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Screening of Rice Germplasm/cultivar Against Rhizoctonia Oryzae-sativae, the Causal Organism of Aggregate Sheath Spot of Rice

SB Jahan*
Department of Botany, Rajshahi University

MA Ali
Plant Pathology Division, Bangladesh Rice Research Institute,

S Alam
Department of Botany, Rajshahi University

ZR Moni
Plant breeding division, Bangladesh Rice Research Institute, Joydebpur, Gazipur-1701.

MS Mian
Plant Pathology Division, Bangladesh Rice Research Institute, Gazipur-1701

MA Alam
Plant breeding division, Bangladesh Rice Research Institute, Joydebpur, Gazipur-1701.

Abstract/ Executive Summary:

Three field experiments were conducted to screen sixty rice germplasm /cultivars against aggregate sheath spot disease caused by Rhizoctonia oryzae-sativae during T. Aus, T. Aman and Boro seasons of 2012-2013 under field conditions in Bangladesh. The disease growth and development in all the three rice growing seasons among the germplasm and cultivars were tested. None of the tested germplasm or cultivars found immune (no disease) to aggregate sheath spot disease. Without considering the varietals difference, the RLH was lower in Boro season compared to either T. Aman or T. Aus. The RLH appeared in a similar range during T. Aman and T. Aus season. Among 60 germplasm and cultivars tested, the highest RLH was observed in Kurchi binni (26.24%) followed by Akuee (24.18%). The highest number of tillers infected in Akuee (75.78%) followed by Lotabhog (75.43%) and Aus boro (73.26%). The lowest RLH (9.80%) corresponding to 49.5% tiller was found infected in Panisail during T. Aman. There were significant negative correlations between plant height and relative lesion height (RLH) in all the three seasons. Similar results were also found between plant height and disease incidences. Field trial results indicated that almost all Bangladeshi dwarf and semi dwarf cultivars or germplasm were more vulnerable to the disease than tall cultivars.

Keywords: Screening, Rice cultivars, Aggregate sheath spot disease

Location: Experimental farm of Bangladesh Rice Research Institute (BRRI), Gazipur

Start Date: 00-03-2012

End Date: 00-06-2013

Program Area: Pest Management

Commodity: Rice

Objectives:

The present experiment was undertaken to know the disease reaction of the germplasm/cultivar against aggregate sheath spot disease.

Methodology:

The experiments were conducted at the experimental farm of Bangladesh Rice Research Institute (BRRI), Gazipur during March, 2012 to June, 2013. Three experiments were conducted separately in T. Aus, T. Aman and Boro seasons. A total of 60 germplasm/cultivars were investigated during T. Aus, T. aman and Boro seasons each with 20 germplasm/cultivars. 70-90 cm long rice plants were treated as dwarf, 95-100 cm long rice plants were treated as semi-dwarf and 105-140 cm long rice plants were treated as tall. Land preparation Land was cultivated first at 15 days before transplanting. Ploughing and cross ploughing followed by laddering was done by power tiller to attain puddle condition before transplanting. Weeds were cleaned manually. A levee was made surrounding the experimental area to maintain standing water up to 5.0 cm. Seedling rising Seeds were treated with hot water at 52°C for 20 min. Treated seeds were then soaked for 24 hours in water. Sprouted seeds were sown in tray for seedling growing after the required incubation in each season. Transplanting Seedlings were transplanted in the field after 21 days, 30 days, and 35 days of seeding in T. Aus, T. Aman and Boro seasons respectively with 3-4 seedlings per hill. Spacing was 15 cm x 20 cm. All fertilizers were applied in basal except urea. Urea was applied in three equal splits at 15, 35 and 55 days after transplanting. BRRI recommended rice production procedures were followed in the respective season. Preparation of inoculums and inoculation Isolate of Rhizoctonia oryzae-sativae (MY-1) was collected from laboratory of Plant Pathology Division, BRRI, Gazipur. Pure culture of the isolate was grown on 9 cm PDA plate and incubated at ambient temperature for 7 days to allow approximately full plate growth. PDA plates with 7 days old inocula were divided into 8 equal splits. Each portion of the PDA with mycelia plugs was inserted at the base of each hill following Lanoiselet et al. (2001). There were three replications for each germplasm/cultivars. Three plants in each cultivar and each replication were inoculated artificially at maximum tillering stage. Data recording All the inoculated hills were cut from the ground level after 21 days of inoculation. Data ie. Plant height, lesion height, incidence (% tiller infection) were taken from all the infected hills at the plant pathology laboratory in BRRI. The relative lesion height were calculated using the following formula- RLH (%) = (Lesion height/Plant height) X 100. The scale was developed by Ahn et al. (1986). This is a qualitative scale which differentiates varietal reactions. Incidence was calculated by the following formula: Incidence (%) = (No. of infected tiller/No. of total tiller) X 100. Data analysis: Data were subjected to analysis of variance followed by mean separation through least significant difference (LSD) test at α=0.05 using CropStat (version 7.2). The correlation analyses were done by using computer software Stata (version 12).

Source of Information: Eco-friendly Agril. J. 7(08): 76-80, 2014 (August)

Article Link (Online Journal): http://efaj-international.com/wp-content/uploads/2014/12/1-EFAJ-708-76-80-2014.pdf

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The present study revealed that Balam, Agoan from T. Aus, Panisail from T. Aman and BR7, BR9 and BRRI dhan27 from Boro found better among the tested materials against the pathogen. Since resistance was dominated by plant height therefore modern varieties should be targeted to moderate plant height with high yield potential. Cultivars architecture showed greatly influenced by physiological, morphological and ecological factors (Lee and Rush, 1983). During winter, Boro season starts usually from November when temperature and humidity remain low until end of February. During this time the pathogen remain dormant at the base of the plant. When temperature starts to increase from March, the pathogens become active until crop harvest in April and May (Ali 2002). Therefore, low level of upward progress is not unusual as found in this experiment in Boro season while T. Aus and T. Aman temperature and relative humidity remain optimum for the disease development. Therefore, cultivars that showed least disease reaction (incidence and RLH) may be useful for resistant breeding program. Field trial results also indicated that almost all Bangladeshi semi dwarf cultivars or germplasm were more vulnerable to the disease than tall cultivars that perhaps induces favorable microclimate conditions for pathogen growth and development compared to the tall cultivars. The dwarf and semi dwarf cultivars that have greater tillering capacity pathogen could easily spread horizontally and vertically but in tall cultivars the microclimate particularly in the upper canopy level relative humidity become lower as breeze and higher sunlight penetration hampers mycelelial growth, colonization and disease establishment.

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