Breeding for more phosphorus (P)-efficient crops is one strategy to reduce the use of P fertilizers, thus mitigating the environmental and economic impacts of agriculture. Variation in root architecture and the response to P deficiency were studied in C. melo. Forty accessions representing genetic diversity within the species were screened for their root systems in normal and deficient P conditions at the seedling stage. Various parameters of P-uptake and P-use were analyzed in a subset of accessions at 40 days. Significant differences in root architecture were observed, with the taproot systems prevailing among the wild and exotic accessions, and more branched root systems in cultivated stocks. Moreover, differences in the plastic response of roots to P starvation were observed. Variation in different P-use and -uptake traits correlated with the root architecture. Within ssp. melo, the inodorus and flexuosus landraces had larger and more branched roots and more efficient P-uptake, thereby providing a close genepool for breeding. Within ssp. agrestis, conomon and momordica accessions can be sources of interest for the enhancement of variation in root architecture and P-use efficiency into cultivated melons. Therefore, the diversity observed within C. melo species could be useful in breeding P-efficient melon cultivars. © 2011 Springer Science+Business Media B.V. ; Generalitat Valenciana [GVPRE/2008/131] ; ERA-PG programme [GEN2006-27773-C2-2] ; INIA [RF2008-00003-C02-02] ; Fita, A.; Nuez Viñals, F.; Picó Sirvent, MB. (2011). Diversity in root architecture and response to P deficiency in seedlings of Cucumis melo L. Euphytica. 181(3):323-339. doi:10.1007/s10681-011-0432-z. ; Senia ; 323 ; 339 ; 181 ; 3