ISSN (Online) 2287-3406 Journal of Life Science 2021 Vol. 31. No. 7. 609~616 DOI : https://doi.org/10.5352/JLS.2021.31.7.609

Evaluation of Bioassay Methods to Assess Bacterial Soft Rot Resistance in Cultivars

Tania Afroz1, Onsook Hur1, Nayoung Ro1, Jae-eun Lee1, Aejin Hwang1, Bichsaem Kim1, Awraris Derbie Assefa1, Ju Hee Rhee1, Jung Sook Sung2, Ho-sun Lee3* and Bum-Soo Hahn1* 1National Agrobiodiversity Center, National Institute of Agricultural Sciences, Rural Development Administration, Jeonju 54874, 2National Institute of Crop Science, Rural Development Administration, Miryang 50424, Korea 3International Technology Cooperation Center, Rural Development Administration, Jeonju 54875, Korea Received April 22, 2021 /Revised July 25, 2021 /Accepted July 27, 2021

Bacterial soft rot, caused by Pectobacterium carotovorum subsp. carotovorum (Pcc), is one of the destruc- tive diseases of radish ( sativus) in Asian countries. The objective of this study was to estab- lish an efficient bioassay method for the evaluation of bacterial soft rot resistance in commercial radish cultivars. First, an efficient bioassay method for examining resistance to bacterial soft rot in commer- cial radish cultivars was investigated. Six commercial radish cultivars were tested under various con- ditions: two temperatures (25℃ and 30℃), three inoculations methods (drenching, spraying, and root dipping), and two growth stages (two- and four-leaf stages). The results suggested that spraying with 1×106 cfu/ml of bacterial inoculums during the four-leaf stage and incubating at 30℃ could be the most efficient screening method for bacterial soft rot resistance in commercial radish cultivars. Second, we investigated the degree of resistance of 41 commercial radish cultivars to five Pcc isolates, namely KACC 10225, KACC 10343, KACC 10421, KACC 10458, and KACC 13953. KACC 10421 had the stron- gest susceptibility in terms of moderately resistant disease response to bacterial soft rot. Out of the 41 radish cultivars, 13 were moderately resistant to this pathogen, whereas 28 were susceptible. The moderately resistant radish cultivars in this investigation could serve as resistance donors in the breed- ing of soft rot resistance or could be used to determine varietal improvement for direct use by breed- ers, scientists, farmers, researchers, and end customers.

Key words : Bacterial soft rot, disease, evaluation, Raphanus sativus, resistance

Introduction ingredient in foodstuffs such as (a traditional fer- mented food), dongchimi, kkakdugi, chonggak kimchi, na- Radish (Raphanus sativus L.) is one of the most popular bak-kimchi, seokppakjji, and pickled radish. Some research root vegetable crops in the Brassicaceae family, and it can indicates that radish can reduce the risk of chronic or life- be grown throughout the year in many parts of the world, threatening illnesses including heart disease, diabetes, and including Asian countries such as China, Japan, and South colon cancer [8, 28]. Korea. According to the Korean Statistical Information Ser- Bacterial soft rot is caused by Pectobacterium carotovorum vice (KOSIS), the area under radish cultivation was about subsp. carotovorum (Pcc). Pcc inflicts serious damage and eco- 71,030 hectares and total production was 4.04 million tons, nomic losses in most vegetable crops, including radish, Chi- with an average productivity of 56.38 tons per hectare in nese cabbage, cabbage, carrot, potato, and all Brassica spp. South Korea [17]. are low in calories and sugar [9, 13, 14, 16, 24, 34]. It is one of the most destructive diseases and high in fiber. In South Korea, radish is an important affecting radish (Raphanus sativus) in China, Japan, and South Korea, where the crop is widely cultivated [5]. Pcc *Corresponding authors produces large amounts of extracellular plant cell wall-de- *Tel : +82-63-238-1118, Fax : +82-63-238-4859 grading enzymes (PCWDE, exoenzymes) including pectate- *E-mail : [email protected] (Ho-sun Lee) *Tel : +82-63-238-4930, Fax : +82-63-238-4859 lyases (Pel), polygalacturonases (Peh), proteases (Prt), and *E-mail : [email protected] (Bum-Soo Hahn) cellulases (Cel), which damage the cell membrane and there- This is an Open-Access article distributed under the terms of by cause leakage of electrolytes, extensive tissue maceration, the Creative Commons Attribution Non-Commercial License rotting, and subsequent plant death [3, 29]. This results in (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction losses in marketable yield in the field and also during transit, in any medium, provided the original work is properly cited. storage, and marketing [4]. 610 생명과학회지 2021, Vol. 31. No. 7

Disease-resistant crops can reduce crop losses with mini- bacterial culture was centrifuged at 4,000 rpm at 4℃ for 10 mum effort by growers in an environmentally safe and cost- min (Labogen, 1248R, South Korea), the supernatant was dis- effective manner. Additionally, disease-resistant crops can carded, and sterile water was added to the pellet and shaken be combined with other control measures to optimize dis- to generate a bacterial suspension. This suspension was di- ease management. Identification of crops and genetic re- luted with water and the optical density at 600 nm (OD600) sources associated with disease resistance requires suitable was measured using a UV spectrophotometer (Optizen Pop, screening techniques, and once these crops and genetic re- Daejeon, Korea). Bacterial density was adjusted to an OD600 sources are discovered, it is necessary to develop effective of 0.1 (1×108 cfu/ml), and the bacterial suspension was di- inoculation methods [15, 30, 33]. Several screening techni- luted (1/10) with sterile water to yield a 1×106 cfu/ml ques for identifying disease resistance in vegetables have suspension. been reported, including needle pricking, dipping, and de- tached leaves [25]; wooden toothpick pricking of stems of Pathogen inoculation and disease monitoring 3-4-week-old seedlings [32]; injection; and overhead spray- One or two seeds of each cultivar were planted in a 50- ing and drop-nozzle spraying of bacterial suspensions on hole seedling tray (width 540 mm × length 280 mm) contain- plants in the field [1, 2]. Several screening methods have ing sterilized soil. After germination, the seedlings were been established for diverse germplasms; identification of thinned to one plant per pot. The pots were maintained in the most effective screening method for a particular patho- a greenhouse with photoperiod for 16 hr at 15-18℃. After gen is crucial for resistance breeding [6]. We established an the development of two leaves (13 days old) or four leaves efficient bioassay method for bacterial soft rot of radish and (20 days old), seedlings were inoculated with Pcc by drench- identified sources of resistance to bacterial soft rot affecting ing, spraying, or root dipping. For drenching, a 10-ml sam- 41 commercial radish cultivars. ple of bacterial inoculum were drenched onto each plant. For spraying, 0.1% Tween 20 was added to the bacterial in- Materials and Methods oculum and shaken to mix well; a 10-ml sample of inoculum was then sprayed onto each plant using a fine atomizer. For Plant materials root dipping, 10 plants were uprooted and dipped into 50 We investigated resistance among 41 commercial radish ml of suspension for 20 min; inoculated plants were replanted cultivars purchased from seed companies in Korea. All ex- in the pot from which they were originally uprooted. After periments were conducted in a greenhouse and growth inoculation, all plants were incubated in a plant growth chamber at the National Agrobiodiversity Center (NAC), chamber at 25 or 30℃ and 80% relative humidity for 12 hr National Institute of Agricultural Sciences, Jeonju, Republic light and 12 hr dark periods. An equal number of plants of Korea. Experiments used seedlings at the two-leaf (13 serving as controls was inoculated with sterilized distilled days old) and four-leaf (20 days old) stages. water. After 5 days, the disease indices (DI; 0–4) of bacterial soft rot were recorded [18] (Fig. 1a–e). The scoring was as Bacterial isolates and inoculum preparation follows: 0 = healthy plant; 1 = chlorosis or rot 1-25%; 2 = We used five Pcc isolates (KACC 10225, KACC 10343, chlorosis or rot 25-50%; 3 = chlorosis or rot 50-75%; 4 = chlo- KACC 10421, KACC 10458, and KACC 13953) from the rosis or rot 75-100% or plant dead. Disease response was Korean Agricultural Culture Collection (KACC) and con- also classified as resistant (R), DI ≤ 1.0; moderately resistant firmed their pathogenicity to radish plants. The bacterial iso- (MR), 1.1 < DI ≤ 2.0; or susceptible (S), DI > 2.0. lates were stored at -70℃. In preparation for experiments, bacteria were spread on nutrient agar (NA; Becton, Dickin- Statistical analysis son, and Co., Sparks, MD) in a Petri dish and incubated for The experiment involved a completely randomized de- 1 day. Next, 5 ml of nutrient broth (NB; Becton, Dickinson, sign (CRD) with three replications: 20 plants per replication and Co.) were added and the cultures were mixed. Bacterial were used for each method. Statistical analysis was per- suspension (2 ml) was inoculated into 200 ml of fresh NB formed by Duncan’s new multiple range test at α = 0.05 us- and cultured at 30℃ with shaking at 200 rpm for 36 hr. The ing R software version 3.1.0 [21]. Journal of Life Science 2021, Vol. 31. No. 7 611

Fig. 1. Disease index (0–4) of radish soft rot. a, DI = 0; b, DI = 1; c, DI = 2; d, DI = 3 and e, DI = 4. Scale bar, 4.8 cm.

Results and Discussion jaealtaimu also had a DI of 4.0 by spraying at 25℃. In con- trast, at the two-leaf stage Gmchorong, and Jeonmuhoomu Effect of temperature, inoculation method, and growth has a DI of 3.8 and 3.77, respectively, by spraying at 30℃. stage on bacterial soft rot DI Environmental factors such as temperature and free mois- To evaluate the bioassay methods, we used six commer- ture affect the development of soft rot disease [20]. High cial radish cultivars (Gangjamoojeok [SAM1], Gmchorong temperature plays an important role in soft rot infection and [SAK1], Seonbongaltari [S1], Worldminong [N2], Jeonmu- symptom development, and we found that 30℃ resulted in hoomu [K1], and Heongjaealtaimu [NS1]); two temperatures the highest DI (4) in each radish cultivar. Raju et al. reported (25 and 30℃); three inoculation methods (drenching, spray- that soft rot occurred at 20-35℃ and was most severe at 35℃ ing, and root dipping); and two growth stages (two- and and 100% relative humidity [22]. Farrar et al. reported that four-leaf stages). Table 1 and Fig. 2 present the effects of 30-37℃ was optimum for soft rot development in various temperature, inoculation method, and growth stage on the vegetable species [12]. However, Lee et al. found that a tem- bacterial soft rot DI. Of the six cultivars, at the four-leaf stage perature of 25℃ promotes bacterial soft rot of radish [18], Gangjamoojeok had the lowest DI of 3.8 and the others had and Walker reported that bacterial soft rot caused the great- a DI of 4.0 by spraying at 30℃; Jeonmuhoomu and Heong- est damage at high humidity and 26℃ [31]. We found that

A

B

Fig. 2. Radish (Raphanus sativus) cultivar, Gmchorong (SAM1) showing soft rot symptoms at 25℃ (A) and 30°C (B) after inoculation by the drenching (a, d), spraying (b, e), and root-dipping (c, f) methods. Spraying and 30℃ resulted in the highest DI (DI 4). For drenching, a 10-ml sample of bacterial inoculum was drenched onto each plant; for spraying, a 10-ml sample of inoculum was sprayed onto each plant using a fine atomizer; for root dipping, each plant was dipped into a 50-ml sample of bacterial suspension for 20 min. 612 생명과학회지 2021, Vol. 31. No. 7

Table 1. Resistance of six commercial cultivars to Pectobacterium carotovorum subsp. carotovorum KACC 10421 by growth stage, in- oculation method, and temperature Incubation temperature Cultivar Growth stagex Inoculation methods 25℃ 30℃ Drenching 2.5 dy 2.6 d 2 leaf Spraying 2.7 cd 3.6 ab Dipping 2.3 d 2.7 cd Gangjamoojeok (SAM1) Drenching 3.2 bc 3.4 ab 4 leaf Spraying 3.1 bc 3.9 a Dipping 2.7 cd 3.3 b Drenching 2.4 e 3.0 bc 2 leaf Spraying 3.0 bc 3.8 a Dipping 2.4 e 2.9 bcd Gmchorong (SAK1) Drenching 2.7 cde 3.8 a 4 leaf Spraying 3.1 bc 4.0 a Dipping 2.5 de 3.3 b Drenching 2.6 f 2.7 def 2 leaf Spraying 2.8 def 3.1 cd Dipping 2.3 f 2.5 f Seonbongaltari (S1) Drenching 2.6 ef 3.3 bc 4 leaf Spraying 3.6 ab 4.0 a Dipping 2.6 ef 3.1 cde Drenching 2.6 f 2.7 def 2 leaf Spraying 2.8 def 3.1 cd Dipping 2.3 f 2.5 f Worldminong (N2) Drenching 2.6 ef 3.3 bc 4 leaf Spraying 3.6 ab 4.0 a Dipping 2.6 ef 3.1 cde Drenching 2.6 cd 3.1 b 2 leaf Spraying 3.3 b 3.8 a Dipping 2.3 d 2.9 bc Jeonmuhoomu (K1) Drenching 2.9 bc 3.8 a 4 leaf Spraying 4.0 a 4.0 a Dipping 3.0 b 3.1 b Drenching 2.6 cd 3.1 b 2 leaf Spraying 3.4 b 3.8 a Dipping 2.3 d 2.9 bc Heongjaealtaimu (NS1) Drenching 2.9 bc 3.8 a 4 leaf Spraying 4.0 a 4.0 a Dipping 3.0 b 3.1 b xGrowth stage; two leaf stage (13-days-old) and four leaf stage (20-days-old). yMeans with the same letters are not significantly different based on Duncan’s multiple range test (DMRT) at p<0.05. the DI of soft rot on radish increased with increasing culti- oculum, thereby delaying colony growth and plant infection. vation temperature (Table 1). Spraying inoculation accelerates disease development. Spraying is the optimum inoculation method; it promotes Tissue age, particularly leaf age, affects the susceptibility rapid bacterial entry through natural openings such as lenti- of radish to infection by Pcc. The DI was higher at the cels or stomata, facilitating subsequent invasion, colo- four-leaf stage (20 days old) compared with the two-leaf nization, and expansion [19, 27]. In contrast, root dipping stage (13 days old). Lee at al. reported that radish seedlings and drenching methods involve drenching soil with the in- at the four-leaf stage (20 days old) were more susceptible Journal of Life Science 2021, Vol. 31. No. 7 613

Table 2. Resistance of 41 commercial radish cultivars to five isolates of Pectobacterium carotovorum subsp. carotovorumx

Inoculation isolates (KACC number) Resistance Cultivar name z 10225 10343 10421 10458 13953 Mean response (RS) Asiakaeuljeojang mu (A 1) 2.2±0.3y 3.4±0.2 2.0±0.2 2.6±0.3 2.4±0.3 2.5±0.5 S Gimjangmu asiaga euljeojang (A 2) 1.7±0.2 2.6±0.3 2.1±0.3 2.4±0.3 1.4±0.2 2.0±0.5 S Chamjueun (A 3) 2.0±0.5 3.5±0.2 2.4±0.3 3.1±0.2 2.4±0.3 2.7±0.6 S Jeilcheongpungmeong-wolmu (J 1) 2.3±0.3 3.6±0.2 1.9±0.2 3.6±0.2 1.8±0.3 2.6±0.9 S Chunlongmu (A 4) 2.5±0.3 3.6±0.2 1.8±0.2 3.4±0.2 1.3±0.2 2.5±1.0 S YR mujeog (N 1) 2.7±0.4 3.6±0.2 2.7±0.3 3.6±0.2 3.7±0.2 3.1±0.5 S Seonbongaltari (S 1) 3.3±0.2 3.8±0.1 3.1±0.3 3.3±0.2 3.6±0.2 3.4±0.4 S Baekjamu (A 5) 2.7±0.3 3.5±0.2 2.6±0.3 3.3±0.2 2.5±0.3 2.9±0.4 S Cheongomabimu (A 6) 2.6±0.3 3.1±0.2 1.2±0.1 3.8±0.1 2.9±0.3 2.7±1.0 S Dolyeong-altarimu (J 2) 2.3±0.3 3.2±0.2 3.0±0.3 3.4±0.2 2.9±0.3 3.0±0.4 S Chunhyang-i (J 7) 2.0±0.2 2.1±0.2 3.8±0.1 1.4±0.2 2.1±0.3 2.3±0.9 S Yeoleum-yeolmu (N 4) 2.1±0.3 3.1±0.3 3.8±0.1 3.0±0.3 2.4±0.3 2.9±0.7 S Danong-eutteum-yeolmu (D 1) 2.0±0.3 1.8±0.2 2.6±0.2 2.3±0.3 2.0±0.2 2.1±0.3 S Cheongchima (P 1) 2.0±0.2 1.4±0.2 2.4±0.3 2.6±0.2 1.8±0.2 2.0±0.5 S Haeugdan-yeolmu (J 6) 2.0±.0.2 2.0±0.2 2.5±0.3 2.3±0.2 3.1±0.2 2.4±0.5 S Chamjuayeolmu (P 2) 3.3±0.2 2.7±0.3 3.6±0.2 3.2±0.2 2.4±0.3 3.0±0.5 S Ilsanyeolmu (PP 1) 2.7±0.3 2.6±0.2 3.1±0.2 3.1±0.2 1.8±0.3 2.7±0.5 S Jinjudaepyeongmu (Jin 1) 2.1±0.3 1.5±0.2 3.0±0.2 1.5±0.2 3.9±0.1 2.4±1.0 S Minongjosaengmu (Asia) (N 6) 1.8±0.2 1.7±0.2 3.7±0.2 2.6±0.3 3.7±0.2 2.7±1.0 S Hallamosdongmu (P 3) 1.0±0.0 1.5±0.2 3.1±0.3 2.6±0.3 3.6±0.2 2.4±1.1 S Gangchu (K 2) 2.3±0.3 2.3±0.3 3.3±0.2 2.9±0.3 3.8±0.1 2.9±0.6 S Jeilgeongangsilaegimu 1 ho (JS 1) 1.3±0.1 2.0±0.2 3.0±0.2 2.9±0.3 3.8±0.1 2.6±1.0 S Seeutailbommu (S 3) 1.7±0.2 1.8±0.2 3.1±0.2 3.6±0.2 3.8±0.1 2.8±1.0 S Meosjinmaskkalmu (P 4) 1.9±0.2 2.4±0.2 3.6±0.2 4.0±0.0 3.9±0.1 3.2±1.0 S Taebaegsanmaeg (P 5) 2.5±0.2 2.1±0.2 3.3±0.2 2.9±0.2 3.2±0.2 2.8±0.5 S Sambagjamu (Sam 3) 1.4±0.2 2.0±0.3 3.7±0.2 3.8±0.1 3.0±0.2 2.8±1.1 S Heongjaealtaimu (NS 1) 3.0±0.2 3.5±0.2 4.0±0.0 4.0±0.0 3.8±0.1 3.7±0.4 S Songjeongmu (Sak 2) 1.6±0.2 1.3±0.2 2.5±0.2 2.8±0.3 2.4±0.3 2.1±0.6 S Worldminong (N 2) 1.1±0.1 1.1±0.1 2.3±0.3 2.3±0.3 1.2±0.1 1.6±0.6 MR Jeilbaegdong (J 3) 1.5±0.2 1.4±0.1 2.1±0.2 1.9±0.2 1.8±0.2 1.7±0.3 MR Taecheong (J 4) 1.7±0.2 1.5±0.2 2.7±0.3 1.8±0.2 1.6±0.2 1.9±0.5 MR Jeonmuhumu (K 1) 1.3±0.1 1.5±0.2 2.3±0.3 1.6±0.2 2.7±0.2 1.9±0.6 MR Alpain goldae (A 7) 1.4±0.2 1.6±0.2 2.7±0.3 1.7±0.2 2.4±0.2 2.0±0.6 MR Neulsaengbumu (N 3) 1.3±0.2 1.6±0.2 2.3±0.2 1.5±0.1 2.0±0.2 1.7±0.4 MR Sanghwang (S 2) 1.1±0.1 1.8±0.2 2.9±0.2 1.7±0.2 1.3±0.1 1.8±0.7 MR Gangjamoojeok (Sam 1) 1.4±0.2 1.5±0.2 1.4±0.3 1.8±0.2 1.7±0.2 1.6±0.2 MR Chengdumu (S 3) 1.4±0.3 1.8±0.2 2.1±0.3 2.3±0.3 2.3±0.2 2.0±0.4 MR Sambogdabal (Sam 2) 1.8±0.3 1.8±0.3 2.8±0.3 1.9±0.3 1.9±0.3 2.0±0.4 MR Gmchorong (Sak 1) 1.1±0.2 2.2±0.3 2.3±0.3 1.4±0.2 0.9±0.2 1.6±0.6 MR Minongjosaengmu (Jeil) (N 5) 2.4±0.3 1.7±0.2 1.9±0.3 1.9±0.3 0.9±0.2 1.8±0.5 MR Khohaeyangsanchonmu (K 3) 1.4±0.1 1.5±0.2 2.6±0.2 1.0±0.0 1.4±0.2 1.6±0.6 MR Mean 2.0±0.2 2.3±0.2 2.7±0.2 2.6±0.2 2.5±0.2 xFour leaf stages (twenty-day-old seedlings) of radish cultivars were inoculated with a bacterial suspension (1.0×106 cfu/ml) of five Pectobacterium carotovorum subsp carotovorum strains by spraying method. The inoculated plants were incubated in a growth chamber at 30°C and relative humidity 80% for 12 hr light and 12 hr dark periods. Five days after inoculation, disease index of each plant was score on a scale of 0-4. yDI, disease index; Each value represents the mean disease index (± standard deviation) of three runs with 10 replicates each. zRS, response; R, resistant, DI ≤ 1.0; MR, moderately resistant, 1.1 < DI ≤ 2.0; S, susceptible, DI > 2.0 614 생명과학회지 2021, Vol. 31. No. 7

A

B

Fig. 3. Radish (Raphanus sativus) Jeonmuhoomu (K1) (A) and Heongjaealtaimu (NS1) (B) exhibiting bacterial soft rot symptoms after inoculation with the Pcc isolates KACC 10225 (a, f), KACC 10343 (b, g), KACC 10421 (c, h), KACC 10458 (d, i), KACC 13953 (e, j). Among them, KACC 10421 exhibited the strongest resistance. to bacterial soft rot [18]. Our results are consistent with pre- Gmchorong, Minongjosaengmu, and vious reports that older leaves are more susceptible to dis- Khohaeyangsanchonmu. Lee et al. reported that the ease [10, 11, 23]. Jeonmuhumu, Cheongdumu, and Taecheong radish culti- vars had moderate resistance to bacterial soft rot [18]. We Resistance of 41 radish cultivars to five Pcc isolates used Jeonmuhum and Cheongdumu as controls. The varia- We evaluated the resistance of 41 commercial radish culti- tion in disease resistance could be the result of the complex vars to five Pcc isolates by spraying. The 41 radish cultivars interactions among the plant, pathogen, and environment were categorized into two groups based on their resistance that influence disease severity [7]. A few genotypes show level (Table 2). The bacterial soft rot DIs of Jeonmuhoomu resistance to pathogens by identifying and excluding them (K1) and Heongjaealtaimu (NS1) were 1.3 and 3, 1.5 and 3.5, via a hypersensitivity response; others are susceptible be- 2.3 and 4.0, 1.6 and 4.0, and 2.7 and 3.8 for KACC 10225, cause they cannot recognize the pathogen sufficiently early KACC 10343, KACC 10421, KACC 10458, and KACC 13953, [26]. respectively (Fig. 3). The mean DIs of bacterial soft rot were In conclusion, spraying at the four-leaf stage and in- 2, 2.3, 2.7, 2.6, and 2.5 for KACC 10225, KACC 10343, KACC cubation at 30℃ are optimal conditions for screening for rad- 10421, KACC 10458, and KACC 13953, respectively. Among ish germplasms resistant to bacterial soft rot; the MR ac- the five Pcc isolates, KACC 10421 was the most pathogenic cessions could serve as resistance donors for development in the 41 radish cultivars. The commercial radish cultivars radish varieties resistant to bacterial soft rot. reacted differently to five Pcc isolates causing bacterial soft rot disease but were grouped into only two classes Acknowledgements (moderate resistance, MR or susceptible, S) according to the classification system (Table 2). Of the 41 cultivars, 13 were The authors would like to acknowledge funding through classified as MR (mean DI 1.6 to 2.0) and 28 as S (mean grants allocated to B.S.H. from the Rural Development DI 2.1 to 3.7) (Table 2); none were classified as R (no disease). Administration (Project No. PJ01450101), Republic of Korea. The MR cultivars were Worldminong, Jeilbaegdong, This study was also supported by the 2021 Postdoctoral Taecheong, Jeonmuhumu, Alpain goldae, Neulsaengbumu, Fellowship Program (T. A.) of the National Institute of Sanghwang, Gangjamoojeok, Cheongdumu, Sambogdabal, Agricultural Sciences, RDA, Republic of Korea. Journal of Life Science 2021, Vol. 31. No. 7 615

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초록：무 품종의 세균성 무름병 저항성 생물검정법 평가

타니아 아프로즈1․허온숙1․노나영1․이재은1․황애진1․김빛샘1․아와리스 데비 아세파1․이주희1․ 성정숙2․이호선3*․한범수1* (1국립농업과학원 농업유전자원센터, 2국립식량과학원 남부작물부, 3농촌진흥청 국제기술협력과)

세균성 무름병 균[Pectobacterium carotovorum subsp. carotovorum (Pcc)]에 의해서 일어나는 무름병은 아시아 국 가에서 재배되는 무에 있어서 심각한 질병 중의 하나로 알려져 있다. 이번 연구의 목적은 상업적으로 시판되는 무 품종의 세균성 무름병의 저항성에 대한 효율적인 생물검정법을 확립하고자 하였다. 첫째, 무 품종에 대해 세균 성 무름병의 효율적인 생물검정 방법을 조사하였다. 6개의 무 품종을 다양한 조건[두 가지 온도(25℃와 30℃), 3가 지 접종방법(관주, 분무, 침지), 두 발생단계(2와 4잎 단계)]으로 조사하였다. 연구 결과는 무름병균 1×106 cfu/ml 농도를 분무한 4잎 단계와 30℃에서 배양한 생물검정 방법이 무 품종에 대해 가장 효율적인 방법임을 알 수 있었 다. 둘째, 41개의 무 품종에 5가지 세균(KACC 10225, KACC 10343, KACC 10421, KACC 10458, KACC 13953)을 접종하여 저항성을 조사하였다. KACC 10421가 세균성 무름병의 감수성 및 저항성 질병 정도를 가장 잘 나타냈 다. 41개의 무 품종 중 13개는 무름병 균에 대해 중도 저항성을 나타냈고 28개는 감수성을 나타냈다. 이 연구에서 중도저항성 무 품종은 세균성 무름병 저항성 육종을 위한 저항성 자원으로 활용 가능하고 육종가, 농민, 연구자, 최종 소비자에 의해서 다양한 목적을 위해 사용 가능할 것으로 사료된다.