키다리병 내성벼의 생리·생화학적 특성 연구를 알아보기 위해 남평벼와 호품벼를 비교하여 실시한 실험결과는 다음과 같다. 1. 키다리병 발병률은 품종에 관계없이 병원균 포자의 농도,노출시간에 비례하여 증가하며 특히 감수성 품종인 호품벼는그 증가 속도가 더욱 심함을 알 수 있었고 이들 감수성 품종들은 염수선을 통한 종자정선이 키다리병 예방에 중요한 역할을 한다. 2. 키다리병 감염조건에서 남평벼가 호품벼에 비해 체내 전분 및 단백질 감소 정도가 더 작았으며 α-amylase, CAT,SOD 항산화 효소 활성은 다소 높게 유지되었다. 3. 키다리병 감염조건에서 SOD를 제외한 CAT, POD, APX유전자들은 남평벼가 호품벼에 비해 모두 2 ~ 3배 이상의 강한 발현증가를 보인 반면 호품벼에서 GA positive gene인Gα(D1), GID2의 발현이 높은 반면 GA deactivating gene인EUI의 발현은 남평보다 낮은 것으로 나타났다.

벼 키다리병에 감염된 농백과 운봉산종자를 물못자리에서 육묘하여 못자리도장묘와 건전묘를 구분, 이앙하였다. 못자리도장묘는 대부분의 잎이 단시일안에 고사하였으나 남은 줄기에서는 분생포자의 형성이 많았다. 이보다 먼저 실시한 실내시험에 운봉산종자는 농백은 의 종자감염율을 나타냈다. 한편, 못자리에서 건전하게 보였던 묘에서는 이앙후 약 2주되는 6월중순부터 전형적인 병징을 나타내기 시작하여 1주일후에는 포자형성과 동시에 고사하기 시작하였다. 도장묘의 상태를 완전고사주와 부분고사주로 구분하여 조사한 결과, 완전고사주는 시일이 경과하면서 증가하지만 부분고사주는 줄어 들었다. 또한 완전고사주에서는 흠주수가 증가하고 분생포자형성주는 큰 변동이 없으나 무형성주는 초기에만 존재하였다. 도장묘에서의 분생포자형성높이는 점차 높아지는데 8월초순 운봉산은 포자형성높이가 초장의 약 , 평균높이는 약 , 농백에서는 최고높이 약 , 평균 높이는 전경였다. 결론적으로 못자리에서 도장한 묘는 이앙후 대부분이 곧 고사하지만 육안으로 식별불능의 보균묘가 문제시되며 포장에서 도장하면 1주일 후 에는 분생포자형성이 시작되고 벼알감염의 주전염원은 7월순의 도장묘로 관찰되었다.

본 연구는 황토유황을 활용하여 벼 키다리병 발병을 최소화할 수 있는 최적 종자소독조 건을 선발하기 위해 수행되었다. 키다리병에 이병된 ‘신동진’ 품종 벼 종자를 공시하였고 황토유황 농도, 침지온도, 시간, 온탕여부를 구분하여 실내 및 온실검정을 통해 침지시간은 48시간, 침지농도는 1%로 최적 소독조건을 선발하였다. 그리고 모판과 포장시험을 수행하 여 온탕처리 후 20℃, 1% 황토유황에 48시간 침지 처리구와 30℃, 1% 황토유황에 48시간 단독 침지할 때 가장 효과가 높았다는 것을 확인하였고 위 처리조건으로 소독한 종자가 육 묘, 이앙, 출수기를 거치면서도 100%의 높은 방제효과가 유지되는 것을 확인할 수 있었다. 그러나 20℃에서 1% 황토유황으로 침지한 처리구에서는 포장에서 78.2%의 낮은 방제가를 보였다. 또한, 온탕소독만 수행한 처리구에서도 60℃, 10분간 충실히 수행될 경우 효과적인 벼 키다리병 방제가 가능함을 보여주었지만 온탕처리 후 황토유황으로 추가 침지함으로서 많은 양의 종자를 소독할 때 좀 더 나은 키다리병 방제 효과를 가져다 줄 수 있을 것으로 판단된다. 이상의 결과를 종합하여 볼 때 농가에서 온탕소독기와 종자소독기 둘 중 한가지 만 구비하더라도 황토유황을 이용하여 충분한 소독효과를 낼 수 있기 때문에 현장에서 보 다 쉽게 활용될 수 있을 것으로 판단되며 제조방법이 쉽고 비용이 적게 드는 황토유황의 특성상 농가의 경영비 절감효과도 클 것으로 기대된다.

We investigated the effect of silicate coating of rice seeds on bakanae disease incidence and the quality of seedlings raised in seedling boxes and transplanted into pots. The silicate-coated rice seed (SCS) was prepared as follows. Naturally infested rice seeds not previously subjected to any fungicidal treatment were dressed with a mixture of 25% silicic acid at pH 11 and 300-mesh zeolite powder at a ratio of 50 g dry seed - 9 mL silicic acid - 25 g zeolite powder. The following nursery conditions were provided : Early sowing, dense seeding in a glass house with mulching overnight and no artificial heating, which were the ideal conditions for determining the effect on the seed. The nursery plants were evaluated for Gibberella. fujikuroi infection or to determine the recovery to normal growth of infected nursery plants in the Wagner pot. Seedlings emerged 2-3 days earlier for the SCS than they did for the non-SCS control, while damping-off and bakanae disease incidence were remarkably reduced. Specifically, bakanae disease incidence in the SCS was limited to only 7.8% for 80 days after sowing, as compared to 91.6% of the non-SCS control. For the 45-days-old SCS nursery seedlings, the fresh weight was increased by 11% and was two times heavier, with only mild damage compared to that observed for non-SCS. Even after transplanting, SCS treatment contributed to a lower incidence of further infections and possibly to recovery of the seedlings to normal growth as compared to that observed in symptomatic plants in the pot. The active pathogenic macro-conidia and micro-conidia were considerably lower in the soil, root, and seedling sheath base of the SCS. In particular, the underdeveloped macro-conidia with straight oblong shape without intact septum were isolated in the SCS ; this phenotype is likely to be at a comparative etiological disadvantage when compared to that of typical active macro-conidia, which are slightly sickle-shaped with 3-7 intact septa. A active intact conidia with high inoculum potential were rarely observed in the tissue of the seedlings treated only in the SCS. We propose that promising result was likely achieved via inhibition of the development of intact pathogenic conidia, in concert with the aerobic, acidic conditions induced by the physiochemical characteristics associated with the air porosity of zeolite, alkalinity of silicate and the seed husk as a carbon source. In addition, the resistance of the healthy plants to pathogenic conidia was also important factor.

Bakanae (foolish seedling) disease caused by Gibberella fujikuroi creates serious problems in the foremost rice growing countries. This study was conducted to identify new resistance genetic sources to Bakanae disease. Bioassay showed that 11 varieties including Gwangmyeongbyeo, Hawn, Wonseadaesoo, Erguailai etc. were resistant to bakanae disease among 254 rice germplasm. Mismatch ratio between phenotype on bakanae disease bioassay and allele type of RM9, a SSR marker closely linked the bakanae disease resistant QTL, qBK1, were 38.3%. These results suggest that RM9 might be used for selecting qBK1, but it cannot be used for wide range of rice germplasm. Resistant germplasm in this study might be have resistant genes different from qBK1. The eleven varieties resistant to selected in this study will be used to identify new resistant alleles or genes to improve bakanae disease resistance in rice.

To investigate the effect of soluble silicate zeolite dressing of the rice against bakanae disease, field trial in reclaimed land and in vitro were carried out. The coated rice seeds (SCS) which were dressed with the mixture of 25% silicic acids (binder), and the zeolite (coating powder). In wet direct seeding, uniform scattering of rice seeds on the soil surface and the better seedling establishment were shown in SCS treatment plots. The incidence of bakanae disease began from the mid tillering stage toward the heading stage. Around heading stage, the ratio of infected tillers reached its highest point by 9.9% in non-SCS treatment plots. While, in SCS treatment plots, the ratio of infected tillers was no more than 0.01%. The vitality of the pathogenic fungi of bakanae disease in the SCS and non-SCS samples were assessed. Samples were incubated for one week keeping proper humidity at 30°C after inoculated with panicles of infected rice plants from experimental field plots. In non-SCS treatment, pinkish colonies were formed on the grain surface of panicle of infected plants, and mycelium, macro-conidia and micro-conidia were developed actively inside part of infected grain inoculated. While in SCS treatment, micro-conidia and mycelium were not survived and the growth of macro-conidia, mycelia were greatly inhibited and withered. Based on the results, it is concluded that the environmental friendly control of bakanae disease by use of SCS is possible and soluble silicate can be applied as agents for replacement of seed disinfection.

Bakanae disease is one of the most serious and oldest problems of rice production, which was first described in 1828 in Japan (Ito and Kimura 1931). This disease may infect rice plants from the pre-emergence stage to the mature stage, with severe infection of rice seeds resulting poor germination or withering (Iqbal et al. 2011). Under favorable environmental conditions, infected plants have the capacity to produce numerous conidia that subsequently infect proximate healthy plants, resulting in major yield loss (Ou 1985). One hundred sixty nine NILs, YR28297 (BC6F4) generated by five backcrosses of Shingwang with the genetic background of susceptible japonica variety, Ilpum were used for QTL analysis. Rice bakanae disease pathogen, CF283, was mainly used in this study and inoculation and evaluation of bakanae disease was performed with the method of the large-scale screening method developed by Kim et al. (2014). A major QTL for resistance against bakanae disease on chromosome 1 was identified using SSR marker, RM9, which explaining 65 % of the total phenotype variation. The major QTL designated as qBK1 and mapped to a 4.4 Mbp region between RM24 (19.30 Mb) and RM11295 (23.72 Mb). The results of this study are expected to provide useful information toward developing resistant rice lines to this detrimental fungal disease.

Bakanae disease incidence threat is an increasing trend in the top rice growing countries. Despite it is essential to identify the resistant genes and underlying mechanisms of bakanae disease to develop resistant varieties, there are very limited genetic studies on bakanae disease in rice. The indica rice variety Shingwang was selected as resistant donor to bakanae disease. One hundred sixty nine NILs, YR28297 (BC6F4) generated by five backcrosses of Shingwang with the genetic background of susceptible japonica variety, Ilpum were used for QTL analysis. Rice bakanae disease pathogen, CF283, was mainly used in this study and inoculation and evaluation of bakanae disease was performed with the method of the large-scale screening method developed by Kim et al. (2014). The proportion of healthy plants of Shingwang and Ilpum after inoculation was confirmed using bakanae disease pathogen, CF283. While inoculated Ilpum showed thin and yellowish-green phenotype which is typical symptom of Bakanae disease, Shingwang showed similar healthy phenotype with control plants. A major QTL for resistance against bakanae disease on chromosome 1 was identified using SSR marker, RM9, which explaining 65 % of the total phenotype variation. The major QTL designated as qBK1 and mapped to a 4.4 Mbp region between RM24 (19.30 Mb) and RM11295 (23.72 Mb). The information of qBK1 could be useful for improving rice bakanae disease resistance in marker-assisted breeding.

Bakanae disease of rice, caused by Fusarium moniliforme Sheldon, the imperfect stage of Gibberella fujikuroi, is one of the most important rice diseases worldwide, but no rice variety has been found to be completely resistant to this fungus. Cultivation of resistant cultivars is the most beneficial way of reducing quantitative or qualitative losses to for bakanae disease in rice. To facilitate the study of this disease, accurate and large scale screening methods were developed for the inoculation and evaluation of Bakanae disease. Even and large scale infection was achieved by using F. moniliforme spore in tissue embedding cassette and seedling tray. The efficiency of F. moniliforme infection with the concentration of 1×106 spore/ml caused better distribution (F-value=33.96) than 1×102 (F-value=10.69), and 1×104 spore/ml (F-value=2.63). We established new criteria of healthy and non-healthy plant, and introduced calculation of proportion of healthy plants to meet fast evaluation of resistance level of each variety. The effect of F. moniliforme strains containing different genetic background was also evaluated with rice varieties to figure out the stability of resistance level. GA3 response of rice variety was significantly correlated with bakanae disease, but it did not adequate for direct indicator of bakanae disease resistance. These results indicated that a large scale infection method developed in this study is fast and reproducible, as well as a disease evaluation system provides an accurate measurement of bakanae disease resistance of rice.

Bakanae disease, a typical seed-borne disease of rice, caused by Gibberella fujikuroi which affected rice quality and yields seriously throughout the country. The disease could be transmitted to other healthy plants in heading dates, and the environment-friendly agricultural practices could be one of the reasons for the outbreak of disease because of the chemical-free agriculture. Studies were conducted to investigate the effects of instrument devised to protect the bakanae disease. The newly developed device consists of aquarium heater and oxygen generator. The temperature of water remained stable as 32.6±0.9℃, and it was effectively applied to sterile seeds for high quality seedlings. In the field tests of infected seeds with bakanae disease, the ripened grain ratio decreased in the 30% infected seeds, and the yields of polished rice dropped as 28%. The secondary infection of bakanae disease was effectively prevented with 500 fold fludioxonil treatments just prior to the planting in the field.

2006년도에 생산한 일품벼 종자의 키다리병 이병종자와 건전종자를 사용하여 소독 방법별(관행-프로크로라츠 2,000배액 상온 24시간 침지후 침종 5일, 발아상-프로크로라츠 2,000배액 33℃ 에서 48시간 침지 및 침종, 무처리-상온 6일 침종) 생육 특성과 수량 등을 분석한 결과는 다음과 같다. 키다리병 이병 종자의 소독 방법별 키다리병 발생율은 파종 후 10일째 무처리와 관행은 각각 76.0%, 5.0%였으나 발아 상 33℃ 에서 프로크로라츠 2,000배액에 48시간 동안 소독 시는 발생하지 않았으며, 수확기 때는 발아상 소독시 발병율 3.3%로 관행 9.2%에 비해 낮아 효과적이었다. 수수는 발아상 소독시 30개/주였으나 관행이나 무처리시는 각각 27개, 24개로 적었다. 등숙율은 발아상 소독시 81.3~80.3% 로서 관행 75.4%에 비해 5.9~4.9% 향상 되었고 수량은 512~517kg/1,000m2 로 관행에 비해 6~7% 증수되었다. 키다리병 이병 종자라도 발아상 이용 소독시 키다리병은 건전 종자와 비슷하게 발생하여 매우 효과적인 방법이라 할 수 있겠다.

This study was carried out to compare the growth and yield characteristics between bakanae diseases (Gibberella fujikuroi) infected and normal rice plants. The infected rice seeds, harvested in last year, were disinfected by prochloraz for 48 hours at 33℃ using sprouting machine, 24 hours at room temperature and not disinfected. In the methods of disinfection, it is more effective in disinfected by prochloraz for 48 hours at 33℃ using sprouting machine near to 0% of infection rate, followed by conventional method as 5.0% and 76% in not disinfected rice seeds. In the rice yield components among the disinfection methods, panicles were increased about 11% in the disinfected seeds using sprouting machine for 48 hours compared to conventional method. Ripening grain rate also increased at the disinfected using sprouting machine as 80.3~80.3%, improved more than 4.9~5.9% comparing to the conventional disinfection. From these results, the rice yield was 512~517kg/1,000㎡ at the disinfected using sprouting machine which increased more than 6~7% compared to the conventional disinfection.