False smut is a disease of rice inflorescence. The existing systems of disease severity assessment for rice false smut disease are not very sensitive as the ball quality and also the impact of false smut on filled grain number and grain‐filling were not under consideration. Here, a precise assessment method to evaluate the severity of the disease was developed. The ‘yield representative’ (YR) based on ‘mean floret wt.’ and ‘filled grain %’ was simulated for the precise disease severity assessment of rice false smut disease. The single floret weight envisages major yield components irrespective of the type of panicle. Correlation between YR and major yield attributes was studied, and it was observed that YR had significant correlation with ‘filled grain %’ (0.77–0.95) and ‘single spikelet weight’ (0.88–0.98). Significant negative correlation of YR was observed with the chaff percentage, false smut ball number and ball weight. This YR‐based methodology was utilized to assess the disease severity in nine rice cultivars. The disease severity in those nine cultivars was evaluated by the already existing methodologies also. The disease severity measured by the present technique was compared with the disease severity assessed by the old methodologies. The procedure adapted here for disease severity measurement was found to be more informative and useful. It was observed that in case of mild infection, the false smut was enhancing yield attributes. The high‐yielding rice varieties Savitri and Gayatri were found to be tolerant to false smut and may be used as resistant donors.
Fusarium species mainly produce fumonisins group of mycotoxins which are classified as Group 2B human carcinogen by International Agency for Research on Cancer (IARC). In poor storage conditions, Fusarium species producing fumonisins can infect rice or paddy (Oryza sativa L.) which is the highest produced and consumed staple food in India. A rapid molecular method using primer Fum5F and Fum6R detected 85% fumonisin producers among 28 Fusarium isolates from Indian rice cultivars. Genetic variability of the isolates was studied by PCR based RAPD assay using 13 random primers. A total of 169 polymorphic bands were obtained by 13 markers with an average polymorphism information content (PIC) of 0.665 and overall polymorphism of 88%. Primer 3B showed a polymorphism of 96% with PIC value of 0.66 and it amplified 26 scorable fragments hence may be useful for the analysis of genetic variation among Fusarium isolates. Four strains (F47, F90, F92 and F96) in which fum gene wasn't amplified by Fum5F and Fum6R and supposed to be non producer of fumonisin have been consistently placed in one separate group by RAPD primers. Genetic variation of toxic Fusarium in rice from India is less studied. RAPD proved to be a suitable tool for depicting Polymorphism among the isolates. The high genetic variability among the Fusarium isolates used in the current study is a matter of concern considering the importance of Rice in India.
Highlights• Fumonisins are Group 2B human carcinogen produced by Fusarium species.• Fum5F and Fum6R primer pair detected fumonisin producers.• RAPD primers deciphered 88% polymorphism among 26 Fusarium isolates.
Mycotoxins produced by many food spoilage fungi cause serious damage to human as well as to livestock. Aflatoxins are one such group of mycotoxins produced by Aspergillus flavus in many agricultural and food products including rice. The fungus can virtually grow in any environment and also produces resistive structures such as sclerotia to overcome unfavourable environmental conditions. Hence, the need of the time is to control this toxigenic and sclerotic fungus through an eco-friendly approach. In the current study four biocontrol bacteria belonging to Bacillus species were isolated from Indian cow shed environment and these bacteria could efficiently control not only the mycelia growth of A. flavus but also the germination and growth of sclerotia. Both active bacterial culture broth and cell free culture filtrate could limit the growth of the fungus up to more than 90%. Older culture broth and filtrate lost their inhibition efficiency. Unlike many similar studies the current investigation emphasizes the importance of cowshed environment instead of cow dung and the control of sclerotia instead of fungal spores.
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