Density and Distribution of False Smut Balls on Infected Rice Panicles

Abstract

Rice false smut (RFSm), considered as a minor importance, has become a serious disease in many rice growing areas of Bangladesh and other parts of the world. Many aspects of its epidemiology still remained unclear, notable the life cycle of RFSm pathogen, its infection site and the smut ball formation on infected panicles. Present research was undertaken to investigate the density and distribution of false smut balls on infected rice panicles aiding to understand on how severe the disease can be in a rice-ecosystem, on which position the smut balls form on infected panicles and likely yield reduction from such disease severity. This study included field observation of natural RFSm infection during 2014, 2015 and 2016, and simulated infection during 2015 in T. Aman rice in the experimental farm of the Bangladesh Rice Research Institute (BRRI), Gazipur, Bangladesh. While the number of smut balls reached as many as 136 (recorded in one panicle in 2015), the study shows there was 81, 54 and 30% probability that maximum of nine, three and only one smut ball would form, respectively. With the scenarios of density of smut ball formation in the study area, the yield loss was estimated as 0.15% for each 1% incidence level. The level of smut ball density varied between years; this severity was most likely influenced by low daily minimum temperature. In the natural observation 34.4, 53.9 and 11.7% of the smut balls were located at the base, mid and apex part of the infected panicles, respectively. When compared the balls of these three positions in relation to potential grain number, the proportion accounted for the base and mid remained almost similar, whereas the proportion in the apex was much lower. It is concluded that false smut balls predominantly form on the lower half of the infected rice panicles.

Seed Germination and Grain Quality of Rice as Affected by False Smut Disease

“…The yield loss from RFSm has been reported in many countries in varying figures ranging from ~1 (Atia, 2004) to over 75% (Upadhyay and Singh, 2013). The density of smut balls can reach as high as 136; there is ~30% probability that 1, ~14% probability that 2, ~10% probability that 3, ~7% probability that 4 and ~6% probability that 5 smuts balls will form on an infected panicle (Nessa et al, 2016). Sarker et al (2016) recorded on average 0.72% yield loss in four surveyed 'unions' of Natore district of Bangladesh; however, in severe cases the loss went up to 4.5% in few fields.…”

Survey and symptomatology of false smut [Ustilaginoidea virens (Cooke)Takahashi] of rice

“…The disease occurs in more than 40 countries, especially in the rice producing countries of Asia and U. S. In India, the disease has been observed in severe form since 2001 in major rice-growing states, viz., Haryana, Punjab, Uttar Pradesh, Uttaranchal, Tamil Nadu, Karnataka, Andhra Pradesh, Bihar, Jharkhand, Gujarat, Maharashtra, Jammu and Kashmir and Pondicherry (Dodan and Singh, 1996;Mandhare et al, 2008). In Gazipur, Bangladesh, 136 smut balls and 53.9 per cent infected grains were recorded per panicle (Nessa et al, 2016). In India, disease incidence of 10 to 20 and 5 to 85 per cent has been reported, respectively from Punjab and Tamil Nadu on different rice cultivars (Ladhalakshmi et al, 2012).…”

Weather Condition, Seasonal Variation and Ball Development Pattern in Relation to Rice False Smut Disease in Bangladesh

“…It has been recorded in the pattern of aggregation in spaces in most of the fields (Nessa et al 2015b). On infected panicles, there is about 60% probability that maximum of four smut balls will appear and about 88% of those balls will locate in the mid to basal part (Nessa et al 2016). Further, the grain quality issues in relation to RFSm have been studied (Nessa et al 2018).…”