Flag Leaf Sheath Research Articles

Phenotypic characterization of two-row barley (Hordeum vulgare L. ssp. vulgare) germplasm conserved in Osman Tosun Genebank of Türkiye by multivariate analysis model

AbstractBarley is a crucial cereal crop with a diverse genetic heritage that includes landraces-traditionally cultivated variants that have adapted to varying agro-climatic conditions over centuries. Preserving barley landraces in genebanks is of utmost importance for safeguarding genetic diversity and aiding future breeding endeavors.This study aims an agro-morphological characterization of a selected collection of two row barley landraces conserved in the Osman Tosun Genebank. A total of 262 barley accessions were assessed in controlled field conditions to analyze various agro-morphological traits. The study unveiled notable disparities in the morphological traits of the genotypes, specifically in flag leaf anthocyanin, flag leaf sheath wax, spike shape, spike density, lemma color, grain color, lodging tendency, days to 50% flowering, plant height, spike length, spikelet quantity, and thousand grain weight, among other critical agronomical characteristics. To scrutinize the morphological disparities, the research utilized principal component analysis and ascertained that nearly 77.22% of the overall variance was accounted for by the first two principal components. The first four principal components accounted for 90.96% of the total variation, thus indicating significant genetic diversity among genotypes. The results of the cluster analysis revealed the presence of diverse genetic resources within the collection, with distinct groups of genotypes exhibiting similar traits being identified. The results of the agro-morphological characterization are a valuable resource for researchers and breeders, aiding them in making informed decisions regarding the management and application of barley landraces in breeding programs.

Expression profiling of yield related genes in rice cultivars under terminal drought stress.

Rice crop may experience a significant reduction in yield-up to 50%-due to two occurrences during drought stress: unsuccessful peduncle elongation in panicle exertion and ineffective grain filling. The comprehension of mechanisms that promote drought tolerance during these growth phases is crucial for the production of rice that can withstand drought conditions, thus averting a decrease in crop yield. The expression of two xyloglucan endo transhydrolase/glucosylase genes (OsXTH 5 and 19) in peduncle tissue and a sucrose transporter gene (OsSUT1) in flag leaf sheath were assessed. An experiment was carried out in a factorial arrangement based on completely randomized design in which, factor A was two rice cultivars (Vandana as tolerant and Tarom mahalli as local susceptible to drought) and factor B was five drought stress treatments (full irrigation, drought stress duration in 72 and 96h, re-watering after 120 and 192h). Results showed that expression of OsXTH19 and OsXTH5 genes were upregulated in both Vandana and Tarom mahalli cultivars due to stress treatments. OsXTH19 expression was found to decrease while OsXTH5 expression increased during re-watering treatments. It is likely that the persistence of peduncle growth in the drought-tolerant Vandana cultivar can be attributed to the presence of OsXTH19 under drought conditions and OsXTH5 after re-watering. The expression of OsSUT1 in flag leaf sheath of Vandana in re-watering treatments was reached 8-60-fold re-watering. Peduncle elongation was attributed to two XTH genes under drought stress condition. Panicle exertion may be promoted by sustaining peduncle growth despite drought stress. Consequently, this may led to reduce in non fertile florets and decrease in grain yield by 50%. As grain filling depend to expression of OsSUT1 in flag leaf sheath under drought stress, to improve rice cultivars under aerobic production system and drought stress, it is advised to apply these findings in rice breeding programs.

Night warming from tillering to jointing increases post-anthesis flag leaf photosynthetic capacity and wheat yield

Global warming is asymmetric, with the increase in temperature at night being greater than that during the day. The objectives of this study were to assess the effects of night warming during different growth stages on the wheat grain yield, dry matter accumulation and distribution, photosynthetic characteristics, and enzymes related to sucrose metabolism. For that, field experiments with passive night warming were conducted using local spring type cultivars ‘Yangmai 18′ and ‘Sumai 188′ and semi-winter type cultivars ‘Yannong 19′ and ‘Annong 0711′ in two growing seasons in the Yangtze River Basin of China (average night time temperature increases of 1.45 °C and 1.56 °C for 2019–2020 and 2020–2021, respectively). The cultivars were exposed to night warming between four different growth stages (tillering to jointing [NWT-J], jointing to booting [NWJ-B], and booting to anthesis [NWB-A]) after 50% of plants had attained the treatment-start stage (tillering: Zadoks growth stage 21, main shoot and one tiller; jointing: Zadoks growth stage 31, the 1st node was detectable; booting: Zadoks growth stage 41, flag leaf sheath extension stage; anthesis: Zadoks growth stage 60, the beginning of pollination). Plants grown under ambient conditions were considered as the control (NN). Treatment NWT-J increased dry matter accumulation in flag leaves and spikes at anthesis and maturity, ultimately benefiting the yield, and the increase was higher in the semi-winter type cultivars. NWT-J increased not only the chlorophyll content, photosynthetic traits (net photosynthetic rate, stomatal conductance, and transpiration rate), and the activities of the maximum efficiency of PSII photochemistry under dark-adapted wheat flag leaves at the grain-filling stage (14 days after anthesis) but also the activities of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), fructose-1,6-bisphosphatase (FBPase), and glycolate oxidase (GOX), and thus improved the photosynthetic capacity of wheat flag leaves and facilitating photosynthate accumulation. NWT-J also increased sucrose-phosphate synthase activity in flag leaves at the grain-filling stage, which could improve sucrose content. Collectively, early vegetative night warming (warming during tillering-jointing) improved the photosynthetic capacity of the flag leaves during the grain-filling stage and promoted the post-anthesis accumulation of dry matter and the transfer of dry matter to the grains, which ultimately benefited the yield.

Base Editing of EUI1 Improves the Elongation of the Uppermost Internode in Two-Line Male Sterile Rice Lines

The use of male sterile lines (MSLs) of rice is essential for heterosis utilization. However, MSLs have a common defect in the elongation of the uppermost internode, eventually leading to incomplete panicle exsertion, blocking pollination, and reducing the hybrid rice seed yield. Previously, the elongated uppermost internode 1 (EUI1) was identified as an active gibberellin-deactivating enzyme that plays a key role in panicle exsertion from the flag leaf sheath in rice (Oryza sativa L.). We used an adenine base editor to edit EUI1 and obtained two types of homozygous transgenic plants (eui1-1 and eui1-2). The transcription and translation levels of EUI1 in the two mutants were significantly lower than in the wild type, as was the oxidation activity of EUI1 to active gibberellins (GAs), which also decreased. The contents of the plant hormones GA1, GA3, and GA4 in eui1-1 (1.64, 1.55, and 0.92 ng/g) and eui1-2 (0.85, 0.64, and 0.65 ng/g) panicles were significantly higher than the wild type (0.70, 0.57, and 0.42 ng/g). The uppermost internode lengths of the mutant were 26.5 and 23.6 cm, which were significantly longer than that of the wild type (18.0 cm), and the cell lengths of the mutant were 161.10 and 157.19 μm, which were longer than that of the wild type (89.28 μm). Our results indicate that the adenine base editing system could increase the content of endogenous bioactive GAs in young panicles by fine-tuning EUI1 activity, reduce the defect of panicle enclosure in MSLs and increase the yield of hybrid rice seed production.

Response of alley-cropped pearl millet (Pennisetum glaucum) to nitrogen and zinc schedules under semi-arid regions

Realizing the importance of tree-based cropping system and scheduling of nitrogen (N) and zinc (Zn) in the semi-arid region, an on-field trial was conducted with pearl millet [Pennisetum glaucum (L.) R. Br.] during the rainy season of 2017 at RGS Campus of Banaras Hindu University, Mirzapur, Uttar Pradesh. The trial was laid out in factorial randomized block design with 4 N and 4 Zn treatment applications in different schedules. The results revealed that, N scheduled at ¼ [basal] + ½ (3rd visible leaf (VL) + ¼ panicle extended in flag-leaf sheath (PEFLS) produced the most synergetic effect on growth and yield of pearl millet. The grain yield increased up to 65% compared to no N application. Conversely, Zn schedules did not significantly influence the growth parameters (except dry-matter), while Zn application at 2.5 kg/ha (basal) + 0.25% panicle initiation (PI) + 0.25% PEFLS recorded about 37% more grain yield, than no Zn application. Additionally, the maximum biological and straw yields recorded with 2.5 kg/ha (basal) + 0.25% panicle emergence (PE) + 0.25% milk stage (MS) Zn application compared to the other treatments. Moreover, N and Zn interacted significantly to produce synergetic effect on the dry-matter, test weight, grain, straw, and biological yields. The maximum grain yield was observed with conjunctive application of N at ¼ [basal] + ½ [3rd VL] + ¼ [PEFLS] and Zn at 2.5 kg/ha [basal] + 0.25% [PI] + 0.25% [PEFLS], whereas the maximum biological and straw yields were recorded with application of the N at ¼ [basal] + ½ [3rd VL] + ¼ [PEFLS] and Zn at 2.5 kg/ha [basal] + 0.25% [PE] + 0.25% [MS].

Heavy metal distribution in wheat plant components following foliar Cd application

Atmospheric deposition of Cd, from anthropogenic activities, can be directly deposited onto and absorbed into wheat plants, yet, how foliar absorbed Cd is translocated in wheat plants is not well understood. A pot experiment investigated foliar Cd application on the accumulation and distribution of heavy metals in various wheat parts. Wheat was grown in a Cd/heavy metal contaminated soil, and from grain heading to the filling stage, 0, 10, 20, 30 and 40 mg kg−1 Cd solution was sprayed repeatedly on leaves (grain heads were covered). Foliar Cd application had no effect on grain yield and Cd concentration (3.01–3.51 mg kg−1 for all treatments), while increased flag leaf blade and sheath Cd concentrations by 1.06–2.77 and 0.00–0.66 times, respectively. Cadmium concentration in the center of the peduncle, from the 40 mg kg−1 Cd solution treatment, was 1.41 times that of the control (10.3 vs 7.30 mg kg−1). Foliar Cd application also increased Cd accumulation (concentration × mass) of the flag leaf blade and sheath. Rachis and grain Pb concentrations were reduced, while stem Pb concentration was increased by Cd application. Cadmium application negatively affected whole plant Ni accumulation and concentration of certain wheat parts; Ni absorption inhibition may have occurred in roots via the downward transport of Cd. Overall results implied that the predominant portion of foliar applied Cd was retained in leaves, while lesser portions migrated to peduncle or root and affected the absorption/distribution of other metals in wheat plants. These results are important for further discerning the mechanism of wheat grain Cd accumulation, especially when grain is raised in areas where atmospheric deposition of Cd (e.g., near smelting facilities) is an issue from an environmental and human health perspective.

First report of Burkholderia gladioli causing bacterial panicle blight of rice in Malaysia.

Rice (Oryza sativa) is a staple food for most of the world's populations, particularly in Asia (Gumma et al. 2011). The rice sector provides Malaysians with a food supply, food sufficiency, and income for growers (Man et al. 2009). From January to February 2022, panicle samples showing symptoms of bacterial panicle blight (BPB) disease, including reddish-brown, linear lesions with indistinct margins on flag-leaf sheaths and blighted, upright, grayish straw-colored florets with sterile and aborted grains on panicles were collected in granary areas in Sekinchan, Selangor, Malaysia with 90% disease incidence in fields. Surface-sterilization of infected leaf tissue was performed using 75% ethanol and 1% sodium hypochlorite, followed by rinsing three times in sterilized water. Leaf tissue was macerated in sterilized water and aliquots were spread on King's B agar medium, then cultured for 24 h to 48 h at 35 °C. All isolated bacteria were Gram-negative rods, positive for catalase and gelatinase but negative for indole, oxidase and hydrogen sulfide (H2S), and utilized sucrose, inositol, mannitol, glucose, and citrate. Colonies were circular and smooth-margined, producing a diffusible yellowish-green pigment on King's B agar medium, which are characteristics of Burkholderia species (Keith et al. 2005). Five representative isolates (UPMBG7, UPMBG8, UPMBG9, UPMBG15, UPMBG17) were selected for molecular and pathogenicity tests. PCR using specific primers targeting the gyrB gene for molecular characterization was performed, and the ∼470 bp amplicons were sequenced (Maeda et al. 2006) and deposited in GenBank (OM824438 to OM824442). A BLASTn analysis revealed that the five isolates were 99% identical to the B. gladioli reference strains MAFF 302533, GRBB15041, and LMG19584 in GenBank (AB190628, KX638432, and AB220898). A phylogenetic tree using Maximum-likelihood analysis of the gyrB gene sequences showed that the five isolates were 99% identical to B. gladioli reference strains (AB190628, KX638432, and AB220898). To verify the identification of these isolates, the 16S rDNA gene was amplified using 16SF/16SR primers (Ramachandran et al. 2021), producing ~1,400 bp amplicons. The resulting sequences of the five isolates (OM869953 to OM869957) were 98% identical to the reference strains of B. gladioli (NR113629 and NR117553). To confirm pathogenicity, 10 ml suspensions of the five isolates at of 108 CFU/ml were inoculated into the panicles and crowns of 75-day-old rice seedlings of local rice varieties MR269 and MR219 grown in a glasshouse with temperatures ranging from 37 °C to 41 °C (Nandakumar et al. 2009). Control rice seedlings were inoculated with sterilized water. All isolates produced BPB disease symptoms like those originally found in the rice fields at four weeks after inoculation. Control seedlings remained asymptomatic. To fulfill Koch's postulates, the bacteria were reisolated from symptomatic panicles and were confirmed as B. gladioli by sequence analysis of the gyrB and 16S rDNA genes. To our knowledge, this is the first report of B. gladioli causing BPB disease of rice in Malaysia. Since BPB disease causes a significant threat to the rice industry, it is crucial to investigate the diversity of this destructive pathogen for effective disease management strategies in Malaysia.

First Report of Fusarium Sheath Rot of Rice Caused by Fusarium incarnatum-equiseti Species Complex in the United States.

Fungal diseases, including sheath rot (Sarocladium oryzae), cause significant losses of yield and milling quality of rice (Oryza sativa). In August 2021, symptoms like sheath rot were observed on 20% of rice plants (cv. Presidio) in 1-hectare field in Eagle Lake, Texas. Initial lesions occurred on the upper flag leaf sheaths and were oblong or irregular oval, with gray to light brown centers, and a dark reddish-brown diffuse margin. Lesions enlarged, coalesced, and covered a large area of the sheath. Infection led to panicle rot with kernels turning dark brown. Unlike sheath rot, sheath infection also led to inside culm infection with irregular dark brown lesions. Infected tissue pieces were sterilized with 1% NaOCl for 2 min, followed by 75% ethanol for 30 s, washed in sterile H2O three times, air dried and incubated on PDA at 27℃. Fungal isolates were obtained from 15 diseased plant samples and their singled-spored fungal colonies were whitish, loosely floccose and produced light yellow pigmentation. On carnation leaf agar, macroconidia were slightly curved and tapered at the ends, with 3 to 5 septa, and measured 17.5 to 34.3 × 3.1 to 5.0 µm. Microconidia were ovoid, usually with 0 to 1 septum and were 4.0 to 15.5 × 2.5 to 4.5 µm. Spherical shaped chlamydospores were produced in chain. These morphological characteristics were consistent to those described for Fusarium incarnatum-equiseti species complex (O'Donnell et al. 2009), including F. incarnatum (Wang et al. 2021) and F. equiseti (Avila et al. 2019). For molecular identification, DNA of a representative isolate was extracted and ITS, LSU, and EF1 of the fungus were amplified using the primers of ITS1/ITS4 (Wang et al. 2014), D1/D2 domain region of LSU (Fell et al. 2000), and EF1 (Wang et al. 2014), respectively, and sequenced. The ITS sequence (OL344049) was 99.61% identical to F. incarnatum-equiseti species complex (FD_01692) in Fusarium-ID database and 99.61% identical to F. equiseti (LC514690, KY523100, MW016539) and F. incarnatum (MH979697) in NCBI database. The LSU sequence (OK559512) was 98.77% similar to F. equiseti (MN877913, MN368509) and F. incarnatum (MH877332, MH877326); the EF1 sequence (OK570044) was 99.27% similar to F. equiseti (MK278902) in NCBI database. A phylogenetic analysis based on the concatenated nucleotide sequences grouped this isolate in the F. incarnatum-equiseti species complex clade at 100% bootstrap support. To evaluate pathogenicity, a conidial suspension of 1 x 106 conidia/ml or sterilized water (the controls) was injected into the sheaths and young panicles of three rice plants (cv. Presidio) at boot. Treated plants were maintained in a greenhouse at 25 to 30℃. After 3 weeks, typical symptoms, like those observed in the field, developed on the inoculated plants but not on the controls. The same fungus was consistently re-isolated from the diseased plants. To our knowledge, this is the first report of Fusarium sheath rot caused by F. incarnatum-equiseti species complex in rice in the U. S. F. incarnatum-equiseti species complex has been reported to be associated with panicle infection in wild rice (O. latifolia) in Brazil (Tralamazza et al. 2021). F. incarnatum has also been reported to cause panicle rot in China (Wang et al. 2021). F. proliferatum has been reported to cause Fusarium sheath rot in India (Prabhukarthikeyan et al. 2021) and the U. S. (Cartwright et al. 1995). This research demonstrates the potential of different pathogens being involved in causing sheath rot of rice.

Genetic Diversity Assessment of Iranian Kentucky Bluegrass Accessions: II. Nuclear DNA Content and Its Association with Morphological and Geographical Features.

Poa pratensis L. is a perennial turfgrass with high regeneration and fertility, resistance to cold and drought, and quick colonization. By facultative apomixis, this plant can create a wide range of ploidy levels (2n = 22 to 2n = 154), resulting in a wide range of chromosomal numbers and sexual and apomictic reproductive diversity. The plant materials included fifty accessions from Iran's Center, South, North, North-East, North-West, and West ecoregions. UPOV standards were used to measure the qualities that were researched. The squash technique of chromosome counting revealed that Iranian Kentucky bluegrass accessions had chromosomal counts ranging from 24 to 87. The relative sizes of the 2C genomes were measured using laser flow cytometry. The range of DNA content was fairly wide, ranging from 4.92 to 11.52pg. DNA content has a strong positive correlation with elevation, a moderately positive correlation with flag leaf length and leaf sheath width, and a negative correlation with inflorescence anthocyanin color and leaf anthocyanin color. The genotypes and ecological zones of this plant in Iran were distinguished based on morphological diversity and DNA content. The results from this study could be useful in identifying and studying wild Kentucky bluegrass genotypes. It aids in predicting the location of rare genotypes used as breeding materials. It can also increase the plant's variability for future generations by introducing new ecotypes, with particular genomicand morphological traits, to previously cultivated populations. We expect that the findings of this study will aid in understanding the evolution of this plant in the context of Iran's climatic variety.

Source-Sink Dynamics in Field-Grown Durum Wheat Under Contrasting Nitrogen Supplies: Key Role of Non-Foliar Organs During Grain Filling.

The integration of high-throughput phenotyping and metabolic approaches is a suitable strategy to study the genotype-by-environment interaction and identify novel traits for crop improvement from canopy to an organ level. Our aims were to study the phenotypic and metabolic traits that are related to grain yield and quality at canopy and organ levels, with a special focus on source-sink coordination under contrasting N supplies. Four modern durum wheat varieties with contrasting grain yield were grown in field conditions under two N fertilization levels in north-eastern Spain. We evaluated canopy vegetation indices taken throughout the growing season, physiological and metabolic traits in different photosynthetic organs (flag leaf blade, sheath, peduncle, awn, glume, and lemma) at anthesis and mid-grain filling stages, and agronomic and grain quality traits at harvest. Low N supply triggered an imbalance of C and N coordination at the whole plant level, leading to a reduction of grain yield and nutrient composition. The activities of key enzymes in C and N metabolism as well as the levels of photoassimilates showed that each organ plays an important role during grain filling, some with a higher photosynthetic capacity, others for nutrient storage for later stages of grain filling, or N assimilation and recycling. Interestingly, the enzyme activities and sucrose content of the ear organs were positively associated with grain yield and quality, suggesting, together with the regression models using isotope signatures, the potential contribution of these organs during grain filling. This study highlights the use of holistic approaches to the identification of novel targets to improve grain yield and quality in C3 cereals and the key role of non-foliar organs at late-growth stages.

Improving Grain Yield via Promotion of Kernel Weight in High Yielding Winter Wheat Genotypes.

Simple SummaryImproving plant net photosynthetic rates and accelerating water-soluble carbohydrate accumulation play an important role in increasing the carbon sources for wheat kernel growth and yield. The objective of this study was to quantify the relative yield contribution by analyzing the photosynthesis rate of flag leaf, water-soluble carbohydrate content of flag leaf, flag leaf sheath and stem, and other agronomic and physiological traits in 15 wheat cultivars released in Shandong Province, China between 1969 and 2006. Our results suggest that increase of flag leaf photosynthesis and WSC had a positive effect of 0.593 on the TKW, and thus benefit for developing high yielding wheat cultivars.Improving plant net photosynthetic rates and accelerating water-soluble carbohydrate accumulation play an important role in increasing the carbon sources for yield formation of wheat (Triticum aestivum L.). Understanding and quantify the contribution of these traits to grain yield can provide a pathway towards increasing the yield potential of wheat. The objective of this study was to identify kernel weight gap for improving grain yield in 15 winter wheat genotypes grown in Shandong Province, China. A cluster analysis was conducted to classify the 15 wheat genotypes into high yielding (HY) and low yielding (LY) groups based on their performance in grain yield, harvest index, photosynthetic rate, kernels per square meter, and spikes per square meter from two years of field testing. While the grain yield was significantly higher in the HY group, its thousand kernel weight (TKW) was 8.8% lower than that of the LY group (p < 0.05). A structural equation model revealed that 83% of the total variation in grain yield for the HY group could be mainly explained by TKW, the flag leaf photosynthesis rate at the grain filling stage (Pn75), and flag leaf water-soluble carbohydrate content (WSC) at grain filling stage. Their effect values on yield were 0.579, 0.759, and 0.444, respectively. Our results suggest that increase of flag leaf photosynthesis and WSC could improve the TKW, and thus benefit for developing high yielding wheat cultivars.

A Sheathed Spike Gene, TaWUS-like Inhibits Stem Elongation in Common Wheat by Regulating Hormone Levels.

The elongation and development of wheat (Triticum aestivum L.) stem play an important role in plant architecture. The shortened stem would result in a sheathed spike and a low yield in crops. Unraveling the molecular mechanisms underlying a sheathed spike would be beneficial for plant architecture and yield improvement. We identified a novel gene, TaWUS-like (WUSCHEL-related homeobox-like), which regulated sheathed spike and plant architecture in wheat. The plant height of overexpression transgenic lines was significantly decreased and the spike was not completely elongated and enclosed in flag leaf sheaths. Moreover, the increase in tiller angle resulted in loose plant architecture and lower yield. The statistical and cytological analysis demonstrated that the length of the uppermost and secondary internode was significantly shortened, especially the uppermost internode which was only half the length of the wild-type. The size of parenchyma cells was obviously reduced and cell length on the longitudinal section was elongated insufficiently compared with wild-type. The analysis of hormone content showed that there was a lack of gibberellin A 3 (GA3) in internodes but a higher brassinosteroid (BR) content. TaWUS-like may inhibit the synthesis of GA3 and/or BR, thus affecting the function of signal transduction of these hormones, which further caused stem shortening and plant dwarfing in wheat.

Infection and colonization of triticale by Puccinia graminis f. sp. tritici

Histological investigations elucidate infection structure development and the subsequent colonization process of rust pathogens in their cereal hosts. No comprehensive information exists for the infection process of the wheat stem rust fungus, Puccinia graminis f. sp. tritici (Pgt), on triticale, an amphiploid species carrying both the wheat and rye genomes. The adult plant stem rust response of the triticale cultivars ‘Kiewiet’, ‘Coorong’ and ‘Satu’ and the bread wheat control, Line 37–07, was determined under controlled conditions using Pgt pathotypes UVPgt56, UVPgt60 and UVPgt62. Flag leaf sheaths were sampled 24 and 48 h post-inoculation (hpi) for scanning electron microscopy (SEM), 120 hpi for fluorescence microscopy, and 16 days post-inoculation for a fungal biomass assay. Although slight differences were observed between the epidermal morphology of triticale and wheat stem sheaths, SEM results indicated that this did not influence early infection by Pgt. Fluorescence microscopy revealed that colony size was affected by both host genotype and pathotype. Colony size strongly corresponded with fungal biomass accumulation, except in ‘Kiewiet’, where fungal growth was not restricted to the same degree as in other incompatible interactions. This study shows that methods commonly used for studying histopathology of Pgt in wheat are equally applicable to triticale.

Metabolomic and Transcriptomic Changes Induced by Potassium Deficiency During Sarocladium oryzae Infection Reveal Insights into Rice Sheath Rot Disease Resistance

Rice sheath rot disease caused by Sarocladium oryzae (S. oryzae) infection is an emerging disease, and infection can cause yield losses of 20–85%. Adequate potassium (K) application is a feasible strategy for rice tolerance to S. oryzae infection. However, little is known about the metabolic mechanisms regulated by K that allow rice to cope better with S. oryzae infection. The present study performed a comparative metabolome and transcriptome analysis of rice with different K nutrition statuses before and upon S. oryzae infection. Sarocladium oryzae infection triggered a hydrogen peroxide (H2O2) burst, and K starvation aggravated the accumulation of H2O2 in the flag leaf sheath (FLS), which resulted in lipid peroxidation. Likewise, K deficiency altered the lipid homeostasis of the host plants by hyperaccumulation of 1-alkyl-2-acylglycerophosphoethanolamine. K starvation decreased the content of glycoglycerolipids including monogalactosyldiacyglycerol and digalactosyldoacylglycerol during S. oryzae infection, which destroyed the stability of bilayer membranes. In contrast, sufficient K supply increased antioxidant-related transcript expression (for example, the genes related to glutathione-S-transferase biosynthesis were upregulated), which activated the antioxidant systems. Additionally, upon S. oryzae infection, K starvation amplified the negative impacts of S. oryzae infection on flag leaf photosynthetic potential. These results provide new insight into the role of K in alleviating S. oryzae infection. Adequate K supply decreased the negative impacts of sheath rot disease on rice growth by alleviating lipid peroxidation and maintaining lipid homeostasis.

Genome‐wide investigation and transcriptional profiling of the oxidosqualene cyclase (OSC) genes in wheat (Triticum aestivum)

AbstractTriterpene scaffolds are cyclized by differential functional genes of the oxidosqualene cyclase (OSC) gene family, which are widely present in plant species. Thirty‐nine OSCs were identified from the hexaploid bread wheat (Triticum aestivum L.) genome. The gene structure organization and the distribution of conserved motifs of OSCs gene family revealed that the TaOSC proteins are highly conserved. By phylogenetic analysis, all OSC proteins from wheat and other cereal crops were clustered into 11 subfamilies (I–XI). Based on the publicly available transcriptional profiling, the tissue‐specific expression patterns of TaOSC during several developmental stages revealed diverged expression patterns, indicating that the TaOSC family has undergone subfunctionalization. Furthermore, homeolog expression bias was commonly detected in the TaOSC subfamilies, such as the expression of Ta5A004900 and Ta5D011800 in the subfamily II were specifically expressed in the leaf sheath and flag leaf sheath. In addition, two genes were strongly induced by Pst, indicating that the two homolog genes are involved in the resistance to powdery mildew. Molecular evolution analysis indicated that the TaOSC family genes were undergone purifying selection. So, the powdery mildew response may be very conservative and important biological function of the Ta5A004900 and Ta5D011800 in wheat. In conclusion, these results can be used to explore the diversity of triterpenes and clarify the mechanism of triterpene cyclization, and also provide useful information for future studies on the function of the TaOSC gene family in bread wheat and other important crops.

Applying potassium fertilizer improves sheath rot disease tolerance and decreases grain yield loss in rice (Oryza sativa L.)

Sheath rot disease (ShR) is a new threat in rice production, causing yield losses of 10–85%. Potassium (K) plays an important role in improving rice tolerance to disease and ensuring yield stability. Two-year field studies with four K application rates were conducted to investigate the impacts of K application on ShR disease incidence and yield loss caused by ShR. The results showed that K application significantly decreased the ShR disease incidence by 20.0–72.1% and 37.8–89.9% in the 2017 and 2018 rice growing seasons, respectively. Similarly, K application profoundly alleviated the severity of ShR. Therefore, the total yield loss rate (TYLR) considerably decreased with increasing K application rates. Compared with the zero-K application, K application decreased the TYLR by averages of 59.3% and 74.4% in 2017 and 2018, respectively. The filled-grain rate decrease contributed the most to the TYLR in ShR disease. In addition, K starvation increased the C/N ratio of the flag leaf sheath (FLS), which was negatively correlated with the ShR disease index (DI). In contrast, soluble sugar (SS) accumulation in the FLS was positively correlated with the DI. K application significantly increased the apparent transferred mass of non-structural carbohydrates (NSCs) from stems to grains (ATMNSC). Moreover, the stem ATMNSC of diseased plants contributed more to the final grain yield than did that of healthy plants. During ShR disease, K application significantly alleviated the decrease in the filled-grain rate and harvest index by enhancing the stem ATMNSC, according to an exponential equation relationship between the stem ATMNSC and the filled-grain rate of diseased rice. Maintaining the stem K concentration in the range of 1.53–1.74% at the heading stage could increase the stem ATMNSC to mitigate the TYLR. These results emphasize the importance of K in rice to improve the potential for alleviating ShR disease.

Assessment of Genetic Diversity for Some Egyptian Wheat Varieties based on Morphological Characters and SSR Markers

The genetic diversity estimates can be useful in important genotypes selection for plant breeders. Eight durum and three bread wheat cultivars were used to study and compare morphological traits with molecular study using SSR technique based genetic diversity estimates. Significant and highly significant differences among wheat genotypes were observed for all traits except flag leaf attitude and outer glume pubescence. Highly significant differences were obtained between durum and bread wheat genotypes for most studied traits. Moderate to low broad-sense heritability estimates were obtained for morphological studied traits. Positive and high significant correlation was found for ear density with foliage color (r= 0.51), waxiness of flag leaf sheath (r= 0.57), waxiness of peduncle (r= 0.60) and peduncle length (r= 0.53), whereas a negative correlation was found between ear density and plant height (r= -0.52, P

Poa (Poaceae) of Colombia: A Taxonomic Revision

The grass genus Poa L. is widespread throughout temperate areas of the Andes, being a common constituent in the highly diverse but threatened high-elevation páramo grasslands of northwest South America. Knowledge of Poa from these páramo areas is very limited, however, with no comprehensive taxonomic treatments available for Colombia, which contains the largest area of páramo in the Neotropics and its surrounding countries. We present a taxonomic revision of Poa for Colombia accepting 15 species, including two recent combinations of Poa previously circumscribed in Aphanelytrum (Hack.) Hack. We describe a new species, P. colombiana Soreng &amp; Sylvester, and a new variety, P. subspicata (J. Presl) Kunth var. glabrata Soreng &amp; Sylvester, for Colombia and Ecuador. Poa colombiana is similar to P. aequatoriensis Hack. but differs in having lemmas pubescent on the keel and marginal veins, lemma apices weakly acute, flag leaf sheath margins fused 20%–38% their length, and anthers generally larger, &gt; 1.2 mm long. Poa subspicata var. glabrata differs from P. subspicata s. str. in having glabrous lemmas. We provide two new records for Colombia of P. huancavelicae Tovar, and P. mucuchachensis Luces. Two species, P. orthophylla Pilg. and P. reclinata (Swallen) Soreng &amp; P. M. Peterson, are considered endemic to Colombia. Poa soderstromii Negritto &amp; Anton is placed as a subspecies of P. orthophylla, and P. leioclada Hack. is synonymized under P. mulalensis Kunth. The names P. annua L. var. exilis Tomm. ex Freyn, P. humilis Ehrh. ex Hoffm., P. infirma Kunth, P. leioclada, P. orthophylla, P. pauciflora Roem. &amp; Schult., P. pratensis L. subsp. irrigata (Lindm.) H. Lindb., P. puberula Steud., P. pubiflora Benth., P. subcaerulea Sm., P. subspicata, and P. trachyphylla Pilg. are lectotypified, P. mulalensis is neotypified, and P. trachyphylla is epitypified. Four species are exotic and introduced from Europe: P. annua, P. infirma, P. pratensis, and P. trivialis L. We provide a key, descriptions, illustrations, distribution and habitat information, vouchers, and notes for each species.

Study of correlation and path analysis in finger millet. [Eleusine coracana (L.) Gaertn

A field experiment was conducted to study correlation and path analysis in finger millet [Eleusine coracana (L.) Gaertn]. Total 158 genotypes of finger millet were sown in a randomized block design with two replications during kharif 2017 at College of Agriculture Badnapur Dist. Jalna Maharashtra. The correlation study was undertaken in 158 genotypes of finger millet in order to find out interrelation of different yield components at genotypic and phenotypic level. The genotypic and phenotypic correlation coefficient for fifteen characters seed yield per plant had significant positive association with thousand grain weight, flag leaf sheath length, finger length, finger width, flag leaf sheath width, flag leaf blade width, finger number per panicle, calcium content and iron content is mainly because of increase in one or more of the above characters and selection of genotypes on the basis of these traits will be effective for yield improvement. Path coefficient analysis was carried out to find out the direct and indirect contribution from each of the characters towards seed yield per plant, path coefficient analysis. The genotypic correlation coefficients are being more important only partitioned to direct and indirect effects. The positive direct effect on seed yield per plant were observed for days to 50 per cent flowering (0.1543), flag leaf sheath length (0.1194), flag leaf blade width (0.1351), finger number per panicle (0.2248), finger length (0.1352), finger width (0.1207), days to maturity (0.0334), thousand grain weight (0.1621), calcium content (0.1621) and iron content (0.0283).

Comparing infection and colonisation of Puccinia graminis in barley and wheat

Barley, host to the wheat and rye attacking forms of the stem rust pathogen, Puccinia graminis (Pg), is considered inherently more resistant to Pg than wheat. To investigate whether this enhanced basal defence is associated with early infection or colonisation processes, adult plants of selected barley and wheat entries were inoculated with Pg f. sp. tritici (Pgt) races BNGSC and PTKST, and Pg f. sp. secalis (Pgs) isolate UVPgs1. Flag leaf sheaths on the last stem internode were sampled for analysis. Using scanning electron microscopy and epidermal stripping, early Pg infection structure development was compared between barley and wheat. Sub-stomatal vesicle appearance and production of haustorial mother cells were similar at 24 and 48 h post inoculation (hpi), respectively. Significant variation occurred among host entries (P ≤ 0.01) for colony size and fungal biomass at 120 hpi. Differences between the Pgt races and the Pgs isolate as well as the host entry-Pg isolate interaction proved insignificant (P ≥ 0.05). The period between 120 and 240 hpi may hold some explanation for the perceived lower stem rust receptivity in barley, since a steep increase in accumulated fungal biomass observed in the susceptible wheat Line 37 − 07 was not seen in the susceptible barley entries at the same time interval.