Southwestern Japan Research Articles

Provenance of granitic gravestones in graveyard of feudal lords evaluated by multiple non-destructive rock analyses

• The Yamauchi clan gravestones were sourced from southwestern Kochi Prefecture, Japan. • Magnetic susceptibility is a handy indicator, but not enough to identify the origin. • Fraction and grain size of colored minerals are useful for determining provenance. Magnificent graveyards were constructed for feudal lords during the Edo period throughout Japan. The large gravestones of feudal lords, which measured up to several meters high, reflected the political and economic status of the people commemorated at these sites. While the locations of the quarries and the methods used to transport the stones that were used for gravestones also provide clues about the culture of the time, few documents describing the origin of the stones remain. There are several granite gravestones of feudal lords of the Yamauchi clan in Kochi Prefecture in southwestern Japan. However, there is some debate as to their origin and whether they are made of granite from southwestern Kochi Prefecture or Sanyo granite from areas around the Seto Inland Sea. In this study, we conducted multiple non-destructive rock analyses on the granitic gravestones of feudal lords of the Yamauchi clan to clarify their origin. These analyses included magnetic susceptibility measurements, grain-size analysis of colored minerals, and color measurement of K-feldspar. The results were compared with those for granite obtained from southwestern Kochi Prefecture and Sanyo granite. The K-feldspar in the gravestone was white in color. The magnetic susceptibilities of the granite blocks for the gravestones were similar, and followed a Gaussian distribution. The grain size of colored minerals in the granite followed a log-normal distribution, and the areal fraction and grain size of colored minerals were larger than those in other granites. Similarities in color, magnetic susceptibility, and grain size were observed with granite from southwestern Kochi Prefecture. For Sanyo granite, no granite had features that matched all of the measured characteristics. The results indicate that the granite used for the Yamauchi clan gravestones was most likely sourced from southwestern Kochi Prefecture. Stone structures in Kochi Prefecture that were built in the Middle Ages before the Edo period were previously considered to be derived from Sanyo granite. The results of this study provide important insights into whether the routes used to transport stone materials in Kochi Prefecture changed before the Edo period, and if so, what triggered this change. Further, the origin of medieval stone structures in Kochi Prefecture should be reevaluated.

Nonstructural carbohydrate content in the stubble per unit area regulates grain yield of the second crop in rice ratooning

AbstractRice (Oryza sativa L.) ratooning has attracted attention due to its higher yield potential. In the present study, a field experiment on rice ratooning using two rice genotypes, near isogenic line (NIL)‐GN1ATakanari and Koshihikari, was conducted in 2019 and 2020 in southwestern Japan to obtain direct evidence for the role of stubble nonstructural carbohydrate (NSC) concentration and/or content per unit area on grain yield of the second crop and to determine the effectiveness of a gene producing more spikelets. NIL‐GN1ATakanari is a near isogenic line carrying an allele of GN1A, which is a gene regulating the number of spikelets per unit area derived from an indica cultivar Takanari in the genetic background of a japonica cultivar Koshihikari, and it can produce more spikelets than Koshihikari. NIL‐GN1ATakanari did not produce a higher grain yield of the first crop than Koshihikari in both years because NIL‐GN1ATakanari had more spikelets m−2 but fewer filled spikelets and a lower grain weight. NIL‐GN1ATakanari produced a lower grain yield of the second crop than Koshihikari because NIL‐GN1ATakanari had fewer spikelets m−2 due to the fewer panicles. Also, NIL‐GN1ATakanari had a lower NSC content than Koshihikari due to the lower leaf sheath plus stem weight in the stubble in 2019. Thus, the lower grain yield in the second crop of NIL‐GN1ATakanari may result from the lower NSC content in the stubble. Additionally, the ability to produce more spikelets per unit area of NIL‐GN1ATakanari was not demonstrated in ratoon crop under the condition of low NSC content in the stubble.

Rocky coastal cliffs reinforced by vegetation roots and potential collapse risk caused by sea-level rise

Evaluation of the effect of vegetation roots on the stability of rocky coastal cliffs is necessary to understand geomorphological, environmental and ecological changes in coastlines caused by sea-level rise (SLR). To better understand these topics, coastal cliffs with and without vegetation were investigated. Study cliffs were selected on Taketomi-jima Island and Kuro-shima Island, both in Okinawa, southwestern Japan, because their environmental settings are similar except for the vegetation cover: the islands are only 10 km away from each other and comprise uplifted coral limestone, with an elevation below 5 m. Pandanus odoratissimus (PO) covers the seaward edge of the top surface of the coastal cliffs in Taketomi-jima but is absent in Kuro-shima. Field investigations were conducted on both islands to map the distribution of blocks with the dimension of one side exceeding 1 m to obtain the parameters required for stability analysis. The results indicate that the actual coastal cliff elevation is higher in Taketomi-jima than that in Kuro-shima by approximately 1 m, which results in the presence of PO on the seaward edge of the coastal cliffs in Taketomi-jima and its absence in Kuro-shima. The PO root system likely reinforces the cliffs in Taketomi-jima because the stability analysis results revealed that these cliffs are unstable in terms of their dimensions. Therefore, the possible disappearance of PO in Taketomi-jima caused by an SLR of 1 m in the following several decades or hundred years can increase the apparent frequency of cliff collapses by approximately tenfold.

Ambient noise tomography for a high-resolution 3D S-wave velocity model of the Kinki Region, Southwestern Japan, using dense seismic array data

Research interest in the Kinki region, southwestern Japan, has been aroused by the frequent occurrence of microearthquake activity that do not always coincide with documented active fault locations. Previous studies in the Kinki region focused mainly on deep, large-scale structures and could not efficiently resolve fine-scale (~ 10 km) shallow crustal structures. Hence, characterization of the upper crustal structure of this region at an improved spatial resolution is required. From the cross-correlation of the vertical components of the ambient seismic noise data recorded by a densely distributed seismic array, we estimated Rayleigh wave phase velocities using a frequency domain method. Then, we applied a direct surface wave tomographic method for the measured phase velocity dispersion data to obtain a 3D S-wave velocity model of the Kinki region. The estimated velocity model reveals a NE–SW trending low-velocity structure coinciding with the Niigata–Kobe Tectonic Zone (NKTZ) and the active Biwako-seigan Fault Zone (BSFZ). Also, we identified fine-scale low-velocity structures coinciding with known active faults on the eastern side of the NKTZ, as well as sets of low-velocity structures across the Tanba region. Furthermore, sedimentary basins manifest as low-velocity zones extending to depths ranging from ~ 1.5 to 2 km, correlating with those reported in previous studies. Our results therefore contribute towards fundamental understanding of earthquake faulting as well as tectonic boundary and will be useful for hazard assessment and disaster mitigation.Graphical abstract

Hydrological evaluation of radar and satellite gauge-merged precipitation datasets using the SWAT model: Case of the Terauchi catchment in Japan

Study regionThe Terauchi catchment, southwestern Japan Study focusThis paper evaluates two gauge-merged precipitation datasets derived from weather radars (R/A) and satellites (GsMAP_G) based on their capability to improve streamflow simulation using the Soil and Water Assessment Tool (SWAT) model. A third dataset includes measurements from local rain gauges used for producing the R/A database but not the GsMAP_G product was prepared for comparison reasons. The R/A and GsMAP_G data were first compared to gauge observations. The performance and prediction uncertainty of the SWAT model forced by the evaluated datasets were subsequently quantified and compared. New hydrological insights for the regionThe R/A dataset overestimated the precipitation, while the GsMAP_G underestimated it. After calibration, the R/A performed best (NSE = 88–91%), followed by the Gauge (NSE = 84%) and GsMAP_G (NSE = 54%) scenarios. The R/A product improved the overall simulation performance by 6.50% and 62.40% in terms of NSE and absolute percent bias compared to the Gauge model. The performance of the evaluated datasets varied depending on streamflow occurrence exceedance probability (OEP). The R/A dataset improved the simulation of extremely high (OEP < 1%) and low (OEP > 60%) streamflow events as it resulted in the lowest simulation biases and errors. The current investigation suggests the use of the R/A product for improving the simulation of daily streamflow, including hydro-climatic extremes.

Extremely Stochastic Connectivity of Island Mangroves

Studies of mangrove population connectivity have focused primarily on global to regional scales and have suggested potential for long-distance connectivity, with archipelagos serving as stepping stones for trans-oceanic dispersal. However, the contribution of propagule dispersal to connectivity is still largely unknown, especially at local-scale. Identifying fine-scale propagule dispersal patterns unique to individual island systems is important to understand their contribution to global species distributions, and to select appropriate sizes and locations for mangrove conservation in archipelagos. Using population genetic methods and a release-recapture method employing GPS drifting buoys, we investigated the spatiotemporal scale of propagule dispersal of Rhizophora stylosa, one of the widely distributed mangrove species in the Indo-West Pacific. This study sought to quantify intra- and inter-island connectivity and to assess their contributions to oceanic scale dispersal of R. stylosa from the Ryukyu Archipelago, which spans over 545 km in southwestern Japan. Using 7 microsatellite markers, we tested 354 samples collected from 16 fringing populations on 4 islands. We identified 3 genetic populations, indicating distinct genetic structures comprising 3 distinguishable bioregions (genetic clusters). The western end of the archipelago receives relatively frequent migration (m &amp;gt; 0.1), but is genetically isolated from other sites. Based on genetic migration rates, we found that the central area of the archipelago serves as a stepping stone for southwestward, but not northeastward dispersal. On the other hand, with in-situ drifting buoys, we did not confirm prevailing dispersal directionality within the archipelago, instead confirming local eddies. Some buoys trapped in those eddies demonstrated potential for successful beaching from another island. A large portion of buoys were carried predominantly northeastward by the Kuroshio Current and drifted away from the coastal areas into the Pacific, contrary to local migrations. We found that the spatiotemporal scale of propagule dispersal is limited by the distance between islands (&amp;lt; 200km), propagule viability duration, and fecundity. Over all, recruitment does not occur frequently enough to unify the genetic structure in the archipelago, and the Ryukyu Archipelago is isolated in the center of the global mangrove distribution.

Three new species of Eimeria (Apicomplexa: Eimeriidae) from the Amami rabbit, Pentalagus furnessi (Mammalia: Leporidae).

The Amami rabbit, Pentalagus furnessi (Mammalia: Lagomorpha: Leporidae), is a relict and endangered species endemic to the Amami-Oshima and Tokunoshima Islands, located in southwestern Japan. Here, we described three new species of Eimeria (Apicomplexa: Eimeriidae) parasites detected from fecal samples of wild Amami rabbits. Eimeria furnessi n. sp., recorded in 21 (58.3%) samples, has ellipsoidal oocysts with two walls and micropyle, 26.0 × 16.6 μm, and elongate-ovoidal sporocysts, 13.1 × 6.3 μm, with Stieda body. Eimeria hilleri n. sp., recorded in 9 (25.0%) samples, has ellipsoidal oocysts with two walls and micropyle, 34.7 × 21.4 μm, and elongate-fusiform to elongate-ovoidal sporocysts, 15.7 × 8.3 μm, with Stieda and substieda bodies. Eimeria sagentae n. sp., recorded in 13 (36.1%) samples, has ellipsoidal oocysts with two walls and micropyle, 20.9 × 14.5 μm, and elongate-ovoidal sporocysts, 10.4 × 5.0 μm, with Stieda body. The three new species can be distinguished by the size and color of their oocysts. Further studies related to the pathogenicity of these parasites can improve the breeding and propagation procedures of the Amami rabbit.

A new species of the flat bug genus Aneurus from Japan (Hemiptera: Heteroptera: Aradidae).

A new aneurine flat bug species, Aneurus (Aneurodes) taterasanus sp. nov. (Hemiptera: Heteroptera: Aradidae), is described from western and southwestern Japan, as the fifth species of the subgenus Aneurodes Heiss, 1998, and the first record of the subgenus from the country. The structure of the phallus of this new species with the endosoma everted and inflated is documented in detail for the first time in the subfamily Aneurinae. A key to species of the subgenus Aneurodes and another one to species of the genera Aneurus Curtis, 1825 and Paraneurus Jacobs, 1986 occurring in Japan are provided.

Cabotegravir, the Long-Acting Integrase Strand Transfer Inhibitor, Potently Inhibits Human T-Cell Lymphotropic Virus Type 1 Transmission in vitro.

Human T-cell lymphotropic virus type 1 (HTLV-1) is a deltaretrovirus most prevalent in southwestern Japan, sub-Saharan Africa, Australia, South America, and the Caribbean. Latest figures approximate 10 million people worldwide to be infected with HTLV-1. This is likely a significant underestimation due to lack of screening in endemic areas and absence of seroconversion symptoms. The two primary diseases associated with HTLV-1 infection are adult T cell leukaemia-lymphoma, a malignant and, sometimes, aggressive cancer; and HTLV-1 associated myelopathy/tropical spastic paraparesis, a debilitating neurological degenerative disease. Unfortunately, despite the poor prognosis, there is currently no effective treatment for HTLV-1 infection. We previously showed that integrase strand transfer inhibitors (INSTIs) clinically used for human immunodeficiency virus type 1 (HIV-1) prophylaxis and treatment are also effective against HTLV-1 transmission in vitro. In 2021 a new INSTI, cabotegravir, was approved by the FDA for HIV-1 treatment. We thus set out to evaluate its efficacy against HTLV-1 infection in vitro. Strand transfer assays performed using recombinant HTLV-1 integrase treated with increasing concentrations of cabotegravir, effectively inhibited strand transfer activity, displaying an IC50 of 77.8 ± 22.4 nM. Furthermore, cabotegravir blocked HTLV-1 transmission in tissue culture; we determined an EC50 of 0.56 ± 0.26 nM, similar to bictegravir. Alu-PCR confirmed the block in integration. Thus, there are four INSTIs and one reverse transcriptase inhibitor approved by the FDA for HIV-1 treatment, that potently block HTLV-1 infection in vitro. This should strongly encourage the establishment of a new standard of HTLV-1 treatment – particularly for pre-exposure prophylaxis and prevention of mother-to-child transmission.

Is the Long-Term Probability of the Occurrence of Large Earthquakes along the Nankai Trough Inflated?—Scientific Review

Abstract The Earthquake Research Committee (ERC), the Headquarters for Earthquake Research Promotion, Japan, issued a new report on long-term evaluation of the occurrence of large earthquakes along the Nankai trough, southwestern Japan, in 2013, which was made along the line of the revision of national earthquake counter measures according to the 2011 Great Eastern Japan Earthquake Disaster. The central issue was the 30-yr probability, but the method to estimate probability was not changed from the previous one issued in 2001 based on the time-predictable model, which led to a 60%–70% chance of M ≥ 8 event during the coming 30 yr. However, there are several drawbacks in this evaluation such as neglect of errors in uplift data, inconsistency between uplift rate and geodetic and geomorphological data, mechanical interpretation of time-predictable model, and contradiction between the assumptions in Brownian passage time model and time-predictable model. Because ERC calculates probability with average recurrence intervals for other subduction and active fault zones, the same scheme should be adopted to the Nankai trough.

Genetic Diversity and Structure of Quercus hondae, a Rare Evergreen Oak Species in Southwestern Japan

Conservation of rare species is essential for maintaining ecosystem function. Quercus hondae is a rare evergreen oak species (Cyclobalanopsis) endemic to Japan. This species is found in several locations in Southwestern Japan; small populations remain in the tutelary forests of the Japanese shrine. To evaluate the genetic diversity and phylogeographic structure of this rare species, 11 microsatellite loci and chloroplast DNA sequences are analyzed for 12 populations of Q. hondae and 8 populations of the more widespread congeneric species, Q. glauca. It is found that heterozygosity at both the population and species level is substantially lower in Q. hondae than in Q. glauca. Genetic differentiation among populations of Q. hondae was high, in contrast to Q. glauca, in which populations exhibit largely insignificant differentiation. STRUCTURE analysis shows that at K = 7, the clusters largely corresponded to major predefined populations. This study suggests that there is little gene flow among extant Q. hondae populations and that Q. hondae is genetically differentiated due to the greater effect of genetic drift in small populations. This pattern is in sharp contrast to that of a more common congeneric species, which will be an important consideration in the conservation of Q. hondae.

Survival and growth of Japanese cedar (Cryptomeria japonica) planted in tree shelters to prevent deer browsing: a case study in southwestern Japan

ABSTRACT Tree shelters are used in forestry to prevent large herbivores from browsing on young trees. Although tree shelters can generally prevent browsing damage while the young trees are within the tree shelters, they have been observed to fail in some cases. In this study, to clarify the protective capacity of tree shelters against damage due to deer browsing, the condition of tree shelters on planted Japanese cedar (Cryptomeria japonica) seedlings 2 to 7 years after installation was investigated at 42 sites in southwestern Japan where the density of sika deer (Cervus nippon) is high. The results showed that tree shelters failed for three reasons. Firstly, the shelter had collapsed or incline and could no longer protect the saplings within. Secondly, the saplings in the shelters died relatively shortly after they were planted. Thirdly, and possibly most importantly, the saplings are browsed upon by deer after they extended beyond the top of the shelter. Since there was no correlation between the damage rate and the number of years after planting, it is likely that the damage occurred immediately after the young trees protruded form the shelter. Shelters with a height of only 140 cm, which are widely used in Japan, may be too short to completely prevent herbivory damage by deer.

Seasonal habitat use by warmwater fishes in a braided river, southwestern Japan: effects of spatiotemporal thermal heterogeneity

Seasonal habitat use by warmwater fishes in a braided river, southwestern Japan: effects of spatiotemporal thermal heterogeneity

Age, growth and reproductive biology of a widespread coral reef fish, yellowfin goatfish Mulloidichthys vanicolensis (Valenciennes, 1831).

Yellowfin goatfish Mulloidichthys vanicolensis (Valenciennes, 1831) is a widely distributed commercial fish in the Indo-Pacific. The authors examined the age, growth, sexual maturity and spawning season of M. vanicolensis around Okinawa Island, southwestern Japan, based on sectioned otolith and gonadal histology. Monthly changes in the appearance of an opaque edge indicate the annual formation of otolith bands. This fish shows sexual size dimorphism due to the faster growth and larger size of females compared to males. The von Bertalanffy growth functions were Lt =31.0{1-exp(-0.39(t + 1.62))} for females and Lt =28.3{1-exp(-0.42(t + 1.45))} for males. This species has a short life span, with a maximum age of 7.75 years, and reaches maturity in its first year of life. Observed fork lengths at 50% maturity were 19.4cm for female and 16.2cm for male. The main spawning season occurs from May to October. The authors compared their findings with those of previous studies on the life-history characteristics of M. vanicolensis. Spawning season, growth and maturity size differed from those found in previous studies in areas with genetic continuity. Differences in life-history traits between genetically continuous populations suggest a high degree of environmental adaptability for this species, which may be one of the reasons for its widespread distribution.

A synthetic model of Palaeolithic seafaring in the Ryukyu Islands, southwestern Japan

ABSTRACTThe rise of water transport technology enabled early modern humans to expand their habitable territory to insular environments. However, apart from intensive discussion for Wallacea, developmental process and regional variation of Palaeolithic seafaring remain unclear. To contribute this issue, the author presents a synthetic model for Palaeolithic seafaring in another region of the western Pacific, the Ryukyu Islands (Ryukyus). Here, some islands were more than 100 km away and invisible beyond the horizon, and one of the world’s strongest ocean currents intervened the seaways. Despite these challenging situations, Palaeolithic sites appeared throughout much of the 1,200 km chain of the islands ~35,000–30,000 years ago. By integrating currently available information from archaeology, skeletal morphology, genetics, palaeogeography, oceanography and our own experimental voyage project, the author discusses probable migration routes, possible watercrafts, preparation and strategy needed for successful maritime migrations, and other issues relevant to deeper understanding of the origins and development of human maritime activities.

Complementary distribution of non-native white-spotted charr and native red-spotted masu salmon in Shikoku Island, southwestern Japan: a consequence of interspecific interactions?

Complementary distribution of non-native white-spotted charr and native red-spotted masu salmon in Shikoku Island, southwestern Japan: a consequence of interspecific interactions?

Diversity and distribution of climbing plants under different anthropogenic disturbance regimes in a forest–orchard mosaic landscape in southwestern Japan

Diversity and distribution of climbing plants under different anthropogenic disturbance regimes in a forest–orchard mosaic landscape in southwestern Japan

A possible linkage of Eurasian heat wave and East Asian heavy rainfall in Relation to the Rapid Arctic warming

In June–July 2020 two remarkable weather events occurred in northern Eurasia. One is a severe heat wave that produced a record-breaking temperature of 38 °C at Verkhoyansk, eastern Siberia on 20 June. The other one is heavy rainfall events observed in East Asia (southern China and southwestern Japan) in early July, causing severe floods that brought about considerable damage to infrastructure and the economy, as well as the loss of human lives. Despite the accumulated evidence of stronger and more extreme heat waves and heavy rainfall as a result of global warming, little is known about the linkage between these phenomena. Given that the Arctic is warming twice as fast as the global mean, Arctic warming might be enhancing the increase of heavy rainfall events in East Asia.Here, we investigated the relationship between the Siberian heat wave and the East Asian heavy rainfall that occurred summer in 2020. An empirical orthogonal function (EOF) analysis applied to atmospheric reanalysis data of 1958–2020 period captures dominant summer circulation patterns reflecting atmospheric internal variability and externally forced anomalies. On the basis of these EOF patterns, operational forecasts of summer 2020 using the global model from the Japan Meteorological Agency (JMA) and a global climate model experiment based on 2-K warming future projection are utilized to examine roles of the internal variability and external forcing, respectively. Consistent results between them reveal that development of the blocking high over eastern Siberia has certain impacts on rainfall anomalies over East Asia. By a statistical technique applied to the ensemble forecast data, prediction of the East Asian precipitation is improved by 10–20% of its amplitude.Our research demonstrates possibility that East Asian rainfall is being enhanced by high-latitude atmospheric circulations due to the Arctic warming even in the current climate in which the tropical warming is not yet severe. Suggestions are given that continued Arctic warming and a future increase of tropical warming will lead to increases of the frequency and severity of heavy rainfall events in East Asia.

River Stage Modeling with a Deep Neural Network Using Long-Term Rainfall Time Series as Input Data: Application to the Shimanto-River Watershed

The increasing frequency of devastating floods from heavy rainfall—associated with climate change—has made river stage prediction more important. For steep, forest-covered mountainous watersheds, deep-learning models may improve prediction of river stages from rainfall. Here we use the framework of multilayer perceptron (MLP) neural networks to develop such a river stage model. The MLP is constructed for the Shimanto river, which lies in southwestern Japan under a mild, rain-heavy climate. Our input for stage estimation, as well as prediction, is a long-term rainfall time series. With a one-year time series of rainfall, the model estimates the stage with RMSE less than 67 cm for about 10 m of stage peaks, as well as accurately simulating stage-time fluctuations. Furthermore, the forecast model can predict the stage without rainfall forecasts up to three hours ahead. To estimate the base flow stages as well as flood peaks with high precision, we found that the rainfall time series should be at least one year. This indicates that the use of a long rainfall time series enables one to model the contributions of ground water and evaporation. Given that the delay between the arrival time of rainfall at a rain-gauge to the outlet change is well-simulated, the physical concepts of runoff appear to be soundly embedded in the MLP.

Pollination efficiency of bumblebee, honeybee, and hawkmoth in kabocha squash, Cucurbita maxima, production in Kagoshima, Japan

Kabocha squash, Cucurbita maxima Duchesne, in delayed-start culture is one of the major cultivation systems in southwestern Japan. Honeybee introduction or hand-pollination has been practiced in this crop system, but the species composition, abundance, and pollination efficiency of major pollinators remain unclear. In the current study, we investigated which insect(s) accomplish pollination of kabocha squash. Among the total visitations to female flowers, honeybees, mostly Apis mellifera L. (Hymenoptera: Apidae), dominated at 94.4% and 85.3% at the experimental field in 2019 and 2020, respectively, followed by the bumblebee Bombus diversus diversus Smith (Hymenoptera: Apidae) and the hummingbird hawkmoth Macroglossum pyrrhosticta Butler (Lepidoptera: Sphingidae). The number of pollen grains on the body surface of B. diversus diversus individuals was significantly greater than that on honeybees, such that a single visit by B. diversus diversus deposited 5–6 times more pollen grains on a stigma than a honeybee visit, meaning that the bumblebee is a more efficient pollinator at the individual level. However, visitations by numerous honeybees compensated for their lower individual efficiency and resulted in fruit set. In addition, we report for the first time that a lepidopteran can pollinate squash: our data indicate that pollen grains deposited by several visits of M. pyrrhosticta were likely to exceed the estimated minimum number of pollen grains required for fruit set. Our survey at the experimental field and at three private farms revealed that far more pollen than is required for fruit set was deposited on the stigmas by wild pollinators and wintering honeybees. These findings indicate that kabocha squash production in delayed-start culture in this region is practicable without pollination enhancement effort, such as honeybee introduction or hand-pollination.