Aluminum Stress Induces Irreversible Proteomic Changes in the Roots of the Sensitive but Not the Tolerant Genotype of Triticale Seedlings

Triticale is a wheat–rye hybrid with a higher abiotic stress tolerance than wheat and is better adapted for cultivation in light-type soils, where aluminum ions are present as Al-complexes that are harmful to plants. The roots are the first plant organs to contact these ions and the inhibition of root growth is one of the first plant reactions. The proteomes of the root apices in Al-tolerant and -sensitive plants were investigated to compare their regeneration effects following stress. The materials used in this study consisted of seedlings of three triticale lines differing in Al3+ tolerance, first subjected to aluminum ion stress and then recovered. Two-dimensional electrophoresis (2-DE) was used for seedling root protein separation followed by differential spot analysis using liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS/MS). The plants’ tolerance to the stress was evaluated based on biometric screening of seedling root regrowth upon regeneration. Our results suggest that the Al-tolerant genotype can recover, without differentiation of proteome profiles, after stress relief, contrary to Al-sensitive genotypes that maintain the proteome modifications caused by unfavorable environments.

Root system architecture and seed weight relations in forage pea (Pisum sativum ssp. arvense L. Poir.)

ABSTRACT: Forage pea (Pisum sativum ssp. arvense (L.) Poir.) is an important legume crop for fresh and dry herbage production with high input costs as irrigation and fertilization. Selection and breeding of accessions for improved drought tolerance, water, and mineral uptake efficiency become a necessity, rather than a choice. This study evaluated a set of forage pea accessions for the seedling root system architecture diversity and seed reserve utilization, under controlled conditions. Eight cultivars and an elite breeding line were evaluated for the first time in a plexiglass system. The number and lengths of the roots in each depth zone (0, 5, 10, 15+ cm) were evaluated and significant diversity was identified. The cultivar Livioletta had the highest number of roots and total root length. There was a significant correlation between seed weight, seed reserve utilization ratio, and root system vigor. Accessions with the highest seed reserve utilization had the highest total root length and numbers. Seedling root system vigor seems to be effective in predicting the fate of the accessions through maturity. The results suggested a possibility of “seedling root selection” for forage crop breeding.

Phenotyping and Identification of Reduced Height (Rht) Alleles (Rht-B1b and Rht-D1b) in a Nepali Spring Wheat (Triticum aestivum L.) Diversity Panel to Enable Seedling Vigor Selection

Nepal is facing more intense early-season drought stress associated with climate change. The introgression of reduced height (Rht) alleles to enable stem dwarfism in bread wheat (Triticum aestivum L.) inadvertently reduced coleoptile length and growth plasticity in seedlings, making improved varieties less suitable for deep seeding; these alleles may have also reduced seedling root length. Therefore, with the long-term objective of breeding wheat for early-season drought stress, a Nepali spring wheat panel was evaluated to assess allelic variation at the most common dwarfing-associated loci (Rht-B1, Rht-D1) and their impact on coleoptile/seedling root traits, and to identify accessions with longer and/or more GA-responsive coleoptiles as parents for future breeding. Here, Kompetitive Allele Specific PCR (KASP) was used to genotype accessions. The panel was phenotyped using the cigar-roll method in the presence/absence of GA3. Plant height was measured under field conditions. The results showed that Nepali landraces had a significantly higher frequency of the non-dwarfing allele Rht-B1a. The dwarfing alleles Rht-B1b and Rht-D1b had negative effects on coleoptile length but positive effects on the length of the longest seedling root. However, 40 potential semi-dwarf accessions (possessing Rht-B1b and/or Rht-D1b alleles) with long and/or more plastic coleoptiles suited for deep sowing were identified. This included 12 accessions that exhibited significant changes in coleoptile length in response to GA3 treatment.

Genotype-Dependent Effect of Silencing of TaCKX1 and TaCKX2 on Phytohormone Crosstalk and Yield-Related Traits in Wheat

The influence of silenced TaCKX1 and TaCKX2 on coexpression of other TaCKX gene family members (GFMs), phytohormone regulation and yield-related traits was tested in awned-spike cultivar. We documented a strong feedback mechanism of regulation of TaCKX GFM expression in which silencing of TaCKX1 upregulated expression of TaCKX2 genes and vice versa. Additionally, downregulation of TaCKX2 highly upregulated the expression of TaCKX5 and TaNAC2-5A. In contrast, expression of these genes in silenced TaCKX1 was downregulated. Silenced TaCKX1 T2 lines with expression decreased by 47% had significantly higher thousand grain weight (TGW) and seedling root mass. Silenced TaCKX2 T2 lines with expression of TaCKX2.2.1 and TaCKX2.2.2 decreased by 33% and 30%, respectively, had significantly higher chlorophyll content in flag leaves. TaCKX GFM expression, phytohormone metabolism and phenotype were additionally modified by Agrobacterium-mediated transformation. Two novel phytohormones, phenylacetic acid (PAA) and topolins, lack of gibberellic acid (GA) and changed phytohormone contents in the 7 days after pollination (DAP) spikes of the awned-spike cultivar compared to a previously tested, awnless one, were detected. We documented that major mechanisms of coregulation of the expression of TaCKX GFMs were similar in different spring wheat cultivars, but, depending on content and composition of phytohormones, regulation of yield-related traits was variously impacted.

Allelopathic Impact of Cover Crop Species on Soybean and Goosegrass Seedling Germination and Early Growth

Cover crops can provide a variety of benefits to an agricultural system: weed suppression, soil quality improvement, and soil water infiltration. Although there is ample research documenting weed suppression from cover crops, the mechanics of the suppression are not implicitly understood. Along with the aforementioned positive attributes, negative allelopathic effects on row crops planted into cover crop systems have been documented. The objective of this study was to evaluate the allelopathic potential of certain cover crop species on soybean (Glycine max L.) and goosegrass (Eleusine indica L.) germination and early seedling growth under controlled environments in petri dish and pot experiments. Leachates from above-ground biomass of five cover crop species, wheat (Triticum aestivum L.), cereal rye (Secale cereale), hairy vetch (Vicia villosa), crimson clover (Trifolium incarnatum L.), and canola (Brassica napus L.), from two locations (East and Middle Tennessee) were extracted and applied at 0 (water) and 50 v/v. In experiment I, both soybean and goosegrass seeds were examined, and, in experiment II, only soybean seeds were examined under the application of cover crop leachates. Most cover crop leachates from both locations significantly reduced the soybean seedling root length (p < 0.01). Overall, the application of canola extract (East Tennessee) suppressed soybean seed germination the most (28%) compared to deionized water. For goosegrass, the wheat cover crop leachate significantly reduced seedling root length (p < 0.01). In experiment II, the soybean root nodulation was significantly increased with the wheat extract treatment compared to deionized water. While the results indicate that the location and environment may change cover crop species allelopathic potential, the wheat cover crop leachate had the most potent allelopathic impact on goosegrass germination and growth; however, had the lowest observed adverse effect on our tested row crop, soybean.

Effect of planting into a green winter cereal rye cover crop on growth and development, seedling disease and yield of corn

Terminating winter cereal rye (Secale cereale L.) cover crops (CCs) 10 or more days before planting corn is recommended to minimize seedling disease and potential yield loss. In Iowa, cold temperatures and frequent precipitation can prevent farmers from following that recommendation and sometimes forcing them to plant corn while the rye plants are still green, referred to as planting green (PG). A field trial was established to evaluate the effect of rye termination shortly before or after corn planting on growth, seedling root disease, and yield of corn. A rye CC was terminated 17 and 3 days before planting (DBP), and 6 and 12 days after planting (DAP) corn; corn planted following no rye was included as a control. Rye biomass, C:N ratio, and N accumulation increased when terminated 6 or 12 DAP corn compared with rye terminated 17 or 3 DBP corn. Corn seedlings were taller from the PG treatments. More radicle root rot was observed when rye was terminated 3 DBP, 6 DAP, and 12 DAP corn than for the 17 DBP treatment and the no-rye control. Generally, greater Pythium Clade B populations were detected on radicles and seminal roots of corn from the PG treatments. Corn populations, ears, or barren plants were not affected by the treatments. In both years, the no-rye control had the greatest corn yield and the 12 DAP treatment had the lowest yield. Our results suggest that PG increased corn seedling root disease and contributed to reduced corn yield.