Two different strategies of Diversispora spurca-inoculated walnut seedlings to improve leaf P acquisition at low and moderate P levels

Abstract

Walnut (Juglans regia) is an important nut tree species in the world, whereas walnut trees often face inadequate phosphorus (P) levels of soil, negatively limiting its growth and yield. Arbuscular mycorrhizal fungi (AMF) can colonize walnut roots, but whether and how AMF promotes walnut growth, physiological activities, and P acquisition is unclear. The present study aimed to evaluate the effects of Diversispora spurca on plant growth, chlorophyll component concentrations, leaf gas exchange, sugar and P concentrations, and expression of purple acid phosphatase (PAP) and phosphate transporter (PT) genes in leaves of J. regia var. Liaohe 1 seedling under moderate (100 μmol/L P) and low P (1 μmol/L P) levels conditions. Three months after inoculation, the root mycorrhizal colonization rate and soil hyphal length were 45.6−53.2% and 18.7−39.9 cm/g soil, respectively, and low P treatment significantly increased both root mycorrhizal colonization rate and soil hyphal length. Low P levels inhibited plant growth (height, stem diameter, and total biomass) and leaf gas exchange (photosynthetic rate, transpiration rate and stomatal conductance), while AMF colonization significantly increased these variables at moderate and low P levels. Low P treatment limited the level of chlorophyll a, but AMF colonization did not significantly affect the level of chlorophyll components, independent on soil P levels. AMF colonization also increased leaf glucose at appropriate P levels and leaf fructose at low P levels than non-AMF treatment. AMF colonization significantly increased leaf P concentration by 21.0−26.2% than non-AMF colonization at low and moderate P levels. Low P treatment reduced the expression of leaf JrPAP10, JrPAP12, and JrPT3;2 in the inoculated plants, whereas AMF colonization up-regulated the expression of leaf JrPAP10, JrPAP12, and JrPT3;2 at moderate P levels, although AMF did not significantly alter the expression of JrPAPs and JrPTs at low P levels. It is concluded that AMF improved plant growth, leaf gas exchange, and P acquisition of walnut seedlings at different P levels, where mycorrhizal promotion of P acquisition was dominated by direct mycorrhizal involvement in P uptake at low P levels, while up-regulation of host PAPs and PTs expressions at moderate P levels.

Sod Culture with Vicia villosa Alters the Diversity of Fungal Communities in Walnut Orchards for Sustainability Development

“…Interplanted walnuts reduce abundance of soil Funneliformis, resulting in a decrease in soil mycorrhizal hyphae. In turn, this appears to cause more Funneliformis to colonize walnut or V. villosa roots, leading to an increased rate of root mycorrhizal colonization, which benefits the growth and nutrient absorption of walnut [23][24][25], thus encouraging sustainable production of walnut. Furthermore, sod culture in orchards also improved soil fertility, thereby reducing nitrogen fertilizer inputs [55].…”

“…Walnut plants can form ectomycorrhizae as well as arbuscular mycorrhizae in their roots [23]. Mycorrhizae have been demonstrated to play critical roles in nutrient absorption and growth promotion of walnuts [24,25]. Moreover, walnut as a deep-rooted plant serves as a reservoir of AMF propagules for the restoration of surrounding vegetation [26].…”

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“…The decrease in the content of chlorophyll in sweet cherry leaves under the influence of inoculation with endomycorrhiza and endo-ectomycorrhiza can be explained by the competition of natural grasses for the right to mycorrhiza with trees. Mycorrhizal fungi offer a selective advantage in supplying water, nutrients, vitamins, hormones, and enzymes to their host over competing non-host species (Zou et al, 2023). It is known that natural herbs are better at establishing symbiosis with mycorrhizal fungi than cultivated plants (Trinchera et al, 2019), which is probably manifested in the loss of nutrients by sweet cherry trees.…”

Growth Performance and Osmolyte Regulation of Drought-Stressed Walnut Plants Are Improved by Mycorrhiza

“…Pfeiff., C. Walker and Bloss) C. Walker and A. Schüßler having a prominent effect among five AMFs [14]. Moreover, mycorrhizal extraradical hyphae transferred the walnut's juglone outside the rhizosphere, thus affecting the growth of neighboring plants [15]. In addition, root colonization of AMFs promoted mineral nutrient (e.g., N, Zn, and P) acquisition, total phenol levels, and peroxidase activity in drought-stressed walnut plants [16,17].…”

“…A previous study screened an AMF strain, D. spurca, which had an outstanding plant growth-promoting effect on walnuts [14,15], but it is not clear whether this strain affects the osmolytes of walnut plants under drought stress. 'Qingxiang' is a popular walnut cultivar in China, with well-shaped nuts, a strong flavor, and resistance to cold but not drought.…”