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Site and Saccharum spontaneum introgression level drive sugarcane yield component traits and their impact on sucrose yield in contrasted radiation and thermal conditions in La Réunion

Gouy M., Luquet D., Rouan L., Martiné J.F., Thong-Chane A., Costet L., Nibouche S., Gozé E.. 2015. Field Crops Research, 171 : p. 99-108.

Improving sucrose yield is one of the main objectives of sugarcane breeding. Splitting this complex traitinto yield components should make this task easier, as each component may be influenced in its own wayby environmental factors and by genetic background. Abiotic conditions experienced by sugarcane acrossits cropping areas differ in many respects; among them, water availability and photo-thermal conditionsparticularly affect sucrose yield formation.In this study, sucrose yield was divided into seven component traits and studied in a panel of 155 sugar-cane accessions phenotyped at two sites under contrasting photo-thermal conditions: one in low altitudeand the other in higher altitude. The accessions were hybrids developed during the last century and rep-resenting the worldwide cultivated genetic diversity. The proportion of Saccharum spontaneum genomein the genome of each accession was estimated by analyzing the genetic structure of the panel associ-ated with two outgroups formed by 19 S. spontaneum and 29 S. officinarum accessions genotyped with419 DArT markers and using a Bayesian clustering method implemented in STRUCTURE software. A K = 2number of clusters clearly separated S. spontaneum from S. officinarum, while the estimated proportionsof the S. spontaneum genome in the genome of hybrid accessions ranged from 0.5 to 0.Multivariate mixed model of log transformed yield components was adjusted to estimate each com-ponent's contribution to sucrose yield genetic variance, taking into account interrelationships amongcomponents. Each component's contribution to sucrose yield variance was site-dependent. On the lowaltitude site with high photo-thermal conditions, stalk section was the main contributor to yield variance,while on the high altitude site with low photo-thermal conditions, stalk height was the main contribu-tor. A linear regression showed that the estimated proportion of S. spontaneum genome in the hybrids'genome had significant effects on sucrose yield and its components. These effects also varied with the site:under low altitude conditions, the estimated proportion of S. spontaneum genome in the hybrid's genomeexerted a significant negative effect on sucrose yield, whereas no significant effect was found under highaltitude conditions. These results suggest that both efforts toward introgression and selection on yieldcomponents for sugarcane breeding purposes should depend on the targeted cropping environment. (Résumé d'auteur)

Mots-clés : modèle mathématique; régime lumineux; phénotype; variation génétique; région de basse altitude; région d'altitude; saccharose; teneur en glucides; hybridation; génome; facteur du milieu; rendement des cultures; introgression; amélioration des plantes; saccharum spontaneum; réunion

Thématique : Physiologie et biochimie végétales; Génétique et amélioration des plantes; Physiologie végétale : croissance et développement; Culture des plantes

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