Plant Disease

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ISSN / EISSN : 0191-2917 / 0191-2917
Published by: Scientific Societies (10.1094)
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, Javier Felipe Tabima, ,
Published: 2 December 2021
Abstract:
Winter squash (Cucurbita maxima cv. ‘Golden Delicious’) produced in Oregon’s Willamette Valley for edible seed production has experienced significant yield losses due to a soilborne disease. The symptoms associated with this disease problem include root rot, crown rot and vascular discoloration in the stems leading to a severe late season wilt and plant collapse. Through field surveys, Fusarium oxysporum, F. solani, F. culmorum-like fungi, Plectosphaerella cucumerina, and Setophoma terrestris were identified to be associated with diseased tissues, and each produced symptoms of root rot, crown rot or stem discoloration in preliminary pathogenicity trials. In this study, 219 isolates of these species were characterized by molecular identity analyses using BLAST of the ITS and EF1α genomic regions and by pathogenicity testing in outdoor, large-container trials. Molecular identity analyses confirmed the identity of isolates at 99 to 100% similarity to reference isolates in the database. In pathogenicity experiments, F. solani produced the most severe symptoms, followed by F. culmorum-like fungi, F. oxysporum, P. cucumerina, and S. terrestris. Some treatments of mixed species inoculum produced symptoms above what was expected from individual species. In particular, the mixture of F. culmorum-like fungi, F. oxysporum, and P. cucumerina and the mixture of F. culmorum-like fungi, F. solani, and S. terrestris had equally severe symptom ratings than that of F. solani by itself. Results indicate that this soilborne disease is primarily caused by Fusarium solani, but interactions among the complex of F. solani, F. culmorum-like fungi, F. oxysporum, and P. cucumerina, can exacerbate disease severity.
Fanfan Wang, , Tao Tang, Xiaoliang Guo, Yuanyuan Duan,
Published: 2 December 2021
Abstract:
Walnuts are an important perennial nut crop widely cultivated in China, which are rich in protein, carbohydrate, renieratene, and other beneficial nutrients. China is the largest producer of walnuts in the world, with the largest planting area and output. At the end of April 2020, several unknown necrotic spots on leaves of walnut trees were observed in a Juglans regia field located in Sancha Town, Enshi, China (30°28′N, 109°64′E). Initially, lesions were black, small, sunken, and turning to yellowish-brown, irregular, well surrounded by brown margins. Severely, leaf spots coalesced and resulted in withered and abscised. In order to identify the pathogen, infected leaves were collected. Sections of leaves were aseptically excised from the margins of necrotic spots following surface sterilization and placed on potato dextrose agar (PDA) at 28℃. After 4 days, fungal isolates were obtained and purified by hyphal tip isolation. The isolates looked morphologically similar, producing colonies that appeared hyphae with dark grey, lobed margins, and aerial mycelium with white to light gray. After 15 days of incubation, subglobose, dark brown pycnidia (100-176 μm in wide, 75-95 μm in length) were formed with an orifice in the center, producing conidia. Conidia (3.5 to 9.0 × 1.6 to 4.5 μm) were oval to round, aseptate, occasionally 1-septate. These morphological characteristics lead to the conclusion that the isolates may be identified as Phoma sp. (Boerema et al. 1976). A single isolate was randomly selected and designated for further verification. To confirm the identity, the internal transcribed spacer region (ITS), actin (ACT) and beta-tubulin genes were amplified and sequenced ITS1/ITS4, ACT-512F/ACT-783R, and Bt2a/Bt2b, respectively (White et al. 1990, Groenewald et al. 2013). BLAST analysis of the ITS 505-bp sequence (GenBank accession no. MW282913), actin 269-bp sequence (GenBank accession no. MW201958), and beta-tubulin 347-bp sequence (GenBank accession no. MW273782) showed ≥99% homology with the sequences of B. exigua available in GenBank (GenBank accession no. AB454232, LT158234, and KR010463, respectively). Base on the above results, the strain HTY2 was identified as B. exigua. Pathogenicity was tested. Walnut plants were spray-inoculated with a spore suspension (5 x 105 CFU/mL). Controls were inoculated as described above except that sterile distilled water in the dark at 25 ℃. After seven days, lesions were evident at inoculation points, and equivalent to those observed in field were observed. Control leaves remained symptomless. The pathogenicity test was repeated thrice and the results were the same, fulfilling the Koch’s postulates. The pathogen has been reported on various plants around the world, causing a series of symptoms. Infected plants rarely died, but the presence of lesions decreased their fruit quality and yield. Previous identification of the disease is essential in formulating management strategies.
David Strickland, , Kerik Cox
Published: 2 December 2021
Abstract:
Powdery mildew, caused by the ascomycete Podosphaera leucotricha, is an endemic disease found wherever apples are grown that negatively impacts both tree vigor and fresh market yield. In the absence of durable host resistance, chemical management is the primary means of disease control. Demethylation inhibitor (DMI) fungicides are widely used to manage apple powdery mildew, but members within this fungicide class have been observed to differ in efficacy with respect to disease control. Moreover, debate exists as to the optimal timing of DMI fungicide applications for management of apple powdery mildew. In this regard, the goal of this study was to determine the best-use practices for DMI fungicides to manage apple powdery mildew in New York State. Multi-year trials were conducted to evaluate the potential differential efficacy performance of four common DMI fungicides, as well as additional trials to assess optimal application timing. In all years, we observed that treatments of flutriafol and myclobutanil consistently had the lowest incidences of powdery mildew compared to difenoconazole and fenbuconazole. In the 2018 and 2021 trials, the newly registered mefentrifluconazole was more comparable to the difenoconazole program with respect to powdery mildew disease incidence. We hypothesize that differences in DMI efficacy may be due to each fungicides’ water solubility and lipophilicity characteristics, and thus their ability to move systemically in the host or more easily penetrate the surface of germinating conidia. Applications timed between petal fall and first cover resulted in the lowest incidence of powdery mildew on terminal leaves of apple shoots compared to applications timed prior to petal fall. These observations are contrary to previous studies conducted in regions with differing climates. We also found that the incidence of secondary powdery mildew observed two weeks after petal fall was influenced by applications of DMI fungicides during the previous season. For example, management programs consisting of applications of flutriafol or myclobutanil in the prior season tended to have lower incidence of apple powdery in the following spring, presumably owing to reductions in overwintering inoculum. Despite reports of DMI resistance in other apple pathosystems, the DMI fungicide class is still relevant for the successful management of apple powdery mildew in New York State.
Published: 2 December 2021
Abstract:
Maize striate mosaic virus (MSMV; genus Mastrevirus), was recently reported in maize plants in Brazil, and also detected by metagenomic analyses in the corn leafhopper, Dalbulus maidis (DeLong & Wolcott). Although these findings suggested that D. maidis is a potential vector, no transmission studies have been performed. Here, we tested the transmission of MSMV by D. maidis from field-collected infected plants and plants infected with MSMV via leafhopper-mediated transmission in the laboratory; all plants were confirmed positive for MSMV by PCR. In each one of three transmission replicates, aviruliferous D. maidis nymphs and adults were confined together on a source plant during a 4-day acquisition access period (AAP), and subsequently transferred to healthy maize seedlings (10 individuals per test plant) in a series of 4-day inoculation access periods (IAPs). We also tested transmission by the corn aphid, Rhopalosiphum maidis (Fitch) and by mechanical inoculation of healthy maize seedlings. Only D. maidis transmitted MSMV, with overall transmission rates of 29.4 and 39.5% using field-collected infected plants, and 18.5% using infected plants in laboratory. D. maidis transmitted MSMV until the third (8-12 days after the AAP) or fourth successive IAP (12-16 days) with gradual loss in transmission efficiency and rate of viruliferous insects over time, suggesting a persistent, but non-propagative mode of transmission. Infected test plants showed mottling symptoms with mild chlorotic streaks and height reduction. This is the first report of transmission of a mastrevirus by D. maidis, facilitating the completion of Koch’s postulate for MSMV.
Published: 2 December 2021
Abstract:
Grapes (Vitis vinifera L.) are very popular in China as fresh fruit. Due to its storability, some grape varieties can be kept fresh until winter, increasing the popularity of fruit grapes. However, in 2019, rot symptoms were observed on cv. Crimson in Wuhan, Hubei (30°52′N, 114°31′E), and Chengdu, Sichuan (30°67′N, 104°06′E). Subsequently, from 2019 to 2021, Liangshan (28°33′N, 102°42′E, cv.Crimson), Ya’an (29°40′N, 102°66′E, cv. Red globe), and Nanchong (30°80′N, 106°06′E, cv. Victoria), Sichuan also experienced the same decay symptoms. Initial symptoms of this disease were slightly sunken lesions on the berries 5 to 7 days in storage at 28℃, and then white mycelial growth on the surface of lesions. The growth became bluish-green following the occurrence of abundant sporulation, along with softening and collapsing the whole berry (Fig. 1a). Twenty symptomatic berries from each city were collected (100 samples in total) and twenty isolates were obtained using the single spore isolation technique developed by Chomnunti et al. (2014). The colony on PDA media initially appeared as white mycelium, and later developed into greenish-gray to grayish-green sporulation with white margins, the colony diameter reached 32.5 to 34.5 mm after ten days of incubation at 28±1℃. The reverse side of the colony was oblive-brown or grayish-yellow. Morphological characteristics of the twenty isolates showed that the conidiophores were broom-shaped and verticillate, the stipes smooth-walled and measured 120 to 300 × 2.5 to 4.0 μm; the ramus (n = 2 to 3) measured 6.0 to 15 × 2.5 to 3.6 μm; the metulas (n = 2 to 4) were verticillate, with sizes ranging from 8.7 to 9.8 × 2.0 to 3.2 μm; the phialides (n = 3 to 7) were elongate and ampulliform, with sizes ranging from 2.0 to 3.5 × 2.0 to 2.4 μm; the conidia (2.0 to 3.5 × 2.0 to 2.4 μm) were sub-globose to ellipsoidal in shape, with thick and finely roughened walls. Based on these cultural and morphological characteristics, the isolates were identified as Penicillium olsonii Bainier & Sartory (Frisvad et al., 1990). A multi-locus approach was performed to accurately identify a representative WHG5 isolate. The internal transcribed spacer regions (ITS), calmodulin (CaM,), beta tubulin (BenA), and 18S ribosomal RNA (18S) of isolate WHG5 were amplified and sequenced as described by Walker et al. (2012). The pairwise alignments of ITS, CaM, BenA, and 18S sequences was nearly 100% identical to Penicillium olsonii with GenBank accession numbers KX056230.1 (524/524 bp, 100%), DQ645807.1 (570/572 bp, 99%), AY674444.1 (472/472 bp, 99%), and FJ717701.1 (1299/1301 bp, 99%), respectively. The resulting sequences were deposited in GenBank (Accession no. ITS: MW192867; CaM: MZ936474; BenA: MZ936475; and 18S: MZ936476). The phylogenetic analysis performed with the Neighbor-Joining method classified WGH5 into the P. olsonii clade with a posterior probability of 100% based on the concatenated sequences of the ITS CaM, BenA, and 18S (Fig. 2). Combined with the above morphological characteristics, we finally confirmed the identity of isolate WGH5 as P. olsonii. To fulfill Koch’s postulates and confirm the pathogenicity of WGH5, a 10 μL conidial suspension (1 × 106 spores/mL) aliquot was inoculated into the healthy grape berry (cv. Crimson) while using sterile distilled water as a control. Thirty berries were surface disinfected with 2% sodium hypochlorite then artificially wounded prior to inoculation with the conidial suspension. The artificial wound was made using a sterilized steel needle with a diameter of 0.5 mm and a depth of 0.3 cm. All the inoculated fruits were placed in sealed and sterilized Petri dishes and incubated at 28±1℃. The experiments were done in triplicate. After five days, the inoculated grape berries showed typical symptoms (Fig. 1b) while the control remained asymptomatic. Using the same protocol as above, the fungus P. olsonii was re-isolated from the symptomatic inoculated berries but not successfully from mock-inoculated berries. Previously, P. olsonii has been reported from Portuguese wine grapes (Serra et al., 2007). This study is the first time that P. olsonii was reported as a plant pathogen in China. Since the grapes were collected from grocery stores, details of post-harvest management that could have affected disease presence and progression of rotting were not available.
Published: 2 December 2021
Abstract:
Phytophthora nicotianae is the most common pathogen in nurseries and gardens, infecting both woody and herbaceous ornamental plants. Phytophthora aerial blight symptoms such dull water-soaked lesions on shoot tips and leaf petioles, girdling on the main stem, necrosis, and wilting of annual vinca were observed in a commercial greenhouse in Warren Co., Tennessee, USA in May 2016. The objective of this study was to identify the causal agent of Phytophthora aerial blight and develop a fungicide management recommendation for ornamental producers. Attempts to isolate the pathogen from symptomatic leaf tissue were conducted and excised leaf pieces were embedded in the V8 agar medium. Morphological characterization, polymerase chain reaction (PCR), sequencing, and pathogenicity test of the isolate FBG2016_444 were conducted to confirm the pathogen identification. The sequence identity was 100% identical to Phytophthora nicotianae, and a combined phylogenetic tree (internal transcribed spacer [ITS]), the large subunit [LSU] of rDNA, and ras-related protein gene [Ypt1]) grouped isolate FBG2016_444 within the clade of P. nicotianae. In the pathogenecity study, all inoculated annual vinca plant showed the Phytophthora aerial blight symptoms and P. nicotianae was re-isolated whereas non-inoculated annual vinca plant remained symptomless. These findings confirmed P. nicotianae as the causal agent of Phytophthora aerial blight of annual vinca. In addition, two rates (0.078 and 0.156 mL·L-1) and three application intervals (7, 14 and 21 days before inoculation [DBI]) of oxathiapiprolin (Segovis®) were evaluated for their ability to reduce the Phytophthora aerial blight severity on annual vinca plants. The control groups were positive (non-treated inoculated) and negative (non-treated non-inoculated) plants. Both rates and application timings of oxathiapiprolin significantly reduced Phytophthora aerial blight severity and disease progress (area under disease progress curve [AUDPC]) on annual vinca plants compared to the positive control. However, 0.078 and 0.156 mL·L-1 of oxathiapiprolin applied at 7 or 14 DBI were the most effective treatments in reducing the disease severity and AUDPC on annual vinca plants. The plant growth parameters such as increase in height and width, total plant weight, and root weight were not influenced by the application of oxathiapiprolin. The finding reported in this study will help ornamental growers with better management of Phytophthora aerial blight of annual vinca.
Yongyan Zhang, Fan Liu, Bin Wang, Dongliang Qiu, Jiapeng Liu, , , Xuejun Bei, Peitao Lü
Published: 2 December 2021
Abstract:
Banana (Musa acuminata) is one of the most popular and widely consumed fruit crops in the world. During late October to early November 2020, a banana finger-tip rot disease was observed in the banana (cultivar ‘Brazil’, AAA group) orchard of about 12 hectares located in Zhongcun, Zhangmu Town, Fumian District, Yulin City, Guangxi province, China. The disease incidence was about 0.5% at the surveyed field. Infected fingers and their tips were usually normal in the appearances and then turned to brown to black discoloration in the central fruit pulp adjacent to the fingertips (Fig. 1A). In severe infection, diseased fingers showed brown to black discoloration in both the central and the periphery fruit pulp, and along the longitudinal axis throughout the fruit (Fig. 1B-C). The symptomatic banana fingers were surface-disinfected with 1% sodium hypochlorite for 30 sec, 75% ethanol for 30 sec then rinsed three times with sterile distilled water. The flesh tissues were ground in a sterile mortar and soaked in 1 ml of sterile distilled water for 30 min. A 50 μl of tissue suspensions was streaked onto Luria-Bertani (LB) medium. Single colonies were picked and re-streaked onto new LB medium. The cultures were incubated at 37°C for 24 h. Two representative strains, GX and GX2, were obtained from symptomatic pulps and used in the following studies. To molecularly identify the bacterial species, we performed a polymerase chain reaction (PCR) using 16S rRNA and recA primers (Turner et al. 1999; Lee and Chan 2007) and amplified 1,442 bp and 1,019 bp sequences, respectively. The amplified sequences were deposited in GenBank under the accession numbers MZ267253 and MZ961355 for the 16S rRNA and MZ287336 and MZ983484 for the recA genes. BLASTn searches shared more than 99% similarity with the reference sequences of B. cepacia strains (MK680073.1 and KC261418.1 for 16S rRNA; AY598028.1 and KF812859.1 for recA). Phylogenetic trees were constructed using the 16 rRNA and recA sequences and showed that the representative strains, GX and GX2, strongly clustered with B. cepacia type strains (Fig. 2). To further determine the genomovars of strain GX, we used specific PCR primers to the B. cepacia epidemic strain marker (BCESM), type III secretion gene cluster (bcscV) and cable pilin subunit gene (cblA) (Lee and Chan 2007; Ansari et al. 2019). The presence of bcscV and BCESM were confirmed by PCR, while cblA was not observed in the strains GX and GX2, suggesting that the isolated strains belong to B. cepacia genomovar III and are slightly different from the Iranian and Taiwan strains of B. cepacia (Lee and Chan 2007; Ansari et al. 2019). Pathogenicity test was conducted on banana fingers (cultivar ‘Zhongjiao No.3’) at the immature and full ripe stages. A final suspensions of 106 CFU/ml, was injected into the banana fingers (100 μl per finger) through the center of the stigma (Lee and Chan 2007; Ansari et al. 2019). The fingers inoculated with sterile water were used as negative control. To maintain humidity, the treated fingertips were wrapped with Parafilm. For each treatment, ten independent replicates were conducted. At 10 days post-inoculation (dpi), the pulp of immature bananas exhibited reddish brown decaying tissue, which symptoms were similar to those observed in the field (Fig. 1D). Moreover, the pulp tissues of ripe bananas showed a dark brown discoloration in the tip at 5 dpi, whereas the controls remained symptomless (Fig. 1E). The same bacterium was re-isolated from diseased tissues and its identification confirmed by 16S rRNA, thus fulfilling the Koch’s postulates. This disease was first described in Honduras in Latin America, and then reported in Taiwan province of China, and Iran (Buddenhagen 1968; Lee et al. 2003; Ansari et al. 2019). To our knowledge, this is the first report of banana finger-tip rot caused by B. cepacia in the Guangxi province, China. It is necessary to determine the distribution of B. cepacia and to prevent its spread in Guangxi province of China.
Xiaoqiao Huang, Yan Wu, Yuan Li, Haiping Lin, Liangjin Ma, ,
Published: 2 December 2021
Abstract:
Phoebe sheareri (Hemsl.) Gamble is a high-value timber tree species with a wide range of uses. It can also be applied for landscape afforestation considering its beautiful shape and luxuriant branches. Previous studies disclosed that Neofusicum parvum can cause ulceration and necrosis on the main stems of P. sheareri (Chen et al. 2019), and branch wilt of P. zhennan (Zhu et al. 2019). In September 2019, anthracnose was observed from P. sheareri leaves in Lishui, Zhejiang province, China. The diseased leaves are characterized by dark brown lesions. The infection usually starts from the leaf tip or edge, then the infected leaves turn yellow, wither and fall finally. The infection sometimes occurrs on the small twigs, causing the whole branch to wither. Plants from 15 plantations were surveyed, and the disease incidence was about 30%. A total number of 15 freshly infected leaves were collected and cut into small pieces (5×5 mm), sterilized in 75% ethanol solution for 30 s, and washed with sterile water three times. They were further sanitized in 2% sodium hypochlorite solution for 2 to 3 minutes and dried in sterile filter paper after being washed with sterile water another three times. Leaf pieces were transferred to potato dextrose agar (PDA) plates and incubated at 25℃ in the dark for 3 days. The fungal cultures were purified and the typical isolate (TJ01) was selected for further morphological characterization and DNA sequence comparison. The strain was initially grayish white, villous, and posteriorly grayish green, and produced orange red spore clumps. The spores are single celled after maturation, oblong, colorless, and the size ranges from 8.5-19.5 × 4.5-5.5 μm. Morphological characteristics of the obtained isolate are consistent with those in the genus of Colletotrichum. DNA of the isolate was extracted and sequence data obtained and compared with those downloaded from GenBank. The internal transcribed spacer (ITS), intronic glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin (ACT), beta-tubulin (TUB2), and calmodulin (CAL) genes were partially amplified and sequenced using the primer pairs ITS-1 + ITS-4, GDF + GDR, ACT-512F + ACT-783R, T1 + Bt2b, CL1C + Cl2C, respectively (Fu et al. 2019). The resulted nucleotide sequences were individually subjected to BLAST searche in GenBank. The nucleotide sequences of ITS (MZ088144), GAPDH (MZ133607), ACT (MZ133608), TUB2 (MZ133609), CAL (MZ133610) of the isolate showed 99.83% similarity to ITS sequence (MN829453), 98.24% similarity to GAPDH sequence (MN525875), 98.94% similarity to ACT sequence (MK341539), 100% similarity to TUB2 sequence (MG657352), and 100% similarity to CAL sequence (MN525839). The phylogenetic tree was constructed using MEGA 7 based on the tandem of five genes (ITS-GAPDH-ACT-TUB2-CAL). The result revealed that the isolate resides in the clade of C. fructicola species. Inoculation was done on leaves of ten P. sheareri plants in the field to verify its pathogenicity. Three healthy leaves of each plant were surface sterilized with 75% ethanol and dried up. The leaves were punctured using a sterilized needle, inoculated with 5-mm-diameter PDA plugs excised from 7-day-old cultures, and wrapped with parafilm. Nine pieces of healthy leaves inoculated with sterilized PDA plugs were served as controls. Disease symptoms developed on all the C. fructicola-inoculated leaves 5 days after inoculation, and a yellow brown lesion became apparent 16 days later, whereas the control leaves remained asymptomatic. C. fructicola was reisolated from the lesions, but not from the control leaves, fulfilling the Koch’s postulates. This fungus is a well-known pathogen and has led to anthracnose on many plant species globally. However, our study represents the first report of C. fructicola causing anthracnose on P. sheareri worldwide and its potential threat should be evaluated.
Wenrui Wang, Huagang He, Huiming Gao, , Wenyue Song, Xu Zhang, Lipei Zhang, Jiancheng Song, Cheng Liu, Kaichang Liu, et al.
Published: 1 December 2021
Abstract:
Wheat powdery mildew, caused by Blumeria graminis (DC.) Speer f. sp. tritici is a destructive disease seriously threatening yield and quality of common wheat (Triticum aestivum L., 2n=6x=42, AABBDD). Characterization of resistance genes against powdery mildew is useful in parental selection and for developing disease-resistant cultivars. Chinese wheat breeding line KN0816 has superior agronomic performance and resistance to powdery mildew at all growth stages. Genetic analysis using populations of KN0816 crossed with different susceptible parents indicated that a single dominant gene, tentatively designated PmKN0816, conferred seedling resistance to different B. graminis f. sp. tritici isolates. Using a bulked segregant analysis, PmKN0816 was mapped to the Pm6 interval on chromosome arm 2BL using polymorphic markers linked to the cataloged genes Pm6, Pm52, and Pm64, and flanked by the markers CISSR02g-6 and CIT02g-2, both with genetic distances of 0.7 cM. Analysis of closely linked molecular markers indicated that the marker alleles of PmKN0816 differed from those of other powdery mildew resistance genes on 2BL, including Pm6, Pm33, Pm51, Pm64, and PmQ. Based on the genetic and physical locations and response pattern to different B. graminis f. sp. tritici isolates, PmKN0816 is most likely a new powdery mildew resistance gene and possesses effective resistance to all the 14 tested B. graminis f. sp. tritici isolates. In view of the elite agronomic performance of KN0816 combined with the resistance, PmKN0816 is expected to become a valuable resistance gene in wheat breeding. To transfer PmKN0816 to different genetic backgrounds using marker-assisted selection (MAS), closely linked markers of PmKN0816 were evaluated, and four of them (CIT02g-2, CISSR02g-6, CIT02g-10, and CIT02g-17) were confirmed to be applicable for MAS in different genetic backgrounds.
Jiaxin Xing, Dunyu Zhang, Fuyou Yin, Qiaofang Zhong, Bo Wang, Suqin Xiao, Xue Ke, Lingxian Wang, Yun Zhang, , et al.
Published: 1 December 2021
Abstract:
Bacterial blight (BB) disease caused by Xanthomonas oryzae pv. oryzae is a common, widespread, and highly devastating disease that affects rice yield. Breeding resistant cultivars is considered the most effective measure for controlling this disease. The introgression line G252 derived from Yuanjiang common wild rice (Oryza rufipogon) was highly resistant to all tested strains, including C5, C9, PXO99, PB, T7147Y8, Hzhj19, YM1, YM187, YJdp-2, and YJws-2. To identify the BB resistance gene(s) of G252, we developed an F2 population from the cross between G252 and 02428. A linkage analysis was performed for the phenotype and genotype of the population. A segregation ratio of 3:1 was observed between the resistant and susceptible individuals in the F2 progeny, indicating a dominant resistance gene, Xa47(t), in G252. The resistance gene was mapped within an approximately 26.24-kb physical region on chromosome 11 between two InDel markers, R13I14 and 13rbq-71. Moreover, one InDel marker, Hxjy-1, co-segregated with Xa47(t). Three genes were predicted within the target region, including a promising candidate gene encoding a nucleotide-binding domain and leucine-rich repeat (NLR) protein (LOC_Os11g46200) by combining the structure and expression analysis. Physical mapping data suggested that Xa47(t) is a new broad-spectrum BB resistance gene without identified allelic genes.
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