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Dragon fruit (Hylocereus polyrhizus) is a high value newly introduced fruit crop in Bangladesh. It has drawn considerable public attention due to its appealing flesh color, sweet taste and fruit qualities. Recently, basal rot of dragon fruit plants was observed in several farmer's fields, nurseries and in the research field of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) where about 10-15% of plants were infected in each location. Initially, the symptoms appeared in the basal part near the soil as brown lesions which gradually extended to the upper stem and finally becoming soft and watery (Figure 1a). Infected plants were collected from Kapasia of Gazipur district (Latitude 24.266 and Longitude 90.633) to isolate the causal organism. Isolations were carried out following the procedure reported by Briste et al. (2019). Briefly, infected plant parts were surface sterilized in 2% NaOCl for 1 min followed by 70% ethanol for 5 min and rinsed 3 times with sterile double distilled water. A large piece of a surface sterilized plant was cut into small pieces (2 mm × 2 mm) from the margin of the necrotic lesion and placed on half strength potato dextrose agar (PDA) and incubated for 7 days at 25 °C. The BTFD1 and BTFD4 isolates were purified from single spores resulting in white colonies with a growth rate of 1cm/day on PDA (Figure 1b). Colonies produced single celled microconidia from unbranched, short monophialidic conidiophores and septate macroconidia as well as chlamydospores in PDA which is consistent with Fusarium oxysporum (Figure 1c). To confirm the identity of the isolates, the internal transcribed spacer (ITS1, 5.8S rRNA and ITS2) and translation elongation factor-1alpha (EF-1α) were amplified using primers ITS-1/ ITS-4 and EF1-728F/ EF1-986R, respectively (Surovy et al. 2018). The ITS sequences of the isolates BTFD1 and BTFD4 (GenBank accession # MN727096 and MN727095, respectively) showed 100% similarity with the sequence from F. oxysporum strain JJF2 (MN626452). Sequence identity for EF-1α (GenBank accession # MN752123 and MN752124, respectively) was 100% with the sequence from F. oxysporum strain CAV041_EO (MK783088). The isolates (BTFD1 and BTFD4) were identified as F. oxysporum based on the aligned sequences of ITS and EF-1α, molecular phylogenetic analyses by maximum likelihood tree (Figure 2a) and maximum parsimony tree methods (Figure 2b). The isolates were stored at 4°C on dried filter paper as well as in an ultra-low temperature freezer (-80°C) at IBGE, BSMRAU, Bangladesh and are available on request. To ensure pathogenicity, isolate BTFD1 was grown on PDA, incubated at 25°C for 7 days and 250 ml conidial suspension (with 1 × 105 conidia/ml) was prepared. Twelve,three-month-old healthy dragon fruit plants were inoculated. Pathogenicity tests were carried out in two sets using three replications in each set. In one set, only the basal part of the plants was dipped into the conidial suspension and in another set the whole plant was dipped into the conidial suspension for two hours. Sterile distilled water was also used in another set of plants as a control. The inoculated plants were placed on wet tissue in a plastic box (31cm × 24cm × 8cm) covered and incubated at 25°C. After 10 days, all inoculated plants in both sets developed rot symptoms similar to those observed in the field, while the control plants remained healthy (Figure 1d). The pathogen was successfully re-isolated from the inoculated symptomatic parts on half strength PDA medium and had morphology as characterized before, thus fulfilling Koch's postulates. This disease has been reported in Argentina and Malaysia (Wright et al. 2007; Hafifi et al. 2019). To the bet of our knowledge, this is the first report of Fusarium basal rot of dragon fruit in Bangladesh caused by F. oxysporum.

Strawberry (Fragaria × ananassa) was introduced to Bangladesh in 1996 and has gained remarkable acceptance. However, with the expansion of acreage, anthracnose crown rot (ACR) is posing a challenge to strawberry growers. In March 2016, typical ACR symptoms were observed on cultivar Strawberry Festival in a farmer’s field in Rajshahi District. Symptoms were evident on approximately 10% of plants and included flagging of young leaves, mimicking lack of water, and wilting of the entire plant in daytime heat. A lengthwise cut through the crown of diseased plants showed characteristic shades of red and white marbling similar to that described by Weir et al. (2012). Crowns of seven symptomatic strawberry plants were obtained after excising foliage and roots and washed under running water for 1 h. Crowns were then surface disinfested with 70% ethanol followed by 1% NaClO for 2 and 3 min, respectively. Small pieces (2 × 2 mm) of the internal infected marbled red tissues were cut with a sterile scalpel, placed on corn meal agar, and incubated for 7 days at 25°C. Conidia grown on tissue pieces and hyphal mats from the tissues were streaked on PDA plates to obtain single conidial colonies. Two of the single-conidial isolates (BRSP08 and BRSP09) that had white margins with circular, dull orange centers were selected to prove Koch’s postulates. The average mycelial growth rate was 9.8 mm/day at 25°C on PDA with cottony aerial growth and pale yellowish to pinkish color. Conidia were hyaline, cylindrical, with round ends, and measuring 14.90 to 18.19 × 4.05 to 6.20 μm (average ± SD, 16.22 ± 1.20 × 5.90 ± 0.84 μm) (n = 30). Appressoria were brown, globose to cylindrical, lobbed, and measuring 7.50 to 12.70 × 6.08 to 8.4 μm (10.72 ± 1.30 × 7.20 ± 0.80 μm) (n = 20). The morphological characteristics of these isolates are consistent with some Colletotrichum species within the C. gloeosporioides complex including C. siamense (Afanador-Kafuri et al. 2003; Weir et al. 2012). BRSP09 was used for molecular identification. Internal transcribed spacer regions and intervening 5.8S nrRNA gene (ITS) and genes encoding chitin synthase (CHS-1), actin (ACT), β-tubulin (TUB2), calmodulin (CAL), and the Apn2–Mat1–2 intergenic spacer and partial mating type (Mat1–2) gene (ApMat) of the selected isolate were amplified using primers ITS1F/ITS4, Bt2a/Bt-2b, CHS-79F/CHS-354R, ACT512F/ACT783R, CL1C/CL2C, and AM-F/AM-R, respectively (Silva et al. 2012; Weir et al. 2012). Sequencing of the purified polymerase chain reaction products was performed by Macrogen (Korea), and sequences were deposited in GenBank (LC420017 to LC420022). Neighbor-joining and maximum likelihood phylogenetic trees were inferred using MEGA 6.0 (Tamura et al. 2013) based on the multilocus alignment (ITS, TUB2, ACT, CHS-1, CAL, and ApMat) of the present isolate and related Colletotrichum spp. sequences previously deposited in GenBank. BLAST search and phylogenetic analysis revealed that BRSP09 is C. siamense (Mills et al. 1992). To confirm the pathogenicity of the fungus, ten 3-month-old tissue-cultured Strawberry Festival plants were inoculated by dipping the roots and crowns into either 300 ml of conidial suspension (8 × 10⁶ conidia/ml) of the isolates BRSP08 and BRSP09 or sterile distilled water (control) for 30 min. The inoculated plants were transplanted into plastic pots with artificial peat-based soil mix and maintained in the greenhouse with 28/20°C day/night temperature. The experiment was conducted twice. After 4 weeks, all plants inoculated with BRSP08 or BRSP09 were stunted and developed typical wilt symptoms similar to those observed in the field, whereas the control plants remained healthy. C. siamense was reisolated from crown tissues with typical ACR symptoms and identified using morphological and molecular methods mentioned above, fulfilling Koch’s postulates. This is the first report of ACR of strawberry caused by C. siamense and the members of C. siamense complex in Rajshahi District.

Strawberry (Fragaria × ananassa) is a newly introduced small fruit crop in Bangladesh, which has gained considerable interest from both growers and consumers. Increasing incidence of wilt and crown rot diseases is a challenge for strawberry growers. In March 2016, wilted foliage and dead strawberry plants of cv. Strawberry Festival were found in a strawberry nursery in Rajshahi district of Bangladesh affecting 10% of the plants. Symptoms included wilting of foliage, drying and withering of older leaves, stunted growth, and reduced fruit production, leading to eventual plant collapse. A lengthwise cut through the crown of diseased plants showed distinct brown to reddish discoloration similar to that described by Koike et al. (2009). The crowns were surface sterilized in 2% NaOCl for 1 min followed by 70% ethanol for 5 min. Small pieces (2 × 2 mm) of the internal discolored tissue were placed on half-strength potato dextrose agar (PDA) medium and incubated for 7 days at 25°C. Single-spore isolates (BRSP-02 and BRSP-12) were obtained and plated to PDA, cornmeal agar, and V8 juice agar. Isolates had a growth rate 0.8 cm/day on PDA medium and produced sporodochia with septate macroconidia. Colonies also produced single-celled microconidia from unbranched, short, monophialidic conidiophores on PDA consistent with Fusarium oxysporum (Nelson et al. 1983). The internal transcribed spacer (ITS1, 5.8S rRNA, and ITS2), actin (ACT), and translation elongation factor 1-alpha (EF-1α) of the isolates were amplified using primers ITS-1/ITS-4, ACT-512F/ACT-783R, and EF1-728F/EF1-986R, respectively (Carbone and Khon 1999; White et al. 1990). ITS sequences of the isolates BRSP-02 and BRSP-12 (GenBank accession nos. LC383470 and LC383471, respectively) showed 99% similarity with the sequence from F. oxysporum strain SHBV2 (KY090783). Sequence identity for EF-1α (GenBank accession nos. LC383472 and LC383473, respectively) was 98 to 99% with the sequence from F. oxysporum isolate BRIP59170 (KX434915). The ACT sequences (GenBank accession nos. LC383784 and LC383785, respectively) showed 97 to 98% similarity with the sequence from F. oxysporum isolate C-11 (KY798318). Based on the aligned sequences of ITS and EF-1α, molecular phylogenetic analysis by the maximum likelihood method and maximum parsimony method, the isolates (BRSP-02 and BRSP-12) were named as F. oxysporum. The isolates are archived in the Department of Biotechnology at Bangabandhu Sheikh Mujibur Rahman Agricultural University in Bangladesh on dried filter paper at 4°C and are available on request. To confirm the pathogenicity of the fungus, five 3-month-old tissue-cultured ‘Strawberry Festival’ plants were inoculated by dipping the roots into either 400 ml of conidial suspension (with 5 × 10⁶ conidia/ml) of the isolate BRSP-12 or into sterile distilled water (control) for 15 min. The inoculated plants were transplanted into plastic pots with artificial peat-based soil mix and maintained in the greenhouse with a high daytime temperature of 25°C and low nighttime temperature of 20°C. After 3 weeks, all plants inoculated with isolate BRSP-12 were stunted and developed wilt symptoms similar to those observed in the field, whereas the control plants remained healthy. Plants were then dug out, and crowns were cut longitudinally to check for internal discoloration. Light orange discoloration of crown tissues was observed in inoculated plants, but all the control plants remained symptomless. The fungus was successfully reisolated on half-strength PDA medium from 100% of crowns and had morphology as characterized before, fulfilling Koch’s postulates. To the best of our knowledge, this is the first report of Fusarium wilt of strawberry in Bangladesh. This disease has been reported from a number of other countries including Argentina, Australia, China, South Korea, Spain, the United States, and Japan (Koike et al. 2009; Williamson et al. 2012).