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Inoculation Techniques for Screening Rice Cultivars Against Bacterial Leaf Streak Disease

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

M. A. Ali
Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh, Bangladesh.

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

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

Abstract/ Executive Summary:

Eight inoculation techniques, namely tooth brush hard, tooth brush medium, tooth brush soft, coir rope, coir rope injury - spraying BS clipping method, foliar spray and iron scrapper, were evaluated for bacterial leaf streak disease development of rice during three seasons (Aus 1986, T. Aman 1986 and T. Aman 1994). Among the methods, tooth brush medium is recommended for small scale and specific inoculation in evaluating rice entries/ cultivars against BLS in the greenhouse and coir rope method is recommended for large scale inoculation in the field for screening purpose. Iron scrapping method is effective but it is troublesome as well as tedious. Clipping method of inoculation completely failed to cause any BLS infection.

Keywords: Bacterial leaf streak, Inoculation techniques, Rice cultivar

Location: Bangladesh Rice Research Institute.

Start Date:

End Date:

Program Area: Pest Management

Commodity: Diseases

Objectives:

To find out convenient methods for screening rice cultivars/varieties against bacterial leaf streak disease.

Methodology:

BLS susceptible cultivar, Purbachi was used in this experiment. Clay soil collected from the field was mixed with cowdung (5: 1) along with potash and TSP. Finally, the soils were filled in earthen pots (12 cm diam) and kept saturated with water. Five sprouted seeds were sown in each pot. Ten days after sowing (DAS), three seedlings of equal height per pot were maintained. At 30 DAS, homogeneous population was maintained by thinning out the weak plants. Finally, one plant per pot was allowed to grow and fertilized with urea (1g/pot). A local isolate, Bxtl of Xanthomonas oryzae pv. oryzicola, was collected from the field of Bangladesh Rice Research Institute. The isolate was cultured on peptone sucrose agar (PSA) medium and was incubated at 28 ± 1°C for its growth and development. Forty eight hrs old bacterial cultures were suspended having 10^8-10 cfu/ml of water. A total of eight inoculation techniques were evaluated for their effectivity on the BLS development. Among them, initially five inoculation techniques namely, tooth brush hard (TBH), tooth brush medium (TBM), tooth brush soft (TBS), iron scrapper (IS) and foliar spray (FS) were evaluated during Aus, 1986. During transplanted Aman (T. Aman) 1986, TBM was compared with other inoculation techniques vir. coir rope spraying (CRS) and clipping method (CM). IS and FS methods were excluded in T. Aman 1986 because of low disease development in the previous season. The suitability and effectivity of CR and TBM for screening rice varieties or lines against BLS were observed during T. Aman, 1994. The inoculation methods were as follows. Tooth brush with different qualities of nylon bristles such as hard, medium and soft was used. The bristles of the tooth brush were dipped in BS. The head of the brush was placed on the leaf blade with the handle at right angle to the midrib. The leaf blade was then rubbed gently along the midrib from base to tip. After each five leaves inoculation, the bristles of the brush was again dipped in bacterial suspension. A threefold coir rope made of coconut fibre was used in this method. For inoculation, the middle portion of rope was dipped in the BS and splashed on the leaf by rapid and sudden pulling of the rope from base to tip. Four splashes were made on the four sides of the plant covering all the leaves. Inoculation was done by spraying BS on the leaves following injury by coir rope as mentioned above instead of dipping the rope in BS. A pair of sterile scissors (15 cm) was dipped in BS. The tip (1.5 - 2.0 cm) of the leaf blades were clipped with the help of scissors. The scissors were regularly dipped in the suspension after clipping each of the five leaves. BS was sprayed on the surface of the leaf blades with the help of a fine hand sprayer made by CIBA - GAIGY. One hand press per leaf was practiced to inoculate the test plants. The iron scrapper composed of two jaws (made at BRRI). The lower jaw was flat, the upper jaw was serrated like saw teeth to facilitate leaf injury. The lower jaw was wrapped with a mass of cotton and was soaked with BS prior to inoculation. The leaf blade was placed in between the two jaws of the scrapper. Finally, the lower jaw was placed on the lower side of the leaf and the upper jaw of the scrapper was pressed down slightly and pulled up slowly along the length of the leaf blade. After inoculation of every three leaves, lower jaw was dipped in BS. The disease reaction was recorded at 14 and 21 days after inoculation (DAI) following standard evaluation system (SES) developed by IRRI. The rate of disease development for each of the inoculation techniques was also determined along with the incubation period.

Source of Information: Bangladesh J. Bot. 26(1): 43-49, 1997 (June), ISSN:0253-5416.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

For inoculation of specific leaf of the plant CR method is less effective than TBM which is the most effective especially for genetic studies. IS method is effective but it is troublesome as well as tedious. Considering all the situations, TBM is recommended for small scale and specific inoculation in evaluating rice entries/cultivars against BLS for genetic studies in the greenhouse and CR method is recommended for large scale inoculation in the field for screening purpose.

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