Bulletin of The Iwate Agricultural Research Center No.3

Occurrence and Control of Chrysanthemum Stunt Disease in Iwate Prefecture Using Stock Plants Selected as Viroid-free
Kazunori KATSUBE, Takehiko KAWAMURA, Manami WATANABE and Teruo SANO

  In 2000, chrysanthemums showing irregular stunting were observed widely in Iwate prefecture. The causal agent of the irregular stunting of chrysanthemum was investigated and practical control was established. Obtained results were as follows:

(1) Low molecular weight viroid-like RNA nucleic acid was detected by return-gel electrophoresis (R-GE) from stunted chrysanthemum collected in Ichinoseki, Mizusawa, Esashi, Shiwa and Ninohe with. From Ichinoseki samples, Chrysanthemum stunt viroid (CSVd) was detected with dot blot hybridization using DIG-labeled complementary RNA probe (DBH). In this hybridization, CSVd was detected even from symptomless plants which were negative for the viroid-like RNA by R-GE. These results indicated that chrysanthemum stunt disease, caused by CSVd, occurred in Iwate prefecture. This is the first report on the detection of CSVd from chrysanthemums cultivated in Iwate prefecture. Cultivars from which CSVd was detected were Benitonbo, Irifune, Shirafune, Haruka, Manzashi and Yayoi.

(2) Tissue blot hybridization (TBH) was easy to perform compared to R-GE and DBH, and sensitive enough to diagnose CSVd in field-growing chrysanthemums.

(3) The chrysanthemum cutting propagated from mother stocks which were negative for CSVd by TBH diagnosis, did not show any stunting symptoms in the next growing season in the field.

(4) These results indicate that TBH is a practical method for screening CSVd-free mother stocks and is available for sustainable chrysanthemum production.

The Occurrence of Bacterial Palea Browning of Rice in Iwate Prefecture and Removal of the Damaged Rice
Kazunori KATSUBE and Shin-ichi TAKEDA

  In the summer of 1994, a disease similar to bacterial palea browning disease occurred widely in rice in Iwate prefecture.

  1.  Bacterial isolates, which formed colonies with yellow pigment, were obtained from affected paleas of rice. Six isolates showed weak pathogenicity to rice by an artificial inoculation at the flowering stage. All isolates obtained were identified to be the pathogen of bacterial palea browning disease through bacteriological studies. Those characteristics indicated that the isolates stood between Pantoea ananas and P.agglomerans. The authors, however, identified the present isolates to be P.ananas.

2.  This bacterial disease was observed in all investigated municipalities of Iwate prefecture. The proportion of diseased paddy fields were 30% to 100% (avg. 75.1%), and had a tendency to be high in area between mountains.

  3.  In Takizawa, Iwate prefecture, rain at the heading time was an important factor in accelerating the disease. A Correlation with the different cultivars was not clear, because all cultivars were diseased insignificantly and similarly.

  4.  The characteristic of brown rice derived from diseased paddies was damaged as rusty and opaque-kernel rice. The damaged rice was removed by filtering it through 1.9mm-mesh size screen.

  This is the first report on the occurrence of bacterial palea browning of rice in Iwate prefecture. If this bacterial disease wrer to occurr widely in a cool district such as our prefecture, we could remove the damaged rice by filtering it through 1.9mm-mesh size screen.

Breeding Experiment on the Development of a Strain of Landrace Pigs
Tetsuo FUJIWARA, Hiroaki ATSUJI, Naoto SATOH, Tsuyoshi WASHIMORI, Hiroshi NISHOJI, Tsutomu ONODERA and Shigeki KOMATSU

  A strain breeding experiment with Landrace pigs has been carried out with closed population of 15 boars and 50 sows from 1993 to 2000 (for seven generation), to improve their meat performance and leg soundness. Meat performance selection was based on dairy gain (DG), back fat thickness (BF) and eye muscle area (EM), by breeding values that were estimated by restricted BLUP for the desired relative genetic gain. Leg soundness selection was based on a leg movement score assigned by observation. In spite of a high ranking meat performance breeding value, an individual that leg soundness score was worse than standard was culled.

 The results were as follows;
1.Meat performance and leg soundness were improved in the desired direction. The genetic gains from the basic to 7th generation were 54.7g(boars) and 56.5g(sows) in DG, -0.65cm(boars) and -0.66cm(sows) in BF1, -0.59cm(boars) and -0.59cm(sows) in BF2, 3.26cm2(boars) and 3.30cm2(sows) in EM, and 0.52points(boars) and 0.55points(sows) in the leg movement score.

2.Heritablity of meat performance traits were as follows; DG 0.41, BF1 0.56, BF2 0.64, EM 0.35. Heritability of leg soundness traits were around 0.2-0.4 . The genetic correlation between meat performance traits and leg movement score was low.

 3.The coefficients of inbreeding and relationship in 7th generation were 5.94% and 24.9%. 13 boars and 38 sows, from 15 and 50 in the base generation contributed to the 7th generation.

 The strain of landrace pigs with high meat production and leg soundness was produced by this experiment.

Effect of a Large Investment of Local Animal Compost in Non-Allophanic Andosol in Southern Iwate Prefecture
Tsuyoshi ONO, Takashi SATOH and Kenya KIKUCHI

  Non-allophanic andosol has strong acidity and low fertility and distributed widely in the south of Iwate prefecture. There are many livestock farms in this area, producing huge amounts of animal dung and urine. Fertilizer elements in livestock manure produced from this area were at a maximum in the manure of hens and decreased in the manure of pigs > cows > pigs with bark. Elementally dense manure was expected to be effective as chemical fertilizers, and weak manure as soil amendment fertilizers. The manure was mixed with non allophanic andosols from non-cultivated forest area in IAJC by the mixing rates of 5, 10 and 20g per 100g dry soil which correspond to 50, 100 and 200Mgha-1 and were incubated at 30C for 4 weeks at upland moisture conditions. 1MKCl extractable NH4+ and NO3- were analyzed weekly and soil diagnosis was done after incubation. Large increases of NH4+ were observed in proportion to the mixing rate of all manure. Most increases were observed in the manure of hens followed by pigs. Bark and cow manure showed lower NH4+ appearances. NO3- occurrences from all types of manures were smaller than NH4+. Soil diagnosis after incubation showed large investment resulted in the amendment of soil acidity and enrichment of nutrients.  Germination of komatsuna-seed was suppressed in the plots over 100Mgha-1 of hen's manure and over 200Mgha-1 of pig's manure, however, cow and bark manure did not show suppression even in 200Mgha-1 plot.

Autmun harvesting Lettuce was cultivated in an upland field at Iwate Agricultural Research Center, where Non Allophanic Andosols invested with 25 and 50Mgha-1 of hen manure and 50 and 100Mgha-1 of pig manure were compared with chemical fertilizer (CF). The total yield order of Lettuce was pig50 = pig100 = hen50 > hen25Mgha-1 >> CF. Thechemical properties of the soil in these plots showed increase in CEC, exchangeable cations and available nitorogen and phosphate. These results strongly suggest that livestock manure produced in the same area is useful for the amending the strong acidity of non allophanic andsol and can also be used as fertilizer. Such usage of organic waste is one way of looking forward to creating less environmental pollution within our environmental capacity.

The Exchangeable Potassium Level in Soil which Enables Paddy Rice Cultivation without Potassium Fertilizer
Yoshinori TAKAHASHI, Teruo SHIMA, Yoshinori TAKAHASHI, Masaki TAKAHASHI and Tsuyoshi ONO
Rice straw contains most of the potassium absorbed by a rice plant. The number of farmers incorporating rice straw in paddy fields at rice harvesting time has increased with the spread in the use of combine-harvester machines. Incorporating the rice straw returns most of its absorbed potassium to paddy soil. Thus, the quantity of soil exchangeable potassium in paddy soil is increasing in Iwate prefecture.

We carried out potassium fertilizer application at different soil exchangeable potassium levels and found that soil exchangeable potassium level which enables paddy rice cultivation without potassium fertilizer is 400mg(K
2O) per 1kg oven-dry soil. Today, more than 20 percent of paddy fields meet the soil exchangeable potassium level in Iwate prefecture. It is very important for cutting fertilizer application costs and for environmental conservation to use nutrients that are accumulated in the soil.
15 years of Change in the Management of Organic Material and Chemical Fertilizer and Chemical Proparties of Paddy Soil in Iwate Prefecture
Masaki TAKAHASHI, Tsuyoshi ONO and Teruo SHIMA
A Basic Survey of the Soil Environment was practiced at 785 points in Iwate prefecture at five-year intervals from 1979 and expired after 20 years on 1998. 15 years trends of management and soil properties at each fixed point was obtained. We arranged 355 survey points in paddy fields for inquiry into the trends in the management of organic matter and fertilizer and the soil chemical properties of soil.

Organic management: The number of farmers who use farmyard manure is decreasing and the number who apply rice straw is increasing. The latter exceeded the former in 4 cycle periods. Although the application rate of farmyard manure for each farmer is increasing, total manure amount put into paddies in Iwate prefecture was decreasing.

Fertilizers: The dosage of N, P, and K elements by chemical fertilizer is decreasing and the dosage of Ca, P, and Si elements as the soil amendment fertilizers is decreasing more significantly.

Soil chemical properties: TC was constant, TN was increasing and C/N ratio was decreasing which seemed to suggest a change in the quality of soil organic matter. As the result, available N tended to increase. Available P and exchangeable K was also increasing, however, the former increase tended to slow down at the 4th interval of the survey. Exchangeable Ca and CEC was increasing and pH was decreasing. Available Si was decreasing.
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