Estimation of sequestered carbon in Article-3.4 private planted forests in the first commitment period in Japan

The purpose of this study was to predict the likely amounts of carbon sequestration on a national scale for Japan in the Article-3.4 private planted forests of the Kyoto Protocol during the first commitment period. We regarded the planted forests that had undergone silvicultural practices such as weeding, pruning, and thinning since 1990 as Article-3.4 planted forests in accordance with the definition given by the Forestry Agency of Japan. Regression models were developed to predict the forest areas that had undergone silvicultural practices, employing silvicultural subsidies and forest workers' wages as predictor variables. Then the time series changes in the predictor variables were provided by extending their recent trends, with the result being that the forest areas that have undergone silvicultural practices were predicted on the basis of the three scenarios of the variables. Thus, the Article-3.4 forest area was calculated considering overlaps of silvicultural practices over fixed stands, and the area was converted into the amount of carbon sequestration by multiplying it by coefficients such as a volume table, biomass expansion factor, and others. The result implied that Article-3.4 private planted forests were expected to sequester 8.16–8.87 Mt-C year⁻¹ during the first commitment period. These amounts cover 63%–68% of the carbon sequestration goal by land-use change and forestry activities capped under the Marrakesh Accords. To realize this prediction, it is important to provide a sufficient silvicultural subsidy to last until the end of the first commitment period and to implement silvicultural practices on the forest stands that have not undergone such practices since 1990.     

Genetic variation of mitochondrial and nuclear genomes in carrots revealed by random amplified polymorphic DNA (RAPD)

Mitochondrial and nuclear genomic diversities of 8 carrot (Daucus carota ssp. sativus) varieties, including 6 pure lines and 2 cytoplasmic male sterile (cms) lines, were taxonomically identified using PCR with 19 RAPD primers. Dendrograms based on polymorphisms of both mitochondrial and nuclear genomes were constructed. According to the dendrogram of the mitochondrial genome revealed by RAPD, 4 differentiated clusters formed, in good accordance with the classification based on analyses with restriction enzyme digestion. Two cms lines were grouped into the same cluster, as genetically separated from the others. Thus, the cytoplasm donors of these male sterile lines were thought to be wild carrots. Conversely, RAPD analysis of the nuclear genome for these eight cultivars revealed no evident clusters although some cultivars were of a similar origin or place of cultivation. A correlation between nuclear and mitochondrial dendrograms was absent. RAPD has proved to be a useful tool for identifying mitochondrial and nuclear genomes. This technique will greatly aid in promoting efficient improvement of carrots. This revised version was published online in July 2006 with corrections to the Cover Date.     

Biological control of Fusarium wilt by <Emphasis Type="Italic">Bacillus amyloliquefaciens</Emphasis> IUMC7 isolated from mushroom compost

Bacillus amyloliquefaciens IUMC7 isolated from mushroom compost inhibited growth of Fusarium oxysporum f. sp. lycopersici (FOL) on culture plates, and a culture supernatant of IUMC7 inhibited in vitro germ tube elongation of FOL. When compared with control soils, mushroom compost inoculated with IUMC7 significantly reduced disease severity caused by FOL in tomato plants. PCR tests for expression of PR genes indicated that IUMC7 did not induce resistance in tomato plants. These results suggested that the suppression of disease was mainly caused by antimicrobial compounds produced by IUMC7.     

Development of cultivar-specific DNA markers based on retrotransposon-based insertional polymorphism in Japanese pear

We developed retrotransposon-based insertional polymorphism (RBIP) markers based on the long terminal repeat (LTR) sequences of copia-like retrotransposon Ppcrt4 and flanking genome sequences, which were derived from 454 sequencing data from Japanese pear (Pyrus pyrifolia) ‘Hosui’. Out of 40 sequences including both LTR and flanking genome regions, we developed 22 RBIP markers and used them for DNA profiling of 80 pear cultivars: 64 Japanese, 10 Chinese (Pyrus ussuriensis) and 6 European (Pyrus communis). Three RBIP markers were enough to differentiate ‘Hosui’ from the other Japanese pear cultivars. The 22 RBIP markers could also distinguish 61 of the 64 Japanese pear cultivars. European pears showed almost no amplification of the 22 RBIP markers, which might suggest that retrotransposons had transposed during Asian pear evolution or reflect the genetic relationship between Asian and European pears. Sixteen of the RBIP markers could be positioned on a genetic linkage map of ‘Hosui’. The RBIP loci were distributed in 10 linkage groups, and some loci were very closely located within the same linkage group. The information obtained will be applicable to developing cultivar-specific RBIP marker sets in plants.     

Identification of QTLs for fruit quality traits in Japanese apples: QTLs for early ripening are tightly related to preharvest fruit drop

Many important apple (Malus × domestica Borkh.) fruit quality traits are regulated by multiple genes, and more information about quantitative trait loci (QTLs) for these traits is required for marker-assisted selection. In this study, we constructed genetic linkage maps of the Japanese apple cultivars ‘Orin’ and ‘Akane’ using F₁ seedlings derived from a cross between these cultivars. The ‘Orin’ map consisted of 251 loci covering 17 linkage groups (LGs; total length 1095.3 cM), and the ‘Akane’ map consisted of 291 loci covering 18 LGs (total length 1098.2 cM). We performed QTL analysis for 16 important traits, and found that four QTLs related to harvest time explained about 70% of genetic variation, and these will be useful for marker-assisted selection. The QTL for early harvest time in LG15 was located very close to the QTL for preharvest fruit drop. The QTL for skin color depth was located around the position of MYB1 in LG9, which suggested that alleles harbored by ‘Akane’ are regulating red color depth with different degrees of effect. We also analyzed soluble solids and sugar component contents, and found that a QTL for soluble solids content in LG16 could be explained by the amount of sorbitol and fructose.     

Pheophytinase activity and gene expression of chlorophyll-degrading enzymes relating to UV-B treatment in postharvest broccoli (Brassica oleracea L. Italica Group) florets

Pheophytinase (PPH) activity and gene expression of chlorophyll (Chl)-degrading enzymes relating to UV-B treatment in postharvest broccoli (Brassica oleracea L. Italica Group) florets were determined. PPH is involved in the dephytylation of Mg-free Chl a, pheophytin (Phy) a. However, in vitro chlorophyllase (Chlase, EC.3.1.1.14) also uses Phy a as a substrate to produce pheophorbide (Pheide) a by dephytylation. For an accurate determination of PPH activity, the PPH protein fraction was separated from Chlase protein by ammonium sulfate precipitation. The protein precipitated by 45-60% saturated ammonium sulfate included a little bit of Chlase activity and was suitable for PPH determination. PPH activity in broccoli florets treated with a UV-B dose of 19 kJ m⁻² was repressed for the first 2 d of storage at 15 °C, whereas it increased gradually with senescence of control broccoli florets. The expression level of BoCLH1 was reduced in broccoli florets on day 4 of storage, while BoCLH2 and BoCLH3 were up-regulated with UV-B treatment. A high BoPAO expression level was found in senescent broccoli florets, and the up-regulation of this gene was delayed by UV-B treatment. The highest expression level of BoPPH was found in the control, and its expression was clearly repressed by UV-B treatment on day 2 of storage. We suggest that the up-regulation of Chl-degrading enzyme genes could be delayed by UV-B treatment, resulting in the suppression of floret yellowing in stored broccoli.     

Dynamics of soil biota at different depths under two contrasting tillage practices

One aim of conservation tillage is to preserve soil biological properties. This study was conducted to examine the effects of two contrasting tillage treatments on soil biota at different depths. We investigated the population dynamics and vertical distributions of microbes and several soil faunal groups for 2 years in field Andosols in northeastern Japan. The experimental plots were under no tillage (NT) or conventional tillage (CT, rotary tilled to 20 cm) management. In the 0–10-cm soil layer, bacterial and fungal substrate-induced respiration (SIR) and the population density of enchytraeids were higher under NT than under CT, but the population densities of protozoa, mites, and collembolans did not differ significantly. In contrast, at 10–20 cm, both SIR values were higher under CT, where larger populations of mites and collembolans were recorded. At both depths, nematodes were more abundant under CT. Thus, the effects of tillage on these soil organisms differed according to soil depth, and negative impacts of tillage were smaller in the deeper layer. Larger amounts of earthworm casts at the soil surface in NT plots showed a greater biomass of earthworms than in CT. To evaluate the activities of soil biota, we buried litterbags with three different mesh sizes at the two depths and examined the rate of decomposition. The daily decay constant of litter in the surface soil layer (1.5–8.5 cm) was greater under NT. We suppose that the activities of soil biota in this layer were stimulated under NT, and that especially microbes and enchytraeids, which were abundant at 0–10 cm, contributed greatly to the decomposition.     

Soil organic carbon pools in ploughed and no‐till Alfisols of central Ohio

No‐till (NT) farming can restore the soil organic carbon (SOC) pool of agricultural soils, but the SOC pool size and retention rate can vary with soil type and duration of NT. Therefore, the objectives of this study were to determine the effects of NT and soil drainage characteristics on SOC accumulation across a series of NT fields on Alfisols in Ohio, USA. Sites under NT for 9 (NT9), 13 (NT13), 36 (NT36), 48 (NT48) and 49 (NT49) years were selected for the study. Soil was somewhat poorly drained at the NT48 site but moderately well drained at the other sites. The NT48 and NT49 on‐station sites were under continuous corn (Zea mays), while the other sites were farmers' fields in a corn–soybean (Glycine max) rotation. At each location, the SOC pool (0–30 cm) in the NT field was compared to that of an adjacent plough‐till (PT) and woodlot (WL). At the NT36, NT48 and NT49 sites, the retention rate of corn‐derived C was determined using stable C isotope (¹³C) techniques. In the 0‐ to 10‐cm soil layer, SOC concentration was significantly larger under NT than PT, but a tillage effect was rarely detected below that depth. Across sites, the SOC pool in that layer averaged 36.4, 20 and 40.8 Mg C/ha at the NT, PT and WL sites, respectively. For the 0‐ to 30‐cm layer, the SOC pool for NT (83.4 Mg C/ha) was still 57% greater than under PT. However, there was no consistent trend in the SOC pool with NT duration probably due to the legacy of past management practices and SOC content differences that may have existed among the study sites prior to their conversion to NT. The retention rate of corn‐derived C was 524, 263 and 203 kg C/ha/yr at the NT36, NT48 and NT49 sites. In contrast, the retention rate of corn‐C under PT averaged 25 and 153 kg C/ha/yr at the NT49 (moderately well‐drained) and NT48 (somewhat poorly drained) sites, respectively. The conversion from PT to NT resulted in greater retention of corn‐derived C. Thus, adoption of NT would be beneficial to SOC sequestration in agricultural soils of the region.