Phenotypic and Molecular Analyses of Rhizoctonia spp. Associated with Rice and Other Hosts.

Regina Faye C Sandoval,Christian Joseph R Cumagun

doi:10.3390/microorganisms7030088

Regina Faye C Sandoval, Christian Joseph R Cumagun

Open Access

https://doi.org/10.3390/microorganisms7030088

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Abstract

Forty-two Rhizoctonia isolates were collected from rice, mung bean, and grasses from Laguna, Philippines. Sixteen isolates were binucleate Rhizoctonia (BNR), while 26 were multinucleate Rhizoctonia (MNR). BNR isolates produced white to brown, small sclerotia (<1.0 mm) except for mung bean isolates. Twenty MNR isolates produced big (>1.0 mm), light to dark brown sclerotia, three produced salmon-colored masses in the medium, and three did not produce sclerotia. Twenty-three MNR isolates were identified as R. solani AG1-IA using specific primers. Deduced Internal Transcribed Spacer (ITS) sequences of BNR isolates D1FL, NVL, and ScNL shared 100, 97, and 100% identity with R. oryzae-sativae, respectively, while MNR isolates BMgL, IbMgL, and MaSL that produced salmon-colored masses shared 100, 90, and 100% identity with R. oryzae, respectively. Preliminary analysis of the DNA fingerprint patterns generated by repetitive-element PCR (rep-PCR) clustered the 42 isolates into three: R. solani, R. oryzae-sativae, and R. oryzae, together with Ceratobasidium sp. R. solani isolates were pathogenic on rice (TN1), barnyard grass, mungbean (Pagasa 3), and tomato (Athena), while R. oryzae and R. oryzae-sativae isolates were only pathogenic on rice, Echinochloa crus-galli, and tomato. R. solani and R. oryzae were found to be more virulent than R. oryzae-sativae.

Highlights

Rice is a staple food in many countries across the globe including the Philippines
R. solani isolates were pathogenic on rice (TN1), barnyard grass, mungbean (Pagasa 3), and tomato (Athena), while R. oryzae and R. oryzae-sativae isolates were only pathogenic on rice, Echinochloa crus-galli, and tomato
Samples with sheath blight symptoms were collected from 59 barangays from 16 towns in Laguna and one town in Quezon

Summary

Introduction

Rice is a staple food in many countries across the globe including the Philippines. In 2009, it was recorded that Filipinos eat an average of 123 kg of rice per person annually—which was among the highest in the world [1]. About 4.7 million hectares is planted with rice in the country, producing about 18.9 million metric tons [2]. Rice sheath blight caused by Rhizoctonia solani was the second most important pathogen of rice in rice-growing countries for the last two decades [3]. When susceptible cultivars were planted in United States, a yield loss as high as 50% was observed [4]. In Asia, annual yield losses of 10% and 20% due to sheath blight are observed in India and Thailand, respectively [5]. In the Philippines, Dilla observed 3.59 to 27.01% (0.34 to 1.09 t/ha) and 3.16 to 28.62% (0.35 to 1.66 t/ha) yield reduction during the wet and dry seasons, respectively [6]

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