Pathogenicity of <I>Rhizoctonia solani</I> AG 1-IA on Major Weeds Prevalent in Rice and Maize Ecosystem in Meghalaya

Abstract

Rhizoctonia solani Kühn (Teleomorph: Thanatephorus cucumeris) is an economically important soil borne basidiomycetous pathogen of worldwide distribution. It causes sheath blight disease of rice and banded leaf and sheath blight (BLSB) disease in maize. Twenty three lowland rice weeds and thirty one upland (maize) weeds were collected and used. Rice isolate (SRS) was pathogenic on all the lowland rice and upland weeds. Maize isolate (RSM2) was not pathogenic on Cyperus difformis, C. haspans, C. odoratus, Sagittaria sagittifolia, Celosia argentea, Commelina diffusa and Floscopa scandens. Minimum days for scleriotia formation was 3 days on C. bengalensis, maximum sclerotia production was observed on Echinochloa crusgalli (14 nos.) with the isolate SRS. Minimum days for sclerotia formation was 2 days after inoculation on Euphorbia hirta, Fimbristylis dichotoma, Rotala indica and Scirpus juncoides. Maximum sclerotia production was observed on Alternanthera philoxeroides (11 nos.) with the isolate RSM2. Area under disease progress curve was calculated and mean separation was done using REGWQ test (Ryan/Elinot/Gabriel/Welsch procedure). The weeds Ageratum houstonianum (10.2), A. sessilis (14), A. philoxeroides (25.3), Imperata cylindrica (14), Paspalum distichum (17.8) and Ambrosia artemisiifolia (23.3) were susceptible whereas Dactyloctenium aegyptium (115.6), E. colona (115.6) and Bidens pilosa (111.9) were highly susceptible to the isolate SRS. The weed A. houstonianum (43.7) was susceptible and R. indica (267.4) and E. hirta (266.2) were highly susceptible to the isolate RSM2.

Pathogenicity of Rhizoctonia solani AG 1-IB on common weeds in Meghalaya

“…Kannaiyan and Prasad (1979) have also reported that R. solani occured on 21 weed hosts and it was severe on weeds like Eriochloa procera, Andropogon asper, Cynodon dactylon and Ischaemum indicum. Saveinai et al (2017) did similar kind of work on pathogeniticity of R. solani AG 1-IA on weeds and results showed that isolate SRS (isolated from rice) was pathogenic on all the weeds and isolate RSM2 (isolated from maize) was found to be pathogenic on all weeds except Cyperus difformis, C. haspans, C. odoratus, S. sagittifolia, Celosia argentea, Commelina diffusa and F. miliacea. In our findings, R. solani AG 1-IB (isolated from soybean) was pathogenic on all the weeds.…”

“…Experiments related to "Pathogenicity of R. solani AG 1-IB on common weeds in Meghalaya" were conducted at ICAR Research Complex for NEH Region, Umiam, Meghalaya during 2016-2017. Infected soybean samples exhibiting web blight symptoms were collected from experimental plots of ICAR, Umiam and isolation was done following the method as described in Saveinai (2016) PCR was used for amplification of extracted DNA with specific primers for AG 1-IA and IB (Matsumoto 2002 andSayler andYang 2007). Both positive and negative controls were also used.The DNA extraction, PCR (with minor modifications), gel documentation and identification was done following the procedure described by Mahendra et al (2016).One isolate (PPJ3) was also amplified and Highly susceptible weeds identified in this study should be avoided for mulching purpose since this will increase the inoculum load of this pathogen sequenced by using universal primers for ITS region (ITS 5 and 4) (White et al 1990) and the sequence was deposited in Genbank.…”

“…Same method was used for testing pathogenicity of PPJ3 isolate on common weeds. The area under disease progress curve (AUDPC) was calculated and analysis was done as mentioned in Saveinai et al (2017).…”

“…The weeds P. dilatatum (18.1) E. crusgalli (18.6) and A. bengalensis (20.1) were least susceptible and statistically at par followed by E. colona (23.4). Saveinai et al (2017) have conducted the susceptibility analysis of R. solani AG 1-IA on weeds by using AUDPC criteria. They also observed great variation in susceptibility of weeds to R. solani AG 1-IA using this criteria.…”

“…Several weeds and cultivated plant species are known to act as alternate and collateral hosts of R. solani in different agro-climatic regions of India (Chahal et al 2003 andSaveinai et al 2017). Information related to pathogencity of R. solani on different weeds is scarce.…”