Sources of Nitrogen in Combination with Systems of Irrigation Influence the Productivity of Modern Rice(Oryza sativa L.)Cultivars during Dry Season in Sub-Tropical Environment

In irrigated agricultural systems,nitrogen(N)and water are the vital resources for sustainability of the crop production in the modern era of climate change.The current study aimed to assess the impact of water and N management on the productivity of irrigated rice cultivars.In the context,a field observation was done at the research farm of Bangladesh Agricultural University,Mymensingh,during dry seasons in consecutive two years(2018–2019 and 2019–2020).The experiments were set up following split-plot design assigning water management in the main plots,nitrogen management in the sub-plots,and the cultivars were approved in the split-split plot with three replications.After two years observation,it was revealed that rice cultivar Binadhan-8 gave the maximum value of leaf area index,number effective tillers hill-1 and grains panicle-1 which lead to the higher grain yield(GY).Substantial relationships were observed among the concentration of N,growth,total dry matter(TDM)and N content,N uptake,N utilization effectiveness,and GY.However,with little exception,the Combined effect of water and N,cultivars and water management were varied significantly for all parameters.Finally,the results of the current study concluded that application of irrigation at 8 days after the disappearance of ponded water and source of 105 kg N ha-1 from PU+Poultry manure are the best management approach for the excellent performance of rice cultivar Binadhan-8.

Experimental and genomic evidence for the indica-type cytoplasmic effect in Oryza sativa L.ssp.japonica

Cytoplasmic effects are important agronomical phenomena that have generated widespread interest in both theory and application. In the present study, five high yield rice cultivars（Oryza sativa L. ssp. japonica） in large-scale cultivation in northeast China were determined to possess Oryza sativa L. ssp. indica-type cytoplasm using cytoplasmic subspecies-specific molecular markers. This was confirmed by cytoplasmic genome-wide single nucleotide polymorphisms（SNPs） and functional gene sequencing. Two of these five japonica cultivars were core breeding parents with high yield and the other three were super-high-yield varieties registered by the Ministry of Agriculture of China. We constructed nuclear substitution lines to further demonstrate whether and how this indica-type cytoplasm contributed to yield improvement by comparing yield components. The results showed that under the same japonica nuclear background, the lines with indica-type cytoplasm had a significant decrease in tillers in exchange for increased grain number per panicle compared with their recurrent parents. Our results implied that botanical basis of this cytoplasmic effect was to reduce the plant＇s branching differentiation to produce more floral organs under the constant nutrition. Our findings open another door for the utilization of inter-subspecific hybridization for the improvement of rice cultivar.