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Evaluation of Potato Cultivars for Resistance to Soft Rot Bacteria in Bangladesh (2017 - 2018)

FERDOUS-E-ELAHI
Plant Pathology Division, BARI, Gazipur

Abstract/ Executive Summary:

Thirteen potato cultivars were collected from Tuber Crop Research Center (TCRC), Bangladesh Agricultural Research Institute (BARI), Gazipur to evaluate them against soft rot bacteria. There were significant differences among the potato cultivars in soft rot disease severity. BARI Alu 25 showed the least soft rot disease severity compared to other potato cultivars. Calcium content but not dry matter percentage of tubers was correlated with soft rot severity. Regression analysis of both calcium percentage and dry matter percentage with rotted tissue percentage showed that calcium percentage of potato had a negative correlation with soft rot percentage (p<0.05) but no relation with the dry matter percentage changes.

Keywords: Potato, Bacterial Soft rot, Resistant

Location: Plant Pathology Division, BARI, Gazipur

Start Date:

End Date:

Program Area: Pest Management

Commodity: Bacteria, Potato

Objectives:

The objectives of this study were i) to quantify the resistance in BARI-released potato cultivars and ii) to determine the correlation of tuber susceptibility with different concentration of calcium (Ca) and dry matter content of tuber.

Methodology:

Previously characterized Pectobacterium carotovorum ssp. carotovorum strain Pki2 (GenBank acc. no- KX098357, collected from Plant Pathology Division, BARI, Gazipur) was streaked on LBA medium and incubated at 28° C for 48 hours. The concentrations of bacterial suspensions were adjusted to 10⁸CFU/mL (0.2 OD at 600 nm). Tubers of 13 BARI potato cultivars harvested at the same time in February 2018 were collected from the storage of Tuber Crop Research Center (TCRC), BARI where the potatoes are kept at 2.5° C. Twelve randomly selected tubers from each cultivar were washed with 0.5% sodium hypochlorite. The bacterial inoculum was stirred with a magnetic stirrer to avoid sedimentation. Potato tubers were cut in half and two wells, 5 mm in diameter x 5 mm deep, were made in each site on each half tuber using a sterilized metal screw. A 40µL aliquot of P. carotovorum ssp. carotovorum Pki2 inoculum was placed in each well and the wells were wrapped with Parafilm. Three randomly selected tubers from each cultivar mock-inoculated with sterilized distilled water served as a negative control. After inoculation, tubers were placed in moistened plastic containers in the dark for 3 days at 28° C. After incubation tubers were weighed, rotted tuber tissue was separated from healthy tissue with a spatula and the fresh weight of the rotten portion was measured in grams and later converted to a percentage (Pasco et al. 2006). The experiment was designed in a randomized complete block design (RCBD) with three replications. Four tubers from each potato cultivar were peeled, cut into thin slices, weighed and dried at room temperature. Potato slices were oven-dried at 65° C for 2 days and mixed all the replications sample of each cultivar together to make a sufficient sample. Samples were digested with H₂SO₄ and H₂O₂(Thomas et al. 1967) weighed. Dry matter percentage was calculated following the formula:

Dry matter % = (dry weight/fresh weight) x100

Dried potato samples were sent to the Department of Soil Science, BARI, Bangladesh to measure the percentage of calcium in medullar tissues using flame atomic absorption spectrometry following a wet digestion method (Habib et al. 2004).

Data analysis. R statistical software was used for the analysis of variance (ANOVA), correlation and multivariate regression. Differences in means were assessed using the Least significant difference (LSD) with an error rate of α=0.05.

Source of Information: Annual Research Report 2017-18, Plant Pathology Division, BARI, Gazipur

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

All the 13 potato cultivars tested showed tuber soft rot damage 3 days after inoculation. There were statistically significant differences among the potato cultivars in soft rot disease severity (p<0.05). Mean soft rot of potato tuber tissue ranged from 27.5% (BARI Alu 25) to 97.5% (BARI Alu 40). BARI Alu 25 exhibited significantly less damage than four other most susceptible cultivars BARI Alu 40, BARI Alu 70, BARI Alu 64 and BARI Alu 66, whereas the percentage of soft rot was statistically similar for all these four observed potato cultivars. The percentage of tuber calcium ranged from 0.57-1.31% in the thirteen potato varieties tested, and differences among varieties were significant (p<0.001). Percent calcium content was the highest in BARI Alu 25 followed by BARI Alu 40 (1.06) and was lowest in BARI Alu 70 followed by BARI Alu 56 (0.68). Percentage tuber dry matter ranged from 24.56 (BARI Alu 61) – 36.90 % (BARI Alu 70), and differences among varieties were significant (p<0.001). BARI Alu 28, BARI Alu 40, BARI Alu 45, BARI Alu 64 and BARI Alu 66 were relatively high in dry matter percentage, whereas BARI Alu 13, BARI Alu 37, BARI Alu 56 and BARI Alu 61 were relatively low in dry matter percentage. The correlation coefficient (r=0.237) for the relationship of rotted tissue and dry matter was not statistically significant (p=0.144). However, the correlation coefficient (r=-0.374) for the relationship of rotted tissue and calcium was statistically significant (p=0.018). The regression model considering both calcium and dry mater percentage was significant (p<0.05) at a 5 % significance level.

The regression model is: Rotted tissue (%) = 58.74 + 1.85 Dry matter (%) – 51.02 Ca

Knowledge Management: Report/Proceedings