Crops, Volume 2, Issue 1 (March 2022) – 6 articles

The lack of seedling emergence uniformity in corn (Zea mays L.) is concerning for producers in the Midwestern U.S. These producers believe that just a few hours delay in emergence can increase interplant competition and decrease single-plant yield, thus reducing overall crop yield. It is speculated that lack of uniformity in seedling emergence occurs due to a variation in seed size within a commercial bag of seed, and variation in seed depth placement at sowing throughout the field. Due to these concerns, producers evaluate size seed variation within the bag before sowing. To date, research has investigated sowing dates, growing degree days, or varying sowing depths to simulate a delay in seedling emergence. These studies are important for understanding the effects of delayed emergence on overall yield, but they fail to examine the effect of inter-plant competition on single-plant yield. The objective of this study was to understand the effect of seed size and sowing depth on emergence and subsequent single-plant yield in a bare soil and a perennial groundcover (PGC) cropping system. Commercially sized seed and seed sized further in the laboratory to obtain a narrower seed size distribution were sown in Kentucky bluegrass and bare soil systems and at two sowing depths of 3.18 and 6.35 cm. The two-year experiment was planted in a split-plot design with four replications. Individual plants were flagged at emergence, and harvested individually. Seed placement was crucial to uniform emergence in both cropping systems, while seed size did not affect emergence in either system. The PGC cropping system delayed seed corn emergence and reduced grain yield as much as 50%. Single-plant yield decreased with delayed corn emergence in both cropping systems. Yield decrease as a function of emergence date followed either a quadratic or linear trend in each growing season, likely related to post emergence environmental factors. This information is important for producers and seed companies to understand the effect of seed size and sowing depth on yield and emergence. This study demonstrates that uniform sowing depth is more important than seed size distribution. Full article

Stripe rust is a devastating disease in wheat that causes substantial yield loss around the world. The most effective strategy for mitigating yield loss is to develop resistant cultivars. The wild relatives of wheat are good sources of resistance to fungal pathogens. Here, we used a genome-wide association study (GWAS) to identify loci associated with stripe rust (causal agent: Puccinia striiformis f. sp. tritici) resistance in wild emmer (Triticum dicoccoides) at the seedling stage, in the greenhouse, and at the adult plant stage, in the field. We found that the two major loci contributing to resistance in our wild emmer panel were the previously cloned seedling-stage resistance gene, Yr15, and the adult-plant-stage resistance gene, Yr36. Nevertheless, we detected 12 additional minor QTLs that additionally contribute to adult plant resistance and mapped a locus on chromosome 3AS that tentatively harbors a novel seedling resistance gene. The genotype and phenotype data generated for the wild emmer panel, together with the detected SNPs associated with resistance to stripe rust, provide a valuable resource for disease-resistance breeding in durum and bread wheat. Full article

Green grains that are harvested before maturity and dehulled have been reported to have higher nutritional value than fully matured brown rice. Two years of aerobic field experiments were conducted to determine the effect of variety, early harvest and their interaction, on grain yield and pasting properties of brown rice. Eight varieties were grown under well-watered or water deficit conditions and harvested between 15–35 days after flowering (DAF). The maximum yield of green rice was obtained when crops were harvested between 20–25 DAF for well-watered condition and 15–20 DAF for water deficit condition. The paddy yield on these early harvest dates was on average 66% of mature paddy rice yield. Varieties were consistent in paddy yield at early harvest 20–25 DAF with correlation coefficient being 0.897 ** between the two years. Rapid visco-analysis (RVA) showed that developing grains had lower pasting viscosities than mature grains. However, the variety difference had a greater effect on pasting viscosities than the harvest time. Varieties were consistent in pasting characteristics between early and mature harvests, and between growing seasons. Water deficit reduced grain yield but did not significantly affect the pasting characteristics of flour gel, amylose and protein content. The RVA showed that final viscosity and setback viscosity in brown rice flour harvested at 15 DAF were only 84% and 76% of those in mature brown rice, indicating that developing grains were likely to produce softer cooked rice than mature grain. The results on differences in pasting characteristics between developing and mature grains provide more options in developing food products with desired gel properties. Full article

Maize (Zea mays L.) is among the three most important food crops worldwide. Maize growth is affected by high aluminium content in acid soils, which constitute nearly 50% of the world’s cultivable area. Therefore, the cultivation of aluminium-tolerant maize hybrids could be a healthier alternative and an attractive food source in these regions. In this regard, to produce hybrids kernels, 16 inbred lines aluminium-tolerant (Al-T) and aluminium-susceptible (Al-S) maize were screened for their constitutive patterns of selected nutrients and phytochemicals. Proximate analysis, free phenolic acids (FPA) and cell wall-bound phenolic acids (CPA) contents, as well as antioxidant capacity (AOX) were assayed in the anatomical kernel parts (pericarp, endosperm, and germ). Kernels of Al-T maize contained significantly higher germ protein, oil, and fibre (2.9, 3.0, and 0.5%, respectively) than Al-S kernels (1.9, 1.8, and 0.3%, respectively). Importantly, the nutraceutical contents in terms of pericarp FPA and germ CPA were significantly higher in kernels belonging to Al-T maize (92 mg and 140 mg EGA/100 g). The highest AOX was observed in germ CPA of Al-T kernels (9.0 mmol TE/100 g). The results herein indicate that Al-tolerance mechanisms induce positive changes in the nutrients and phytochemicals; this implies that the hybrids generated using Al-T maize inbred lines could emerge as an attractive source of nutrients and phytochemicals in farming regions containing acid soils. Full article

The framework conditions for chemical weed control in oilseed rape (OSR) are becoming increasingly unfavorable in Central Europe. On the one hand, weed resistance is spreading and, on the other, there is a growing social desire to reduce or eliminate the use of chemical crop protection products. In a field experiment, hoeing, as a weed control measure performed two times per growing season (one time in autumn and one time in spring) in oilseed rape (Brassica napus; two varieties), was compared to chemical control by herbicides and a combination of hoeing and herbicide application (five treatments altogether). The chemical control by herbicides consisted of a broad-spectrum pre-emergence treatment and a post-emergence graminicide application. The trial was set up in each of three periods (years 2014/2015, 2015/2016, and 2016/2017) at the experimental station Ihinger Hof, University of Hohenheim, Stuttgart, Germany. The effect of the treatments on weed plant density, weed biomass at the time of harvesting, and on OSR grain yield was investigated. Weed plant density was measured four times per trial year, each time before and after hoeing. In 2015/2016 after spring hoeing, and in 2016/2017 at all data collection times, weed plant density was significantly higher in hoeing without herbicide application than in the other variants. No significant differences occurred at the other data collection times. The weed plant density ranged from 0.5 to 57.8 plants m⁻². Regardless of the trial year, pure hoeing always resulted in a significantly higher weed biomass at the time of harvesting than the herbicide applications or the combinations. The weed biomass at the time of harvesting ranged between 0.1 and 54.7 g m⁻². No significant differences in grain yield between hoeing and herbicide application occurred in all three trial years. According to the results, hoeing is a suitable extension of existing integrated weed control strategies in OSR. Full article