In orchards, measuring crown characteristics is essential for monitoring the dynamics of tree growth and optimizing farm management. However, it lacks a rapid and reliable method of extracting the features of trees with an irregular crown shape such as trained peach trees. Here, we propose an efficient method of segmenting the individual trees and measuring the crown width and crown projection area (CPA) of peach trees with time-series information, based on gathered images. The images of peach trees were collected by unmanned aerial vehicles in an orchard in Okayama, Japan, and then the digital surface model was generated by using a Structure from Motion (SfM) and Multi-View Stereo (MVS) based software. After individual trees were identified through the use of an adaptive threshold and marker-controlled watershed segmentation in the digital surface model, the crown widths and CPA were calculated, and the accuracy was evaluated against manual delineation and field measurement, respectively. Taking manual delineation of 12 trees as reference, the root-mean-square errors of the proposed method were 0.08 m (R2 = 0.99) and 0.15 m (R2 = 0.93) for the two orthogonal crown widths, and 3.87 m2 for CPA (R2 = 0.89), while those taking field measurement of 44 trees as reference were 0.47 m (R2 = 0.91), 0.51 m (R2 = 0.74), and 4.96 m2 (R2 = 0.88). The change of growth rate of CPA showed that the peach trees grew faster from May to July than from July to September, with a wide variation in relative growth rates among trees. Not only can this method save labour by replacing field measurement, but also it can allow farmers to monitor the growth of orchard trees dynamically.
Fig mosaic virus (FMV), a negative-strand RNA virus, is recognized as a causal agent of fig mosaic disease. We performed RT-PCR for 14 FMV isolates collected from symptomatic fig plants in Japan and Serbia using primers corresponding to the conserved 13 nt stretches found at the termini of FMV genomic segments. The resulting simultaneous amplification of all FMV genomic segments yielded four previously identified segments of FMV and two novel segments. These novel FMV genomic RNA segments were found in each of the 14 FMV isolates analysed. In Northern blot studies, both the sense and antisense strands of these novel RNA molecules accumulated in FMV-infected fig leaves but not in uninfected fig leaves, confirming that they replicate as FMV genomic segments. Sequence analysis showed that the novel RNA segments are similar, in their structural organization and molecular evolutionary patterns, to those of known FMV genomic RNA segments. Our findings thus indicate that these newly discovered RNA segments are previously unidentified FMV genomic segments, which we have designated RNA5 and RNA6.
We report the impact of radiocesium released by the Fukushima Daiichi nuclear power plant accident on fruit trees in the vicinity. Specifi cally, we discuss our fi ndings related to the absorption and translocation of radiocesium in peach ( Prunus persica L. Batsch) trees because peaches are a major crop in Fukushima Prefecture.At the time of the nuclear accident, the majority of deciduous fruit tree species had no foliage and had not entered the fl owering stage. This was also the case for peach trees, although we confi rmed at harvest time that radiocesium had migrated to new plant parts. One possible explanation for this is that the presence of radiocesium in the new leaves and fruits, which was not present at the time of the nuclear accident, was affected by direct radiocesium deposition on the existing aboveground plant parts and this may have been absorbed by the tree. In the year of the accident, the root uptake of radiocesium deposited on the soil contributed very little to the overall contamination compared with absorption by the trees through the above-ground plant parts. The magnitude of radiocesium translocation from the old to new plant parts was signifi cantly different between the year of the accident and the year after the accident. We report the fi ndings since the Fukushima Daiichi nuclear power plant accident and speculate the pathways of radiocesium entry and release in peach trees.
Following the accident at the Tokyo Electric Power Company, Fukushima Daiichi Nuclear Power Plant (FDNPP), radiocesium ( 134 Cs + 137 Cs) concentrations in deciduous mature fruits were determined in orchards in the northern area of Fukushima Prefecture. At the time of the nuclear accident, most deciduous fruit trees were in the dormant stage prior to bud burst. To evaluate the relationship between radiocesium deposition in the soil and fruit contamination, radiocesium concentrations were measured from the 5-cm topsoil and from six fruit species across 17 orchards in 2011. The vertical distribution of radiocesium in the topsoil (0-30 cm in depth) and its spatial distribution in the 5-cm topsoil underlying the tree canopy of a peach, Prunus persica (L.) Batsh, orchard ("Akatsuki" cultivar) were also investigated. Significant correlations between the radiocesium concentration in the mature fruit and that in the 5-cm topsoil layer were observed for the 17 orchards as well as for the trees of the peach orchard. However, 93% of the 137 Cs found in the 30-cm soil core was retained within the top 3 cm of the soil in the peach orchard. Considering the profile of the root of this deciduous fruit tree, we assumed a negligible level of radiocesium uptake via the roots. However, the possibility of inward migration via the bark was undeniable, because some radiocesium adhered to the tree canopy before bud burst while depositing on the soil surface. Additionally, transfer factors for peach and grape, hybrid of Vitis labrusca L. and Vitis vinifera L., from young, uncontaminated trees cultivated with contaminated soil were lower than those previously reported.Key words: Fukushima Daiichi nuclear accident, inward migration via the bark, radiocesium in fruits, vertical distribution in orchard soil.
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