Differential Maize Yield Hybrid Responses to Stand Density Are Correlated to Their Response to Radiation Reductions Around Flowering

Altered stand density affects maize yields by producing changes in both numerical yield components, kernel number per plant (KNP), and kernel weight (KW). Kernel number is determined by the accumulation of ear biomass during the flowering period, whereas KW is determined by the sink potential established during flowering and the capacity of the plant to fulfill this potential during effective grain filling. Here, we tested if different short shading treatments during different stages around flowering can help discriminate genotypic differences in eco-physiological parameters relevant for maize stand density yield response and associated yield components. Our specific objectives were to: (i) identify hybrids with differential shading stress response, (ii) explore shading effects over eco-physiological parameters mechanistically related to KNP and KW, and (iii) test if shading stress can be used for detecting differential genotypic yield responses to stand density. The objectives were tested using four commercial maize hybrids. Results indicated that KNP was the yield component most related to yield changes across the different shading treatments, and that the specific shading imposed soon after anthesis generated the highest yield reductions. Hybrids less sensitive to shading stress were those that reduced their plant growth rate the least and the ones that accumulated more ear biomass during flowering. Genotype susceptibility to shading stress around flowering was correlated to stand density responses. This indicated that specific shading stress treatments are a useful tool to phenotype for differential stand density responses of commercial hybrids.

Identification of Genetic Loci on Chromosome 4B for Improving the Grain Number per Spike in Pre-Breeding Lines of Wheat

The grain number per spike (GNPS) is an important yield component, and much attention is given to the increase in GNPS for current yield improvement of common wheat. Here, a panel of 259 pre-breeding lines and elite commercial varieties were collected for the investigation of 12 agronomic traits, especially for spike-related traits, with 2-year replicates. The high correlation between GNPS and kernel number per spikelet (KNS) suggested that the high GNPS trait in our pre-breeding lines was mainly controlled by grain set number per spikelet. Genome-wide association studies (GWAS) using the 660K SNP genotyping assay suggested that a major locus on chromosomes 4BS contributed to the high GNPS trait, which contributed to 33% and 48% of the variation in KNS and GNPS, respectively. A good diagnostic KASP marker AX-109286577 flanking the 4BS locus was developed for easy selection of the large spike trait. Taken together, the results suggested that untapped rare allele variation in our pre-breeding lines can be used for improvement of the yield component of set grain number per spike.

Long-Term Dynamic of Cold Stress during Heading and Flowering Stage and Its Effects on Rice Growth in China

Short episodes of low-temperature stress during reproductive stages can cause significant crop yield losses, but our understanding of the dynamics of extreme cold events and their impact on rice growth and yield in the past and present climate remains limited. In this study, by analyzing historical climate, phenology and yield component data, the spatial and temporal variability of cold stress during the rice heading and flowering stages and its impact on rice growth and yield in China was characterized. The results showed that cold stress was unevenly distributed throughout the study region, with the most severe events observed in the Yunnan Plateau with altitudes higher than 1800 m. With the increasing temperature, a significant decreasing trend in cold stress was observed across most of the three ecoregions after the 1970s. However, the phenological-shift effects with the prolonged growing period during the heading and flowering stages have slowed down the cold stress decreasing trend and led to an underestimation of the magnitude of cold stress events. Meanwhile, cold stress during heading and flowering will still be a potential threat to rice production. The cold stress-induced yield loss is related to both the intensification of extreme cold stress and the contribution of related components to yield in the three regions.

Maize Growth Responses to a Humic Product in Iowa Production Fields: An Extensive Approach

Field evaluations of commercial humic products have seldom involved replication across location or year. To evaluate the consistency of humic product efficacy in field conditions, we determined the effects of a humic product on maize (Zea mays L.) growth in high-yielding Midwestern (US) fields through the following two extensive approaches: (i) replicated strip plots in five site—year combinations from 2010 to 2013; and (ii) demonstration strips in 30–35 production fields annually from 2009 to 2011 that covered major areas of Iowa. Mechanized combine measurements of grain yield showed increases of 0.2–0.4 Mg ha–1 (1–4%) with humic product application for all five site—year combinations of the replicated strip plots. Six of 10 humic treatments within the fields responded positively (P < 0.07), and the positive responses of two more treatments approached significance at the benchmark of P = 0.10. In the demonstration strips, maize grain weight in hand-collected samples increased significantly (P < 0.004) with humic product application in each of the three growing seasons, and across all the three seasons by 6.5% (P < 0.001). Grain weight increased numerically for 76 of the 98 demonstration strips. Yield component analysis for both the replicated strip plots and the demonstration strips attributed the yield boosts largely to increased ear length, especially of the shorter ears. Humic product application caused significantly (P < 0.10) greater total leaf area in all eight field treatments at three site—year combinations. Humic product application did not consistently affect nutrient concentrations of the grain or stover or any measured soil property. These results represent among the widest geographic evaluations published on field efficacy of a humic product. They demonstrate the capability of a humic product to improve maize growth in high-yielding conditions.

Impact of Sowing Time on Chickpea (Cicer arietinum L.) Biomass Accumulation and Yield

Chickpea growth, development and grain yield are affected by a range of climatic and environmental factors. Experiments were conducted across four sowing dates from mid-April to the end of May, over two years at Trangie in central western New South Wales (NSW), and Leeton, Wagga Wagga and Yanco (one year) in southern NSW, to examine the influence of sowing time on biomass accumulation, grain yield and plant yield components. Climatic and experimental location data were recorded during the growing seasons. Early sowing (mid-April) resulted in taller plants, higher bottom and top pod heights, fewer pods, more unfilled pods and greater biomass accumulation, but low harvest index due to reduced grain yield compared with late sowing (end of May). Grain number was positively correlated with grain yield and was the main yield component accounting for most of the variation in yield. There was largely a positive correlation between biomass and yield, especially with delayed sowing except for Leeton experiments. This study concludes that sowing around the end of April in central western NSW and mid-May in southern NSW is conducive to higher grain yield as it minimises exposure to abiotic stresses at critical growth periods and allows efficient conversion of biomass to grain yield.

Corn Starch: Quality and Quantity Improvement for Industrial Uses

Corn starch serves as food, feed, and a raw material for industrial use. Starch makes up most of the biomass of the corn hybrid and is the most important and main yield component in corn breeding programs. Starch is composed of two polymers, branched amylopectin and linear amylose, which normally constitute about 75% and 25% of the corn starch, respectively. Breeding for corn starch quality has become economically beneficial because of the development of niche markets for specialty grains. In addition, due to the increased demands of biofuel production, corn ethanol production is receiving more attention. Consequently, improving starch quantity has become one of the most important breeding objectives. This review will summarize the use of corn starch, and the genetics and breeding of grain quality and quantity for industrial applications.

Environmental Variability of Thousand Kernel Weight in Maize Hybrids of Different Maturity Groups

Thousand kernel weight (TKW) is an important yield component trait affected by the environmental conditions. This study’s objectives were to determine an environmental variability for the TKW in 32 maize hybrids, sorted in four FAO maturity groups (FAO300, 400, 500 and 600), and to compare 12 environments in Croatia (six locations in two years) according to the joint linear regression and stability analyses across the maturity groups. In general, the effects of the environment, genotype, and their interaction (GEI) were significant. A three-factor ANOVA revealed the greatest and highly significant year effect, while the location effect was non-significant across all four FAO groups. A stability analysis did not detect any preferences with regard to the locations and trends across the FAO groups. It indicates that all locations in the Pannonian region included in this study were suitable for an evaluation of the TKW in maize genotypes belonging to all maturity groups. The TKW seems to be an appropriate yield-component trait for maize breeding due to a high heritability and linear GEI nature.

IMPACT OF DIFFERENT LEVELS OF BULK DENSITIES COMBINATION ON YIELD AND YIELD COMPONENT OF WHEAT (TRITICUM AESTIVUM L.)

An experiment was conducted on the impact of different levels of bulk densities combination on yield and yield components of wheat. Three bulk density levels 1.00-1.30 (A) g cm-3, 1.30-1.60 (B) g cm-3 and 1.60-1.90 (C) g cm-3 with three different depths (0-15, 16-30 and 31-45 cm) were used in the experiment using silt loam soil (Pedocals). The total treatments were 27 in the experiment with three replications. The experimental design was completely randomized design (CRD). The treatment means were checked at the confidence level of 95% of probability. The soil 0-45 cm deep was shifted from the field (no-till) to the net house and was act as control. The results showed that the number of tillers plant-1, number of leaves plant-1 and thousand grain yield were non-significantly affected by all the treatments while number of seed emerged, root length, dry root weight, plant height, grain yield , biological yield and harvest index were significantly influenced by various treatments. The highest number of seed germinated (8.00) was found in the treatment BBB (1.30-1.60 g cm-3 in 0-15 cm, 15-30 cm, 30-45 cm soil depth), BAB (1.30-1.60 g cm-3 in 0-15 cm, 1.00-1.30 g cm-3 in 15-30 cm and 1.30-1.60 g cm-3 in 30-45 cm soil depth) and BCB (1.30-1.60 g cm-3 in 0-15 cm, 1.60-1.90 g cm-3 in 15-30 cm and 1.30-1.60 g cm-3 in 30-45 cm) while the lowest number of seed emerged (3.6) was found in AAA (1.00-1.30 g cm-3 in 0-15 cm, 15-30 cm and 30-45 cm soil depth), ACA (1.00-1.30 g cm-3 in 0-15 cm, 1.60-1.90 g cm-3 in 15-30 cm and 1.00-1.30 g cm-3 in 30-45 cm soil depth) and CAC (1.60-1.90 g cm -3 in 0-15 cm, 1.00-1.30 g cm-3 in 15-30 cm and 1.60-1.90 g cm-3 in 30-45 cm soil depth). The highest root length (13.12 cm) was found in the treatment AAA while the lowest root length (10.05 cm) was found in CAC. The highest dry root weight (5.67g) was found in the treatment ABA while the lowest dry root weight (4.79g) was found in control treatment. The highest plant height (42.67 cm) was found in the treatment of BBA while the lowest plant height (29.67 cm) was found in control. The highest biological yield (12.1 metric ton ha-1) was found in the treatment ABA while the lowest biological yield (6.8 metric ton ha-1) was found in control. The highest grain yield (4.4 metric ton ha-1) was found by ABB while the lowest (2.7 metric ton ha-1) was found in the control. The highest harvest index (39.79%) was found in the control while the lowest harvest index (34.54%) was found in CCA. The experiment showed that increasing bulk density above 1.60 g cm-3 resulted in decreasing the yield and yield component of the winter wheat. The number of seed emerged, root length, dry root weight, plant height, grain yield, biological yield and harvest index of wheat were significantly affected by soil bulk density in various depths.

Growth and Yield of Soybean (Glycine max L. Merill) at Various Doses of Bokashi Fertilizer on Ultisol

Soybean is a type of secondary crop that is widely cultivated and used as raw material for tofu, tempe, milk, and so on by the people of Indonesia. Soybean consumption is always increasing but soybean production has decreased. This study aims to obtain the optimum dose of Bokashi fertilizer on plant growth and yield in Ultisol. The study was carried out in Medan Baru, Kandang Limun Village, Muara Bangkahulu District, Bengkulu City from December 2018 to April 2019. This study used a Completely Randomized Block Design (RCBD) with one factor, namely the dose of Bokashi fertilizer with five levels, namely 0 tons ha-1, 25 tons ha-1, 35 tons ha-1, 45 tons ha-1, and 55 tons ha-1. The results showed that the optimum dose of Bokashi fertilizer was not found in the growth component or yield component. The dose of Bokashi fertilizer had a significant effect (p<0.05) on the growth of Bokashi and the number of leaves.