Intrapopulation recurrent selection targeting early flowering and grain yield in upland rice

In upland rice breeding programs, it is crucial to develop both high-yielding and early flowering lines. A successful strategy for accumulating favorable alleles in a population and increasing selection gains is the recurrent selection. This method involves repeatedly selecting and intercrossing progenies that exhibit favorable traits, with the goal of accumulating these traits in the population and subsequently extracting superior lines. Thus, the aim of the present study was to evaluate F2:4 and F2:5 progenies from the recurrent selection population UFLA-P1 at cycle 0 for early flowering and grain yield. The total of 152 F2:4 progenies was evaluated in 12 × 13 triple alpha-lattice design, totaling 468 plots. From this evaluation, 26 genotypes were selected to be included in the elite lines trial of the upland rice breeding program (MelhorArroz). Among these, 100 progenies were assessed: 26 F2:5 progenies from the recurrent selection program, 72 F4:6 progenies from MelhorArroz, and two commercial lines as controls. The annual gain achieved through recurrent selection for days to flowering was -3.48%. Additionally, 11 F2:5 progenies from the UFLA-P1 population demonstrated superior performance for early flowering, grain yield, and other favorable phenotypic traits. These progenies were selected for advancement, with the aim of releasing superior lines. This study demonstrates the potential to develop superior lines for early flowering and grain yield in upland rice, starting from cycle 0 in recurrent selection.

High grain yields of upland rice (Oryza sativa L.) can be achieved in no-tillage systems. However, managing nitrogen (N) fertilization for rice in succession to forage grasses is a challenge because forage residues change N cycling and increase microbial immobilization of N, thereby reducing N availability to the subsequent cash crop. In the present study, two field experiments were conducted to determine if applying all or part of the N fertilizer on preceding palisade grass (Urochloa brizantha) and ruzigrass (Urochloa ruziziensis) or their desiccated residues immediately before rice seeding can supply N to the subsequent rice crop. Forage biomass yield (8–16 Mg ha− 1), N accumulation, and N supply to the subsequent upland rice were highest when all of the N fertilizer was applied on forage grasses at 50, 40 or 35 days before rice seeding (DBS), as opposed to the conventional split application at rice seeding and at tillering. On average, the grain yield of upland rice was 54% higher in succession to palisade grass compared with ruzigrass. The grain yield of rice was higher when N was applied to palisade grass at 35 DBS and ruzigrass at 50 DBS, reaching 5.0 Mg ha− 1 and 3.7 Mg ha− 1, respectively. However, applying N to ruzigrass was less effective for increasing upland rice yields since the yields did not differ from the treatments with the conventional split application. Adjusting the time of N application to forage grasses to increase the grain yields of subsequent upland rice is a sustainable alternative that can promote the economic viability of upland rice production.

Blue revolution for food security under carbon neutrality: A case from the water-saving and drought-resistance rice

This study explored the response in grain yield and quality of upland and wetland rice varieties to a combination of zinc (Zn) and nitrogen (N) fertilizers under two water management regimes. A factorial arrangement based on a randomized complete block design composed of three factors was carried out with three independent replications. Upland and wetland rice varieties were grown with three fertilizer treatments; the optimum N rate (86 kg N ha−1) without Zn application, the optimum N rate with Zn (50 kg ZnSO4 ha−1), and the high N rate (172 kg N ha−1) with Zn under waterlogged and well-drained conditions. Grain yield was 27% lower in the well-drained than in the waterlogged condition in wetland rice, while there was no effect in upland rice. Application of optimum N with Zn application produced the highest grain yield in upland rice, while yield was the highest in wetland rice in high N with Zn application. Upland rice grown in the well-drained condition with the optimum and high N with Zn treatments enhanced Zn concentration by 45% and 29% higher than the treatment without Zn, respectively, while it had no difference among three treatments in the waterlogged condition. Wetland rice variety grown under the well-drained condition in optimum and high N rate with Zn treatments were equally effective in improving grain Zn concentration at the average of 88% compared to the control. While rice grown under the waterlogged condition in the high N with Zn treatment had improved 92% the concentration. The optimum N rate with Zn application increased grain yield in upland rice, while the higher N input is required for wetland rice. Grain Zn concentrations of upland and wetland rice varieties were enhanced by applying Zn fertilizer; however, the increased level was depended on N application rate in the individual water condition.

Effects of Nitrogen Nutrition on Grain Yield of Upland and Paddy Rice Under Different Cultivation Methods

Rice is a major staple food, and, hence, doubling its productivity is critical to sustain future food security. Improving photosynthesis, source–sink relationships and grain-filling mechanisms are promising traits for improvement in grain yield. To understand the source–sink relationship and grain yield, a set of contrasting rice genotypes differing in yield and biomass were studied for physiological, biochemical and gene-expression differences. The physiological and yield component traits of selected rice genotypes were analyzed in 2016 and 2017 under field conditions. This led to the categorization of genotypes as high yielding (HY) and high biomass, viz., Dular, Gontra Bidhan 3, Way Rarem, Patchai Perumal, Sahbhagi Dhan, Indira Barani Dhan-1, MTU1010, and Maudamani; while, low yielding (LY) and low biomass, viz. Anjali, Ghanteswari, Parijat, Khao Daw Tai, RKVY-104, Ghati Kamma Nangarhar, BAM4510 and BAM5850. The HY genotypes in general had relatively better values of yield component traits, higher photosynthetic rate (Pn) and chlorophyll (Chl) content. The study revealed that leaf area per plant and whole plant photosynthesis are the key traits contributing to high biomass production. We selected two good-performing (Sahbhagi Dhan and Maudamani) and two poor-performing (Ghanteswari and Parijat) rice genotypes for a detailed expression analysis of selected genes involved in photosynthesis, sucrose synthesis, transport, and starch synthesis in the leaf and starch metabolism in grain. Some of the HY genotypes had a relatively high level of expression of key photosynthesis genes, such as RbcS, RCA, FBPase, and ZEP over LY genotypes. This study suggests that traits, such as leaf area, photosynthesis and grain number, contribute to high grain yield in rice. These good-performing genotypes can be used as a donor in a breeding program aimed at high yields in rice.

The objective of this study was to investigate the grain yield and the phosphorus utilization efficiency in responses to phosphorous (P) fertilizer and the interaction between cultivation methods and P levels in upland rice and paddy rice. One japo- nica upland rice cultivar Zhonghan 3 and one japonica paddy rice cultivar Yangfujing 8 were grown under the moist cultivation (MC, control) or bare dry-cultivation (DC) with low amount of P (LP, 45 kg ha-1), normal amount of P (NP, 90 kg ha-1), and high amount of P (HP, 135 kg ha-1). Under DC, with the increase of P level, both upland rice and paddy rice significantly increased grain yield and P accumulation, and upland rice showed a significant decrease and paddy rice had no difference in P use efficiency of matter production and P use efficiency of grain yield production. Under MC, there was no significant difference in grain yield, P accumulation amount, and P use efficiency of grain yield production.There was a significant decrease in P use efficiency of matter production between HP and NP for the upland rice, but the grain yield and P accumulation at HP were lower than at NP, there was no significant difference in P use efficiency of matter production and P use efficiency of grain yield production between HP and NP for paddy rice. When compared with MC, DC showed less number of adventitious roots, lower P accumulation amount, higher P use efficiency of matter production, lower P use efficiency of grain yield production, and lower grain yield for both upland and paddy rice with more reduction in grain yield for upland rice than for paddy rice. Compared with paddy rice, upland rice showed less number of adventitious roots, lower P accumulation amount, fewer panicles, higher seed setting rate and higher 1000-grain weight, lower grain yield, higher P use efficiency of matter production and higher P use efficiency of grain yield production. Upland rice showed a faster declining in chlorophyll content (SPAD value) of the flag leaf after anthesis. The cultivation methods and phosphorus nutrition had significant or very significant effects on the P accumulation amount after anthesis, P use efficiency of grain yield production, and adventitious roots for both upland rice and paddy rice. The P accumulation amount after anthesis was very significantly and positively correlated with grain yield and adventitious roots, and very significantly and negatively correlated with P use efficiency. Increase in P levels could increase grain yield for both upland and paddy rice under DC, and the response of the two types of rice cultivars to P levels is different under either DC or MC.

Understanding the yield attributes of rice crops grown at super high-yielding sites is useful for identifying how to achieve super high yield in rice. In this study, field experiments were conducted in 2021 and 2022 to compare grain yield and yield attributes of ten high-yielding hybrid rice varieties between Xingyi (a super high-yielding site) and Hengyang (a site with typical yields). Results showed that Xingyi produced an average grain yield of 13.4 t ha−1 in 2021 and 14.0 t ha−1 in 2022, which were, respectively, 20% and 44% higher than those at Hengyang. Higher panicles per m2 and higher grain weight were responsible for the higher grain yield at Xingyi compared to Hengyang. The higher values of panicles per m2 and grain weight at Xingyi compared to Hengyang were due to greater source capacity resulting from improved pre-heading biomass production. This study suggests that simultaneously increasing panicle number and grain weight through improving pre-heading biomass production is a potential way to achieve super high yield in rice.

Agronomic and physiological performance of high-yielding wheat and rice in the lower reaches of Yangtze River of China

Upland rice and dry-cultivated paddy rice have been attracted more and more attention because of limited water re- sources in China. Researches on interaction between water and nitrogen supplies for crop resistance to drought stress has become the hot topic regarding regulation on nutritional physiology. However, there is little information available on effect of nitrogen (N) nutrition on grain yield and its components of upland rice and paddy rice under different cultivation methods. The objective of this study was to evaluate the difference between upland rice and paddy rice and interaction between cultivation methods and N levels. One upland rice cultivar Zhonghan 3 (japonica) and one paddy rice cultivar Yangjing 9538 (japonica) were grown under moist cultivation (MC, control) or bare dry-cultivation (DC) with three N levels, low amount of N (LN, 100 kg ha-1), normal amount of N (NN, 200 kg ha-1), and high amount of N (HN, 300 kg ha-1). The results showed that, compared with NN, the grain yield under HN was lower for both upland and paddy rice under DC and for paddy rice under MC, whereas higher for upland rice under MC. With the increase in N levels, upland rice and paddy rice showed higher productive tillers, more or fewer spikelets per panicle, lower percentage of ripened grains under two cultivation methods. However, the percentage of ripened grains was reduced more for paddy rice than for upland rice. There was no significant difference in 1 000-grain weight for upland rice among three N levels, whereas grain weight was reduced with the increase in N levels. Compared with MC, DC showed no significant difference in grain weight for upland rice, whereas a significant decrease for paddy rice. DC significantly increased the percentage of ripened grains for both upland and paddy rice, and that were more for upland rice than for paddy rice. Compared with paddy rice, upland rice showed less number of adventitious roots, lower nitrogen absorption ability and lower productive tillering ability, fewer pani- cles, fewer spikelets per panicle and lower grain yield. However, upland rice exhibited quicker increase in adventitious roots and slower declining in leaf nitrogen content from jointing to heading, and a faster declining speed in chlorophyll content (SPAD value) after flowering. Also, upland rice had less negative response to water stress and more positive response to N. The results suggest that the response to cultivation methods and N levels varies largely between upland rice and paddy rice. The approaches to in- crease the grain yield of both paddy and upland rice were discussed.

Upland rice and dry-cultivated paddy rice have been attracted more and more attention because of limited water re- sources in China. Researches on interaction between water and nitrogen supplies for crop resistance to drought stress has become a hot topic in crop physiology. However, the information linking to the effect of nitrogen nutrition on grain quality of upland rice and paddy rice under different cultivation methods is unavailable. The objective of this study was to evaluate the difference be- tween upland rice and paddy rice and interaction between cultivation methods and N levels. One upland rice cultivar Zhonghan 3 (japonica) and one paddy rice cultivar Yangjing 9538 (japonica) were grown under either moist cultivation (MC, control) or bare dry-cultivation (DC) conditions, with three N levels, low amount of nitrogen (LN, 100 kg ha-1), normal amount of nitrogen (NN, 100 kg ha-1), and high amount of nitrogen (HN, 300 kg ha-1). The results showed that, compared with NN, the grain yield under HN was lower for both upland and paddy rice under DC and for paddy rice under MC, whereas it was higher for upland rice under MC. Under both DC and MC, the percentage of chalky grains and the chalkiness of upland rice were increased under NN and reduced under HN. With the increase in N levels, amylose content was reduced and protein content was increased for both upland and paddy rice. However, the percentage of chalky grains and the chalkiness of paddy rice was decreased under DC and increased under MC. Breakdown viscosity was the highest and setback viscosity was the lowest for upland rice under NN and for paddy rice under LN. The bare dry cultivation can improve appearance quality and nutrient quality for upland rice. There was no significant difference in other rice quality indices between upland rice and paddy rice under DC. Compared with paddy rice, upland rice showed better nutrient quality and poor appearance quality and cooking quality. The correlation coefficient between cooking and nutrient quality and leaf nitrogen content was smaller for upland rice than for paddy rice. The results suggest that the response to cultivation methods and nitrogen levels varies largely between upland rice and paddy rice. The approaches to increase grain yield and grain quality for both paddy and upland rice were discussed.

Effects of Nitrogen Nutrition on Grain Quality in Upland Rice Zhonghan 3 and Paddy Rice Yangjing 9538 Under Different Cultivation Methods

Coastal land located in the lowlands near the coast has a marginal Entisol soil type. Entisols have the following characteristics: loose soil aggregate, sensitive to erosion, and low levels of nutrients, organic matter, water holding capacity, and soil fertility. The nature of this Entisol is less able to produce maximum upland rice production. The technology used to overcome this problem is by applying macro and micro fertilizers to the soil, which is planted with upland rice seeds, inoculated with biological fertilizers so that it is hoped that upland rice production can be maximized. The purpose of this study was to obtain high upland rice production in coastal areas. The research was carried out from June to December 2020 in Beringin Raya Village, Muara Bangkahulu District, Bengkulu City. The research location is located at coordinates S 03?45'23'' E 102?15'41''. The experimental design used was Completely Randomized Block Design (CRBD) with 2 factors, namely types of fertilizers and varieties of upland rice. The first factor consists of P0 = No fertilizer; P1 = compound micro fertilizer; P2 = Fertilizer recommended for upland rice from the Institute for Agricultural Research and Technology). The second factor consists of V1 = red upland rice; V2 = white upland rice) The results showed that there was an interaction between the type of fertilizer and upland rice varieties on soil pH (KCl 1:2.5 w/v). the interaction of microfertilizers with white upland rice varieties resulted in the highest soil pH (5.06). The best type of fertilizer is micro-compound fertilizer which produces soil pH (KCl 1:2.5 w/v), P nutrient uptake, the highest root colonization and the highest number of production tillers and the highest grain weight per plant and upland rice yield per plot. The best upland rice variety was the white variety which produced the highest uptake of P nutrients, the number of productive tillers, the weight of grain per plant and the highest yield per plot.

Water stress is an enormous problem facing food production, especially in arid and semi-arid regions. Production of free radicals during water stress has led to oxidative stress, which eventually causes death of cells in plants. Therefore, it is important to tackle this issue knowing that rice is one of the most important cereal crops largely cultivated and consumed by humans and animals. The studies aimed at the effect of selenite on physiological and biochemical activities of water-stressed upland rice. Three Upland rice cultivars namely Nerica U4, Nerica U7 and Vandana were collected in Africa Rice Centre, Ibadan. The seeds were sterilized and soaked for 10 hours in different concentrations of Selenite (Se) (0 mg/l, 50 mg/l and 100 mg/l). Primed seed were planted into sterilized-sieved top soils. Plants were subjected to 0 (irrigated) and 8 days (non-irrigated) water stress. Selenite 50 mg/l improved plant height, number of leaves, total carotene, chlorophyll contents, biomass, grain number of upland rice during water stress. Selenite increased activities of APX as water stress progressively increased consequently, low MDA content was observed in cultivar Vandana. Furthermore, selenite significantly improved total carotene, chlorophyll contents, anthocyanin, and dry shoot weight in cultivar Nerica U7 during water stress. Selenite significantly stabilized activities of anthocyanin and CAT in cultivar Nerica U4 during water stress. Hence high grain yield was recorded in Nerica U4 and U7 in selenite primed upland rice during water stress. Selenite reduced lipid peroxidation in upland rice at 100mg/l. Therefore, it can be concluded that response of rice to selenite during water stress is based on tolerance capacity of the cultivars and also, selenite 50mg/l can help to improve growth and yield of upland rice in drought-prone area.

The high yield of irrigated rice in Yunnan, China: ‘A cross-location analysis’