Winter Tolerance Potential of Genetically Diverse Sugarcane Clones under Subtropical Climate of Northern India

The low temperature (LT) conditions that prevail during winter in subtropical regions of India drastically affect the growth and yield of sugarcane. To identify low-temperature-tolerant agronomical acceptable genotypes for immediate deployment as donor parents in the subtropical sugarcane breeding program, 34 sugarcane clones belonging to 7 genetically diverse groups were evaluated under three crop environments, viz., spring planting, winter ratoon and spring ratoon, during 2015–2016 and 2016–2017. In the winter ratoon crop, commercial cane sugar and cane yield were reduced, whereas sucrose % was increased over the spring planted crop and the spring ratoon crop. The wild species and introgressed hybrid groups showed improvement for yield and quality traits in the winter ratoon crop, whereas commercial and near commercial groups showed reduction for these traits over the plant and spring ratoon crops. The tropical cultivars group was the poorest performer irrespective of the traits and crops. Yield per se under a stress environment was adjudged as the best selection criteria. For classification of sugarcane clones according to their low temperature tolerance, an index named winter tolerance index (WTI) is proposed which takes into account the winter sprouting index (WSI), winter growth and yield per se of the winter ratoon crop. The WTI had significant positive association with WSI, cane yield, millable cane population and cane length. As per the WTI ratings, the wild species of Saccharum complex and introgressed hybrid groups were rated as excellent WT clones. Subtropical commercial or advanced generation groups were poor WT clones, and tropical commercial cultivars group were winter sensitive clones. Clones such as AS04-635, AS04-1687, IK76-48, GU07-2276, IND00-1040, IND00-1038 and IND00-1039 had excellent tolerance, and GU07-3849, AS04-245, Co 0238, AS04-2097 and GU07-3774 had good WTI scores. The variety, Co 0238, may be continued for cultivation under LT regions with prophylactic measurers for red rot, while other clones listed above may be utilized in subtropical breeding programs.