The influence of mycorrhization and organic mulches on mycorrhizal frequency in apple and strawberry roots

Abstract

The aim of the experiments was to study the natural colonization of the roots of apple trees cv. 'Gold Milenium' and the roots of strawberry plants cv. 'Kent' by arbuscular mycorrhizal (AM) fungi, One-year-old apple maidens cv. 'Gold Milenium' were planted in 4 replicates, each consisting of 3 apple trees planted 4 m x 1.2 m apart, with a 1-metre-wide isolation strip between the plots. Strawberry plants cv. 'Kent' were planted in 3 replicates, each consisting of 20 plants planted at 1.0 m x 0.25 m spacing, with 0.5-metre-wide breaks between the plots. For each of the experimental combinations: control, peat mulch, bark, sawdust, manure, compost, straw and mycorrhizal inoculum, root samples were collected with a cork borer for microscopic analyses. The roots were cold-stained using a method involving treatment with 10% KOH, acidification with 5% lactic acid, staining with 0.01 aniline blue and treatment with 80% lactic, and observed under microscope. The extent of micorrhization was assessed according to Trouvelot by determining the following parameters: F % ― mycorrhizal frequency, M % ― relative mycorrhizal intensity (for the whole sample), m % - absolute mycorrhizal intensity (for the segments in which there was some evidence of colonization by mycorrhizal fungi) a % ― absolute abundance of arbuscules (for the segments in which arbuscules were found), A % ― relative abundance of arbuscules (for the whole sample). The results obtained were analyzed using Mycocalc computer program. On the basis of the results obtained it was concluded that mycorrhizal fungi colonized the roots of strawberry cv. 'Kent' more often than the roots of apple cv. 'Gold Milenium', and that the mycorrhizal frequency in strawberry roots, in individual combinations, was significantly higher than in apple roots (32-87% in strawberry, and 3-25% in apple). Other parameters, i.e. the abundance of arbuscules and mycorrhizal intensity, also had higher values for strawberry roots than for apple roots (0.31-91% and 0-24% for arbuscule abundance, respectively, and 0.9-13% and 0.25-4.5% for mycorrhizal intensity, respectively). The differences resulted from the different morphological characteristics of the roots in apple and strawberry, and from the significant difference in the size of the respective root systems.