Sugarcane Breeding in Reunion: Challenges, Achievements and Future Prospects

Abstract

All over the world, sugarcane breeding programs are developing new, high-yielding cultivars that are resistant to major diseases to improve the profitability and sustainability of the sugar-energy industries they serve. In Reunion Island, sugarcane genetic improvement efforts began in 1929. Many challenges had to be overcome. Continuous breeding efforts have been made to develop varietal resistances to control some major diseases and are still going on today. Given the extreme agroclimatic diversity that characterizes the different production areas of the industry, it was necessary to gradually develop a large network of seven decentralized breeding programs to support genetic progress throughout the whole industry. This article provides an overview of the sugarcane breeding program of Reunion. It describes historical achievements and gives detailed information about germplasm development, variety exchanges, breeding program and selection scheme and procedures. A review is also made on applied genetics research activities supporting variety improvement. Further progress depends on the optimized functioning of the current breeding program, which has never been so largely extended in terms of target environments. The article discusses prospects of genomics breeding applications in the complex genetic context of sugarcane, which will require large multidisciplinary collaborations.

Effects of orange rust on sugarcane yield traits in a multi-environment breeding program

“…The first two sites (ES and GL) were representative of the irrigated coastal areas of the dry leeward coast of the island, and the three others were representative of the wet windward coast, either near sea level (LM, SB) or in the highlands (MC). Guilly et al (2017) and Dumont et al (2022) reported precise localization, climate and soil characteristics, and selection focus of each of these sites. The five sites were characterized by wet summers (November-April) and more or less dry winters (June-September).…”

“…Breeding and selecting for resistant or tolerant varieties is all the more important because, although harvested annually, a sugarcane crop is established for several years (Van Dillewjin 1952). In Reunion, sugarcane fields are usually only replanted every 10 years (Dumont et al 2022). Therefore, the use of insufficiently resistant cultivars may result in recurrent economic losses for a long period.…”

“…Since its inception almost a century ago, the sugarcane variety development program (SVDP) of Reunion has always paid attention to breeding efforts for disease resistance (Dumont et al 2022). Consequently, production of varieties resistant or tolerant to pathogens that emerged locally during the last decades resulted in successful management of the diseases they cause.…”

“…The main objective of the SVDP in Reunion is to select varieties adapted to the different major agroclimatic regions of sugarcane production of the local industry (Dumont et al 2019(Dumont et al , 2022. Seven decentralized selection programs, strategically located in the major sugarcane growing areas, are run concurrently (eRcane 2009; Guilly et al 2017).…”

“…Each program undergoes a sequential process of clonal selection for 10 years in four successive stages (stages I-IV). Key selection criteria include high biomass and sugar productivity related to cane yield and recoverable sugar, fiber content and good resistance levels to major diseases present in Reunion (Dumont et al 2022). At the end of stage IV, few elite varieties are selected from each selection site and tested across all sites in the final selection stage (stage V) based on multi-environment trials (MET) carried out for four crop cycles (plant crop to third ratoon crop).…”