Identification of DELLA Genes and Key Stage for GA Sensitivity in Bolting and Flowering of Flowering Chinese Cabbage

Flowering Chinese cabbage (Brassica campestris L. ssp. chinensis var. utilis Tsen et Lee) is an important and extensively cultivated vegetable in south China, and its stalk development is mainly regulated by gibberellin (GA). DELLA proteins negatively regulate GA signal transduction and may play an important role in determining bolting and flowering. Nevertheless, no systematic study of the DELLA gene family has been undertaken in flowering Chinese cabbage. In the present study, we found that the two-true-leaf spraying of gibberellin A3 (GA3) did not promote bolting but did promote flowering, whereas the three-true-leaf spraying of GA3 promoted both bolting and flowering. In addition, we identified five DELLA genes in flowering Chinese cabbage. All five proteins contained DELLA, VHYNP, VHIID, and SAW conserved domains. Protein-protein interaction results showed that in the presence of GA3, all five DELLA proteins interacted with BcGID1b (GA-INSENSITIVE DWARF 1b) but not with BcGID1a (GA-INSENSITIVE DWARF 1a) or BcGID1c (GA-INSENSITIVE DWARF 1c). Their expression analysis showed that the DELLA genes exhibited tissue-specific expression, and their reversible expression profiles responded to exogenous GA3 depending on the treatment stage. We also found that the DELLA genes showed distinct expression patterns in the two varieties of flowering Chinese cabbage. BcRGL1 may play a major role in the early bud differentiation process of different varieties, affecting bolting and flowering. Taken together, these results provide a theoretical basis for further dissecting the DELLA regulatory mechanism in the bolting and flowering of flowering Chinese cabbage.

Rice LEAFY COTYLEDONE1 regulates embryonic envelope development and chlorophyll biogenesis in embryo

The scutellum, coleoptile, coleorhiza, and epiblast (if it exists) consist of a complex embryonic envelope to protect the plumule and radicle inside a grass embryo. Controversies have been provoked for centuries regarding homologies of the grass embryonic structures. Here we found that the rice LEAFY COTYLEDONE1 (LEC1) gene, OsNF-YB7, is vital for embryo development. A leaf-like structure (LL) was developed from the scutellum of osnf-yb7 to replace the embryonic envelope that formed in wild-type. Additionally, osnf-yb7 developed chloroembryos due to overactivated chlorophyll biosynthesis. Thus, OsNF-YB7 likely plays a dual role in chlorophyll biogenesis in rice embryos: (1) OsNF-YB7 directly represses genes, such as rice GOLDED-LIKE1 (OsGLK1), involving chlorophyll biosynthesis; (2) OsNF-YB7 binds to OsGLK1 to repress the downstream genes of OsGLK1. Parallel phenotypes shown in osnf-yb7 and lec1 suggest functional conservation of the LEC1-type genes in plants. Both lec1 cotyledons and osnf-yb7 LL displayed true leaf characteristics. Our morphological and transcriptional evidence implied that LL replaces the embryonic envelope in osnf-yb7, raising the hypothesis that the grass embryonic envelope is an analog of Arabidopsis cotyledon. This study demonstrates that OsNF-YB7 acts as a negative regulator in chlorophyll biogenesis and is important for embryonic envelope formation.

Integration of early disease-resistance phenotyping, histological characterization, and transcriptome sequencing reveals insights into downy mildew resistance in impatiens

Downy mildew (DM), caused by obligate parasitic oomycetes, is a destructive disease for a wide range of crops worldwide. Recent outbreaks of impatiens downy mildew (IDM) in many countries have caused huge economic losses. A system to reveal plant–pathogen interactions in the early stage of infection and quickly assess resistance/susceptibility of plants to DM is desired. In this study, we established an early and rapid system to achieve these goals using impatiens as a model. Thirty-two cultivars of Impatiens walleriana and I. hawkeri were evaluated for their responses to IDM at cotyledon, first/second pair of true leaf, and mature plant stages. All I. walleriana cultivars were highly susceptible to IDM. While all I. hawkeri cultivars were resistant to IDM starting at the first true leaf stage, many (14/16) were susceptible to IDM at the cotyledon stage. Two cultivars showed resistance even at the cotyledon stage. Histological characterization showed that the resistance mechanism of the I. hawkeri cultivars resembles that in grapevine and type II resistance in sunflower. By integrating full-length transcriptome sequencing (Iso-Seq) and RNA-Seq, we constructed the first reference transcriptome for Impatiens comprised of 48,758 sequences with an N50 length of 2060 bp. Comparative transcriptome and qRT-PCR analyses revealed strong candidate genes for IDM resistance, including three resistance genes orthologous to the sunflower gene RGC203, a potential candidate associated with DM resistance. Our approach of integrating early disease-resistance phenotyping, histological characterization, and transcriptome analysis lay a solid foundation to improve DM resistance in impatiens and may provide a model for other crops.

Cerium Oxide Nanoparticles Improve Cotton Salt Tolerance by Enabling Better Ability to Maintain Cytosolic K+/Na+ Ratio

BackgroundSalinity is a worldwide factor limiting the agricultural production. Cotton is an important cash crop; however, its yield and product quality are negatively affected by salinity. Using nanomaterials such as cerium oxide nanoparticles (nanoceria) to improve plant tolerance to stresses, e.g. salinity, is an emerged approach in agricultural production. Nevertheless, to date, our knowledge about the role of nanoceria in cotton salt response and the behind mechanisms is still rare. ResultsWe found that PNC (poly acrylic acid coated nanoceria) helped to improve cotton plant tolerance to salinity, showing the better phenotypic performance, the higher chlorophyll content and biomass, and the better photosynthetic performance in PNC treated cotton plants than the control group. Under salinity stress, in consistent to the results of the enhanced antioxidant enzyme activities, PNC treated cotton plants showed significant lower MDA content and ROS level than the control group, both in the first and second true leaf. Further experiments showed that under salinity stress, PNC treated cotton plants had significant higher cytosolic K+ and lower cytosolic Na+ fluorescent intensity in both the first and second true leaf than the control group. This is further confirmed by the leaf ion content analysis, showed that PNC treated cotton plants maintained significant higher leaf K+ and lower leaf Na+ content, and thus the higher K+/Na+ ratio than the control plants under salinity. Whereas no significant increase of vacuolar Na+ intensity was observed in PNC treated plants than the control under salinity, suggesting that PNC enhanced leaf K+ retention and leaf Na+ exclusion, but not leaf vacuolar Na+ sequestration are the main mechanisms behind the PNC improved cotton salt tolerance. qPCR results showed that under salinity stress, the modulation of HKT1 but not SOS1 refers more to the PNC improved cotton leaf Na+ exclusion than the control. ConclusionsNanoceria enhanced leaf K+ retention and Na+ exclusion, but not vacuolar Na+ sequestration are the main mechanisms behind the nanoceria improved cotton salt tolerance. Our results add more knowledge for better understanding the complexity of plant-nanoceria interaction in terms of nano-enabled plant stress tolerance.

Response of Palmer amaranth (Amaranthus palmeri S. Watson) and sugarbeet to desmedipham and phenmedipham

A prepackaged mixture of desmedipham + phenmedipham was previously labeled for control of Amaranthus spp. in sugarbeet. Currently, there are no effective POST herbicide options to control glyphosate-resistant Palmer amaranth in sugarbeet. Sugarbeet growers are interested in using desmedipham + phenmedipham to control escaped Palmer amaranth. In 2019, a greenhouse experiment was initiated near Scottsbluff, NE, to determine the selectivity of desmedipham and phenmedipham between Palmer amaranth and sugarbeet. Three populations of Palmer amaranth and four sugarbeet hybrids were evaluated. Herbicide treatments consisted of desmedipham and phenmedipham applied singly or as mixtures at an equivalent rate. Herbicides were applied when Palmer amaranth and sugarbeet were at the cotyledon stage, or two true-leaf sugarbeet stage and when Palmer amaranth was 7 cm tall. The selectivity indices for desmedipham, phenmedipham, and desmedipham + phenmedipham were 1.61, 2.47, and 3.05, respectively, at the cotyledon stage. At the two true-leaf application stage, the highest rates of desmedipham and phenmedipham were associated with low mortality rates in sugarbeet, resulting in a failed response of death. The highest rates of desmedipham + phenmedipham caused a death response of sugarbeet; the selectivity index was 2.15. Desmedipham treatments resulted in lower LD50 estimates for Palmer amaranth compared to phenmedipham, indicating that desmedipham can provide greater levels of control for Palmer amaranth. However, desmedipham also caused greater injury in sugarbeet, producing lower LD50 estimates compared to phenmedipham. Desmedipham + phenmedipham provided 90% or greater control of cotyledon-size Palmer amaranth at a labeled rate but also caused high levels of sugarbeet injury. Neither desmedipham, phenmedipham, nor desmedipham + phenmedipham was able to control 7-cm tall Palmer amaranth at previously labeled rates. Results indicate that desmedipham + phenmedipham can only control Palmer amaranth if applied at the cotyledon stage and a high level of sugarbeet injury is acceptable.

Germination and Seed Vigour of Indigenous Bean (Phaseolus Vulgaris) Genotype in Nepal

Bean is an important vegetable crop of Nepal but farmers of Jumla district of Nepal are experiencing low productivity, probably due to poor germination. Keeping these points in view, a study was conducted to determine the germination and seed vigour of various indigenous beans genotype of Jumla district during February to March, 2018. The promising lines of Jumli beans namely KBL-3, KBL-2, PB0002, PB0001, KBL-1 and farm saved KBL-3 were used under study. The experiment was laid in completely randomized design (CRD) with four replications and six treatments namely T1 = KBL-3, T2 = KBL-2, T3 = PB0002, T4 = PB0001, T5 = KBL-1 and T6 = Farm-saved KBL-3. Significant differences were observed in germination percentage, speed of germination, seed vigourindex and true leaf emergence among different lines of Jumli beans .The highest germination percentage (96%), seed vigour index (1367) and speed of germination (1.763) was found in the variety of KBL-3 whereas the lowest germination percentage (69%), seed vigour index (947) and speed of germination (0.968) were found in the variety of KBL-1. Days to true leaf emergence was found shortest in the KBL-3 (23.50) and longest in the farm saved KBL-3 (30.25). KBL-3 pureline of Jumli bean was found to be highly responsive to seed germination and vigour characteristics. Thus, it would be better to suggest the indigenous bean growing farmers of Jumla district to cultivate KBL-3 for better germination and seed vigour. SAARC J. Agri., 18(2): 67-75 (2020)

Reassessing the estimation of leaf area in oil palm (Elaeis guineensis Jacq.) by linear regression equation

The area of individual leaves in oil palm has been conventionally estimated from a regression equation that is based on the size and number of leaflets. The aim of the present study is to verify the accuracy of this equation, which became standard in oil palm research. Therefore, true leaf area, measured with a video camera, was estimated from the product of number of leaflets per leaf (n) with mean length (l) times mid-width (w) of six of the longest leaflets (nlw). The database was assembled, annually for the first 4 years after planting, from 2961 leaves of dura × pisifera testcrosses descending from six distinct pisifera origins. The regression coefficients of the regression lines of nlw plotted against true area did not show a trend with age of the palms or a difference among pisifera origins. The common regression equation fitted through all data of this study accurately estimated true leaf area of the testcrosses and also the areas of 2- to 3.5-year-old dura palms of three distinct origins as well as 18-year-old tenera palms. These outcomes are at odds with the conventional regression equation that overestimates the true leaf areas by about 24%. A more recently-developed variant underestimates true area of the young tenera and dura palms by 28%, while overestimating true area of old tenera palms by 19%. Possible causes for these deviations from true area are discussed. The paper argues that parameters depending on leaf area of previous physiological studies need to be reassessed.

Plastic response to early shade avoidance cues has season-long effect on Beta vulgaris growth and development

Early emerging weeds are known to negatively affect crop growth but the mechanisms by which weeds reduce crop yield are not fully understood. In a 4-yr study, we evaluated the duration of weed-reflected light on sugar beet (Beta vulgaris L.) growth and development. The study included an early-season weed removal series and a late-season weed addition series of treatments arranged in a randomized complete block, and the study design ensured minimal direct resource competition. If weeds were present from emergence until the two true-leaf sugar beet stage, sugar beet leaf area was reduced 22%, leaf biomass reduced 25%, and root biomass reduced 32% compared to sugar beet grown season-long without surrounding weeds. Leaf area, leaf biomass, and root biomass were similar whether weeds were removed at the two true-leaf stage (approximately 330 GDD after planting) or allowed to remain until sugar beet harvest (approximately 1240 GDD after planting). Adding weeds at the two true-leaf stage and leaving them until harvest (~1240 GDD) reduced sugar beet leaf and root biomass by 18 and 23%, respectively. It appears sugar beet responded to weed presence by adjusting carbon allocation and leaf orientation to optimize light interception.

Microgreens: A New Specialty Crop

Microgreens are young, tender greens that are used to enhance the color, texture, or flavor of salads, or to garnish a wide variety of main dishes. Harvested at the first true leaf stage and sold with the stem, cotyledons (seed leaves), and first true leaves attached, they are among a variety of novel salad greens available on the market that are typically distinguished categorically by their size and age. Sprouts, microgreens, and baby greens are simply those greens harvested and consumed in an immature state. This article offers production advice for greenhouse microgreen production.https://edis.ifas.ufl.edu/hs1164 This is a minor revision of Treadwell, Danielle, Robert Hochmuth, Linda Landrum, and Wanda Laughlin. 2010. “Microgreens: A New Specialty Crop”. EDIS 2010 (3). https://journals.flvc.org/edis/article/view/118552.