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Nakayama T.,Japan National Agricultural Research Center | Maoka T.,Japan National Agricultural Research Center | Hataya T.,Hokkaido University | Shimizu M.,Hokkaido Prefectural Tokachi Agricultural Experiment Station | And 3 more authors.
American Journal of Potato Research | Year: 2010

Spraing (brown rings or arcs) of potato caused by Potato mop-top virus (PMTV) occurred in a field of Tokachi, Hokkaido, Japan in 2005. To monitor the expansion of spraing-affected areas, we developed a soil diagnostic method that consisted of a bioassay using tomato as bait plant to trap the vector of PMTV, Spongospora subterranea, the causal agent of powdery scab of potatoes, followed by reverse transcription-polymerase chain reaction-microplate hybridization (RT-PCR-MPH) to detect the virus from roots of bait plants. After incubation of tomato seedlings grown with their roots immersed in a soil suspension at 18°C for 9 days, total RNA extracted from bait roots was analyzed by RT-PCR-MPH using PMTV-specific primers and a digoxigenin (DIG)-labeled probe. Soil diagnosis using the present method in an infested area revealed 137 of 224 fields (61.2%) were infested by PMTV although tubers harvested from only one of these fields had spraing. © 2010 Potato Association of America. Source


Oyoo M.E.,University of Tsukuba | Benitez E.R.,Japan National Agriculture and Food Research Organization | Kurosaki H.,Hokkaido Prefectural Kitami Agricultural Experiment Station | Ohnishi S.,Hokkaido Central Agricultural Experiment Station | And 6 more authors.
Crop Science | Year: 2011

In soybean [Glycine max (L.) Merr.], the dominant allele of the T locus for tawny pubescence is associated with chilling tolerance and is useful for breeding for chilling tolerance. Yellow hilum cultivars with the dominant I allele are preferred in Japan because of a better external appearance. However, the II TT allelic combination darkens the entire seed coat and degrades the external appearance. This study was conducted to investigate the genetic basis of seed coat discoloration using DNA markers. F2 populations derived from crosses between soybean breeding lines 0518BW-8 with slight discoloration and 0734BW-1 with severe discoloration were grown at Memuro in 2003 and Kunneppu in 2007. Seed coat discoloration was measured by the L* value with a two-dimensional colorimeter. A total of 104 simple sequence repeat markers were classified into 20 linkage groups (LGs) spanning 1025 cM in 2003 and 19 LGs spanning 789 cM in 2007. A quantitative trait locus (QTL), discol1, was identified by composite interval mapping in LG A2 (chromosome 8) across years and locations. It had an LOD score of 5.58 explaining 22.0% of phenotypic variance in 2003 and a LOD score of 5.62 explaining 20.2% of variance in 2007. The allele from 0518BW-8 increased the L* value at the QTL. Position of discol1 was close to the I locus corresponding to the chalcone synthase (CHS) multigene family cluster. No sequence differences were observed between the two lines in nucleotide sequences of CHS1 and CHS3 genes and the intergenic region between CHS1 and CHS3. © Crop Science Society of America. Source


Ohnishi S.,Hokkaido Prefectural Tokachi Agricultural Experiment Station | Miyoshi T.,Hokkaido Prefectural Tokachi Agricultural Experiment Station | Shirai S.,Hokkaido Prefectural Tokachi Agricultural Experiment Station
Environmental and Experimental Botany | Year: 2010

Pod set, a critical process for legume crop productivity, is sensitive to environmental stress such as low or high temperature or drought. At higher latitudes, pod set at low temperatures is one of the most important processes for efficient soybean production. The present study was carried out to determine which flower developmental stage was most sensitive to low temperature and how low temperature interrupts the pod setting process. Soybean flowers at various developmental stages were subjected to low temperatures, and the percentage elongation of pods was subsequently measured. Two low temperature-sensitive stages were found. The first was an early developmental stage approximately 12.5 days before the anthesis of individual flowers. The second stage occurred 3-4 days before anthesis. An investigation of the pollen grain number on stigma suggests that insufficient pollination causes low pod set under low temperature stress at both temperature-sensitive stages. Tetrad-shaped abnormal pollen grains were observed when flowers were subjected to low temperature at the first sensitive stage; thus, this stage might be the tetrad stage or the stage prior to tetrad formation. Furthermore, at the first sensitive stage, pollen development deficiency was one of the causes of poor pod set under low temperature conditions. © 2010 Elsevier B.V. All rights reserved. Source

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