关键词：
Delayed transplanting;Low temperature stress;Rice
摘要：
The development of mechanised large-scale farming has led to changes in rice production systems. Increases in time of farming operations often occur under large-scale farming conditions, which can lead to delayed transplanting (DTP). In this study, field experiments were conducted in the late rice-growing season in 2016 and 2017 to compare the growth stages, growing-season temperature and yield attributes between normal transplanting with 15- to 20-day-old seedlings and DTP with 30-day-old seedlings of two rice cultivars. DTP resulted in 6- and 12-day delays in heading stage for both cultivars in 2016 and 2017, respectively. As a consequence, low temperature stress occurred at anthesis under DTP in both years, which led to significantly reduced spikelet filling and grain yield under DTP for both cultivars. These results confirm that DTP can reduce spikelet filling and grain yield due to low temperature stress at anthesis in machine-transplanted late-season rice. This finding highlights that greater efforts should be made to develop high-yielding short-duration rice cultivars to meet the development of mechanised large-scale rice farming.
摘要：
Growing oilseed rape in the fallow season may be a feasible alternative to growing green manure (e.g. Chinese milk vetch) for improving rice productivity. The objective of this study was to determine the yield performance of machine-transplanted double-season rice (i.e. early- and late-season rice) grown following oilseed rape. Field experiments were conducted to compare machine-transplanted double-season rice grown following oilseed rape, Chinese milk vetch and fallow (i.e. no crop) at Hengyang and Yueyang, Hunan Province, China in three cropping cycles from 2014 to 2017. Results showed that machine-transplanted double-season rice grown following oilseed rape and Chinese milk vetch produced similar grain yield, which was higher than that grown following fallow across two sites and three cropping cycles. The higher grain yield of machine-transplanted double-season rice grown following oilseed rape and Chinese milk vetch was attributable to improvement in both sink size (spikelet number per m(2)) and source capacity (total biomass). However, the reasons for the improved sink size of machine-transplanted double-season rice grown following oilseed rape and Chinese milk vetch were not entirely the same. Growing oilseed rape increased panicle size (spikelet number per panicle) and panicle number in early- and late-season rice, respectively, while growing Chinese milk vetch increased panicle number in both the early- and late-season rice. Our study suggests that growing oilseed rape in the fallow season is a useful alternative strategy for improving productivity of machine-transplanted double-season rice.
通讯机构：
[Huang, Min] H;Hunan Agr Univ, Coll Agron, Crop & Environm Res Ctr, Changsha 410128, Hunan, Peoples R China.
摘要：
Low light is a common environmental factor that adversely affects rice yields. This study was conducted to evaluate the combined effect of hill density and nitrogen (N) fertilizer rate on yield attributes in hybrid rice under low-light conditions. Field experiments were conducted in 2014 and 2015. Two hybrid rice cultivars (Y-liangyou 1 and Luoyou 9348) were grown under combinations of three hill density levels (high, 40 x 10(4) hills ha(-1); moderate, 27 x 10(4) hills ha(-1); low, 14 x 10(4) hills ha(-1)) and two N rate levels (high, 240 kg ha(-1); moderate, 143-148 kg ha(-1)), and shaded from heading to maturity. Grain yield was highest in the combination of high hill density and moderate N rate and significantly declined with decreasing hill density combined with increasing N rate for both cultivars in both years. Averaged across two cultivars and two years, grain yield declined by about 4% for each 10% decrease in hill density combined with each 10% increase in N rate. A significant reduction in spikelet filling percentage was observed with decreasing hill density combined with increasing N rate in Y-liangyou 1 in 2015 and Luoyou 9348 in 2014. The same trend was observed for grain weight in Y-liangyou 1 in 2014 and Luoyou 9348 in 2015. These results indicate that adopting the practice of decreasing hill density combined with increasing N rate can result in poor grain filling and consequently yield decline in hybrid rice under low-light conditions.
通讯机构：
[Huang, Min] H;Hunan Agr Univ, Coll Agron, Crop & Environm Res Ctr Human Hlth, Changsha, Hunan, Peoples R China.
摘要：
Glutelin and prolamin are the two major proteins in rice grains. Grain content of glutelin is considerably higher than that of prolamin in rice, but there is limited information on the factors determining the different grain contents of glutelin and prolamin. To address this knowledge gap, the present study compared final weight per grain and accumulation characteristics of glutelin and prolamin in four rice cultivars. Results showed that final glutelin weight per grain was 3.24-3.95 times higher than final prolamin weight per grain. Glutelin and prolamin accumulation processes were well fitted by the logistic equation. The initial, maximum, and mean accumulation rates of glutelin were 1.69-4.67 times higher than those of prolamin. The active accumulation duration of glutelin was 2.9-5.1 d longer than that of prolamin. These results indicate that both higher accumulation rate and longer active accumulation duration are responsible for the higher final weight per grain of glutelin compared to prolamin in rice.
摘要：
Amylose content and starch granule size in grains influence rice quality, which differs between the early (ES) and late season (LS). The objective of this study was to determine the variation of amylose content and starch granule size between seasons and find the main reasons (e.g., temperature and solar radiation) for the observed variation. Field experiments with six rice varieties (three high and three low amylose content rice) planted in the ES and LS were conducted in 2016 and 2017, respectively. The mean temperatures during the filling stage were higher in ES, however, the daily temperatures at 7-10 days after flowering (DAF) in 2016, and at 5-10, 13-14 DAF in 2017 were higher in LS. The results showed that amylose content in LS was lower than in ES with high amylose content rice varieties (HACV); the opposite trend occurred with low amylose content rice varieties (LACV). The mean starch granule diameter was higher in LS than ES in 2016, but the opposite result occurred in 2017 with all rice. Our results suggest that higher temperatures increased and decreased the amylose content in HACV and LACV, respectively. Temperatures at 5-15 DAF were important for the formation of starch granules: lower temperatures during 10-14 DAF increased the proportion of larger starch granules (d > 6.21 mu m, some with d > 13.3 mu m), and higher temperatures at 5-6 DAF increased the proportion of starch granules with diameter 4.24-6.21 mu m.
摘要：
Reducing N rate without sacrificing grain yield is crucial for sustainable rice production in China. In this study, field experiments were conducted in 2016 and 2017 to determine whether the response of grain yield to reducing N rate varied between double-season rice (DSR) and single-season rice (SSR). Three N rates were applied for each rice crop, i.e. 150 kg ha(-1) (N150, the locally recommended N rate), 90 kg ha(-1) (N90), and 0 kg ha(-1) (N0). Grain yield was lower under N90 than under N150 in DSR by 11-18%, whereas the difference was not significant in SSR. Grain yield under N0 was 36-63% lower in DSR than in SSR. There was a significant relationship between percentage change in grain yield comparing N90 to N150 with grain yield under N0. Furthermore, it was observed that grain yield under N0 was not significantly associated with growth duration but was closely associated with daily grain yield under N0, and the relationships of daily grain yield under N0 with seasonal average daily mean temperature and solar radiation were not significant. These results indicate that response of grain yield to reducing N rate was more sensitive in DSR compared to SSR due to lower soil N productivity. Growth duration and climatic conditions did not explain the difference in soil N productivity between DSR and SSR. The findings of this study should encourage more research into comparing the inherent traits of plants, especially the morphology and physiology of the root system, between DSR and SSR.
摘要：
Amino acid content in grains is an important nutritional quality trait in rice. High temperature can affect rice quality by accelerating grain filling. However, there is limited information available on the influence of high temperature on amino acid content in rice grains, especially under natural conditions. In this study, grain-filling traits and amino acid content in the grain of two rice cultivars (Luliangyou 996 and Lingliangyou 268) were compared between two years (2016 and 2017) with contrasting temperatures during the early grain-filling period under field conditions. Average daily mean temperature during the period of 0-5 days after full heading in 2016 (30.1 degrees C) was 5.4 degrees C higher than that in 2017. Initial, maximum, and mean grain-filling rates were 42-307% higher in 2016 than in 2017 for Luliangyou 996 and Lingliangyou 268. The time taken to reach the maximum grain-filling rate and active grain-filling duration were 6.3-10.7 d shorter in 2016 compared to 2017 for Luliangyou 996 and Lingliangyou 268. Grain weight was equal to or significantly higher in 2016 than in 2017 for Luliangyou 996 and Lingliangyou 268. N accumulation and N content in the grain were significantly lower in 2016 than in 2017 for both cultivars. The grain contents of all detected amino acids, except for methionine in Luliangyou 996, were significantly lower in 2016 than in 2017. Our study suggests that high temperature during the early grain-filling period can result in an accelerated grain-filling process, reduced N accumulation and content in rice grains, and consequently reduced amino acid content in the grain.
通讯机构：
[Huang, Min] H;Hunan Agr Univ, Coll Agron, Crop & Environm Res Ctr, Changsha, Hunan, Peoples R China.
摘要：
Translocation of biomass produced during pre-heading to grains is a determinant of grain yield, but also plays an important role in adaptation to unfavorable environments during post-heading in rice. In this study, field experiments were conducted to determine the critical factors that regulate biomass translocation in rice. Biomass translocation and production characteristics of two rice hybrids (Guiliangyou 2 and Y-liangyou 1) were compared between two site-year environments (Naning-2014 and Yongan-2018). Results showed that biomass translocation parameters (biomass translocation amount and rate and contribution of biomass translocation to filled grain weight) and ratio of biomass production during pre-heading to post-heading (BPpre/BPpost ratio) decreased in Guiliangyou 2 but increased in Y-liangyou 1 with the environment change from Nanning-2014 to Yongan-2018. The decreased BPpre/BPpost in Guiliangyou 2 was attributable to increased biomass production during post-heading (BPpost), while the increased BPpre/BPpost ratio in Y-liangyou 1 was due to increased biomass production during pre-heading (BPpre). Higher cumulative incident solar radiation and larger diurnal temperature variation were responsible for the increased BPpost in Guiliangyou 2 and the increased BPpre in Y-liangyou 1 grown in Yongan in 2018 compared to in Nanning in 2014. The results of this study indicate that changes in biomass translocation and production with environment (climate) in rice are dependent on genotype and that the BPpre/BPpost ratio is an important factor regulating biomass translocation in rice.
摘要：
In order to solve the problem of labor shortage in double-season rice production areas, machine transplanting, as opposed to manual transplanting, has become the more popular alternative method in rice cultivation. However, the most existing late rice cultivars are not suitable for machine double-season rice cultivation due to their long duration of growth. Therefore, based on the previous studies we chose early season rice cultivars to meet the needs of machine double-season rice cultivation. In this study, field experiments were conducted during the late season in 2015 and 2016 in Liuyang County, Hunan Province, China. Grain yield and yield-related traits were compared among eight early-season cultivars (Liangyou 6, Lingliangyou 211, Lingliangyou 268, Zhuliangyou 819, Xiangzaoxian 32, Xiangzaoxian 42, Zhongjiazao 17, and Zhongzao 39) in 2015 and four cultivars (Lingliangyou 268, Zhuliangyou 819, Zhongjiazao 17, and Zhongzao 39) in 2016, selected from the highest yielding cultivars grown in 2015. Lingliangyou 268 produced 8-44% higher grain yield than did the other cultivars except Zhongjiazao17 in 2015. This higher grain yield was driven by grain weight and aboveground biomass. The greater aboveground biomass in Lingliangyou 268 was mainly attributed to higher apparent radiation use efficiency (aboveground biomass/incident solar radiation). Our study suggests that improvement in grain weight and apparent radiation use efficiency were critical to the high grain yield of early-season rice cultivars grown in late season under machine transplanting conditions.
通讯机构：
[Huang, Min] H;Hunan Agr Univ, Coll Agron, Crop & Environm Res Ctr, Changsha, Peoples R China.
摘要：
High yields of mechanized intensive rice-based cropping systems, e.g. double-season cropping using early- and late-season rice, are important to ensure national food security in China. However, few studies addressing the relationship between grain weight and grain yield of early-season rice under machine-transplanted conditions. A field experiment was conducted to determine the critical grain-filling characteristics and related physiological aspects that contribute to high grain weight in machine-transplanted early-season rice. The results showed that grain yield was significantly positively correlated with grain weight but not with panicles per m2, spikelets per panicle, and spikelet-filling percentage. Furthermore, this study demonstrated that there was a significant positive correlation between grain weight and mean grain-filling rate, which was significantly positively correlated with harvest index and grain cytokinin content. These results indicate that high grain-filling rate driven by good transport of assimilates to grains and strong grain sink strength is responsible for high grain weight in machine-transplanted early-season rice.
作者机构：
[Zou, Yingbin; Huang, Min; Zhao, Chunrong] Hunan Agr Univ, Southern Reg Collaborat Innovat Ctr Grain & Oil C, Changsha 410128, Hunan, Peoples R China.;[Uphoff, Norman; Huang, Min] Cornell Univ, Int Programs Coll Agr & Life Sci, Ithaca, NY 14853 USA.
通讯机构：
[Huang, Min] H;[Huang, Min] C;Hunan Agr Univ, Southern Reg Collaborat Innovat Ctr Grain & Oil C, Changsha 410128, Hunan, Peoples R China.;Cornell Univ, Int Programs Coll Agr & Life Sci, Ithaca, NY 14853 USA.
摘要：
In-field earthworm density can be increased by planting oilseed rape during the non-rice growing season as compared to maintaining the rice-growing fields in fallow. This study was conducted to determine the effect on rice yield of earthworm castings produced during the oilseed rape-growing season in rice-oilseed rape cropping fields and to identify the critical factors that contribute to the yield effect. Field microplot experiments were conducted in 2016 and 2017. In 2016, a rice cultivar was grown under a factorial combination of absence (EC0: 0 kg m(-2)) and presence of earthworm castings (EC1: 17 kg m(-2)) with three N application rates (9, 12 and 15 g m(-2)). In 2017, nine rice cultivars were grown under EC0 and EC1 with the moderate N rate as was used in 2016. Results showed that application of earthworm castings produced during the oilseed rape-growing season in rice-oilseed rape cropping fields had a significant positive yield effect on rice. This was attributed to increased panicle m(-2) and total aboveground biomass while spikelets panicle(-1), spikelet filling percentage, grain weight, and harvest index were not affected. Our study indirectly provides a new evidence that oilseed rape is an excellent previous crop for cereals.
