Ratoon chlorosis evaluation of sugarcane parents and families

【Objective】In order to understand the genetic characteristics of sugarcane ratoon chlorosis and ratoon chlorosis resistance difference among parents,and to provide reference for ratoon-chlorosis-resistant sugarcane breeding and relevant research.【Method】With 383 sugarcane parents and 97 sugarcane families as experimental materials,ratoon chlorosis field trials in 5 ratoon crop seasons were carried out,and trait correlation analysis,analysis of variance,calculation of heritability and breeding values and cluster analysis were performed.【Result】The peak of ratoon chlorosis was from late April to early May. The degree of chlorosis decreased as sugarcane grew,increased as ratoon grew,and was affected by the experimental field. Correlation analysis showed that ratoon chlorosis would affect sugarcane agronomic traits,and it had significant negative correlation with agronomic traits when it was severe(P<0.05). The result of heritability calculation showed that ratoon chlorosis was a trait of low to intermediate heritability,with a broad-sense heritability of 0.22-0.45 for parent tests and 0.22 for family test,and a narrow-sense heritability of 0.25 for family test. Analysis of variance showed that ratoon chlorosis was affected by many factors,including parents,time,experimental field,year and crop season,among which only parent was significant,and the other 4 factors affected sugarcane ratoon chlorosis through interaction,among which the most important were experimental field×time,parent×experimental field,and the effect of parents ranked the 5^th. The period of maximum difference of ratoon chlorosis between parents or families was the middle-later stage of ratoon seedling period rather than the stage when ratoon chlorosis incidence rate was the highest. By phenotypic BLUP,cluster analysis showed that more than 63.6% of parents and 64.9% of families had better ratoon chlorosis resistance. By breeding value,only 30.3% of the parents had better ratoon chlorosis resistance,less than half of its phenotypic value classification result. Differences existed between evaluation results of parental breeding value and phenotypic value.【Conclusion】Sugarcane ratoon chlorosis is a trait of low to intermediate heritability,which is affected by many factors,mainly interaction. This trait is easily affected by the micro environment and field management,which will have an adverse impact on the field experimental research on sugarcane ratoon chlorosis and breeding of new ratoon-chlorosis-resistant varieties.