ISHS Acta Horticulturae 470: II International Symposium on Pistachios and Almonds
ARBUSCULAR MYCORRHIZAL FUNGI ON PISTACHIO ROOTSTOCKS IN CALIFORNIA |
| Authors: | L. Ferguson, S. Kaur, L. Epstein |
| Keywords: | Glomus, Pistacia, Sclerocystis, vesicular-arbuscular mycorrhizae, VAM |
| Abstract:
There are three major pistachio rootstocks used in California: P. atlantica, a cold-tolerant but Verticillium-sensitive, and slower-growing rootstock; P. integerrima, a Verticillium-resistant and faster-growing rootstock which is cold-sensitive; and a new interspecific hybrid (P. atlantica X P. integerrima UCBI) which is cold-tolerant, Verticillium-resistant, and faster-growing. These three rootstocks are planted in a field trial at the Kearney Agricultural Center in Fresno county in the San Joaquin Valley. In 1994 and 1995, when the trees were four- and five-years-old, respectively, we examined the feeder roots for endomycorrhizae. By the earliest sampling date in 1995 (15 June) and by the second sampling date in 1994 (14 July), the cortical cells of young roots were extensively colonized. At these dates and throughout the remainder of the growing season, approximately one-half or more of the young root biomass contained intracellular arbuscular mycorrhizae. There were no significant differences in the extent of arbuscular mycorrhizal colonization between rootstocks in either year. In both 1994 and 1995, at least two genera of arbuscular mycorrhizae were present on all three rootstocks: Glomus sp., and Sclerocystis sp. No differences in the composition of the arbuscular species between the three rootstocks were observed. Glomus spp. were the most common in both years; two species of Glomus may be present. In a pot trial with the three rootstocks, seedlings transplanted into peat containing 1 propagule Glomus intraradix per g fresh wt soil were extensively colonized by G. intraradix. Since all rootstocks are heavily colonized in the field, we propose that pistachio rootstocks should be thought of as a pistachio-mycorrhizal symbiosis. | |
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