Development of high throughput screening protocol and identification of novel sources of resistance against bakanae disease in rice (Oryza sativaL.)

Abstract

Bakanae or foot rot disease caused by Fusarium fujikuroi (teleomorph: Gibberella fujikuroi, Sawada, Wollenweber) is emerging as a serious disease of rice. A simple, reliable and high-throughput method for screening the disease would enable rapid screening of germplasm aimed at identifying resistance sources, mapping QTLs/genes and developing resistant rice cultivars. In the present study, a highthroughput, reliable bioassay to screen rice germplasm for resistance to bakanae disease was developed and compared with the conventional screening technique. This technique involves soaking of rice seeds in fungal spore suspension (1.0x10 6 spores ml-1) for 24 hours at room temperature. Seedling growth at 30°/25° (±3)°C day/night temperature and 60/80(±10)% day/night relative humidity in glasshouse gave the best results. The new protocol described here produces consistent and reproducible bakanae disease symptoms and enables screening of hundreds of rice germplasm within 15 days without any loss of precision in screening of rice genotypes against bakanae disease. The resistant and susceptible genotypes can be used for developing mapping population and identification of QTLs/genes conferring resistance to bakanae disease.

Mapping quantitative trait loci responsible for resistance to Bakanae disease in rice

“…In our previous study, we have developed a high throughput screening technique to screen large number of germplasm and to identify resistant sources against Bakanae disease. Using this method, we have identified Pusa Basmati 1121 as highly susceptible and Pusa 1342 as highly resistant genotypes (Fiyaz et al 2014 ). A mapping population developed earlier in our lab using the above lines as parents (Amarawathi et al 2008 ) was available for mapping QTLs conferring resistance to Bakanae disease.…”

“…Among the potentially important diseases of contemporary importance, Bakanae or foot rot disease, caused by Fusarium fujikuroi (Nirenberg), [teleomorph: Gibberella fujikuroi (Sawada) Ito] has emerged as a disease of major concern (Bashyal et al 2016 ). The disease can cause upto 70 % yield loss and impairs the grain quality as well, under the field conditions (Fiyaz et al 2014 ). Bakanae disease of rice occurs widely throughout Asia and sporadically in other areas of rice production (Sun and Snyder 1981 ; Webster and Gunnell 1992 ).…”

“…In recent times, use of new methods for raising seedlings, especially growing in seed boxes for mechanical transplanting (Rosales and Mew 1997 ) and dry seed-bed raising for hybrid rice, have favoured conditions for several minor diseases, that are not considered serious under open field nurseries. Among these, Bakanae disease is frequently encountered and has become more and more serious (Li and Luo 1997 ; Yang et al 2003 ) leading to outbreaks in many countries like Japan, Korea and is becoming a serious threat in some rice growing regions of India and Philippines (Cumagun et al 2011 , Bashyal et al 2014 ; Fiyaz et al 2014 ).…”

Resistance mechanism of Fusarium fujikuroi to phenamacril in the field

“…On rice, F. fujikuroi can induce the following symptoms: seedling rot and elongation, grain sterility and discoloration . It not only reduces grain yield, but also produces harmful toxins including gibberellins and fusaric acid, which threaten human health …”

“…5 It not only reduces grain yield, but also produces harmful toxins including gibberellins and fusaric acid, which threaten human health. 6,7 Phenamacril (development code number JS399-19), 2-cyano-3amino-3-phenylancryic acetate (Fig. 1), developed by Jiangsu Pesticide Research Institute Co. Ltd (Nanjing, China), is the first identified member of a new chemical group, classified B6 by the Fungicide Resistance Action Committee (FRAC; www.frac.info).…”