Ectomycorrhizal fungal diversity in orchards of cultivated pecan (Carya illinoinensis; Juglandaceae)

Abstract

Carya illinoinensis (pecan) belongs to the Juglandaceae (walnut family) and is a major economic nut crop in the southern USA. Although evidence suggests that some species in the Juglandaceae are ectomycorrhizal, investigations on their ectomycorrhizal fungal symbionts are quite limited. Here we assessed the ectomycorrhizal fungal diversity in cultivated orchards of C. illinoinensis. Five pecan orchards in southern Georgia, USA, were studied, three of which were known to fruit the native edible truffle species Tuber lyonii. We sequenced rDNA from single ectomycorrhizal root tips sampled from a total of 50 individual trees. Mycorrhizae were identified by ITS and LSU rDNA sequence-based methods. Forty-four distinct ectomycorrhizal taxa were detected. Sequestrate taxa including Tuber and Scleroderma were particularly abundant. The two most abundant sequence types belonged to T. lyonii (17%) and an undescribed Tuber species (~20%). Because of our interest in the ecology of T. lyonii, we also conducted greenhouse studies to determine whether this species would colonize and form ectomycorrhizae on roots of pecan, oak, or pine species endemic to the region. T. lyonii ectomycorrhizae were formed on pecan and oak seedlings, but not pine, when these were inoculated with spores. That oak and pecan seedling roots were receptive to truffle spores indicates that spore slurry inoculation could be a suitable method for commercial use and that, ecologically, T. lyonii may function as a pioneer ectomycorrhizal species for these hosts.

Truffle biogeography—A case study revealing ecological niche separation of different Tuber species

“…Although not directly comparable (percentage of field sites vs. percentage of root samples), the high abundance of Tuber spp. recorded in this study is somewhat in disagreement with the results of Bonito, Brenneman, and Vilgalys (), who reported frequency of Tuber spp. OTUs in ectomycorrhizae of Carya ilinoinensis to be ca 10%–15%.…”

“…This points to a higher α‐diversity at landscape level than that reported by Bonito Brenneman, et al. (), who found only four Tuber OTUs at five hardwood sites (albeit with a smaller geographical spread than in our sampling design), but it agrees quite well with previous records from the Czech Republic that are based on ascocarp collections (eight species at country level).…”

Enigmatic Sebacinales

“…Juglandaceae Sebacinoid ECMs were present in orchards of cultivated Carya illinoinensis (Bonito et al 2011). …”

Pecan cultivation: general aspects

“…From these ones emerge roots that grow vertically and have the function of absorbing water and nutrients (SPARKS, 2005). Fibrous roots grow in all directions from the side and are subject to constant death and replacement as a result of different growth conditions, while the mycorrhizal roots are a type of fibrous roots that grow in dense masses throughout the area explored by roots (BONITO et al, 2011). The area explored by the pecan tree roots can expand up to twice beyond the canopy projection and its growth may be limited by the occurrence of drought, excessive moisture in the subsoil and soil temperature lower to 18°C (WELLS, 2017).…”

“…The mycorrhizae that are linked to the absorption roots allow the trees to increase the root system area exploration and to optimize the absorption of N, P, K, Ca, Mg, Zn and Cu from the soil, resulting in production increases (BONITO et al, 2011).…”