Comparative analysis of yield formation and grain quality of Japanese rice cultivars under upland cultivations in Hawai‘i and Japan

Grain yield in rice is a complex trait and highly dependent on the other agronomic characters. Agronomic characters and grain yield of twenty traditional rice cultivars were evaluated at Faculty of Agriculture, University of Ruhuna in Maha-2010/2011 and in Yala - 2011. The experiment was conducted according to the randomized complete block design with three replicates. Twenty plants from each cultivar were evaluated for the selected characters, Plant height, Leaf blade length, Leaf blade width, Number of tillers, Number of reproductive tillers, Panicle length, Number of spikelets per panicle, Number of fertile spikelets per panicle, Number of infertile spikelets per panicle, Seed length, Seed width, 100 seed weight and Yield per plant. Recommended modern rice cultivar Bg 379/2 was used as the reference. Deviations of each character in different traditional rice cultivars from those of recommended rice cultivar Bg 379/2 were recorded. The average plant height of the tallest rice cultivar, Podihatatha was 198 cm and that of the shortest rice cultivar, Rathranwee was 68 cm. The longest leafblade and longest culm length were also belonged to (9.6 tillers per plant) and the highest average number of reproductive tillers (9 per plant), were recorded by rice cultivar Mahasudu wee. The highest value of 100 seed weight was recorded by rice cultivar Galpa wee. However, the most important economical character, the highest yield per plant(28.52g/plant) was recorded by Thanthiribalan which was significantly higher than that of in the recommended rice cultivar Bg 379/2 (26.5 g/plant). Significant correlations were found between the yield per plant and the characters such as number of reproductive tillers (r = 0.692), panicle length (r =0.565) and number of spikelets per panicle (r = 0.761). Agronomic data collected in the present study would be important to understand the suitability of an individual rice cultivar for the farmer field. DOI: http://dx.doi.org/10.4038/jur.v1i1.6150 Journal of the University of Ruhuna 2013 1(1): 3-9

Upland rice production has great potential as a water-saving form of agriculture if yield can be increased and stabilized across a range of environments with different levels of water supply. The objective of this study was to clarify the effects of water supply and plant characteristics on grain yield of rice (Oryza sativa L.) grown under upland conditions. We compared grain yield (ranging from 346-685 g m-2) and yield components of three rice cultivars (‘Yumeno-hatamochi’, YHM; ‘Lemont’, LMT; ‘Nipponbare’, NPB) grown under upland conditions with three water regimes (rain-fed, RU; irrigated, IU; and water deficit during the panicle-formation stage, WD) with those of rice grown under flooded lowland (FL) conditions (ranging from 394-649 g m-2) from 2001 to 2003 at Nishitokyo, Japan. Grain yield and each yield component of NPB in RU were comparable to those in FL when there was ample rain during the 40 days before heading in 2003. However, grain yield of NPB decreased with decreasing water supply during the period of 20-40 days before heading under upland conditions (r = 0.93) as a result of reduced number of spikelets per unit area and reduced harvest index. Water productivity (grain yield per unit water supply) in rice in RU and IU ranged from 0.43 to 1.05 kg m-3 in the three cultivars across the 3 years, and was more than twice the corresponding value in FL. We found a cultivar – water regime interaction for grain yield within each year and a cultivar × environment interaction across all the 5 upland conditions in 2002 and 2003. In FL, NPB and LMT had higher yields than YHM, while LMT had the highest yield under all upland conditions and NPB grain yield under the suboptimal upland environments (i.e. RU and IU in 2002) decreased to the largest extent compared with that under optimal upland environment, i.e. IU in 2003 among the three cultivars. The reasons for the highest grain yield of LMT across upland conditions were maintenance of large panicle and high harvest index. Maximum yield was lowest in YHM. In WD, yield potential and growth recovery, rather than crop growth during water stress, affected the cultivar ranking in terms of grain yield. We conclude that water supply during panicle development is important for maintenance of high yield and that a high potential yield and harvest index, as well as yield stability under different water regimes, are important putative plant characters for developing new elite varieties for water-saving upland rice production.

ABSTRACTWe conducted a quantitative trait locus (QTL) analysis of grain appearance (GA) and agronomic traits of rice, using 128 recombinant inbred lines derived from ‘Emi-no-kizuna’ and ‘Tomohonami’. We detected two promising QTLs associated with GA: qGA4 on chromosome 4 and qGA8 on chromosome 8. qGA4 contributed highly to the greater percentage of perfect grains of the Emi-no-kizuna genotype. In the same region, we detected other QTLs associated with panicle number and spikelet number per panicle. In near-isogenic lines (NILs) in which Emi-no-kizuna alleles were introgressed in the genomic region of only the semi-dwarf 1 (sd1) locus (NIL_1) and both the sd1 locus and qGA8 (NIL_2), respectively, the percentage of perfect grains was significantly higher and the percentages of milky white, basal white, and white back grains were significantly lower than in Tomohonami; and the percentages of milky white and white back grains of NIL_2 were significantly lower than those of NIL_1. These results suggest that introgression in the sd1 region could improve GA, and that the addition of qGA8 could further improve GA. The culm lengths of the NILs were significantly shorter than that of Tomohonami, indicating improved lodging resistance. Grain weight of NIL_2 was significantly smaller than that of NIL_1, suggesting that the effect of qGA8 could be pleiotropic, or the gene that underlies qGA8 could be linked with genes associated with grain weight.Abbreviations: ANOVA: analysis of variance; AT20: mean air temperature in the 20 days after heading; BW: basal white grain; CL: culm length; DAH: days after heading; GA: grain appearance; GW: 1000-grain weight; LOD: logarithm of odds; MW: milky white grain; NIL: near-isogenic line; PG: perfect grain; PL: panicle length; PN: panicle number; PTSN: putative total spikelet number; PVE: percentage of phenotypic variation explained; QTL: quantitative trait locus; RIL: recombinant inbred line; SN: spikelet number per panicle; SNP: single nucleotide polymorphism; WB: white back grain

The effects of nitrogen-free basal dressing (BNo) and top-dressing on the growth and yield of two rice varieties, Akitakomachi and Hitomebore, planted at a standard density (22.2 hills m−2) and sparse density (16.7 hills m−2) were examined. The maximum number of stems and the number of panicles per unit area were lower in both BNo plots with a standard planting density (BNo22) and sparse planting density (BNol7) than in the control plot with standard nitrogen dressing and standard planting density (CONT) in both varieties. The number of panicles and spikelets per unit area was lower in both BNo22 and BNo 17 than in CONT, but the number of spikelets per panicle in BNo 17 was significantly higher than that in CONT, although that in BNo22 was not. In BNo22, the percentage of ripened grains and 1,000 grain weight were significantly higher than those in CONT, but in BNo 17, 1,000 grain weight was similar to that in CONT, although the percentage of ripened grains was higher than that in CONT. Grain yield in both BNo22 and BNo 17 was not significantly different from that in CONT, and that in BNo 17 was 660 and 710 g m−2 in Akitakomachi and Hitomebore, respectively. The leaf area index was lower and crop growth rate was higher in both BNo22 and BNol7 than in CONT at the grain-filling stage. The net assimilation rate and specific leaf weight were significantly higher in BNo22 and BNo 17 than in CONT at the panicle formation and grain-filling stages, respectively. Nitrogen top-dressing at the neck node differentiation stage was found to be very useful for the cultivation of these rice varieties under BNo with sparse planting density in the Tohoku district.

Genetic characterization of introgression lines with the genetic background of the Indica-type rice (Oryza sativa L.) cultivar IR 64 under irrigated lowland and upland conditions

Wayanad district of Kerala State of India, situated in the Western Ghat region has a tribal population of about twenty percent. Kurichyas, Mullukurumas, Paniyas, Kattunaikas, etc. are the most important tribes inhabiting the area. Rice is their staple source of carbohydrate and they cultivate several native rice cultivars from ancient days. Kurichyas and Mullukurumas are traditional rice farmers. The rice cultivars grown by them are phenotypically and genotypically diverse and can be categorized according to ecological and geographical variations. Rice is grown both under wetland and upland conditions by them. Some of the rice cultivars are adapted to upland conditions and others to wetland conditions. However, no efforts have been made in the area to scientifically evaluate the adaptability of the rice cultivars to these conditions. Upland rice farming is very important in peasantry agriculture including tribal farming since this method demands lesser inputs. Moreover, upland rice farming can be carried out in non-conventional areas thus making the crop to spread to new agricultural areas. The present study validates the usability of twelve native rice cultivars cultivated by the tribal farmers of Wayanad both under wetland and upland conditions. These cultivars form an integral part of the native rice germplasm of the area and their conservation and use are the only valid steps that can be adapted to prevent the loss of the unique genes associated with them. The rice cultivars screened successfully for efficient performance both under wetland and upland conditions in the present experiment are Adukkan, Chennelthondi, Jeerakasala, Karimbalan, Kaima, Kothandan, Mahamaya, Marathondi, Thavalakkannan, Thondi, Urunikaima and Vellimuthu. Recently a devastating flood occurred in Kerala State of India including the Wayanad area in the month of August 2018 and the entire rice crop has been devastated. More curiously, after the flood, the surface water level has receded tremendously leaving the entire rice farms dry, which is completely unusual in the area. The only alternative for rice farming in the area in the second crop season is irrigated upland cultivation and invariably the farmers have to resort to it since at least a small crop to keep the seeds viable until the next year’s crop season is to be raised.

In order to explore the effects of sowing date on the numbers of branches and spikelets per panicle of machine-transplanted <italic>indica</italic> hybrid rice on the main stems (MS), primary tillers (PT) and secondary tillers (ST), a split plot field experiment was conducted with five sowing dates by using two <italic>indica</italic> hybrid rice varieties (F you 498 and Yixiangyou 2115) as materials. The results were as follows: (1) The numbers of spikelets on the primary branches and secondary branches, and the numbers of secondary branches on different tiller positions ranked: MS&gt;PT&gt;ST; the numbers of spikelets on the primary branches and secondary branches, and the numbers of secondary branches on the MS and PT, as well as the whole hill, were increased with delaying sowing date. These contributed to the increase in the numbers of total branches and spikelets per panicle on the MS, PT, and averaged over all panicles in a hill with delaying sowing date. (2) The correlation analysis showed that the numbers of total branches and spikelets per panicle on the MS, PT, and ST were significantly positively correlated with the numbers of total branches and spikelets averaged over all panicles in a hill, and the correlation coefficients ranked: MS&gt;PT&gt;ST. Compared to the ST, the numbers of total branches and spikelets of the MS and PT possessed higher contributions to the numbers of total branches and spikelets averaged over all panicles in a hill. (3) The branches and spikelets traits on the MS, PT, and the averaged over all panicles in a hill of different panicle types were significantly affected by the temperature and sunshine duration at panicle differentiation stage. Most branches and spikelets traits on the MS, PT, and the mean per panicle per hill were significantly positively correlated with the average daily maximum and mean temperatures, and average daily sunshine hours. In conclusion, the numbers of branches and spikelets on the MS, PT, and ST were differed to sowing date, and the using of varieties with large panicle type was helpful to increase the numbers of branches and spikelets of machine-transplanted <italic>indica</italic> hybrid rice. Furthermore, on the basis of ensuring high numbers of primary tillers, the increase in the numbers of branches and spikelets per panicle was crucial for the early sowing treatment to increase the grain yield of machine-transplanted <italic>indica</italic> hybrid rice, while the later-sowing treatment could increase the seed-setting rate and grain weight with higher number of spikelets per panicle.

The effect of rice bran on dry matter production of different rice cultivars, namely the Chinese panicle weight types and Japanese panicle number types, was evaluated in field conditions, with growth, canopy production structure and the root system determined over a period of 60 days. The treatments consisted of rice cultivars with 1000 kg ha1 rice bran without agrochemicals (RB), cultivars with chemical fertilizer and cultivars with herbicide, with the latter serving as a control. The crop growth rate (CGR) and mean leaf area index (mLAI) in RB treatment were lower than that of the control; however, the net assimilation rate (NAR) was higher for all growth stages in this treatment. It was noted that CGR in RB and the control treatment depended greatly on mLAI during the early and middle growth stages, whereas CGR was more dependent on NAR in the late growth stage. Correlation between CGR in middle stage and the extinction coefficient of the canopy (k) at heading was apparent (p < 0.05). NAR in middle stage was positively correlated with mean leaf color and specific leaf weight (SLW). The correlations between NAR in the late stage and bleeding rate per number of primary roots, and per leaf area at maturity was apparent (p < 0.01). Root vitality and NAR were higher in RB treatment. The photosynthesis-related traits after heading in RB treatment were better than the control. Reduction of ∆W in RB treatment as well as the spikelets number (SN) was unapparent. The panicle number type cultivars did not inhibit growth during the early and middle growth stages with the presence of rice bran. The difference between growth, panicle number and weight cultivars was insignificant in the late stage. Discipline: Crop production Additional key words: bleeding rate, growth analysis, light extinction coefficient, the panicle number type cultivars, root system. This research was supported in part by Tianjin natural science fund for Scientific Research (No.11JCYBJC27100) from the Tianjin Municipal Science and Technology Commission, China. The Project Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (No.46). This research was supported in part by the ScienceT accepted 2 March 2015 Introduction The use of nitrogen in paddy cultivation in China is three times higher than in Japan. In this context, excess application of chemical fertilizer in paddy cultivation pollutes the environment and has adverse effects on both aquatic and terrestrial organisms. The use of chemical fertilizers increases operation costs, resulting in higher rice and rice product prices. It is, therefore, important to find new alternatives as substitutes for chemical fertilizer in paddy farming to alleviate environmental issues arising from their use. Rice bran is often used in the organic paddy farming in Japan because of its efficacy as a fertilizer and herbicide. This cultivation technique fulfills the growing demand for agriculture products with fewer or no agrochemicals to

Field experiments were carried out in order to study the relationships between the nitrogen absorption by rice plants grown under various cultural conditions and the growth of the plants. The results obtained are as follows; 1) It was found that the rate of nitrogen absorption by the rice plants was the greatest just before the neck node differentiation stage throughout all the growth stages. The greatest rate of nitrogen absorption by the plants at this stage was positively correlated to the length of culms, the sum of lengths of lower three internodes, the sum of lengths of upper three leaf blades (excepting those of the plots of nitrogen top-dressing), and the number of spikelets per panicle (excepting those of the plots of no basal nitrogen, nitrogen top-dressing at the neck node differentiation stage and at the stage of reduction division), respectively. 2) The amount of plant nitrogen per unit area at the early stage of spikelet differentiation was positively correlated to the number of panicles per unit area. Furthermore, the amount of nitrogen in plant per unit area at the ear mergence was positively correlated to the number of spikelets per unit area. 3) It was previously shown by Matsushima et al (3, 4, 5, 6) that lodging resistance and light utilizing efficiency of rice plants were improved by the decrcase of the length of culms, the sum of the lengths of lower three internodes, the sum of the lengths of upper three leaf blades and the number of spikelets p6r panicle and by the increase of number of panicles and spikelets per unit area. In order to obtain the growth of rice plants mentioned above, the rate of nitrogen absorption by rice plants must be decreased just before neck node differentiation stage and be increased at the other growth stages. It was recognized that early transplanting and high plant density was effective means to permit the desirable rate of nitrogen absorption by rice plants and to increase the rice yield per unit area.

Impact of elevated ozone concentration on yield of four Chinese rice cultivars under fully open-air field conditions

A promising new cultivar of rice (Oryza sativa L.) ‘Tachisuzuka’ has been developed for silage use with improved feeding value due to a radical decrease in spikelets. However, ‘Tachisuzuka’ has the problem of inefficient seed production. We investigated the effect of planting density on the spikelet number in ‘Tachisuzuka’ to find out how seed yields of this cultivar can be increased by means of cultivation methods. ‘Tachisuzuka’ was cultivated at six different planting densities, in the range of 7.4–22.2 hills m−2. Unlike in ordinary cultivars, there was a negative correlation between the spikelet number per unit area and hills per unit area. Moreover, the spikelet number increased by 67% under the low planting density. This result implies that the efficiency of seed production of ‘Tachisuzuka’ could be improved by low planting density through an increase in spikelet number per unit area.

After classifying the rice plants which grown under several cultural conditions in last few years into the several groups according to the number of spikelets per unit area, the authors studied the percentage of ripened grains from an analytical investigation of the number of spikelets per unit area, obtaining the following results. 1. When the number of spikelets per unit area was extremely small, no definite relation was found between the percentage of ripened grains and any component of the number of spikelets per unit area (i.e. the number of panicles per unit area, that of spikelets per panicle and that of primary and secondary rachis-branches per panicle). 2. The percentage of ripened grains showed a tendency to decrease progressively with an increase in the number of spikelets per unit area, spikelets per panicle and secondary rachis-branches per panicle, while it seemed to increase with an increase in the number of panicles per unit area. 3. When the number of spikelets per unit area was extremely large, the percentage of ripened grains was positively correlated with the number of panicles per unit area and negatively correlated with the number of spikelets per panicle as well as the number of secondary rachis-branches. 4. In case of the number of spikelets per unit area being large, the fact that the percentage of ripened grains decreased with an increase of the number of spikelets per panicle could be explained from the fact that the number of spikelets per panicle increased with a decrease of the amount of carbohydrates stored in sheaths and culms before heading and that of photosynthetic products after heading.

The total water supply (irrigation plus rainfall) would determine biomass production. This study aimed to elucidate the effects of water supply and cultivar differences on the dry matter production of rice grown under upland conditions. Three rice cultivars ('Yumeno-hatamochi ', YHM; 'Lemont ', LMT; 'Nipponbare ', NPB) were used on an upland site with three water regimes (rain-fed, RU; irrigated, IU; water deficit during the panicle-formation stage, WD) and in a flooded lowland (FL) in Japan from 2001 to 2003. The total amount of aboveground dry matter (TDM) of NPB in RU (1101 g m-2) was 15% lower than that in FL (1302 g m-2) in 2001, when dry spells occurred frequently, but was comparable to FL in 2003 (1313 vs. 1324 g m-2) under favorable soil water conditions with ample rainfall before heading. The nitrogen (N) content of the aboveground part at maturity in RU in 2003 was similar to that in FL, but the growth duration was 9 days longer in RU. The amount of total water supply during the crop growth differed greatly (419 to 1132 mm) among water regimes and years under upland conditions, where TDM and aboveground N content generally increased with increasing water supply. We detected a cultivar – water regime interaction in TDM at maturity in both 2002 and 2003. In FL and under the upland conditions with adequate water supply in 2003, TDM was the largest for NPB, but it was the smallest in this cultivar in 2002 when rainfall was less frequent. The small TDM of NPB in 2002 resulted from asmaller amount of N uptake associated with shallower root system development. In contrast, YHM had a deeper root system and thus the amount of N uptake was larger and TDM was smaller under upland conditions with limited water supply. Our results indicate that the three cultivars responded differently to the water conditions, and that the total water supply greatly affected TDM in uplands through its effects on the amount of N uptake, which was associated with the depth of root development.

Increasing spikelets differentiation, reducing their degradation and promoting big panicle formation are crucial approaches to increasing grain yield in rice. Straw incorporation and nitrogen (N) application have vital effects on rice yield, but the influence of incorporating wheat straw with N fertilizer ratio on spikelet differentiation, degeneration, and grain yield in rice is not clear. In this experiment, hybrid rice Fengyouxiangzhan (FY) and Yongyou 2640 (YY) were used as materials. Under the condition of total nitrogen application rate of 270 kg ha− 2, the effects of local farmers’ fertilizer practice (FP, basal fertilizer: tillering fertilizer: panicle fertilizer = 5: 1: 4) and improving basal fertilizer proportion (IP, basal fertilizer: tillering fertilizer: panicle fertilizer = 7: 1: 2) on the grain yield, branch and spikelet differentiation and degeneration of the above rice varieties were studied under the conditions of non-wheat straw returning (NR) and wheat straw full returning (WR). The 2-year (2020–2021) results in field trials showed that: (1) under NR, compared with FP, although the panicles per unit area were increased, the spikelet number per panicle, filled grains, and grain weight decreased to varying degrees, and finally the grain yield decreased significantly in IP. Under WR, although the filled grains and grain weight were decreased in IP treatment, the total spikelets (panicles per unit area × spikelet number per panicle) was increased significantly, and the grain yield was finally increased significantly compared with FP, with an increase of 6.85 ~ 7.08%. (2) There was a strong positive link between the total spikelets and grain yield, but a substantial negative relationship between the total spikelets and the number of filled grains and grain weight. (3) Straw treatment and nitrogen treatment mainly affected the spikelet number per panicle by affecting the differentiation and degeneration of secondary branches and spikelets. Under WR, IP increased the differentiation number of secondary spikelet in the middle and basal parts of FY by 22.0% and 30.9% with FP, respectively, but also increased the number and rate of secondary spikelet degeneration in the middle and basal parts. Under IP, compared with NR treatment, the differentiated number, degenerated number, surviving number, and degradation rate of the middle and basal parts of the secondary spikelets in the two varieties were increased in WR treatment. Overall, these results demonstrated that under WR, IP was beneficial to increase effective panicle numbers and the spikelet number per panicle. More secondary spikelet differentiation in the middle and basal parts per panicle was a main reason for increasing the spikelet number per panicle to increase grain yield under IP treatment.

The number and development of spikelets on a panicle directly affect the grain yield. In this study, we examined the differences among various rice cultivars in the number of spikelets per panicle (NSP−1) on the main stems (MS), primary tillers (PT) and secondary tillers (ST), and in the numbers of spikelets on the primary and secondary rachis branches. The difference among cultivars in the responses of these characteristics to the practice of nitrogen-free basal dressing accompanied with sparse planting density (BNo) was also elucidated. The results showed that NSP−1 varied with the tiller position on a plant, and it was highest on MS followed by PT and ST in this order in all cultivars. NSP−1 on all MS, PT and ST also varied with the cultivar, and was larger in the cultivars of the panicle-weight type than in those of the panicle-number type. The difference between MS and ST in NSP−1 was larger in the cultivars of the panicle-weight type than in those of the panicle-number type.ǽ NSP−1 was larger in BNo than in the conventional cultivation (CONT) in most cultivars. The difference between BNo and CONT in NSP−1 varied with the tiller position on a plant and with the earliness of the cultivar, but did not clearly vary with the plant type of the cultivar. It was larger in the panicle on ST than on MS or PT, and was larger in the late-maturing cultivars than in the early- and medium-maturing ones. The larger NSP−1 on MS or PT compared with ST, in the cultivars of the panicle-weight type compared with those of the panicle-number type, and in BNo compared with CONT was mainly attributed to the increased number of spikelets on secondary rachis branches.