Shortening the sugarcane breeding cycle at early selection stages and relevance of selection in ratoons

ABSTRACT

Selection of sugarcane (Saccharum L. spp. hybrids) for commercial exploitation is a lengthy, laborious, and expensive process. The program can span more than 15 years in Mauritius. This study aimed at shortening the cycle by evaluating the relevance of testing in ratoons in early generation selection trials and eliminating the least efficient crop cycles or stages without undue loss of information. At the second and third clonal selection stages (Stages 3 and 4), genotypes are evaluated for two and 3 years, respectively. Stage 3 comprises trials with unreplicated genotypes and replicated controls, whereas Stage 4 entails classical replicated trials. Historical selection data available since 1986 for Stage 3 and since 1973 for Stage 4 were analyzed. Simulations made with standard selection threshold for sugar yield for individual crop cycles showed low coincidence of selected populations between plant cane (PC) and ratoon crops. More than 50% of genotypes selected in PC were rejected in ratoons. Heritability, genetic coefficient of variance and correlation values were in favor of ratoon crops. Using crop cycle as environment, the environment-centered GGE biplot analyses confirmed the higher disparity between PC and ratoon crops and a high degree of similarity between first (1R) and second (2R) ratoon crops. The performance of released commercial varieties as test candidates in early stages pointed to a higher reliability of 1R results than those of PC crop. These findings support the policy of maintaining selection in ratoon to ensure high precision.

KEYWORDS:

• Selection efficiency
• retrospective analysis
• resource use
• selection stages
• ratoons

Acknowledgments

We are thankful to former and existing MSIRI personnel involved in the implementation, management, data collection, analysis and storage of preliminary phase selection trials. We are grateful to Dr. Salem Saumtally, Director, and Dr. Asha Dookun-Saumtally, Principal Research Manager, of the MSIRI for their encouragement and support throughout the scientific analyses and reporting of this research project.

Disclosure statement

No potential conflict of interest was reported by the authors.