Desiccation tolerance in relation to soluble sugar contents in seeds of ten coffee (CoffeaL.) species

Large differences in seed desiccation sensitivity have been observed previously among ten coffee species (Coffea arabica, C. brevipes, C. canephora, C. eugenioides, C. humilis, C. liberica, C. pocsii, C. pseudo-zanguebariae, C. sessiliflora and C.stenophylla). Of these species,C. libericaandC. humiliswere the most sensitive to desiccation andC. pseudozanguebariaethe most tolerant. A study was carried out using the same seed lots to investigate if these differences in desiccation tolerance could be correlated with differences in soluble sugar content. Soluble sugars were extracted from dry seeds and analysed using high performance liquid chromatography. The seed monosaccharide (glucose and fructose) content was very low (1.5 to 2 mg g-1dry weight [dw]) in all species studied. The sucrose content ranged from 33 mg g-1dw inC. libericaseeds to 89 mg g-1dw in seeds ofC. pocsii. Raffinose was detected in the seeds of only five species (C.arabica, C.brevipes, C.humilis, C.sessiliflora, C.stenophylla), among which only three species (C.arabica, C.sessilifloraandC.brevipes) also contained stachyose. Both raffinose and stachyose were present in very low quantities (0.3–1.4 mg g-1dw and 0.1–0.7 mg g-1dw, respectively). Verbascose was never detected. No significant relationship was found between seed desiccation sensitivity and: (i) the sugar content; (ii) the presence/absence of oligosaccharides; and (iii) the oligosaccharide:sucrose ratio.