Mycorrhiza (1999) 9 : 97–101 Q Springer-Verlag 1999 ORIGINAL PAPER Ghazi N. Al-Karaki 7 R.B. Clark Mycorrhizal influence on protein and lipid of durum wheat grown at different soil phosphorus levels Accepted: 18 May 1999 G.N. Al-Karaki (Y) Faculty of Agriculture, Jordan University of Science and Technology, P.O. Box 3030, Irbid, Jordan e-mail: gkaraki6just.edu.jo, Fax: c962-2-295123 R.B. Clark Appalachian Soil and Water Conservation Research Laboratory, US Department of Agriculture, Agricultural Research Service, 1224 Airport Rd., Beaver, WV 25813-9423, USA Abstract Root colonization by arbuscular mycorrhizal fungi (AMF) may affect protein and lipid composition of plants by altering P nutrition or by eliciting other metabolic responses in the host plant. This study was conducted to determine the effects of an AMF and soil P on seed protein and lipid contents and yield of two genotypes of durum wheat (Triticum durum L.). Plants were grown in a greenhouse using soil: sand mixes with different levels of P, and with or without the AMF Glo- mus mosseae [(Nicol. and Gerd.) Gerd. and Trappe]. Percentage AMF root colonization decreased as P ad- ded to soil increased. The wheat genotype CR057 had higher AMF root colonization but lower seed P and protein concentrations than CR006. Without added soil P, protein concentration was significantly lower and lip- id concentration and seed dry weight higher in arbuscu- lar mycorrhizal (AM) than in nonAM plants. Seed lipid and protein contents were highly correlated with P con- tent of plants. In nonAM plants, seed lipid and protein contents were low with no added soil P and did not dif- fer with added soil P. Seed protein/lipid (Pro/L) con- centration ratios of AM plants were higher than those of nonAM plants only when no P was added to the soil. The data indicate different patterns of seed P accumu- lation and different relationships between seed P and protein and lipid in AM and nonAM plants. Thus, both the presence and degree of AMF root colonization af- fected seed lipid metabolism in these durum wheat ge- notypes. Key words Glomus mosseae 7 Lipid 7 Phosphorus 7 Protein 7 Seed 7 Triticum durum Introduction Arbuscular mycorrhizal fungi (AMF) have fundamen- tal effects on host plant biochemistry and physiology (Koide and Schreiner 1992; Smith and Gianinazzi-Pear- son 1988). Specific proteins (Gianinazzi-Pearson and Gianinazzi 1989), amino acid fractions (Tawaraya and Saito 1994; Tawaraya et al. 1994), lipids (Bethlenfalvay et al. 1994, 1997), reducing sugars (Tawaraya et al. 1994), and secondary metabolites (Morandi and Giani- nazzi-Pearson 1986) are produced by host plants in re- sponse to AMF root colonization. Such changes in plant tissues indicate that seeds of mycotrophic plants may also be modified, not only in terms of biomass pro- duced but in the relative abundance of storage products such as proteins, lipids, and starch (Bethlenfalvay et al. 1994, 1997; Lu and Koide 1991). Even though wheat seeds are often considered to be a starchy food, these seeds contain other valuable nutritive compounds (e.g., proteins and lipids) in significant amounts (Al-Karaki and Ereifej 1998; Johnson et al. 1978). Seed lipid and protein composition are not only her- itable traits, but depend to a large extent on environ- mental conditions (Burton 1987; Wilson 1987). Since AMF influence expression of genetic differences in host plants (Toth et al. 1984), AMF may also affect seed physiology. However, information on AMF effects on seed composition is limited, possibly because most experiments with AMF are conducted in pot cultures, where plants are not usually grown to maturity and where root-volume constraints limit AMF effectiveness (Koide 1991a). The most pronounced aspect of AMF effectiveness has been enhanced P nutrition of host plants (Al-Karaki and Al-Raddad 1997; Koide 1991b;