpinned increases in production since the 19th century. Cultivars are developed using three components: assembling a described population of parental clones; generating variable progenies by cross-pollination; and selecting useful clones. The paper summarises advances and deficiencies in these components. Movement of germplasm is facilitated by increased adoption of international export quarantine standards additional to long-accepted import procedures, which are being strengthened by molecular pathology screens. The parlous condition of the World Collections is a continuing concern, but the reluctance of sugarcane industries to finance them precludes criticism of the host organisations. The bulk of sexual recombination uses existing Saccharum spp. hybrids. This is despite the outstanding contemporary successes with basic germplasm in Argentina, Australia, and Louisiana. Managed photoperiod facilities, particularly in the tropics, are aiding planned recombinations among parental clones. Failure to use rigorous cross-pollination techniques means a low likelihood of trueness-to-label of progenies from many programs. Prediction of cross performance, using progeny trial data alone, has advanced, but more sophisticated statistical techniques may improve estimation of parental breeding value, and use of family selection for progeny populations has been beneficial. Whether high-performing combinations are predictable is currently debated. Adoption of objective selection was a major advance and will be enhanced by introducing high-speed, quality-component analyses. Inter-genotypic competition in small-plot assessment is important, and plot design should take this into account. Sugarcane improvement lacks purpose-built equipment for small-plot evaluation. Extensive G X E research has not delivered practical, usable solutions to facilitate collaboration between programs. Conventional breeding can provide solutions to many problems, but these may not be the most economical, and minimisation of selection criteria to maximise genetic gain is little understood by industry. However, conventional breeding will be the main system delivering improved cultivars for many decades. Managed photoperiod facilities, more sophisticated selection indices, and improved breeding-value estimation will facilitate this. The system will be increasingly supported by biotechnological techniques. Genetic engineering may correct highly productive, flawed clones, and may allow production of high-value products using novel genes. Regardless, conventional breeding will be pivotal in delivering such enhancements to the industry and, ultimately, to the consumer.