Relationship between bruchid resistance and seed mass in mungbean based on QTL analysis

Bruchids (Coleoptera: Bruchidae) can cause serious damage to mungbean and several other leguminous crops and there is a strong association between small seed size and bruchid resistance. In investigating the feasibility of breeding large-seeded cultivars with high levels of bruchid resistance, we studied the relationship between these two traits by QTL analysis. A major locus conferring resistance to Callosobruchus chinensis was identified from a wild mungbean genotype, 'ACC41' (belonging to Vigna radiata var. sublobata), collected in Australia. The proportion of the C. chinensis resistance response that could be attributed to this single QTL varied among four different resistance assays. The highest value reached was 98.5%, suggesting that bruchid resistance in this genotype is likely conditioned by this single locus. The QTL was robust and its detection was not affected by the use of different sources of the insect, different lengths and conditions of seed storage, or different bruchid resistance assay methods. This bruchid resistance QTL was coincident with one of the loci conferring seed mass detected from the three seed sources produced in Australia. However, such a co-location was not detected for the seed source produced in China. Covariance analysis revealed a complex relationship between seed mass and bruchid resistance. Nevertheless, the effect of the bruchid resistance QTL remained highly significant for all four assays after the effect of seed mass was accounted for. These results, together with the relationship between the bruchid resistance QTL identified in this study and a second one detected previously in a wild mungbean genotype from Madagascar, are discussed. Key words: bruchids, Callosobruchus, seed-feeding weevils, seed mass, mungbean. Les bruchides (Coleoptera : Bruchidae) peuvent causer des dommages importants chez le haricot mungo et plusieurs autres ldgumineuses cultivars. De plus, il y a une association etroite entre la petite taille des graines et la resistance aux bruchides. En investiguant la possibilite de selectionner des cultivars a grosses graines avec une forte resistance aux bruchides, les auteurs ont etudie les relations entre ces deux caracteres par analyse QTL. Un locus majeur conferant la resistance an Callosobruchus chinensis a ete identifiee chez le genotype sauvage 'ACC41' du haricot mungo (appartenant an V. radiata var. sublobata) obtenu en Australie. La proportion de la resistance an C. chinensis attribuable a un unique QTL variait selon les quatre evaluations de la resistance. La plus haute valeur enregistree etait 98,5 %, ce qui suggere que la resistance aux bruchides chez ce genotype est vraisemblablement contrelee par un seul locus. Ce QTL etait robuste et sa detection n'etait pas affectee par l'emploi d'insectes provenant de diffdrentes sources, par la durde et les conditions d'entreposage des grains on par la methode d'evaluation de la resistance aux bruchides. Ce QTL coincidait avec un des locus controlant la taille des graines, lequel avait ete detecte chez trois sources de graines produites en Australie. Une telle co-localisation n'a cependant pas ete observee chez une source provenant de la Chine. Une analyse de covariance a revele une relation complexe entre la taille des graines et la resistance aux bruchides. Neanmoins, l'effet de ce QTL de resistance aux bruchides est demeure hautement significatif pour l'ensemble des quatre evaluations apres avoir tenu compte de l'effet de la taille des graines. Les auteurs discutent ces resultats ainsi que les relations entre le QTL identifie ici et un autre detecte anterieurement chez un genotype sauvage provenant de Madagascar. Mots-cles : bruchides, Callosobruchus, charanrcons de la graine, poids des graines, haricot mungo. [Traduit par la Redaction]
Introduction Bruchids (Coleoptera: Bruchidae) are seed-feeding weevil-like insects. They can cause serious damage to several leguminous crops including cultivated Vigna species such as mungbean, cowpea, and adzuki bean (Singh et [...]