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Screening for Resistance Against Rice Bacterial Blight in Bangladesh

A. H. Mondal
Plant Pathology Division, Bangladesh Rice Research Institute, Joydebpur, Gazipur-1701, Bangladesh.

M. A. Hossain
Plant Pathology Division, Bangladesh Rice Research Institute, Joydebpur, Gazipur-1701, Bangladesh.

Abstract/ Executive Summary:

A total of 6273 rice entries were screened during 1991-'95 against a virulent bacterial isolate BXO9 of Xanthomonas oryzae pv. oryzae which causes bacterial blight (BB) in rice. Results showed that out of 868, 1678 and 3737 entries 152, 189 and 267 were found resistant, respectively in Boro, Aus and T. Aman seasons. Seven entries which showed consistently resistant reaction were reconfirmed in consecutive tests; and the mean Disease Indices (DI) were 2.6 - 3.2 over 5 years. These entries can be used as donors for BB resistance or some, if not all, can be used directly as resistant varieties after subsequent yield trials.

Keywords: Screening, Rice, Bacterial blight, Resistance

Location: Plant Pathology Division, Bangladesh Rice Research Institute, Joydebpur, Gazipur

Start Date:

End Date:

Program Area: Pest Management

Commodity: Rice

Objectives:

To evaluate the screening for resistance against rice bacterial blight in Bangladesh

Methodology:

To standardize a screening system throughout the world IRRI has developed a model for testing rice entries against BB. Following the rules of IRBBN, nurseries were set in Boro, Aus and T. Aman seasons during 1991- 95. A row plot of 2.5 - 3.0 metres long with a spacing of 20 cm x 20 cm was set for each entry for testing. After every ten test entries, a susceptible check and a resistant check were set alternately. Prior to transplanting, the field soil was fertilized with complete fertilizers as per recommendation for the seasons. A virulent local isolate BXO9 of X. oryzae. pv. oryzae was collected from the infested field every year and isolated on Peptone Sucrose Agar (PSA). The isolate was retested for its virulence on a highly susceptible check variety Purbachi and reisolated and multiplied on PSA for inoculation of test entries. Seventy two hours old culture of BXO9 was used to prepare a turbid suspension having a concentration of 10^8-9 cfu/ml. Five hills from the middle of every entry were inoculated with the suspension following clipping method of inoculation. Disease index (DI) was recorded after 21 days in Boro and 14 days in Aus and T. Aman seasons following Standard Evaluation System (SES) for rice (IRRI 1988). Rice entries found resistant were marked and seeds were collected, and those were planted for retest in the next season. The photosensitive entries were retested only in T. Aman season for flowering and seed collection. After confirmation of resistance by artificial inoculation in two consecutive seasons, the entries were retested against the same bacterial isolate for reconfirmation as resistant. The test entries once showed susceptible were discarded. During all the tests susceptible and resistant checks were included to validate the result. The prehistory of seven selected rice entries, namely BR808-10-3-3 (BG90-2/IR2863-39-2), BR4611-14-4-1-5 (BR8/IR7676-12-1-2), BR4611-172-1-1-2 (BR8/IR7676-12-1-2), BR4656-16-4-2-3-2 (BG367-4/IR4744-295-2-3), BR4661-21-1-4-2-5 (BR319-1-HR28/BR161-2B-28), BR4689-17-1-5 (BR161-2B-58/BR319-1-HR11), BR4829-28-2-4 (IR19660-11/BR1081-9-2-5-1), were recorded. Finally, agronomic characters like growth duration, plant height, effective tillering, ability, grain size and shape were recorded from field and pot cultures in different seasons. A preliminary yield trial was set up in Aus season of 1995. For these seedlings of each entry were grown in seedbeds and transplanted as single seedling/hill with a spacing of 20 cm x 20 cm in 1 m x 1 m replicated plots. Grain yield was estimated at 14% moisture content after harvest.

Source of Information: Bangladesh J. Bot. 26(1): 25-29, 1997 (June), ISSN-0253-5416.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Considering the consistent disease reactions and the observed agronomic characters of the seven entries it is concluded that these entries may be used as donors for BB resistance and after subsequent yield trials some of them, if not all, can be used directly as BB resistant varieties.

Knowledge Management: Journal