Grain-filling Duration Research Articles

Soil nitrogen regulation using clinoptilolite for grain filling and grain quality improvements in rice

Controlled-release materials are widely used in agricultural production and are able to alter the supply of soil nitrogen, thus impacting production. However, changes in soil nitrogen supply exhibit a greater potential in the regulation of source-sink-translocation, which can subsequently have significant impacts on grain quality. In order to clarify the correlations among soil nitrogen supply, grain filling and grain quality, 157.5 kg ha−1 nitrogen as urea fertilizer was applied at the same rate, either as a one-time application or in a third-split application with and without 10 t ha−1 zeolite. The results show that zeolite significantly increased grain yield, particularly under the one-time fertilization treatment. The controlled release of zeolite for soil nitrogen was characterized by the initial trigger of nitrogen stress, and the subsequent slow release of nitrogen for 20 days. On average, third-split fertilization significantly increased chalkiness by 16.5 % and reduced amylose content by 2.7 % on average, resulting in a low taste value. However, zeolite significantly reduced chalkiness mainly due to the “peak cutting for valley filling” for nitrogen, which increased rice grain yield, reduced the maximum grain-filling rate, prolonged the grain-filling duration, and allowed for a more stable grain-filling process. In summary, under the one-time fertilization treatment, zeolite slowly released nitrogen for approximately 20 days. Although the released nitrogen was not able to directly participate in the regulation of rice grain quality in the later period, zeolite continuously increased the accumulation of the “source” in the earlier period. This was helpful in stabilizing the grain-filling process, reducing the chalkiness and improving the taste value.

Effects of straw and manure management on soil and crop performance in North China Plain

The North China Plain (NCP) is one of the most intensively farmed agricultural regions in China, and the annual double-cropping system of winter wheat and summer maize produces a large quantity of straw. A field experiment was carried out from 2010 to 2016 to assess the effects of straw and manure management on crop performance, soil physical and chemical characteristics. Four management practices were tested: (1) all the straw from the annual double-cropping system was returned to the soil directly (as a control, WMs); (2) maize straw was removed as yellow silage and winter wheat straw was maintained (Ws); (3) manure produced from dairy farms was added to Ws (Ws + M); (4) extra manure was added to WMs (WMs + M). The results showed that the soil bulk density and soil aggregates were not significantly different among the four treatments. The soil nutrient contents and organic matter (OM) increased continuously under the four treatments. The results indicated that with at least one season of straw returning to the field would maintain an improved soil nutrient contents. The increase rate for organic matter, P and K for the treatments with manure addition was higher than that for the treatments without manure application. Both biomass and grain yield of summer maize were improved with the continuous addition of manure. Although the biomass of winter wheat was improved with manure addition, the grain yield of winter wheat was not affected due to the reduction in the harvest index, which might be related to the shortened grain-filling duration. No significant difference in water use efficiency was found among the four treatments for winter wheat or maize. The improved soil nutrient and organic matter contents affected the production of the two crops differently in this annual double-cropping system. The larger increase in organic matter contents using maize straw changed manure through animal feeding would benefit the grain production of summer maize as well as the soil carbon sequestration.

Roles of phytohormone changes in the grain yield of rice plants exposed to heat: a review.

During its reproductive phase, rice is susceptible to heat stress. Heat events will occur at all stages during the reproductive phase of rice as a result of global warming. Moreover, rice yield traits respond differently to heat stress during panicle initiation, flowering and grain filling. The reduction in the number of spikelets per panicle of heat-stressed plants is due to the attenuated differentiation of secondary branches and their attached florets as well as the promotion of their degradation during the panicle-initiation stage but is not affected by heat stress thereafter. Spikelet sterility as a result of heat stress is attributed not only to physiological abnormalities in the reproductive organs during the flowering stage but also to structural and morphological abnormalities in reproductive organs during the panicle-initiation stage. The reduced grain weight of heat-stressed plants is due to a reduction in nonstructural carbohydrates, undeveloped vascular bundles, and a reduction in glume size during the panicle-initiation stage, while a shortened grain-filling duration, reduced grain-filling rate, and decreased grain width contribute to reduced grain weight during the grain-filling stage. Thus, screening and breeding rice varieties that have comprehensive tolerance to heat stress at all time points during their reproductive stage may be possible to withstand unpredictable heat events in the future. The responses of yield traits to heat stress are regulated by phytohormone levels, which are determined by phytohormone homeostasis. Currently, the biosynthesis and transport of phytohormones are the key processes that determine phytohormone levels in and grain yield of rice under heat stress. Studies on phytohormone homeostatic responses are needed to further reveal the key processes that determine phytohormone levels under heat conditions.

Adjusting sowing date and cultivar shift improve maize adaption to climate change in China

This study investigates the impact of climate change on spring and summer maize (Zea mays) yield and evaluates several adaptation measures to overcome the negative impact of climate change on maize production in China. The results showed that the grain-filling duration of maize would be shortened 6–15 days in the future as a result of climate change. Thus, potential maize yield would decrease by 2–32%, and rainfed maize yield would decrease by 0–24% during 2010–2099 relative to 1976–2005. In response to climate change, adaptive measures should be taken to overcome its projected impact. The adoption of new cultivars while maintaining the same pre-flowering and post-flowering duration in the future as in the present would help to improve potential maize yield by 50–61% in three time slices (2030s, 2050s, and 2070s) and would be a better choice for high yields in the future. The cultivars that would maintain the same post-flowering duration in the future as in the present would be a better choice than the cultivars that would maintain the pre-flowing periods for summer maize in China. Adjusting sowing dates would be another important way to extend post-flowering periods and further improve maize yield. If the maize cultivar currently used was adopted, delaying the sowing date would improve the potential maize yield by 2–25%. If future maize cultivars that maintained the growing period even as warmer temperatures accelerate phenological development were adopted, delaying the sowing date would improve the potential maize yield by 0–8.9%. The interactive effect of sowing and cultivars was quantified. Based on the findings of this study, future maize cultivars maintaining the growing period were adopted, and delaying the sowing date could still improve potential maize yield worldwide. Two regional adaptation strategies to climate change could offset the potential reduction of maize production worldwide, which would provide farmers and policy-makers with explicit guidance.

Amino acid content in rice grains is affected by high temperature during the early grain-filling period

Amino acid content in grains is an important nutritional quality trait in rice. High temperature can affect rice quality by accelerating grain filling. However, there is limited information available on the influence of high temperature on amino acid content in rice grains, especially under natural conditions. In this study, grain-filling traits and amino acid content in the grain of two rice cultivars (Luliangyou 996 and Lingliangyou 268) were compared between two years (2016 and 2017) with contrasting temperatures during the early grain-filling period under field conditions. Average daily mean temperature during the period of 0–5 days after full heading in 2016 (30.1 °C) was 5.4 °C higher than that in 2017. Initial, maximum, and mean grain-filling rates were 42–307% higher in 2016 than in 2017 for Luliangyou 996 and Lingliangyou 268. The time taken to reach the maximum grain-filling rate and active grain-filling duration were 6.3–10.7 d shorter in 2016 compared to 2017 for Luliangyou 996 and Lingliangyou 268. Grain weight was equal to or significantly higher in 2016 than in 2017 for Luliangyou 996 and Lingliangyou 268. N accumulation and N content in the grain were significantly lower in 2016 than in 2017 for both cultivars. The grain contents of all detected amino acids, except for methionine in Luliangyou 996, were significantly lower in 2016 than in 2017. Our study suggests that high temperature during the early grain-filling period can result in an accelerated grain-filling process, reduced N accumulation and content in rice grains, and consequently reduced amino acid content in the grain.

Exogenous Potassium–Instigated Biochemical Regulations Confer Terminal Heat Tolerance in Wheat

Heat stress at spike initiation and flowering is chief constraint hampering the accomplishment of yield potential in wheat crop. The present study was aimed at comparing the thermo-sensitivity of terminal stages, optimizing exogenous potassium to alleviate impacts of heat and to explore biochemical attributes triggered regulations in morphological attributes of wheat. The experiment was performed at the University of Agriculture Faisalabad, Pakistan during winter 2015–2016 and 2016–2017. The experiment was laid out in Randomized Complete Block Design under split arrangement and replicated thrice. The treatments comprised of heat stress in main plots viz. H0 = No heat imposition; H1 = Heat stress imposition from complete emergence of spike to grain filling initiation and H2 = Heat stress imposition from flowering initiation to grain filling initiation and exogenous potassium (K) concentrations in split plots viz. K0 = Control (water spray); K15 = 15 g L−1; K30 = 30 g L−1; K45 = 45 g L−1, and K60 = 60 g L−1. Under “H0,” statistically similar and relatively more activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were quantified with 45 and 60 g L−1 foliar “K.” Contrarily, significantly more SOD, POD, and CAT contents were recorded with 60 g L−1 exogenous potassium under “H1” and “H2” while significantly lesser chlorophyll a, b contents and grain yield were recorded under “H1” compared to “H0” and “H2,” whereas statistically similar and significantly more grain-filling rate (GFR) and statistically similar and significantly lesser grain filling duration (GFD) were observed under “H1” compared to “H0” “H2.” Exogenous application of K at 45 and 60 g L−1 depicted statistically similar and comparatively more chlorophyll a, b contents, GFR, GFD, and grain yield compared to control. Moreover, strong, positive, and significant association of antioxidants and chlorophyll contents with morphological attributes was observed. Conclusively, “H1” proved more deleterious compared to “H0” and “H2” and exogenous K at 60 g L−1 effectively alleviated adversities of heat. Moreover, K-mediated regulations in biochemical attributes improved morphological attributes of heat-stressed wheat crop.

Carbon balance and source-sink metabolic changes in winter wheat exposed to high night-time temperature.

Carbon loss under high night-time temperature (HNT) leads to significant reduction in wheat yield. Growth chamber studies were carried out using six winter wheat genotypes, to unravel postheading HNT (23°C)-induced alterations in carbon balance, source-sink metabolic changes, yield, and yield-related traits compared with control (15°C) conditions. Four of the six tested genotypes recorded a significant increase in night respiration after 4days of HNT exposure, with all the cultivars regulating carbon loss and demonstrating different degree of acclimation to extended HNT exposure. Metabolite profiling indicated carbohydrate metabolism in spikes and activation of the TriCarboxylic Acid (TCA) cycle in leaves as important pathways operating under HNT exposure. A significant increase in sugars, sugar-alcohols, and phosphate in spikes of the tolerant genotype (Tascosa) indicated osmolytes and membrane protective mechanisms acting against HNT damage. Enhanced night respiration under HNT resulted in higher accumulation of TCA cycle intermediates like isocitrate and fumarate in leaves of the susceptible genotype (TX86A5606). Lower grain number due to lesser productive spikes and reduced grain weight due to shorter grain-filling duration determined HNT-induced yield loss in winter wheat. Traits and mechanisms identified will help catalyze the development of physiological and metabolic markers for breeding HNT-tolerant wheat.

Does post‐anthesis heat stress affect plant phenology, physiology, grain yield and protein content of durum wheat in a semi‐arid Mediterranean environment?

AbstractIncreasing air temperature due to changing climate is projected to decrease the length of the growing season, hasten vegetative development and maturation, and ultimately affect yield of many C3 crops. Previous multilocation trials highlighted strong relationships between thermal trends in the interval “beginning of flowering‐end of grain filling” and grain yield, and protein content in durum wheat (Triticum turgidum subsp. durum (Desf.) Husn.). With the aim to confirm these relationships, nine durum wheat genotypes, including old (Capeiti 8, Senatore Cappelli and Trinakria) and modern (Amedeo, Arcangelo, Mongibello, Simeto, and Svevo) varieties and a Sicilian landrace (Russello) were grown at three different sites representing a climate gradient in Sicily, Italy. Moreover, the effect of post‐anthesis heat stress on these durum wheats was further investigated in two contrasting environments: open‐field (control—C) and greenhouse heat stress (HS). HS shortened the interval “beginning‐end of flowering” of 1.5 days across genotypes, and the “end of flowering‐beginning of grain filling” and maturation of 4.9 days, with a range of 1 day in Arcangelo to 11 days in Cappelli. Advances in main phenophases significantly decreased kernel weight (KW) and grain yield (GY), whereas grain protein content (PC) increased. As expected, a negative relationship was observed between GY and PC, while positive relationships were found for GY and grain‐filling duration (GFD), and GY and KW. Genotypes responded differently to heat stress, as evidenced by the net photosynthesis, transpiration rate, instantaneous water use efficiency and dry matter accumulation in kernels. Genotypes were ranked according to the heat susceptibility index (HSI): Amedeo, Arcangelo, Capeiti 8, Svevo and Trinakria resulted heat‐tolerant. These varieties were characterized by an early trigger of dry matter accumulation in kernels under HS (Amedeo, Arcangelo and Trinakria), or showed similar length of the GFD (Capeiti 8) between environments. The multilocation trial confirmed a negative relationship between maximum temperatures and grain yield, and a positive relationship between minimum temperatures and protein content during grain–filling periods. Research focusing on agronomic strategies, phenology and breeding for tolerance to heat stress is of strategic importance to cope with the detrimental effect of global warming in semi‐arid climates.

The spike weight contribution of the photosynthetic area above the upper internode in a winter wheat under different nitrogen and mulching regimes

Besides leaves, non-foliar green organs such as stem and spike are also considered photosynthetic organs. To assess the photosynthetic contributions of these organs, the correlations between these photosynthetic areas and single-spike weight were investigated in a winter wheat (Triticum aestivum L.) under four nitrogen and mulching treatments: N120, N150, N195, and N195 + M. Two-year repeated field experiments were conducted on the Loess Plateau of China. Non-foliar photosynthetic area, grain-filling ratio and duration, grain yield, and in particular, single-spike weight, were measured, recorded and analyzed. Under the N195 + M treatment, plants showed the largest area of photosynthetic organs (flag leaf and non-foliar organs) and the highest grain yield and single spike weight. Single-spike weight was positively correlated with the areas of all examined non-foliar photosynthetic organs, in particular with the area above the flag leaf node (R2 = 0.761⁎) and the area above the exposed part of the peduncle (EXP) (R2 = 0.800⁎⁎). In addition, single-spike weight was highly correlated with average grain-filling ratio (R2 = 0.993⁎⁎), whereas it was less highly correlated with grain-filling duration (R2 = 0.533). The morphological traits of non-foliar photosynthetic organs were also more highly correlated with average grain-filling ratio than with average grain-filling duration. The significant correlation between each of the morphological traits (area, length and width) of EXP and single-spike weight indicates that morphological traits of EXP are important in determining spike weight in the Loess Plateau environment.

Plastic film mulching combined with nutrient management to improve water use efficiency, production of rain-fed maize and economic returns in semi-arid regions

To examine the combined effects of planting models with nutrient management strategies on grain filling rates, productivity, soil water storage, water-use efficiency and economic benefit of rain-fed corn, there for a field research was carried out during 2015–2016 in a semi-arid region of China. Three planting models were tested: ridge furrow system with plastic mulching (M1), furrow planting with soil crust ridges (M2), and flat planting without plastic mulching (M3); in combination with four nitrogen levels: 0 kg ha–1 (N0); 100 kg ha–1 (N1); 200 kg ha–1 (N2), and 300 kg ha–1 (N3). We found that M1 planting model with higher 300 kg-1 N ha-1 could significantly increase soil water availability at different growth stages, as a result significantly increased WUE (56.6%), RUE (71.2%), ET (8.8%), soil water storage, biomass (35.5%), and grain yield (70.8%) of rain-fed maize than that of M3N0 treatment. Increasing the nitrogen level as a result significantly increased the economic benefit, yields and yield components of rain-fed maize under different planting models, but AEN shows a significantly decreasing trend. The M1N3 treatment significantly promoted the LAI and grains filling of the basal, middle and upper seeds than that of M2 and M3 cultivation models with the highest nitrogen level. The M1N3 treatment obtained the highest (12,775 CNY ha-1) net profit, improved the SWS throughout the grain-filling duration, which resulted in higher productivity. Thus, M1N3 treatment can be used to improving productivity, economic benefit, and water use in semi-arid areas.

Physiological maturity as a function of seed and pod water concentration in spring rapeseed (Brassica napus L.)

Determining the optimum time for rapeseed harvest is challenging due to non-uniform seed maturity resulting from asynchronous flowering and pod dehiscence from sequential racemes. Identifying physiological maturity (PM) by visual methods is subjective and results can be affected by environmental conditions. PM can be determined using a quantitative model based on seed water concentration (SWC) as previously demonstrated for several other crops, although not yet developed for rapeseed crop. The objective of this work was to study the relationship between the dynamics of seed dry weight and water concentration in seven spring rapeseed cultivars grown at two contrasting densities (15 and 60 pl m−2) in three experiments at one location in Buenos Aires (Argentina). We evaluated the timing of PM on the basis of SWC in seeds located in the main raceme, second and fourth floral branches. The evolution of seed fresh and dry weight was followed bi-weekly from the beginning of flowering to harvest maturity. In Exp. 1, the grain-filling duration ranged from 39 to 57 days (700–1100 °C d) and the growth of seeds from floral branches finished 3–8 days later than those from the main raceme. Seed dry weight at PM ranged from 2.4 to 2.7 and from 3.0 to 3.2 mg for Lynx and Monty cultivars, respectively, without significant effects of floral position or plant density. Bi-linear functions were used to fit the relationship between relative seed dry weight (RSDW) and SWC relationships (R2 from 0.85 to 0.95). Across cultivars and floral positions, PM was attained when seeds exhibited 46.3 ± 0.7% SWC (R2 = 0.90, P < 0.001, n = 441). This model was validated against independent data from Exps. 2 and 3, successfully simulating the dynamics of relative seed dry weight based on fruit WC (r = 0.88; P < 0.001, n = 275). At PM, the water content (WC) of whole pod was about 70% and the pod shattering began after this point, when the WC of the pod dropped drastically. We conclude that under non-stressful conditions, PM in rapeseed occurs at 46% SWC. Swathing can be conducted from SWC < 46%, instead of the currently recommended 35%, advancing the harvest and leaving the land available for sowing the next crop, which would represent an advantage for double cropping in intensified agricultural systems.

Optimal nitrogen regimes compensate for the impacts of seedlings subjected to waterlogging stress in summer maize.

A field experiment was performed to explore the compensation effects of different nitrogen (N) regimes on the growth and photosynthetic capacity in different leaf layers of the summer maize hybrid of LuYu9105 under waterlogging at the seedling stage. The results showed that waterlogging significantly decreased the maximum green leaf area (gLA) by 10.0~15.3% and 9.3~22.5%, mainly due to the reduction in the below-ear layer leaves at the silking stage in 2014 and 2015, respectively. Waterlogging also significantly decreased the ear leaf photosynthetic rate (PN), and Fv/Fm, Fv/Fo, ΦPSII and qP at the below-ear layer leaves at the mid- and late-filling stages, which was accompanied by a reduction in the duration of grain-filling (T) by 2.6~5.9%, thus resulting in a loss of grain yield by 7.0~18.5%. Interestingly, a shift in N from basal application to topdressing at the big flare stage was shown to compensate the adverse effects of waterlogging by through increased gLA and leaf photosynthetic capacity at the ear layer and the above-ear layer, as well as a greater grain-filling rate, resulting in an increase in grain yield by 9.9~27.0% and 17.8~25.8% compared to other N treatments. Therefore, this study showed that optimal nitrogen regimes during maize growth are capable of compensating for the impacts caused by waterlogging at the seedling stage.

Timing of Water Deficit Limits Maize Kernel Setting in Association With Changes in the Source-Flow-Sink Relationship.

The kernel setting of maize varies greatly because of the timing and intensity of water deficits. This variation can limit leaf productivity (source), the translocation of assimilated sugars (flow), and yield formation (sink). To explain the decline in kernel setting of maize under water deficits from the perspective of source-flow-sink, a 3-year experiment was conducted under a rain shelter. Five water regimes were studied. One regime included well-irrigated (CK) treatment. Four regimes involved water deficits: irrigation was withheld during the 6- to 8-leaf stage (V6−8), the 9- to 12-leaf stage (V9−12), the 13-leaf stage to tasseling stage (V13−T), and the silking stage to blister stage (R1−2). Water deficit effects on kernel setting began when the water deficit occurred at V9 and became more significant with time. Kernel weight was reduced by 12 and 11% when there were water deficits during V9−12 and V13−T, respectively. This was the result of reduced leaf area (limited source) and an altered vascular bundle in the ear peduncles (limited assimilate flow). The reduced vascular bundle number, rather than the ear peduncle cross-sectional area, significantly affected the final kernel weight when exposed to a water deficit prior to the silking stage. The water deficits prior to and close to the flowering stage significantly reduced ear kernel number; that is, 14 and 19% less during V13−T and R1−2, respectively, compared with the kernel number during the CK treatment. This reflects a smaller sink under water deficit conditions. Additionally, ovary size was reduced the most in the V13−T water deficit compared with other treatments. After rewatering, the water deficit before or during flowering stage continued to have residual effects on grain-filling in the late growth period. The grain-filling rate decreased under the V9−12 water deficit; the grain-filling duration shortened under the R1−2 water deficit; and both negative effects occurred under the V13−T water deficit. This study clearly indicated that (1) the water deficit during the vegetative organ rapid growth period both limited leaf source development and assimilate flow and slowed down kernel development, and (2) the water deficit just before and during flowering reduced kernel sink. Deficits at both times could retard grain-filling and reduce maize yield. The results of the present study might guide irrigation practices in irrigated maize or inform the management of sowing time in rainfed maize, to desynchronize the water deficit and the plant’s reactions to such deficits at different stages.

NAM gene allelic composition and its relation to grain-filling duration and nitrogen utilisation efficiency of Australian wheat.

Optimising nitrogen fertiliser management in combination with using high nitrogen efficient wheat cultivars is the most effective strategy to maximise productivity in a cost-efficient manner. The present study was designed to investigate the associations between nitrogen utilisation efficiency (NUtE) and the allelic composition of the NAM genes in Australian wheat cultivars. As results, the non-functional NAM-B1 allele was more responsive to the nitrogen levels and increased NUtE significantly, leading to a higher grain yield but reduced grain protein content. Nitrogen application at different developmental stages (mid-tillering, booting, and flowering) did not show significant differences in grain yield and protein content. The NAM-A1 allelic variation is significantly associated with the length of the grain-filling period. While the NAM-A1 allele a was associated with a short to moderate grain-filling phase, the alleles c and d were related to moderate to long grain-filling phase. Thus, selection of appropriate combinations of NAM gene alleles can fine-tune the duration of growth phases affecting sink-source relationships which offers an opportunity to develop high NUtE cultivars for target environments.

Characterization of the rate and duration of grain filling in wheat in southwestern China

ABSTRACTField trials were carried out during 2011–2013 in three locations on 10 wheat genotypes. Traits that were investigated included grain weight, grain-filling duration, grain-filling rates and the lag phase from flowering to the commencement of effective grain filling. The grain-filling duration and rate were fitted by Richard’s equation in thermal time (growing degree-days (GDD), base temperature 9ºC). A combined ANOVA across environments showed that the grain weight was mainly affected by genotype, while most of the other grain-filling characters were influenced by the environment and G × E interactions. Grain filling lasted between 362 to 400 GDD and included a lag phase that ranged from 67 to 86 GDD. Both the effective and maximum rates of grain filling ranged from 0.12 to 0.15 mg GDD−1 and 0.18–0.22 to GDD−1, respectively. The lag phase was positively correlated with grain weight and rates of grain filling, whereas days to anthesis were significantly negatively correlated with the lag phase and both rates of grain filling. Temperature during grain filling was negatively correlated with the lag phase. The variation in grain weight was positively associated with the rate of grain filling, which, in turn, was related to the grain number per unit area. A compensating variability existed among the genotypes in both the grain number and grain-filling rate. The study of genotypic stability demonstrated that Chuanmai42 and Chuanmai104 had high grain weight and stability among most of the grain-filling parameters, and also had high grain yield. Chuanmai42 and Chuanmai104 were the best genotypes for improving the yield potential and grain weight stability.

Genetics of Grain Yield and its Components in Wheat under Heat Stress

Heat stress is a matter of a great concern for the wheat crop. Heat stress usually either hastens crop development or shortens the grain filling duration, which severely reduces grain yield. Being a complex trait, understanding the genetics and gene interactions of stress tolerance are the two primary requirements for improving yield levels. Genetic analysis through generation mean analysis helps to find out the nature of gene actions involved in a concerned trait by providing an estimate of main gene effects (additive and dominance) along with their digenic interactions (additive × additive, additive × dominance, and dominance × dominance). In the present investigation, we elucidated the inheritance pattern of different yield contributing traits under heat stress using different cross combinations which could be helpful for selecting a suitable breeding strategy. Thus six generations of five crosses were sown normal (non-stress, TS) and late (heat stress, LS) in a randomized block design with three replications during two crop seasons. The model was not adequate for late sown conditions indicating the expression of epistatic genes under stress conditions. The traits i.e. Days to heading (DH), Days to anthesis (DA), Days to maturity (DM), Grain filling duration (GFD), Grain yield (GY), Thousand grain weight (TGW), Grain weight per spike (GWS) and Heat susceptibility index (HSI) under heat stress conditions were found under the control of additive gene action with dominance × dominance interaction, additive gene action with additive × dominance epistatic effect, dominance gene action with additive × additive interaction effect, additive and dominance gene action with dominance × dominance interaction effect, additive gene action with additive × dominance epistatic effect, additive gene action with additive × additive interaction effect and dominance gene action with additive × additive interaction effect, respectively.

Identification of genotypes and marker validation for grain filling rate and grain filling duration in wheat under conservation agriculture

Increase in ambient temperature beyond threshold level as predicted by global climate models may impact wheat production severely in India if it happens during grain filling stage. Grain filling rate (GFR) and grain filling duration (GFD) are critical determinant for final grain yield realization in wheat. GFR in wheat follow a slow-fast-slow pattern, however, wheat genotypes may have quantitative differences in this pattern. Ninty six diverse wheat genotypes were evaluated for GFR in two phases i.e. during first 20 days after anthesis and thereafter up to physiological maturity and grain filling duration. Out of 96 genotypes, six namely, G958, G1203, G1219, G1275, HD2985 and HDCSW18 were having high GFR during initial phase while seven genotypes viz., G949, G1081, G1124, G1159, G1204, HD3059 and HD2380 exhibited high GFR at terminal phase of grain development. Genotypes, G1263, G1207, G1423 along with some of the released varieties, HD2285, WH1105 and HD2864 were having higher GFD. Correlation between the two traits were not significant (r = -0.17959). ANOVA for GFR and GFD indicated highly significant variability among the genotypes. QTLs identified for GFR and GFD elsewhere were validated in Indian breeding material under conservation agriculture. Two SSR markers viz., XCfd42 and Xwmc500 explained about 6% and 1% variation for GFR, respectively. Similarly, already reported marker Xwmc382 was able to explain about 8% of variation for GFD in the Indian breeding material. It has been postulated from the study that by crossing the genotypes with high GFR in different grain growth stages like HD CSW 18 and HD 3059, genotypes with consistently high grain filling rate throughout the grain growth stage can be developed. The markers XCfd42 and Xwmc 382 can be further explored for fine mapping to integrate in the breeding programme for selection.

Grain filling and yield of mung bean affected by salicylic acid and silicon under salt stress

ABSTRACTTwo experiments were carried out in 2013 and 2014, to investigate changes in grain filling rate (GFR), grain filling duration (GFD) and yield of mung bean in response to salicylic acid (SA) and silicon (Si) under salt stress (0, 3, 6 and 9 dS m−1). In experiment 1, four levels of SA (0, 0.5, 1 and 1.5 mM), but in experiment 2, two levels of SA (0 and 1 mM) and Si (0 and 2 mM) were applied. In experiment 1, GFR, GFD, yield components, biological and grain yields and harvest index were decreased with increasing salt stress. Application of different levels of SA, especially 1 mM, increased GFR, but decreased GFD. In experiment 2, GFD under salinity was shorter than that under non-saline condition, resulting in comparatively smaller grains. Application of Si and particularly SA accelerated grain development under all salinity treatments. The superiority of SA treated plants in GFR, grain weight and grains per plant resulted in greater grain yield per plant under saline and non-saline conditions.

Mapping QTLs for grain yield components in wheat under heat stress.

The current perspective of increasing global temperature makes heat stress as a major threat to wheat production worldwide. In order to identify quantitative trait loci (QTLs) associated with heat tolerance, 251 recombinant inbred lines (RILs) derived from a cross between HD2808 (heat tolerant) and HUW510 (heat susceptible) were evaluated under timely sown (normal) and late sown (heat stress) conditions for two consecutive crop seasons; 2013–14 and 2014–15. Grain yield (GY) and its components namely, grain weight/spike (GWS), grain number/spike (GNS), thousand grain weight (TGW), grain filling rate (GFR) and grain filling duration (GFD) were recorded for both conditions and years. The data collected for both timely and late sown conditions and heat susceptibility index (HSI) of these traits were used as phenotypic data for QTL identification. The frequency distribution of HSI for all the studied traits was continuous during both the years and also included transgressive segregants. Composite interval mapping identified total 24 QTLs viz., 9 (timely sown traits), 6 (late sown traits) and 9 (HSI of traits) mapped on linkage groups 2A, 2B, and 6D during both the crop seasons 2013–14 and 2014–15. The QTLs were detected for GWS (6), GNS (6), GFR (4), TGW (3), GY (3) and GFD (2). The LOD score of identified QTLs varied from 3.03 (Qtgns.iiwbr-6D) to 21.01 (Qhsitgw.iiwbr-2A) during 2014–15, explaining 11.2 and 30.6% phenotypic variance, respectively. Maximum no of QTLs were detected in chromosome 2A followed by 6D and 2B. All the QTL detected under late sown and HSI traits were identified on chromosome 2A except for QTLs associated with GFD. Fifteen out of 17 QTL detected on chromosome 2A were clustered within the marker interval between gwm448 and wmc296 and showed tight linkage with gwm122 and these were localized in 49–52 cM region of Somers consensus map of chromosome 2A i.e. within 18–59.56 cM region of chromosome 2A where no QTL related to heat stress were reported earlier. Besides, three consistent QTLs, Qgws.iiwbr-2A, Qgns.iiwbr-2A and Qgns.iiwbr-2A were also detected in all the environments in this region. The nearest QTL detected in earlier studies, QFv/Fm.cgb-2A was approximately 6cM below the presently identified QTLs region, respectively Additionally, QTLs for physiological and phenological traits and plant height under late sown and HSI of these traits were also detected on chromosome 2A. QTL for HSI of plant height and physiological maturity were located in the same genomic region of chromosome 2Awhereas QTLs for physiological and phonological traits under late sown were located 8cM and 33.5 cM below the genomic location associated with grain traits, respectively in consensus map of Somers. This QTL hot-spot region with consistent QTLs could be used to improve heat tolerance after validation.

Character association and path co-efficient analysis in wheat (Triticum aestivum L.)

The experiment was carried out with 50 wheat lines to study their mean, range, cv (%), correlation co- efficient, and path co- efficient considering 14 different morphological characters at the experimental field of Regional Wheat Research Centre (RWRC), Bangladesh Agricultural Research Institute (BARI), Gazipur during December 2010 to April 2011. Significant variation was observed among the genotypes for all characters studied. In general, genotypic correlations were higher than the phenotypic correlations. It indicates that there was an inherent association among them which was adversely influenced by the environment. The correlation coefficients showed that, seed yield was negatively and significantly correlated with days to heading (DTH), plant height (PHT), days to anthesis (DTA), days to physiological maturity (DPM), and canopy temperature at anthesis stage (CTanth.) but only negatively correlated with canopy temperature at vegetative stage (CTveg.), canopy temperature at grain filling stage (CTgf.), spikelets per spike both genotypically and phenotypically and grain per spike showed genotypically negative correlation. Path analysis showed that plant height (PHT), days to physiological maturity (DPM), canopy temperature at grain filling stage (CTgf.), and thousand grain weight (TGW) influenced seed yield directly in positive direction but days to heading (DTH), days to anthesis (DTA), grain filling duration (GFD), grain filling rate (GFR), Chlorophyll content at anthesis stage (CHLA), canopy temperature at vegetative stage (CTveg.), canopy temperature at anthesis stage (CTanth.), spikelets per spike, and grains per spike had negative direct effect on seed yield. Considering analytical findings of correlation co-efficient, path co-efficient analysis and field performance, the genotypes G 3, G 10, G 11, G 12, G13, G 21, G 29, G 35, G 38, G 40, G 46 and G 48 were found suitable for future breeding programme.Bangladesh J. Agril. Res. 42(3): 571-588, September 2017