Hiroo Takaragawa1 and Yoshiaki Shinzato2
1Tropical Agriculture Research Front, Japan International Research Center for Agricultural Sciences, Okinawa 907-0002, Japan; takaragawah0318@jircas.go.jp
2Faculty of Agriculture, University of the Ryukyus, Okinawa 903-0213, Japan
Some abiotic/biotic stress in sugarcane is heterogeneous and varies in a large field during its long growing period among seasons. The negative effects of mechanized harvesting by pulling plants or driving on the rows depend on the operator’s skill and the degree of lodging. Such unpredictable environmental/artificial stress causes missing plant regrowth (also called gaps) in the field, which reduces yield and ratooning ability of sugarcane. This research aimed to evaluate filling of gaps by planting the same or a different sugarcane variety and its effect on growth and yield in the ratoon crop. Mixed cropping of varieties with different growing characteristics and stress tolerance could reduce yield gaps and improve stability of production under stress conditions in sugarcane. First, we attempted to fill the yield gap by supplementing plug seedlings of different varieties with superior initial growth. Supplemental planting of different varieties showed a positive effect on yield not only in that cropping season but also in the following ratoon season. Second, we evaluated the effect of planting different varieties with different tillering ability on ratoon yield by mixing them alternately on a plant-by-plant basis. Mixed planting contributed to maintaining the number of stems and yield in the ratoon crop. From these results, varieties with excellent initial elongation (competitive) and vigorous tillering (compensating) abilities were considered suitable and effective for mixed planting to resolve yield gaps. To mitigate the need for specific variety selection in mixtures, cultivating multiline populations comprising heterogeneous hybrid strains from diverse parent plants may offer a sustainable alternative. This approach can be integrated with traditional selection methods and participatory breeding, collectively referred to as ‘evolutionary breeding,’ which is also applied in other crops.