The effects of co-colonising ectomycorrhizal fungi on mycorrhizal colonisation and sporocarp formation in Laccaria japonica colonising seedlings of Pinus densiflora

Forest trees are colonised by different species of ectomycorrhizal (ECM) fungi that interact competitively or mutualistically with one another. Most ECM fungi can produce sporocarps. To date, the effects of co-colonising fungal species on sporocarp formation in ECM fungi remain unknown. In this study, we examined host plant growth, mycorrhizal colonisation, and sporocarp formation when roots of Pinus densiflora are colonised by Laccaria japonica and three other ECM fungal species (Cenococcum geophilum, Pisolithus sp., and Suillus luteus). Sporocarp numbers were recorded throughout the experimental period. The biomass, photosynthetic rate, and mycorrhizal colonisation rate of the seedlings were also measured at 45days, 62days, and 1year after seedlings were transplanted. Results indicated that C. geophilum and S. luteus may negatively impact mycorrhizal colonisation and sporocarp formation in L. japonica. Sporocarp formation in L. japonica was positively correlated with conspecific mycorrhizal colonisation but negatively correlated with the biomass of seedlings of P. densiflora. The co-occurring ECM fungi largely competed with L. japonica, resulting in various effects on mycorrhizal colonisation and sporocarp formation in L. japonica. A variety of mechanisms may be involved in the competitive interactions among the different ECM fungal species, including abilities to more rapidly colonise root tips, acquire soil nutrients, or produce antibiotics. These mechanisms need to be confirmed in further studies.Peer reviewe

Identification of Cupressaceae species from airborne pollen grains using chloroplastic markers: implications for reproductive interference evaluation in a remnant natural population of <i>Chamaecyparis pisifera</i> (Sieb. et Zucc.) Endl

<p>Many wild populations of <i>Chamaecyparis pisifera</i> (Cupressaceae) are recently fragmented and surrounded by coniferous plantations. To distinguish the species composition of pollens that are dispersed to female flowers of <i>C. pisifera</i>, genetic markers (Chaps-trnL01 and Chaps-trnL02) were developed based on the differences in <i>trn</i>L (UAA) intron region of chloroplast DNA. This region in <i>C. pisifera</i> contains the site of the <i>Cla</i> I restriction enzyme and allows the distinction of <i>C. pisifera</i> from other Cupressaceae species after digestion of the products with the enzyme resulting in the development of cleaved amplified polymorphic sequence (CAPS) markers. The availability of markers was determined by single-pollen genotyping. Amplification success rates of 75.0, 58.3, and 100% were obtained for the pollens of <i>C. pisifera, Chamaecyparis obtusa</i>, and <i>Cryptomeria japonica</i>, respectively. Then, the markers and genotyping methods were applied to airborne pollen grains sampled from a remnant natural stand of <i>C. pisifera</i>. Over 90% of the pollen grains were identified as belonging to <i>C. obtusa</i>. Thus, we concluded that abundant heterospecific pollen dispersal was present during the flowering periods of <i>C. pisifera</i>. These results suggest that the remnant <i>C. pisifera</i> population might suffer reproductive interference due to the lower chances to be pollinated with conspecific pollens.</p

Estimation of the most suitable nitrogen concentration for sporocarp formation in Laccaria japonica colonizing Pinus densiflora seedlings through in vitro mycelial culture

Many ectomycorrhizal (ECM) fungi produce commercially valuable edible sporocarps. However, the effects of nitrogen (N) application on ECM fungal sporocarp formation remain poorly understood. In this study, we investigated the effect of application of various N concentrations (0, 5, 25, 50, 100, and 200 mg/L) on the growth of Laccaria japonica mycelia in vitro for 1 month. The results showed that L. japonica mycelial biomass was highest in the 50 mg/L treatment and was significantly inhibited at N concentrations higher than 200 mg/L. Next, we investigated the effects of N application on mycorrhizal colonization and sporocarp formation in L. japonica colonizing Pinus densiflora seedlings in pots. The seedlings were watered with nutrient solutions containing 0, 5, 25, 50, or 100 mg N/L. The biomass, photosynthetic rate, and mycorrhizal colonization rates of the seedlings were measured at 45 days (first appearance of primordia), 65 days (sporocarp appearance on the substrate surface), and 4 months after seedlings were transplanted. The numbers of primordia and sporocarps were recorded during the experimental period. Total carbon (C) and N content were determined in seedlings at 4 months after transplantation, and in L. japonica sporocarps. Both mycelial growth and sporocarp production reached their maximum at an N application concentration of 50 mg/L, suggesting that the most suitable N concentration for ECM fungal sporocarp formation can easily be estimated in vitro during mycelial growth. This finding may help determine the most suitable N conditions for increasing edible ECM fungus sporocarp production in natural forests.Peer reviewe