Sheath blight development and yield loss on rice in different epidemiological conditions
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ORIGINAL PAPER
Sheath blight development and yield loss on rice in different epidemiological conditions Maryam Khoshkdaman 1 & Sedigheh Mousanejad 1 Fereidoun Padasht-Dehkaei 2
&
Seyed Ali Elahinia 1 & Ali Akbar Ebadi 2 &
Received: 5 May 2019 / Accepted: 27 August 2020 # Società Italiana di Patologia Vegetale (S.I.Pa.V.) 2020
Abstract Rice sheath blight and its causal agent Rhizoctonia solani AG-1 IA are associated with intensive and high input production systems. To our knowledge, resistant varieties have not been introduced for this disease, thus good crop management is expected to be among viable disease control methods. The aims of the present study were to determine the effect of different rates of nitrogen fertilizer, planting spaces and inoculum densities on sheath blight incidence and severity, including grain yield loss. Additionally we aimed to identify those developmental stages that are more susceptible to the disease. Field experiments were conducted over two consecutive years, in 2017 and 2018 in the Guilan province of Iran. Results indicated that higher N rates, denser planting and higher initial inoculum density resulted in greater disease development. Among five different growth stages, inoculation of plants at booting and flowering stages, resulted in maximum disease severity and grain yield loss. Taken together, reasonable use of nitrogen fertilizer, optimum planting space and reduced inoculum density obtained by spraying fungicide at the booting and flowering stages of rice are suggested as the best options to control sheath blight epidemics in rice. Keywords Rice . Sheath blight . Growth rate . Cultural practices . IPM
Introduction Sheath blight (ShB) disease caused by Rhizoctonia solani Kȕhn (teleomorph: Thanatephorus cucumeris (Fronk) Donk) anastomosis group 1 (Gangopadyay and Chakrabarti 1982; Ou 1987) has become an important disease of rice (Oryza sativa L.), * Sedigheh Mousanejad [email protected] Maryam Khoshkdaman [email protected] Seyed Ali Elahinia [email protected] Ali Akbar Ebadi [email protected] Fereidoun Padasht-Dehkaei [email protected] 1
Department of Plant Protection, Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran
2
Rice Research Institute of Iran (RRII), Agricultural Research Education and Extension Organization (AREEO), Rasht, Iran
especially in intensive production systems (Otomo 1989; Savary et al. 1994). Sheath blight disease was first described in Japan at the beginning of the twentieth century (Kozaka 1975) and has been reported in most rice- growing areas worldwide (Ou 1985). The first report of the disease in Mazandaran province, Iran dated back to 1981 (Torabi and Binesh 1984). Since several modern varieties with high yield, early maturity, semidwarf and higher demand for nitrogen fertilizer have been developed, sheath blight is the second most important fungal disease of rice after blast disease in northern Iran (Okhovvat 1999). Several studies have reported the yield losses due to the ShB disease (Hori 1991; Inagaki 200
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