Effect of the Amount and Timing of Ammonium Sulfate Single Top-dressing Application on Growth and Yield of Akitakomachi Rice (Oryza sativa L.)

The effect of the amount and the timing of single top-dressing application of Ammonium sulfate fertilizer on the growth and yield of Akitakomachi rice (Oryza sativa L.) was investigated in this study. Two amounts (20kg.ha-1 and 50kg.ha-1) of Ammonium sulfate ((NH4)2SO4) fertilizer were applied at three timings;14 days after transplanting, panicle initiation, and flowering respectively, giving six treatments (14DAT:20, 14DAT:50, PI:20, PI:50, FL:20 & FL:50). A Randomized Complete Block Design (RCBD) with three replications was used. Growth data were collected on plant length, number of tillers and leaf color, and calculated yield and yield components were determined. Plant length was significantly higher in 14DAT:50 and PI:50, and lowest in FL:20 and FL:50. Tiller number was higher in 14DAT:50 compared to the other treatments. 14DAT:50 and PI:50 produced the highest number of panicles per m2. PI:20 and PI:50 had the highest number of spikelets per panicle. The 1000 grains weight was highest in PI:50 and lowest in 14DAT:50. The highest yields were obtained in 14DAT:50 and PI:50, while FL:20 and FL:50 produced the lowest yields. The results showed that for nitrogen (N) single top-dressing application, high amounts increase both the plant growth and the grain yield if the application is done at vegetative stage or at panicle initiation stage. However, if the nitrogen (N) amount is too high, there exist the risk that the plants may lodge.

Genetic analysis of the hybrid rice population ‘Mavr × Kontakt’

Rice can form not only white-color kernels, but also of red, brown and black colors. In black-color rice kernels, the pericarp contains anthocyanin, which has antioxidant activity and therefore has a positive effect on human health. The purpose of the current study was to develop rice samples with black pericarp. The paper has presented the study results of the hybrid population ‘Mavr × Kontakt’ of the second generation. The variety ‘Mavr’ has a black pericarp, the variety ‘Kontakt’ has a white one. In the process of hybridological analysis there have been identified the patterns of inheritance of the main quantitative traits affecting productivity; there have been identified the best samples, in which formed compact erect panicles and black kernels; there has been selected the initial material for breeding work. The study was carried out in 2020 on the plots of the ES “Proletarskoye” in the Rostov region. There was established that the color of pericarp was inherited according to the type of complementary interaction of two genes. There was found an overdominance and interaction of two pairs of genes of different strengths according to ‘plant height’. There was also seen partial positive dominance, transgressions, and digenic differences of the initial varieties according to ‘panicle length’. According to the traits ‘number of spikelets per panicle’, there was identified overdominance of large values and positive transgression. There were found the forms with well-kerneled panicles. The trait ‘1000 kernel weight’ was characterized by negative dominance and dihybrid cleavage of 9:6:1. There have been selected the best morphotype F2 forms with black pericarp, which possessed optimal plant height, long panicles, larger kernel size, and an average 1000 kernel weight.

Increased Number of Spikelets per Panicle Is the Main Factor in Higher Yield of Transplanted vs. Direct-Seeded Rice

With increasing water shortages and labor costs, rice planting is gradually undergoing a transformation from traditional transplanting to direct seeding. However, the yield of direct-seeded rice is unstable and the reasons for this instability are disputed. Therefore, we established a field experiment conducted over 3 years to investigate the reasons for the difference in rice yield under different planting methods. The planting methods compared were transplanting (TR), broadcast sowing (BS), and sowing in line (SL). The yield of rice under TR was higher (10,390 kg ha−1) than that of BS (7790.7 kg ha−1) and SL (9105.2 kg ha−1). Given that the harvest index showed little variation among the three planting methods, the yield differences reflected that shoot dry matter production under TR was higher. Two reasons for the latter observation are suggested: (1) the planting density under TR was lower than that under BS and SL, thus competition for nutrient resources would have been reduced; (2) the growth period of TR was longer. The higher shoot dry matter accumulation under TR contributed to enhanced panicle number per m2 and number of spikelets per panicle than under BS. A significant correlation between number of spikelets per panicle and yield was observed. Although yield was highest under TR, the costs under TR were the highest among the three planting methods. In contrast, the benefit-to-cost ratio under SL was higher than that of TR and BS. The higher yield under TR reflected the production of larger spikelets per panicle than those produced under direct-seeding methods. However, the benefits of SL are conducive to enhanced profitability of rice production.

AGRONOMIC CHARACTERISTICS AND GRAIN YIELD OF SORGHUM AND MAIZE HYBRIDS GROWN WITH DIFFERENT SOWING TIMES1

ABSTRACT Sorghum is a commonly grown plant in the Central-West region of Brazil as a second crop; however, it is grown almost exclusively as a second crop after maize in the state of Paraná (South region). The growth of sorghum crops is an option for areas or times in which the growth of maize crops can be risky. Thus, the objective of this work was to evaluate the agronomic characteristics of eight sorghum hybrids (ADV-123, ADV-114, 1G100, 50A10, 1G244, 50A40, 50A50, and 1G282) grown in three sowing times in two agricultural years: 2014 (February 20, March 02, and March 03) and 2015 (February 09, February 19, and March 01), and four maize hybrids in 2014 (DKB-330-Pro, P-3431-HX, Formula-TL, and AG-9010-Pro) and five maize hybrids in 2015 (DKB-330-Pro, P-3431-HX, Formula-TL, DKB-275-Pro, and DKB-290-Pro), in the same sowing times used for sorghum. A randomized complete block experimental design with a split-plot factorial arrangement was used, with the sowing times in the plots and the hybrids in the sub-plots. The variables evaluated were: number of days from sowing to flowering, leaf area index, 1,000-grain weight, grain yield, number of spikelets per panicle, for the sorghum crop; and number of rows per ear and number of grains per row, for the maize crop. The comparison between the two crops showed that the sorghum maintained higher production stability in the different sowing times.

Grain-Filling Characteristics in Extra-Large Panicle Type of Early-Maturing japonica/indica Hybrids

Early-maturing japonica/indica hybrids (EJIH) have recently been released, performing a yield potential of 13.5 t ha−1 and greater yield increase over conventional japonica rice (CJ) and hybrid indica rice (HI) in production. More spikelets per panicle and improved grain-filling efficiency underlined the basis for the superior yield performance of EJIH. However, few studies are available on the panicle traits and grain-filling characteristics of EJIH, as well as their differences to CJ and HI. In our study, two EJIH, two CJ, and two HI cultivars with similar growth patterns were grown in the same fields. EJIH had a 12.2–18.8% increased (p < 0.05) grain yield relative to CJ and HI, mainly attributed to their higher daily grain yield. Although it had a lower panicle per m2, EJIH exhibited 28.0–38.3% more (p < 0.05) spikelets per m2 from an increase of 58.0–87.8% (p < 0.05) in spikelets per panicle than CJ and HI. Compared with CJ and HI, EJIH had a higher single panicle weight and more grains in the six parts of the panicle, especially in the upper secondary branches (US) and middle secondary branches (MS). EJIH exhibited a higher leaf area index (LAI), leaf area duration (LAD), leaf photosynthetic rate, and SPAD values after heading, which helped increase shoot biomass weight at heading and maturity and post-heading biomass accumulation. For CJ and HI, the grain-filling dynamics of grains in the six parts were all well simulated by the Richards equation. For EJIH, the grain-filling dynamics of grains in the lower secondary branches (LS) were well fitted by the logistics equation, with the Richards equation simulating grain positioning on the other five parts. EJIH had a lower mean grain-filling rate (GRmean) and longer days and grain filling amounts (GFA) during early, middle, and late stages than CJ and HI. Our results suggest EJIH gave a yield advantage over CJ and HI through a higher daily grain yield. The panicle traits and grain-filling characteristics differed greatly among the three cultivar types. Compared with CJ and HI, EJIH had lower GRmean and higher days and more grains in the panicle during early, middle, and late stages, which contributed to an increased GFA after heading, improved filled-grain efficiency, and higher grain yield.

Improvements in Plant Morphology Facilitating Progressive Yield Increases of japonica Inbred Rice since the 1980s in East China

Grain yield was greatly increased during the genetic improvement of japonica inbred rice since the 1980s in Jiangsu, east China; thus, an improved plant morphology should be expected, considering that plant morphology is a decisive factor determining grain yield. Twelve representative japonica inbred rice released from 1983 to 2013 were grown in the same fields in 2019 and 2020. Grain yield increased (p < 0.01) at 63.3 kg ha−1 year−1 across 2 years among rice cultivars released in different periods. The genetic improvement in grain yield was associated with increased spikelets per panicle. Single panicle weight, number of primary and secondary branches, and number of grains on primary and secondary branches were all increased with a year of release. Generally, the width of top three leaves positively correlated (while angle of top three leaves and light extinction coefficient negatively) correlated (p < 0.01) with year of release. Leaf area per tiller and leaf area index at heading and maturity, specific leaf weight, leaf photosynthetic rate, and SPAD values after heading were all increased linearly with year of release. Plant height exhibited a positive (p < 0.01) trend with year of release, as well as stem weight per tiller and K and Si concentrations of stem. Spikelets per panicle, width of top three leaves, plant height, and leaf area index, and specific leaf weight after heading positively correlated (while angle of top three leaves and light extinction coefficient negatively) correlated (p < 0.01) with grain yield and single panicle weight. Our results suggested that modern japonica inbred rice exhibited expanded sink size by spikelets per panicle, higher leaf area through leaf width, optimized leaf photosynthetic capacity, lower leaf angle and light extinction coefficient, and enhanced stem strength. These improved plant morphologies facilitated yield increases of japonica inbred rice since the 1980s in east China.

Effect of Ammonium Sulfate Application Levels on the Growth and Yield of IR-28 Rice

The study was conducted in JICA Tsukuba experimental rice field RE-2 from April 2018 to September 2018, to determine the effect of different levels of nitrogen fertilizer (Ammonium sulfate) application, on the growth and the yield of IR-28 rice. Four levels of nitrogen fertilizer were applied; 0kg.ha-1 (N0), 40kg.ha-1(N40), 60kg.ha-1(N60) and 80kg.ha-1(N80). For each of the four levels, part of the fertilizer was applied as basal dressing prior to transplanting, and the rest was applied as top-dressing at the panicle initiation stage. The experimental design was a Randomized Complete Block Design (RCBD) with four treatments and three replications. The plant length, the tiller number and the leaf colour were measured for growth data. The number of panicles per m2, the number of spikelets per panicle, the spikelet fertility rate, the 1000 grains weight, and the calculated yield were determined for yield components assessment. The plant length and the tiller number were significantly higher in N80 and N60 compared to N40 and N0, and N80 showed the highest values. There was no significant difference among the four nitrogen levels in terms of the number of panicles per m2 and the number of spikelets per panicle. The spikelet fertility rate and the 1000 grains weight were significantly higher in N80, N60 and N40 compared to N0, and no significant difference was observed among the three. Calculated yield values were higher in N80 (5.74 tons.ha-1) and N60 (5.38 tons.ha-1) compared to N40(4.88 tons.ha-1) and N0 (4.36 tons.ha-1), but there were no significant differences among the four treatments (5% Level of HSD). These results suggest that a high yield of rice can be achieved through the application of high amounts of nitrogen fertilizers. N60 nitrogen level can be recommended for optimum yield of IR-28. Although N80 showed higher yield and yield components, N60 is the best and the most economical nitrogen level required for optimum yield of IR-28.

Marker-Assisted Introgression and Stacking of Major QTLs Controlling Grain Number (Gn1a) and Number of Primary Branching (WFP) to NERICA Cultivars

The era of the green revolution has significantly improved rice yield productivity. However, with the growing population and decreasing arable land, rice scientists must find new ways to improve rice productivity. Although hundreds of rice yield-related QTLs were already mapped and some of them were cloned, only a few were utilized for actual systematic introgression breeding programs. In this study, the major yield QTLs Grain Number 1a (Gn1a) and Wealthy Farmer’s Panicle (WFP) were introgressed and stacked in selected NERICA cultivars by marker-assisted backcross breeding (MABB). The DNA markers RM3360, RM3452, and RM5493 were used for foreground selection. At BC3F4 and BC3F5 generation, a combination of marker-assisted selection and phenotypic evaluation were carried out to select lines with target alleles and traits. Further, genotyping-by-sequencing (GBS) was conducted to validate the introgression and determine the recurrent parent genome recovery (RPGR) of the selected lines. The Gn1a and/or WFP introgression lines showed significantly higher numbers of spikelets per panicle and primary branching compared to the recurrent parents. In addition, lines with Gn1a and/or WFP alleles were comparatively similar to the recurrent parents (RP) in most yield-related traits. This study demonstrates the success of utilizing yield QTLs and marker-assisted selection to develop and improve rice cultivars.

Assessment of genetic variability for quantitative characters in rice (Oryza sativa L.) under post flood situation in sali

Sixteen genotypes of rice (including one check) were evaluated on 18 quantitative traits during sali (August), 2018 in a randomized block design with three replications at Instruction cum Research Farm, Department of Plant Breeding and Genetics, Assam Agricultural University, Jorhat to study the nature and magnitude of variability, heritability and genetic advance under delayed sown condition. The analysis of variance for 18 quantitative traits revealed the presence of significant differences for grain yield and its component characters. The highest genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) was observed for chaffs per panicle followed by grains per panicle, spikelet sterility (%), spikelets per panicle, grain yield (kg/ha). A high heritability coupled with high genetic advance was observed for plant height (cm), spikelets per panicle, spikelet sterility (%), chaffs per panicle, grains per panicle, grain yield (g/hill), grain yield (kg/ha), biological yield (kg/ha), straw weight (kg/ha) and harvest index (%) indicating that selection might be effective for improvement of these characters under delayed sown condition with low input. From the findings of this investigation, one genotype viz., Gandhari emerged as the outstanding genotype which yielded 4170 kg/ha and could be directly used for cultivation in delayed sown situation with low inputs. Some other promising genotypes that yielded higher than the check Manoharsali under delayed sown condition were JR 29, JR 16, Basundhara and JR 60 and could be utilized as potential parental material in the hybridization programmes designed to develop suitable rice varieties for delayed sown situation.

Construction of dominant rice population under dry cultivation by seeding rate and nitrogen rate interaction

This study used the rice cultivar Suijing 18 to investigate the effects of morphological characteristics, photosynthetic changes, yield, as well as nitrogen absorption and utilization. The interaction between seeding rate and nitrogen rate was also assessed to identify the most suitable values of the dominant population for both factors under dry cultivation. Furthermore, the photosynthetic physiological characteristics of the upper three leaves in the dominant population were also explored. The results showed that a combination of 195 kg/ha seeding rate and 140 kg/ha nitrogen rate achieved high yield, high nitrogen utilization, and moderate morphological characteristics. This was achieved by a coordination of the combined advantages of population panicle number and spikelets per panicle. The photosynthetic potential of the population was improved by coordinating the reasonable distribution of light energy in the upper three leaves, which led to the emergence of a dominant rice population under dry cultivation.