Shorter Growth Duration Research Articles

To study the effect of various combinations of Biofertilizer (BF), Biosap (BS) and Chemical fertilizer (CF) on the vegetative growth of crop plant, Amaranthus dubius, and to determine the best combination for maximum yield

The experiment was designed, carried out in duplicate over a period of three months, and the crop chosen was Amaranthus dubius that is known to require a short growth duration and lowmaintenance. The experiment was primarily aimed at analysing the effect of three products created for improving crop health and increasing the water retention of the soil. The biofertilizer used was a new invention with a specific microbial consortia capable of surviving in all sorts of environmental conditions and enhancing nutrient uptake. The other twoproducts provided by Hindustan Gums and Chemicals Ltd. were the Biosap and the Chemicalfertilizer infused Biosap. The Biosap component is a new product which is essentially a polymer that when applied to soil increases its water holding capacity. When used in combination with chemical fertilizer, the uptake of the nutrients seemed to increase in the laboratory results. Accordingly, the experiment was designed with eight treatments to find outwhich combinations of these products would give better yield based on crop type. The treatments were laid down in randomized block design. The parameters analysed were germination percentage, plant height, internode length, photosynthetic area, number of leavesand root spread. From the results obtained, treatment 8, which was the combination of biofertilizer, and chemical fertilizer infused biosap, gave the best results with respect to all the parameters except photosynthetic area. Treatment 2 which contained only chemical fertilizer showed the best photosynthetic area of the plant compared to all other treatments. The best treatments used in the experiment has a future potential for introduction on a large scale into field application that would reduce the amount of chemical fertilizer applied, which is well known to cause soil degradation in the long run and prove to be a cost-effective alternative. KEYWORDS Amaranthus dubius, Biofertilizer, Chemical Fertilizer, Biosap.

A Novel Function of GW5 on Controlling the Early Growth Vigor and its Haplotype Effect on Shoot Dry Weight and Grain Size in Rice (Oryza sativa L.)

Strong early growth vigor is an essential target in both direct seeded rice breeding and high-yielding rice breeding for rice varieties with relatively short growth duration in the double-cropping region. Shoot dry weight (SDW) is one of the important traits associated with early growth vigor, and breeders have been working to improve this trait. Finding stable QTLs or functional genes for SDW is crucial for improving the early growth vigor by implementing molecular breeding in rice. Here, a genome-wide association analysis revealed that the QTL for SDW, qSDW-5, was stably detected in the three cultivation methods commonly used in production practice. Through gene-based haplotype analysis of the annotated genes within the putative region of qSDW-5, and validated by gene expression and knockout transgenic experiments, LOC_Os05g09520, which is identical to the reported GW5/GSE5 controlling grain width (GW) and thousand grain weight (TGW) was identified as the causal gene for qSDW-5. Five main haplotypes of LOC_Os05g09520 were identified in the diverse international rice collection used in this study and their effects on SDW, GW and TGW were analyzed. Phenotypic comparisons of the major haplotypes of LOC_Os05g09520 in the three subpopulations (indica, japonica and aus) revealed the same patterns of wider GW and higher TGW along with higher SDW. Furtherly, the haplotype analysis of 138 rice varieties/lines widely used in southern China showed that 97.8% of the cultivars/lines carry Hap2LOC_Os05g09520. These results not only provide a promising gene source for the molecular breeding of rice varieties with strong early growth vigor, but also elucidate the effect of the LOC_Os05g09520 haplotypes on SDW, GW, and TGW in rice. Importantly, this study provides direct genetic evidence that these three traits are significantly correlated, and suggests a breeding strategy for developing high-yielding and slender grain-shaped indica cultivars with strong early growth vigor.

Selection and Yield Formation Characteristics of Dry Direct Seeding Rice in Northeast China.

Dry direct seeding rice (DSR) is an emerging production system because of increasing labor and water scarcity in rice cultivation. The limited availability of rice cultivars suitable for dry direct seeding hampers the widespread adoption of this cultivation method in Northeast China. This study aimed to investigate grain production and plant characteristics associated with dry direct seeding rice. We conducted a field experiment on 79 japonica rice cultivars in Shenyang City, Liaoning Province, Northeast China, in 2020 and 2021. This study found that the grain yield of the tested rice cultivars ranged from 5.75-11.00 t ha-1, with a growth duration lasting between 144-161 days across the cultivars. These cultivars were then categorized into high yielding (HY), medium yielding (MY), and low yielding (LY) based on daily yield by using Ward's hierarchical clustering method. The higher grain yield for HY compared to MY and LY was attributed to more spikelets per unit area. The HY alleviated the conflict between higher panicle density and larger panicle size by improving the seedling emergence rate and productive stem rate. It also significantly increased shoot biomass at maturity. The HY reduced the period between seeding and beginning of heading (BBCH 51) and the proportion of dry matter partitioned to the leaf at the heading stage. However, it also increased the accumulation of dry matter in the grain and the proportion of dry matter partitioned to the grain at maturity. Furthermore, the HY markedly increased the harvest index and grain-leaf ratio, which are beneficial to coordinate the source-sink relationship. A quadratic function predicted that 98 days is the optimum growth duration before heading (BBCH 51) for achieving maximum yield. In conclusion, for dry direct seeding rice, it is appropriate to select high-yielding japonica inbred rice cultivars with shorter growth duration before heading (about 93-102 day), higher panicle number (about 450-500 × 104 ha-1), more spikelet number per panicle (about 110-130), higher seedling emergence rate (about 70-75%), higher productive stem rate (about 60-70%), and greater harvest index (about 50-55%).

Increasing grain weight and yield stability by increasing pre-heading non-structural carbohydrate reserves per spikelet in short-growth duration rice

Rice yield stability is a breeding goal, particularly for short-growth duration rice, but its underlying mechanisms remain unclear. In an attempt to identify the relationship between yield stability and source–sink characteristics in short-growth duration rice, a field experiment was conducted at three sites (Yueyang, Liuyang, and Hengyang) in 2021 and 2022. This study compared yield, yield components, source–sink characteristics, and their stability between two stable-yielding short-growth duration rice cultivars, Zhongzao 39 (Z-39) and Lingliangyou 268 (L-268), and two unstable-yielding short-growth duration rice cultivars, Zhongjiazao 17 (Z-17) and Zhuliangyou 819 (Z-819). The stability of agronomic parameters was represented by the coefficient of variation (CV). The respective CVs of yield in Z-17, Z-819, Z-39, and L-268 were 10.2%, 10.1%, 4.5%, and 5.7% in 2021 and 19.7%, 15.0%, 5.4%, and 6.5% in 2022. The respective CVs of grain weight were 6.3%, 5.7%, 3.4%, and 4.5% in Z-17, Z-819, Z-39, and L-268 in 2021, and 8.1%, 6.3%, 1.5%, and 0.8% in 2022. The mean source capacity per spikelet and pre-heading non-structural carbohydrate reserves per spikelet (NSCpre) were 7%–43% and 7%–72% lower in Z-819 and Z-17 than in L-268 and Z-39 in 2021 and 2022. The mean quantum yield of photosystem II photochemistry of leaf, leaf area index, and specific leaf weight of L-268 and Z-39 were higher than those of Z-819 and Z-17 at the heading stage. This study suggests that high NSCpre, caused by great leaf traits before heading, increases source capacity per spikelet and its stability, thereby increasing the stability of grain weight and yield. Increasing NSCpre is critical for achieving grain weight and yield stability in short-growth duration rice.

Direct and Indirect Effects of Yield Contributing Characters on Seed Yield in Green Gram (Vigna radiate L.)

The present investigation was carried out to assess the genetic variability parameters, correlation and path analysis in 21 green gram genotypes for 13 quantitative traits at field experimentation center, during kharif 2022 in Department of Genetics and Plant Breeding, Naini Agricultural Institute, Sam Higginbottom University of Agriculture Technology and Sciences, Uttar Pradesh in Randomized Block Design in three replications. Analysis of variance indicated high significant differences among the genotypes for all the traits. Green gram (Vigna radiata L.) is one of the important pulse crops because of its short growth duration, adaptation to low water requirement and soil fertility. Variability is a greater need for initiating a breeding program for yield and yield contributing traits. High seed yield per plant was recorded by SM-2029, SPM-2040, PHULEMOONG-95418, CO-8, CO-7. All the traits showed significant variation among the lines. High Genotypic Coefficient of Variance and Phenotypic Coefficient of Variance was recorded for Number of pods per plant, Number of clusters per plant, Number of primary branches and Plant height where Genotypic Coefficient of Variance exhibited at moderate level and Number of pods per plant exhibited highest percentage of broad sense heritability and also high in genetic advance followed by Plant height and Number of primary branches and Number of clusters per plant. The studies on Genotypic Coefficient of Variance and Phenotypic Coefficient of Variance indicated that the presence of high amount of variation and role of the environment on the expression of these traits. Seed index positively correlated to seed yield per plant at both phenotypic and genotypic levels. Seed index, Biological Yield and Number of Primary branches exhibited high positive direct effect to seed yield per plant at both phenotypic and genotypic path coefficient analysis. Correlation coefficients in most cases were higher than their phenotypic correlation coefficients indicating the association was largely due to genetic reason. At both genotypic and phenotypic levels, significant positive correlations were observed for Seed Index, Days to maturity, Days to 50% pod setting, Plant height, Number of pods per plant and Number of clusters per plant.

Genetic diversity of ayeyarmin mutant rice population revealed by quantitative traits

One of the most important aspects of selecting genotypes with desirable characteristics for a successful breeding program is knowledge of the nature and magnitude of genetic variability. The goal of this study was to estimate the level of genetic divergence among mutant rice genotypes. During the 2020 dry season, a field experiment was carried out using 550 mutant lines with parent Ayeyarmin. The experiment was carried out using a simple CRD design. Six divergent groups were discovered by cluster analysis. Cluster I had the highest cluster mean for grain yield per plant, and the majority of the plants in these clusters resembled the parent Ayeyarmin. Cluster V, which had the fewest mutant lines (9), exhibited dwarf stature, short growth duration, fewer effective tillers per hill, and moderate yielding varieties. Cluster VI, which contained 11 mutant lines, had the most effective tillers per hill and the longest panicle length, both of which were appropriate for yield improvement. Cluster V had the greatest intra-cluster distance (5.77). Cluster V and IV had the greatest inter-cluster distance, followed by Cluster III and V, Cluster II and V, Cluster I and V, and the smallest between Cluster I and IV. Hybridization of Cluster I with V, Cluster V and VI could result in genotypes with desirable characteristics such as dwarf stature, short growth duration, and high yielding rice. The first three eigenvalues were found to have 62% variation using principal component analysis (PCA). Because of the high genetic variability in this mutant rice population, selection could be used to obtain desirable genotypes.

Inquiring the inter-relationships amongst grain-filling, grain-yield, and grain-quality of Japonica rice at high latitudes of China.

The widespread impacts of projected global and regional climate change on rice yield have been investigated by different indirect approaches utilizing various simulation models. However, direct approaches to assess the impacts of climatic variabilities on rice growth and development may provide more reliable evidence to evaluate the effects of climate change on rice productivity. Climate change has substantially impacted rice production in the mid-high latitudes of China, especially in Northeast China (NEC). Climatic variabilities occurring in NEC since the 1970s have resulted in an obvious warming trend, which made this region one of the three major rice-growing regions in China. However, the projections of future climate change have indicated the likelihood of more abrupt and irregular climatic changes, posing threats to rice sustainability in this region. Hence, understanding the self-adaptability and identifying adjustive measures to climate variability in high latitudes has practical significance for establishing a sustainable rice system to sustain future food security in China. A well-managed field study under randomized complete block design (RCBD) was conducted in 2017 and 2018 at two study sites in Harbin and Qiqihar, located in Heilongjiang province in NEC. Four different cultivars were evaluated: Longdao-18, Longdao-21 (longer growth duration), Longjing-21, and Suijing-18 (shorter growth duration) to assess the inter-relationships among grain-filling parameters, grain yield and yield components, and grain quality attributes. To better compare the adaptability mechanisms between grain-filling and yield components, the filling phase was divided into three sub-phases (start, middle, and late). The current study evaluated the formation and accumulation of the assimilates in superior and inferior grains during grain-filling, mainly in the middle sub-phase, which accounted for 59.60% of the yield. The grain yields for Suijing-18, Longjing-21, Longdao-21, and Longdao-18 were 8.02%, 12.78%, 17.19%, and 20.53% higher in Harbin than those in Qiqihar, respectively in 2017, with a similar trend observed in 2018. At Harbin, a higher number of productive tillers was noticed in Suijing-18, with averages of 17 and 15 in 2017 and 2018, respectively. The grain-filling parameters of yield analysis showed that the filling duration in Harbin was conducive to increased yield but the low dry weight of inferior grains was a main factor limiting the yield in Qiqihar. The average protein content values in Harbin were significantly higher (8.54% and 9.13%) than those in Qiqihar (8.34% and 9.14%) in 2017 and 2018, respectively. The amylose content was significantly higher in Harbin (20.03% and 22.27%) than those in Qiqihar (14.44% and 14.67%) in 2017 and 2018, respectively. The chalkiness percentage was higher in Qiqihar, indicating that Harbin produced good quality rice. This study provides more direct evidence of the relative changes in rice grain yield due to changes in grain-filling associated with relative changes in environmental components. These self-adaptability mechanisms to climatic variability and the inter-relationships between grain-filling and grain yield underscore the urgent to investigate and explore measures to improve Japonica rice sustainability, with better adaptation to increasing climatic variabilities. These findings may also be a reference for other global rice regions at high latitudes in addressing the impacts of climate change on future rice sustainability.

Profitability analysis of paddy production in different seasons in Bangladesh: Insights from the Haor

This study aimed to investigate the cost-benefit per hectare of rice production in the haor region in Bangladesh. For doing so, the multi-stage sampling technique was used to collect cross-sectional data during 2018 from four haor districts producing rice in Bangladesh. To achieve the purpose, a total of 368 randomly selected farming households from Habiganj, Sunamganj, Moulvibazar, and Sylhet districts were surveyed using a structured questionnaire. Data analysis was done utilizing descriptive statistics and cost and return analysis. The result revealed that labor costs constituted the largest proportion of gross operating expenses, followed by fertilizer, irrigation, tillage, insecticides and herbicides, and threshing cost. The cost-benefit analysis finding also shows that rice is a profitable enterprise in the haor areas as the lower production cost compared to return. Because of the amount of input used and the price of output, the profitability differs between different seasons, however. The model shows that cost of seed, human labor cost, cost of TSP, cost of MoP, and cost of irrigation were the key factors that influenced rice production. This study also identified some of the problems related to rice production in haor areas. Lower output price, higher input price, unavailability of short growth duration high yielding varieties, and embankment damages, etc., are key obstacles to rice production. Therefore, this study provides the government's concerned authority with appropriate suggestions and policy recommendations to solve the farmers' issues that could boost rice productivity in the haor areas and contribute to food security and self-sufficiency in rice cultivation.

Participatory Variety Testing to Replace Old Mega Rice Varieties with Newly Developed Superior Varieties in Bangladesh

The Bangladesh Rice Research Institute (BRRI) has released more than 100 inbred rice varieties. Still, an old mega variety BRRI dhan28 dominates the farmers’ fields during the dry winter (Boro season: November–June) season. This variety is very susceptible to different diseases and insects, causing lower yield performance than its potential. To replace this variety, current on-farm research was planned to evaluate the newly developed four superior rice varieties: BRRI dhan58, BRRI dhan63, BRRI dhan67, and BRRI dhan74 during Boro season in 2017 and 2018. The objective was to create data and popularize new varieties among farmers all over the country. We conducted 15 on-farm trials with farmers’ active participation at Senbag, Fulgazi, and Mirsarai Upazila of Noakhali, Feni, and Chattogram districts, respectively, in Bangladesh. The results demonstrate that BRRI dhan74 produced the highest grain yield among the tested varieties, followed by BRRI dhan67, BRRI dhan63, and BRRI dhan58, while BRRI dhan28 produced the lowest. However, BRRI dhan67 obtained the highest preference scores from the farmers and extension personnel due to its medium and slender grains, shorter growth duration, resistance to lodging, less disease, and less insect invasion. Moreover, stability indices for yield revealed that BRRI dhan67 was the most stable, adaptive, and appropriate variety, followed by BRRI dhan74, across the locations. Farmers showed keen interest to grow BRRI dhan67 by themselves instead of BRRI dhan28 all over the study locations. The neighboring farmers also expressed their curiosity about cultivating BRRI dhan67 over BRRI dhan28 by collecting seeds from the participating farmers. Thus, BRRI dhan67 could be a perfect replacement for BRRI dhan28. However, conducting participatory varietal evaluation trials across the agroecological zones of the country is recommended to validate the results of this study.

“Born with a silver spoon in the mouth has bad sides too”: Experimentally increasing growth rate enhances individual quality but accelerates reproductive senescence in females of the mealworm beetle, Tenebrio molitor

Senescence occurs because of the decline of the strength of selection with age, allowing late-life reduced performances not being counter selected. From there, several phenomena may explain late-life reduced performances, such as the accumulation of deleterious mutations, the expression of pleiotropic genes or the existence of resource trade-offs between early and late performances. This latter phenomenon is at the core of the disposable soma theory of aging, which predicts that growth and early-life reproduction have costs that increase reproductive and actuarial senescence. Whereas the impact of the cost of early reproduction on reproductive and actuarial senescence has been extensively studied, that of the cost of growth remains overlooked and often inconclusive, possibly because of confounding effects associated with the procedures used to manipulate growth rate. Here, we investigated the cost of growth rate and its impact on reproductive senescence and longevity of females of the mealworm beetle, Tenebrio molitor. For this purpose, we generated insects with contrasted growth rates by raising groups of them in conditions below, above and optimal relative humidity (RH: 55, 85 and 70%, respectively) during the larval stage. The resulting adult females then bred, under the same optimal RH conditions, early in life, then later in life and were followed there until death. We found that larvae grown under the highest relative humidity exhibited the highest larval growth rate, thanks to both shorter growth duration and the achievement of heavier pupae mass. Adult females from this favorable growing condition lived longer, were more fecund early in life, but suffered from lower late-life reproductive investment. Our study shows that growth rate, which is highly dependent on the early-life environment, is an important factor modulating adult reproductive senescence, through the occurrence of early-late life trade-offs.

Modulation of Growth Duration, Grain Yield and Nitrogen Recovery Efficiency by EMS Mutagenesis under OsNRT2.3b Overexpression Background in Rice

Growth duration is an important agronomic trait that determines the season and area of crop growth. Previous experiments showed that overexpression of nitrate transporter OsNRT2.3b significantly increased rice yield, nitrogen use efficiency, and growth duration. Through screening, we obtained four ethyl methanesulfonate (EMS)-mutagenized mutants with shorter growth duration compared with O8 of OsNRT2.3b overexpression line. The nitrogen translocation efficiency and physiological nitrogen use efficiency of the mutants were not significantly different from O8, which were increased by 24.4% and 14.2%, respectively compared with WT, but the growth duration of the mutant was significantly lower than O8. Analysis of O8 and mutants showed that the growth duration positively correlated with grain weight per panicle, grain yield, and nitrogen recovery efficiency. In conclusion, our results provide a new idea for balancing rice yield and growth duration.

Farm level adaptation to climate change: insight from rice farmers in the coastal region of Bangladesh

ABSTRACT Coastal agriculture and livelihoods worldwide are highly vulnerable to changing climates, and Bangladesh is no exception due to its geophysical location. This paper examines rice farmers’ vulnerability, adaptation strategies, and adaptation barriers to managing climate change impacts in the coastal region of Bangladesh. Survey data were collected from 220 randomly selected rice farmers located across two coastal districts of Bangladesh. A multinomial logit model was applied to analyze determinants of adaptation strategies of rice farmers. The results reveal that flood is the main risk to vulnerability, followed by cyclones and storms surges and saline intrusion. The main adaptation strategies are cultivating flood and salinity tolerant rice varieties, direct seeding of rice, supplementary irrigation, cultivation of non-rice crops that have shorter growth duration, and rearing of livestock, poultry, and duck. The econometric analysis shows that factors such as household head's education, household income, farm size, access to information, and extension services significantly influence the choice of adaptation strategies of the rice farmers. We recommend to increase investment in research, training of farmers, and targeted extension services to disseminate climate-smart technologies and information for minimising vulnerability of the farmers.

Phenotypic and Molecular Characterization of Rice Genotypes’ Tolerance to Cold Stress at the Seedling Stage

Rice plants are affected by low-temperature stress during germination, vegetative growth, and reproductive stages. Thirty-nine rice genotypes including 36 near-isogenic lines (NILs) of BRRI dhan29 were evaluated to investigate the level of cold tolerance under artificially induced low temperature at the seedling stage. Three cold-related traits, leaf discolouration (LD), survivability, and recovery rate, were measured to determine the level of cold tolerance. Highly significant variation among the genotypes was observed for LD, survivability, and recovery rate. Three NILs, IR90688-74-1-1-1-1-1, IR90688-81-1-1-1-1-1, and IR90688-103-1-1-1-1-1, showed tolerance in all three traits, while IR90688-118-1-1-1-1-1 showed cold tolerance with LD and recovery rate. IR90688-92-1-1-1-1-1, IR90688-125-1-1-1-1-1, IR90688-104-1-1-1-1-1, IR90688-124-1-1-1-1-P2, IR90688-15-1-1-1-1-1, and IR90688-27-1-1-1-1-1 showed significantly higher yield coupled with short growth duration and good grain quality. Genetic analysis with SSRs markers revealed that the high-yielding NILs were genetically 67% similar to BRRI dhan28 and possessed cold tolerance at the seedling stage. These cold-tolerant NILs could be used as potential resources to broaden the genetic base of the breeding germplasm to develop high-yielding cold-tolerant rice varieties.

Nutritional Composition and Bioactive Components in Quinoa (Chenopodium quinoa Willd.) Greens: A Review.

Quinoa (Chenopodium quinoa Willd.) is a nutrient-rich grain native to South America and eaten worldwide as a healthy food, sometimes even referred to as a ”superfood”. Like quinoa grains, quinoa greens (green leaves, sprouts, and microgreens) are also rich in nutrients and have health promoting properties such as being antimicrobial, anticancer, antidiabetic, antioxidant, antiobesity, and cardio-beneficial. Quinoa greens are gluten-free and provide an excellent source of protein, amino acids, essential minerals, and omega-3 fatty acids. Quinoa greens represent a promising value-added vegetable that could resolve malnutrition problems and contribute to food and nutritional security. The greens can be grown year-round (in the field, high tunnel, and greenhouse) and have short growth durations. In addition, quinoa is salt-, drought-, and cold-tolerant and requires little fertilizer and water to grow. Nevertheless, consumption of quinoa greens as leafy vegetables is uncommon. To date, only a few researchers have investigated the nutritional properties, phytochemical composition, and human health benefits of quinoa greens. We undertook a comprehensive review of the literature on quinoa greens to explore their nutritional and functional significance to human health and to bring awareness to their use in human diets.

Increasing multiple cropping for land use intensification: The role of crop choice

Land use intensification increases crop production without reclaiming new cropland from natural ecosystems. In addition to the yield-improving approaches, scientists began to assess the multiple cropping potential as an alternative for intensification. These existing assessments largely focused on the number of multiple cropping frequency (MCF) while ignoring the crop growth duration (GD) required by a complete cropping circle, which may bring uncertainty on the estimates. In this study, we aim to address such uncertainty by comprehensively considering the relation between MCF and GD. Selecting Jinxian county, Jiangxi Province, as a study area, we use time-series remote sensing imageries to observe MCF and GD, and to estimate the region’s annual growing season (GS) by aggregating the crop-specific GDs corresponding to the MCF. We further apply scenario analysis to understand how crop choice. i.e. longer GD v.s. shorter GD, would influence the exploitation of GS and thus the multiple cropping potential. Results show that without considering GD, 33.63% croplands have the potential to harvest another time and 64.84% cropland could have two-extra harvests, which would result in the harvested area increased by + 163.31%. However, if GD is considered, this potential is estimated much lower in overall and is varied greatly across crop selection scenarios. In the most close-to-reality scenario, roughly 40% croplands have no potential to make extra harvest, because the GS in many areas have been largely exploited and the remaining GS is insufficient to sustain another complete crop growth. Our study shows that crop choice plays an important role in measuring and exploiting the multiple cropping potential, which provides implications for China’s “agricultural supply-side structural reform” through sustainable land use intensification.

Early Maturing Whole Crop Silage Japonica Rice Cultivar 'Jonong' with Short Growth Duration and Numerous Spikelets

Hyun-Su Park, Man-Kee Baek, Woo-Jae Kim, Jeong-Ju Kim, Jong-Min Jeong, Young-Chan Cho, Jong-Cheol Ko, Ji-Ung Jeung, O-Young Jeong, Chang-Min Lee, Suk-Man Kim, Ki-Young Kim, and Jeom-Ho Lee. Korean J. Breed. Sci. 2021;53:318-29. https://doi.org/10.9787/KJBS.2021.53.3.318

Comparison of yield performance between direct-seeded and transplanted double-season rice using ultrashort-duration varieties in central China

Labor scarcity requires double-season rice to be planted by direct seeding as an alternative to transplanting. Only ultrashort-duration varieties can be used in direct-seeded, double-season rice (DSD) in central China where thermal time is limited. Whether ultrashort-duration varieties grown in DSD can be as productive and efficient in nitrogen (N) use as transplanted double-season rice (TPD) remains unclear. Field experiments were conducted in Hubei province, central China with two establishment methods (DSD, TPD) and three N rates in the early and late seasons of 2017 and 2018. Nitrogen treatments included zero-N control (N0), total N rate of 60 kg N ha−1 with equal splits at basal, midtillering, and panicle initiation (N1), and weekly N application at 15 kg ha−1 from seeding/transplanting to heading (N2). Both early- and late-season rice under DSD matured within 95 days, on average 9 days shorter than rice under TPD. The grain yield of DSD was comparable to or higher than that of TDP in both seasons, although the daily yield was significantly higher under DSD than under TDP. Before heading, DSD had higher leaf area, stem number, intercepted radiation, and radiation use efficiency than TPD, which compensated for the negative effect of short growth duration on biomass production. Total dry weight and harvest index under DSD were comparable to or higher than those under TDP. In general, the recovery efficiency of fertilizer-N under DSD was higher than that under TPD, but the reverse was true for physiological N use efficiency. Thus, there was no significant difference in agronomic N use efficiency between DSD and TPD. These results suggested that DSD with ultrashort-duration varieties is a promising alternative to TPD in central China for maintaining high grain yield and N fertilizer use efficiency with less labor input.

The complexity of measuring cropland use intensity: An empirical study

CONTEXTCropland intensification promises additional food supply without further expanding croplands into natural ecosystems. Cropland use intensity measures the degree of intensification by various indicators, both from input and output perspectives; all of these indicators are however not always coherent—which may cause confusion and send contradicting signals to policymakers. Few empirical studies have been conducted to relate and compare various intensity indicators. OBJECTIVEIn this study, we start with a hypothesis that cropland use intensity measured by different indicators may differ. We then test such a hypothesis based on empirical evidence in a typical multi-cropped region (i.e., Jinxian County) in Jiangxi Province—a major breadbasket in Southern China. METHODSWe focus on two widely used indicators, i.e., multi-cropping frequency (MCF) and crop growth duration (GDa), measured by a hybrid time-series remote sensing dataset which fuses MODIS and Gaofen-1 images for the year 2015. We map these two indicators independently at a 16 m spatial resolution. For each pixel, MCF takes value from 1 to 3 corresponding to single-, double- and triple- cropping; while GDa is quantified by the accumulative crop growth days within the study year. We relate the values of two indicators, summarize the descriptive statistics of GDa grouped by MCF categories, and compare MCF and GDa values by using a box-whisker chart, a bivariate map, and a set of statistical tests. RESULTS AND CONCLUSIONSWe find that a significant overlap of GDa exists between single cropping and double cropping both visually and statistically. In other words, the different cropland intensity levels measured by MCF appear to be the same if measured by GDa. The box-whisker chart shows that the GDa of single cropping in the upper quarter is substantially longer than the GDa of double cropping in the lower quarter. The non-parametric tests show that the overlapped GDa between single cropping and double cropping exists substantially, which may cause confusion. Moreover, the bivariate map shows that single cropping with shorter growth duration (i.e., consistent low intensity) and double cropping with longer growth duration (i.e., consistent high intensity) account for 44% and 28%, respectively, while the rest manifested as inconsistent which accounts for another 28% of the total cropland area. SIGNIFICANCEThese results confirm our hypothesis—the inconsistency among intensification indicators. Different measurements may convey contradicting messages for policymakers in pursuing the sustainable intensification goals, which suggests more efforts are required to understand the multidimensionality of the process of cropland intensification for distinct policy measurements.

Sink production and grain-filling ability of a new high-yielding rice variety, Kitagenki

• Kitagenki is a promising high-yielding rice variety adapted to a cool climate in the Hokkaido region, Japan. • Kitagenki showed the maximum grain yield of more than 1000 g m −2 . • Grain yield of Kitagenki was stably superior to the other three varieties. • Kitagenki had higher sink capacity than Tachijoubu and Nanatsuboshi. • Kitagenki had higher grain-filling ability than Kita-aoba, due to higher source ability per spikelet and spikelet fertility. In recent years, several new high-yielding rice varieties (HYV) have been rapidly developed in Japan for multiple uses, including animal feed. Kitagenki (KG) is a new japonica-type HYV growing in the Hokkaido region, the most northern parts of Japan with a cool climate, and it is expected to replace the previously developed HYV: Kita-aoba (KA) and Tachijoubu (TA). However, the physiological traits of KG remain unknown. In this study, a five years field experiment was conducted to elucidate grain yield and physiological traits of KG by comparing with KA and TA as well as with Nanatsuboshi (NA) as a reference. KG showed higher maximum grain yield of 1082 g m −2 , and its grain yield was stably superior to those of KA, TA, and NA, throughout five years. The high grain yield of KG was attributed to its higher sink capacity (1080 g m −2 ) than those of TA (967 g m −2 ) and NA (819 g m −2 ); and higher sink-filling percentage (86.0 %) than that of KA (80.8 %). Compared with TA, KG had a higher harvest index (HI), shorter growth duration (GD), and a lower shoot dry matter at maturity (SDM). Compared with KA, KG had higher grain-filling ability on the secondary rachis branch (SRB), which was due to both higher source ability per spikelet and higher spikelet fertility. These physiological traits contributed significantly to increasing grain-filling ability. In particular, the source ability per spikelet was significantly different between KG and KA during the early grain-filling stage (0–20 days after full-heading [DAH]). As available carbohydrate sources, dry matter production (ΔW) during the grain-filling stage directly contributed to increasing filled grain percentage, whereas stem nonstructural carbohydrate (NSC) translocation played a supportive role in compensating for the shortage of carbohydrate especially when the solar radiation was low. Further increase in grain yield is expected by increasing the source ability in KA, whereas increasing both sink capacity and source ability would be useful in KG.

Sakha108 Egyptian Rice Variety Japonica Type High Yielding and Resistant to Blast

Sakha108 was released in 2018 as a high yielding cultivar amended for enhancing rice production in Egypt. Sakha108 was developed from backcrossing between Sakha101 and HR5824-B-3-2-3 to retrieve blast resistance that was broken in wide spread variety Sakha101. The cross between Sakha101 and HR5824-B-3-2-3 was initiated in 2003, F1 then was backcrossed with Sakha101 as to produce F1BC1. This backcross was advanced up to 2008 to enrich the genetic background of the recurrent parent Sakha101 along with blast resistance and reach homozygosity up to F1BC6. Five selected promising sister lines were evaluated in preliminary yield trial (GZ8564-SP70-20-6-1-1, GZ8564-SP70-20-6-1-2, GZ8564-SP70-2-6-1-3, GZ8564-SP70-20-6-1-4 and GZ8564-SP70-20-6-1-5). The promising line GZ8564-SP70-20-6-1-1 surpassed all selected lines and was evaluated from 2010 to 2015 in multi-location yield trials, regional, final and verification yield trials. The results indicated that GZ8564-SP70-2-6-1-1 exceeded yield potential of recurrent parent Sakha101, yet with shorter growth duration and blast resistance. The selected line grain yield recorded 10.75 and 11.00 t/haduring 2015 and 2016 seasons with total duration 137 day, while Sakha101 recorded 10.32 and 10.50 t/ha, respectively with a total growth duration of 145 day. GZ8564-SP70-2-6-1-1 showed high level of blast resistance in the field and artificial inoculation under greenhouse conditions compared with Sakha101 that showed susceptible reaction to rice blast under both field and greenhouse conditions. The application of 165 kg N/ha-1 and wider space (25x20 cm) significantly increased growth, yield attributes and grain yield of the new cultivar Sakha108. The new cultivar exhibited multiple resistance to other important biotic stresses.