Sugarcane breeding: advances, varietal performance and approval of new varieties.

摘要

In 2005, cane and sugar yield as well as extraction rate were the lowest recorded since 1985, excluding abnormal years. Sugar productivity was lower than in 2004 and 2001 by 0.20 t ha-1 and 2.1 t ha-1 respectively for the miller-planters. The area harvested was lower than in 2004 by 1347 ha. Climatic factors have affected productivity to a considerable extent. The variety situation showed that nine varieties were exploited over 89% of cane lands and four of them, M 1400/86, M 1176/77, R 573 and R 579 are becoming more popular and a wider range of varieties are being adopted by the miller-planters. Islandwise, three varieties R 575, M 695/69 and M 1176/77 had the highest productivity. An analysis of performance in variety trials showed that in B soils, M 387/85 had the best sugar productivity while in both B and F soils, M 1400/86 was generally better performing than M 1394/86 at mid-season harvest. In H soils, M 52/78 was the best variety for early-season harvest. In L and P soils, R 573 and R 575 had similar productivity early in the season while at mid-season harvest M 1400/86 was more productive than R 573 in both irrigated and rain-fed conditions. M 703/89, released in 2004 for B soils, outyielded all standards in F and H soils at early- and mid-season harvest. Its cultivation has been extended for these soil groups as well. M 1861/89, released in 2005, has confirmed its good productivity in the superhumid zone at middle and late-season harvest. An analysis of productivity in a sugar cane plantation in the superhumid zone has demonstrated clearly the impact of planting date on cane yield. Long-season plantations are more productive and economically viable than short-season ones over the whole crop cycle of plant cane and ratoons. Three varieties, M 1672/90, M 2627/92 and M 1112/94 were considered to be promising while M 2238/89 and M 2592/93 were recommended for release, the former for cultivation in B soils and for harvesting in the middle and at the end of the season and the latter for the subhumid irrigated zone for harvesting throughout the season. Progress achieved in the genetic improvement programme during the last ten years was reviewed. The emergence of a sugar cane industry with emphasis on the exploitation of biomass and the breeding of different types of varieties is discussed in the scope of the reduction in the price of sugar.