Genetic improvements for high yield and low soil nitrogen tolerance in rice (Oryza Sativa L.) under a cold environment

Abstract

Eight rice cultivars released in 1905, 1919, 1941, 1954, 1971, 1984, 1987 and 1988 were investigated to identify the traits that contributed to high yield and low soil nitrogen tolerance breeding under cold environment. They were grown in fields at three different nitrogen (N) fertilizer treatments, 0, 6 and 12 g N m(-2) (0 N, 6 N and 12 N) in Sapporo, Northern Japan, in 2001 and 2002. All cultivars; increased their grain yield (GY) with the increase in soil N availability, and better response to N was observed in modern cultivars; released during 1984-1988 compared to old ones (1905-1954). Irrespective of N treatments, the modern cultivars showed better GY than the older ones. Absolute genetic gain was 2.15 or 2.94 g m(-2) year(-1) at 6 N and 12 N. Under 0 N treatment, although the magnitude of yield increase was small, the genetic gain in GY was still observed at 0.78 g m(-2) year(-1). The GY increments were achieved mainly through increasing the number of spikelets (SPK) which depends on the number of panicle (PAN) at any level, and the PAN could be increased by enhancing the number of tillers. The extinction coefficient (k) showed that the older cultivars had a spreading plant type, on the other hand, the modern cultivars had an erect plant type which seemed to be a better plant structure in terms of light distribution. This change on plant structure would allow the modern cultivars to have a larger LAI with improved light capturing resulting in better GY in modern cultivars; than the old cultivars having similar LAI with modern cultivars. These breeding strategies could work for the high-yielding rice breeding program under cold environments irrespective of soil nitrogen conditions

Plant Abiotic Stress: Temperature Extremes

“…The adoption of new cultivars with traits such as more spikelets per panicle and more panicles and tillers with erect plant type even under low soil nitrogen seems to be effective to minimize yield loss in temperate regions (Anzoua et al, 2010). Some management practices such as deep standing water at the panicle initiation stage, low nitrogen supply (to expose minimum biomass to cold nights), and adjusting sowing time (early sowing) are being adopted for cold escape.…”

Breeding rice for nitrogen use efficiency

“…Under low N, for four leaf traits (length, width, thickness and area), the reduction ranged from 18 to 40% (wet) and 6.9 to 17% (dry) at vegetative stage and 14 to 43% (wet) and 10 to 27% at reproductive stage ( Table 1). The increase of leaf related parameters with the increase of N has always been reported for rice (Anzoua et al 2010;Zhang et al 2013;Mahajan et al 2012;Metwally et al 2010). The increased translocation of N to the leaves increases the leaf length, width, area and thickness along with chlorophyll content, thus main effect of N is to increase the rate of leaf expansion, leading to increased interception of daily solar radiation by the canopy and so increased dry matter production (Ohnishi et al 1999).…”

“…Under low N, grain yield (kg/ha), total grain weight, straw weight and total dry matter were reduced by 30 to 50% across seasons. The grain yield increments under recommended N were reported to be possible mainly through increasing the number of spikelets of the panicle and then the number of the tillers (Anzoua et al 2010).…”

“…The nomenclature of NUE indicators sounds similar viz., agronomic nitrogen use efficiency, physiological use efficiency, internal N use efficiency, however, the definitions and parameters used in the various reports are variable (Fagerial and Baligar 2003;Ladha et al 2005;Mahajan et al 2012;Mae et al 2006;Metwally et al 2010;Sui et al 2013;Tirol-Padre et al 1996). NUE indicators have been calculated for low and recommended N individually viz., physiological NUE (total dry weight (g/plant)/total N absorbed (g/plant), NGPE (grain yield/total N accumulation), internal N use efficiency (INUE N grain/ N plant), and NAE (plant N accumulation amount/soil available N), NGPE (grain yield/total N accumulation) (Anzoua et al 2010). And also using the data of both low and recommended N viz., agronomic efficiency, physiological efficiency, agro physiological efficiency, apparent recovery efficiency, utilization efficiency also were calculated (Fagerial and Baligar 2003).…”

Identification of rice landraces with promising yield and the associated genomic regions under low nitrogen

“…In our study, we could identify several genotypes with high NHI% (>70) with higher conversion efficiency. NHI was reported to be around 60% and suggested to be genotype specific in the earlier studies 6 , 23 . Some land races with higher IE and NHI lodged because of their height and weak culm, thus those landraces were identified only as donors of high IE and NHI.…”