MYCORRHIZAE ALTER PROTEIN AND LIPID CONTENTS AND YIELD OF PEA SEEDS

Root colonization by arbuscular-mycorrhizal (AM) fungi may affect seed protein and lipid composition by altering P nutrition or by eliciting metabolic responses by the host plant. These fungi may therefore play a role in plant breeding programs. This study was conducted to determ ine the effects of an AM fungus and different levels of P availability on seed protein and lipid composition and yield. Pea (Pisum sativum L .) plants were grown in a greenhouse under different P regimes (0, 1, 2, or 4 g hydroxyapatite kg(-1) soil) with or without the AM fungus Gl omus mosseae (Nicol and Gerd.) Gerd. and Trappe. At the lowest level o f P availability, protein concentration was significantly lower and li pid concentration and seed dry mass were higher in AM than in non-AM p lants. Protein/lipid concentration ratios were invariant in non-AM pla nts at all soil P levels. Those of the AM plants varied, were highest at an intermediate P level, and coincided with the highest intensity o f root colonization and the greatest reduction of seed yield relative to the non-AM plants at the same level of P availability. Lipid and pr otein contents were highly correlated (second order) with P content in all plants. In non-AM plants, however, lipid and protein contents wer e very low at the lowest soil P level, but statistically not different at the other soil P levels. The data show different patterns of seed P accumulation and different relationships between seed P content and protein and lipid composition in AM and non-AM plants. This suggests t hat both the presence and the intensity of AM-fungal colonization alte red the response of seed Lipid metabolism to increasing P availability , which affected the protein and lipid ratios.