Enumeration, isolation and identification of diazotrophs from Korean wetland rice varieties grown with long-term application of N and compost and their short-term inoculation effect on rice plants

Abstract

Aim: This study has been aimed (i) to isolate and identify diazotrophs from Korean rice varieties; (ii) to examine the long-term effect of N and compost on the population dynamics of diazotrophs and (iii) to realize the shot-term inoculation effect of these diazotrophs on rice seedlings. Methods and Results: Diazotrophic and heterotrophic bacterial numbers were enumerated by most probable number method and the isolates were identified based on morphological, physiological, biochemical and 16s rDNA sequence analysis. Long-term application of fertilizer N with compost enhanced both these numbers in rice plants and its environment. Bacteria were high in numbers when malate and azelaic acids were used as carbon source, but less when sucrose was used as a carbon substrate. The combined application promoted the association of diazotrophic bacteria like Azospirillum spp., Herbaspirillum spp., Burkholderia spp., Gluconacetobacter diazotrophicus and Pseudomonas spp. in wetland rice plants. Detection of nifD genes from different diazotrophic isolates indicated their nitrogen fixing ability. Inoculation of a representative isolate from each group onto rice seedlings of the variety IR 36 grown in test tubes indicated the positive effect of these diazotrophs on the growth of rice seedlings though the percentage of N present in the plants did not differ much. Conclusions: Application of compost with fertilizer N promoted the diazotrophic and heterotrophic bacterial numbers and their association with wetland rice and its environment. Compost application in high N fertilized fields would avert the reduction of N 2 -fixing bacterial numbers and their association was beneficial to the growth of rice plants. Significance and Impact of the Study: The inhibitory effect of high N fertilization on diazotrophic bacterial numbers could be reduced by the application of compost and this observation would encourage more usage of organic manure. This study has also thrown light on the wider geographic distribution of G. diazotrophicus with wetland rice in temperate region where sugarcane (from which this bacterium was first reported to be associating and thereon from other plant species) is not cultivated.

Germinação e vigor de sementes de arroz inoculadas com bactérias diazotróficas

“…Um numeroso e diverso espectro de bactérias diazotróficas tem sido isolado de plantas de arroz (Elbeltagy et al, 2001;Muthukumarasamy et al, 2007). Segundo Peng et al (2002) é possível que muitas dessas bactérias associadas às plantas de arroz estejam envolvidas na promoção do crescimento de plantas.…”

Induction of endophytic colonization in rice (Oryza sativa L.) tissue culture plants by Azorhizobium caulinodans

“…Hence, it is important to develop strategies that enable enhanced diazotrophic bacterial colonization for significant endophytic BNF in rice. N 2 fixation by inoculated diazotrophs per se seems to have minimal but significant effect on the nitrogen content of the biotized plantlets, as it was clear from the data of percent N content of inoculated samples (Muthukumarasamy et al 2007). It is also presumed that the bacteria used for inoculation in the present study appears to act as that of plant growth promoting rhizobacteria (PGPR).…”

Yield Potentials of Rice and Soybean As Affected by Cropping Systems in Mid-mountainous Paddy Soils of Korea

“…리, 재배작물, pH와 유기물 등의 영양성분, 그리고 미생물의 활동 등의 종합적인 영향을 받아 형성되는 것으로 알려져 있다 (Cook, 2006;Im, 1978;Lee et al, 2008;Muthukumarasamy et al, 2007;Olk et al, 2000;Power, 1987). 그리 고 이러한 지력의 효과적인 관리를 위한 경종방법으로 거론되는 것이 작부체계이다 (Cook, 2006;Dias et al, 2015;Park et al, 1993).…”

“…이에 따라 논을 미래 식량안보와 기후변화 대응 측면에서 계속 보전하되 (Turral et al, 2011) 농산물의 수급조절용으로 벼 이외 다양한 작물을 논에 재배하는 것이 권장되고 있다 (Kim et al, 2015). 뿐만 아니라, 농산물의 지속적인 생산전략으로서 농업환경 보전에 좋지 않은 화학농자재의 사용을 줄이고 지력증진에 도 움이 되는 영농방식을 적극적으로 도입해야 할 필요성도 높은 상황이다 (Dias et al, 2015;Kang, 2007;Kang et al, 2016;Kim et al, 2014;Muthukumarasamy et al, 2007;Parr et al, 1992;Wang et al, 2010).…”