Poor Seedling Research Articles

Soil texture involvement in wildflower strip ecosystem services delivery in Mediterranean agro-environment

The biodiversity restoration of the agroecosystem through wildflower strips is one of the most important agronomic strategies of the last few decades. However, poor knowledge of the bio-agronomic characteristics of the various wildflower species often leads to suboptimal performances especially as a result of their poor seed germination and poor seedling emergence due to the erratic soil texture. A two-year experiment involving the sowing of eighteen wildflower species in different texture conditions highlighted how some species emerged earlier or more effectively than others and verifying the consequent ecosystem service provided to pollinators. Species with smaller seeds were more inhibited by sowing in soil with high content of clay. Additionally, an inverse relationship (Boltzmann's sigmoidal regression) was found between seed weight and soil-mediated inhibition. This soil-mediated inhibition was higher in the clayey textured soil, showing that this inhibition was mediated both by seed weight and by the clay particles of the soil. The reciprocal interference between the emerged seedlings also determined a further decline in the wildflower species with small seeds. This differing agronomic performance, after sowing in the two different soil textures, did not affect the number of pollinator visits. Performance differed both in terms of floristic biodiversity and pollinator biodiversity. Finally, the experiment highlighted the importance of the appropriate selection of the wildflower species for biodiversity restoration - not only in terms of pollen and nectar availability for pollinators, but also in terms of compatibility with the soil texture in which the wildflower seeds are sown.

Identification of maize and wheat seedlings and weeds based on deep learning

Introduction: It is well-known that maize and wheat are main food crops in the world. Thus, promoting high quality and abundant maize and wheat crops guarantees the development of the grain industry, which is needed to support world hunger. Weeds seriously affect the growing environment of maize, wheat, and their seedlings, resulting in low crop yields and poor seedling quality. This paper focuses on the identification of maize and wheat seedlings and field weeds using deep learning.Methods: Maize and wheat seedlings and field weeds are the research objects. A weed identification model based on the UNet network model and ViT classification algorithm is proposed. The model uses UNet to segment images. A Python Imaging Library algorithm is used to segment green plant leaves from binary images, to enhance the feature extraction of green plant leaves. The segmented image is used to construct a ViT classification model, which improves the recognition accuracy of maize and wheat seedlings and weeds in the field.Results: This paper uses average accuracy, average recall, and F1 score to evaluate the performance of the model. The accuracy rate (for accurately identifying maize and wheat seedlings and weeds in the field) reaches 99.3%. Compared with Alexnet, VGG16, and MobileNet V3 models, the results show that the recognition effect of the model trained using the method presented in this paper is better than other existing models.Discussion: Thus, this method, which accurately disambiguates maize and wheat seedlings from field weeds can provide effective information support for subsequent field pesticide spraying and mechanical weeding.

Effects of Mixed Planting on Machine Transplanting Adaptability and Grain Yield of Hybrid Rice

Because the current hybrid rice machine transplanting sowing quantity is too large and the high rate of missing hills or poor seedling quality during mechanical transplanting, the mechanized planting of hybrid rice is limited, which results in significant hindrance of large-scale planting of hybrid rice in China. In this study, a mixed sowing technology (replacement of a portion of hybrid rice seeds with conventional rice seeds) in seedling cultivation was adopted to determine the appropriate variety combinations and conventional rice sowing quantity using a variety combination experiment and sowing quantity experiments, respectively. The results of the variety combination experiment showed that combinations of Changyou 4 mixed with Nanjing 5055, and Yuanliangyou mixed with Yangdao 6 could reduce the sowing quantity of hybrid rice, improve the quality of machine transplanting, and not reduce the grain yield. The results of the conventional rice sowing quantity experiment showed that with the increase in conventional rice sowing quantity, the seedling quality, spikelet per panicle, and filled kernel percentage decreased, and the mechanical transplanting quality improved. Compared with pure sowing hybrid rice, the grain yield was not significantly different in the japonica rice treatment when the sowing quantity of Nanjing 5055 was more than 75 g/tray and Yangdao 6 was more than 60 g/tray. With the increase in conventional rice sowing quantity, the missing hill rate decreased significantly and the seedling density increased significantly, so that the panicle number was also improved, which might have compensated the reduction in seedling quality, spikelet per panicle, and filled kernel percentage. As a whole, 90 g Nanjing 5055 seeds mixed with 30 g Changyou 4 seeds per tray and 75 g Yangdao 6 seeds mixed with 30 g Yuanliangyou seeds per tray were suitable sowing quantities for mixed planting that could ensure strong seedlings and better mechanical transplanting quality, while reducing the cost (reduce the sowing quantity of hybrid rice and conventional rice) without reducing the grain yield.

PERFORMANCE OF BLACK PEPPER CUTTINGS AS INFLUENCED BY GROWING MEDIA

Black pepper is a highly valued spice and an important ingredient in traditional medicine. The increase in black pepper cultivation to improve farmers’ income in Nigeria is constrained by poor seedling survival from vine cuttings. Using imported media to reduce mortality is expensive for low- ncome farmers. The objective of this study was to evaluate the influence of local growing media (topsoil, sawdust, and fresh rice hull) on the establishment and growth of black pepper vine cuttings in the nursery under screenhouse conditions. A repeated pot experiment was conducted using a randomised completed block design, with 9 treatments and four replicates. The following treatments were used: 100% topsoil (T1), 100% sawdust (T2), 100% rice hull (T3), 50% topsoil+50% sawdust (T4), 50% topsoil+50% rice hull (T5), 75% topsoil+25% sawdust (T6), 25% topsoil+75% sawdust (T7), 75% topsoil+25% rice hull (T8), and 75% rice hull +25% topsoil (T9). Data on sprouting, mortality and growth were evaluated. The results showed that T2 and T4 significantly reduced the number of days to sprouting compared to T1, T5 and T9, while T6, T7 and T8 exhibited a similar behaviour in the two plantings. Vine mortality was significantly higher in T3 compared to the other treatments, except for T5 and T8 in the second planting. With respect to number of leaves and leaf area, T2 and T6 showed significantly higher values at 8 and 12 weeks after planting (WAP), respectively; whereas T1 had significantly higher values at 16 and 20 WAP compared to the other treatments in both plantings. The results indicated that the most appropriate growing media for early transplanting are 100% sawdust and 50% topsoil+50% sawdust, while 100% topsoil is the most suitable for delayed transplanting.

Identification of Fungi Associated with Different Pigeon Pea Seed Accessions from Iran

A species of Leguminosae family is Cajanus cajan (L.) Millsp. (Pigeon pea) is an herbaceous, annual, self-pollinated legume pulse crop. The pigeon pea is mainly cultivated in many countries of South Asia due to its nutritious quality and a good source of minerals and protein. Seeds are a common carrier of plant pathogens, which act as the primary source for the distribution of diseases. Contaminated seeds can often create defecated germination and poor seedling vigour. They lose viability much faster than non-contaminated seeds. A large number of mycoflora were reported to be associated with the pigeon pea seeds. To assess the seed health and quality of some pigeon pea accessions this experiment was conducted at the genetic department and national plant gene bank of Iran, seed, and plant improvement institute in 2021. In the experiment, a total of 52 accessions from the pigeon pea collection were used for laboratory tests. During this study different species of Alternaria spp., Aspergillus spp., Fusarium spp., Penicillium spp., and Rhizopus spp. were found along with germinating seed and seedlings of contaminated pigeon pea. The most identified species on the contaminated pigeon pea seeds were Rhizopus spp., with 50%, and the least were Alternaria spp. and Aspergillus spp., with 7.2%. The other species Penicillium spp., and Fusarium spp., were measured on 21.4% and 14.2% of the contaminated seeds respectively. On contaminated pigeon pea seeds, 20 to 100% reduction in seed germination has been measured. Paying attention to seed health is the fundamental strategy for the integrated management of the disease for durable crop production and seed conservation.

Seed Germination and Early Seedling Growth Responses to Drought Stress in Annual Medicago L. and Trifolium L. Forages

Climate change in the Mediterranean-like regions of South Africa has resulted in increased rainfall variability, a delayed start to the wet winter season, and increased occurrences of out-of-season summer rainfall events. These changes in bioclimatic conditions are predicted to become more pronounced and, therefore, could result in poor seedling establishment and false breaks from the soil seed bank, followed by seedling desiccation in annual medic and clover pastures. This study therefore aimed to quantify and compare the responses of three annual Medicago species and five annual Trifolium species to drought stress imposed at the seed germination, seedling establishment, and early seedling growth stages. Three separate controlled trials were conducted. Firstly, the seeds were germinated in seed germination chambers at constant temperatures ranging from 5 to 30 °C, in 5 °C increments, with five osmotic treatments within each temperature, and germination was recorded daily. For the second experiment, seeds were planted at 100, 70, 50, and 30% of the soil’s moisture-holding capacity without subsequent watering, and emergence was recorded daily. For the third experiment, one-month-old seedlings were subjected to two water-limitation periods (15 or 30 days), and their subsequent morphological responses were measured. The results from these experiments indicated that the species differed significantly in their responses to drought, and the best-performing species often differed when drought was imposed at different development stages. Five species—M. polymorpha L., M. truncatula Gaertn., T. alexandrinum L., T. vesiculosum Savi., and T. subterraneum L. ssp. subterraneum—were able to tolerate incidences of drought better than other species and, thus, should be prioritized for further research into the variation in drought tolerance between cultivars within these species.

Recent advances in seed priming strategies for enhancing planting value of vegetable seeds

Vegetable crops benefit from seed priming technology by their low volume and high value. Early sowing of vegetables under suboptimal environments is practised often to fetch better remuneration in the market, although simultaneously it compels the farmers to use high seed rates to compensate for poor seedling emergence. To tackle this problem, farmers and seed companies world over practice on-farm and wet/dry priming techniques of seeds as it facilitates synchrony in flowering and fruiting, resulting in improved yields. The various priming strategies used for seed treatment are classified into: conventional/invasive (hydro-, osmo-, hormonal, halo-, solid matrix, nutrient, bio- or nano-priming) and physical/non-invasive (magneto, UV-irradiation, γ-radiation, cold plasma, electron and laser priming). The farmers can reap the benefits of seed priming as it minimizes (i) the time for plant emergence, (ii) expense of re-seeding, (iii) additional irrigation and fertilization, (iv) weed management, (v) ineffectiveness of cultural practices used on a stand of non-uniform growth. This review discusses the recent details about various seed priming techniques used for the enhancement of germination rate as well as vigor in vegetable crops. The biochemical and molecular mechanisms underlying the priming effects have also been comprehensively reviewed to explain the scientific basis of the technology.

Mapping QTLs for anaerobic tolerance at germination and bud stages using new high density genetic map of rice.

Due to its low cost and convenience, direct seeding is an efficient technique for the production of rice in different rice growing areas. However, anaerobic conditions are a major obstacle to the direct seeding of rice and result in poor seedling establishment, which leads to yield losses. We constructed a collection of recombinant inbred lines (RIL) comprising 275 lines derived from the H335 and CHA-1 cross by the method of single seed descent. Via a genotyping-by-sequencing (GBS) strategy, a high-density genetic map containing 2498 recombination bin markers was constructed, the average physical distance between the markers was only 149.38 Kb. After anaerobic treatment, 12 phenotypes related to both the coleoptile at germination and seedling quality at budding were evaluated. There were no significant correlations between seedling and bud traits. Genetic mapping of quantitative traits was performed for these traits across two cropping seasons. A total of 20 loci were detected, named locus 1~20. Three of them were repeatedly detected across both seasons. Six loci overlapped with those in previous reports, and nine loci were associated with multiple traits at both stages. Notably, locus 3, which is located on chromosome 2 (26,713,837 to 27,333,897 bp), was detected for both the germination and bud traits. By focusing on the locus 3 interval and by combining gene annotation and expression analyses, we identified a promising candidate gene, trehalose-6-phosphate phosphatase (OsTPP1, LOC_Os02g44230). Furthermore, RILs (G289, G379, G403, G430 and G454) that have superior phenotypes and that pyramid elite alleles were recognized. The findings of present study provide new genetic resources for direct-seeding rice (DSR) varieties for molecular breeding strategies and expand our knowledge of genetic regulation of seedling establishment under anaerobic conditions.

Comparative Effect of Seed Priming and Growing Media on Germination and Seedling Rootstocks of Mango (Mangifera indica)

The poor seedling rootstock is a key factor in mango yield reduction. Container-based study was conducted to evaluate the effect of seed priming and growing media on seedling rootstocks of mango. Hydropriming of seed was performed by using distilled water, while gibberellic acid (GA3) and NPK fertilizer (Solo plant) were used for hormonal and nutripriming, respectively. In second part, the primed and unprimed seeds were planted in four different growing media (GM) including GM1, GM2, GM3 and GM4. Data showed that seed germination (%), germination index (GI), seedling vigor index (SVI), height of seedling, stem diameter, chlorophyll content, electrolyte leakage of leaf, nutrient (N, P, K, Ca and Mg) contents in leaf tissue was significantly altered by both seed priming and growing media respectively. In case of priming treatments, hormonal primed seeds had the best seed germination (77.01%), stem diameter (9.65 mm) and electrolyte leakage of leaf (13.01%); while N (1.13%), P (0.14%), K (0.87%), Ca (2.40%) and Mg (0.34%) content of leaf tissue was observed maximum in nutripriming treatment. Whereas, seed germination (71.96%), germination index (11.15) and stem diameter (9.41 mm) had greater values in response to the GM2 treatment. While GM4 grown seedlings had higher seeding height (33.81 cm), N (1.17%), P (0.15%), K (0.98%), Ca (2.64%) and Mg (0.38%) content of leaf tissue. It is concluded that seed germination and seedling growth attributes had a greater influence of GA3, while mineral nutrient contents of leaf had a significant effect on nutripriming. Among growing media, GM2 was observed better for growth parameters while GM4 for mineral nutrient contents of leaf..

Experiments on the Influence of Corn Straw Morphological Combinations on Timely No-Tillage Sowing Soil Temperature and Moisture in Cold Regions

After corn mechanical harvest in autumn in the cold region of northeast China, straw mulching leads to high soil topsoil water content and slow ground temperature rise in the spring sowing season, which may result in a no-tillage planter being unable to operate in time, delayed sowing date, poor seedling emergence quality, and low grain yield. Based on the problems of high moisture content and low temperature in soil topsoil in the spring sowing season in conservation tillage with straw mulching, an experimental study on timely sowing in the spring sowing season was carried out from the perspective of combination optimization of attribute parameters of straw mechanical treatment. Taking the four mechanical treatment attributes as experimental factors, including straw length, straw shape, mulching form (surface covering, inter-ridge covering, and inter-ridge mixed soil covering), and stubble height after corn harvest in autumn of 2019 as experimental factors, and soil topsoil moisture content and temperature during spring sowing in 2020 as evaluation indexes, a field plot experiment was carried out by four factors and three levels of orthogonal combination test method. The results showed that all the factors had significant influence on soil topsoil moisture content and soil topsoil temperature (p < 0.05). It is helpful to reduce the moisture content of soil topsoil and increase the temperature of soil topsoil by increasing the length of corn stalk, breaking the stalk moderately, covering the stalk between ridges, and increasing the stubble height of stalk. Design-Expert software was used to optimize the parameters. The results showed that when the length of straw was 150 mm, the shape of straw was half-cut (dividing straw into two parts evenly along the axis), the mulch was between ridges, and the stubble height was 600 mm, the moisture content of soil topsoil was 22~24% and the temperature of soil topsoil was higher than 8 °C during spring sowing. After corn harvest in autumn of 2021, corn stalks were treated in that year according to the results of parameter optimization combination. The soil topsoil moisture content and temperature were measured to be 24.4% and 8.2 °C, respectively, in the spring sowing season of 2022, which proved that the optimization results in this experiment were credible. The experimental results provide a technical reference for the implementation of conservation tillage with straw surface mulching in the cold region of northeast China.

Increasing the appropriate seedling density for higher yield in dry direct-seeded rice sown by a multifunctional seeder after wheat-straw return

Dry direct-seeded rice (DDR) sown using a multifunctional seeder that performs synchronous rotary tillage and sowing has received increased attention because it is highly efficient, relatively cheap, and environmentally friendly. However, this method of rice production may produce lower yields in a rice–wheat rotation system because of its poor seedling establishment. To address this problem, we performed field experiments to determine the rice yield at five seedling density levels (B1, B2, B3, B4, and B5=100, 190, 280, 370, and 460 seedlings m−2, respectively) and clarify the physiological basis of yield formation. We selected a representative high-quality rice variety and a multifunctional seeder that used in a typical rice–wheat rotation area in 2016 and 2018. The proportion of main stem panicle increased with increasing seedling density. There was a parabolic relationship between yield and seedling density, and the maximum yield (9.34−9.47 t ha−1) was obtained under B3. The maximum yield was associated with a higher total spikelet number m−2 and greater biomass accumulation from heading to maturity. The higher total spikelet number m−2 under B3 was attributed to an increase in panicle number m−2 compared with B1 and B2. Although the panicle numbers also increased under B4 and B5, these increases were insufficient to compensate for the reduced spikelet numbers per panicle. Lower biomass, smaller leaf area, and lower N uptake per plant from the stem elongation stage to the heading stage were partially responsible for the smaller panicle size at higher seedling density levels such as B5. The higher biomass accumulation under B3 was ascribed to the increases in the photosynthetic rate of the top three leaves m−2 of land, crop growth rate, net assimilation rate, and leaf area index. Furthermore, the B3 rice population was marked by a higher grain–leaf ratio, as well as a lower export ratio and transport ratio of biomass per stem-sheath. A quadratic function predicted that 260−290 seedlings m−2 is the optimum seedling density for achieving maximum yield. Together, these results suggested that appropriately increasing the seedling density, and thereby increasing the proportion of panicles formed by the main stem, is an effective approach for obtaining a higher yield in DDR sown using a multifunctional seeder in a rice–wheat rotation system.

Management and environmental factors associated with simulated restoration seeding barriers in sagebrush steppe

Adverse weather conditions, particularly freezing or drought, are often associated with poor seedling establishment following restoration seeding in drylands like the Great Basin sagebrush steppe (U.S.A.). Management decisions such as planting date or seed source could improve restoration outcomes by reducing seedling exposure to weather barriers. We simulated the effects of management and environmental factors on seedling exposure to post‐germination barriers for bottlebrush squirreltail (Elymus elymoides), Sandberg bluegrass (Poa secunda), and bluebunch wheatgrass (Pseudoroegneria spicata). We combined germination timing models with daily soil moisture and temperature estimates to calculate yearly germination favorability and post‐germination freezing and drought barriers for three planting dates (15 October, 15 November, and 15 March) and three seed sources or cultivars per species for 5,000 sites in each of 40 years (water years 1980–2019). We tested the effects of site environmental variables (elevation, mean annual precipitation, heat load, and clay content) and management choices (seed source and planting date) on germination favorability and barrier occurrence (mean) and variability (coefficient of variation). Seedling exposure to barriers was strongly linked to management decisions in addition to site mean precipitation and elevation. Later fall plantings and seed sources with slower germination (lower mean germination favorability) were less likely to encounter freezing and drought barriers. These results suggest that management actions can play a role comparable to site environmental variables in reducing exposure of vulnerable seedlings to adverse weather conditions and subsequent effects on restoration outcomes.

Screening Direct Seeding-Related Traits by Using an Improved Mesocotyl Elongation Assay and Association between Seedling and Maturity Traits in Rice

Direct seeding (DS) of rice gained much attention due to labor scarcity and unavailability of water. However, reduced emergence and poor seedling establishment are the main problems of DS which causes significant yield losses. Herein, DS-associated seedling traits of three major rice groups, i.e., Indica (Ind), Japonica (Jap), and aus-type (Aus), were evaluated by using an improved mesocotyl elongation assay. The associations among different traits at the seedling and maturity stage were also studied. Significant variation was observed among the cultivars of different rice groups. The Aus group cultivars showed higher mean values for coleoptile (C, 3.85 cm), mesocotyl (MC, 4.17 cm), shoot length (SL, 13.64 cm), panicle length (PL, 23.44 cm), tillers number (T, 15.95), culm length (CL, 105.29 cm), and plant height (PH, 128.73 cm), while the Indica and Japonica groups showed higher mean values of grain length (GL, 8.69 mm), grain length/width ratio (GL/WR, 3.07), and grain width (GW, 3.31 mm), with 1000 grain weight (TGWt, 25.53 g), respectively. Pairwise correlation analysis showed that MC, C, and SL were positively correlated among themselves and with PL, CL, and PH. Moreover, based on principal component analysis (PCA), C, MC, SL, CL, and PH were identified as the major discriminative factors in the rice cultivars. This study describes the development of desired DS rice variety with long MC and semidwarf in height and suggests that Aus group cultivars can be used as the donor parents of favorable DS-associated traits in rice breeding programs.

Seedling Establishment and Yield Performance of Dry Direct-Seeded Rice after Wheat Straw Returning Coupled with Early Nitrogen Application

Dry direct-seeded rice sown by multifunctional seeders (MS-DDSR) has received increased attention for its high efficiency. Wheat straw returning is widely used as an important agricultural practice because it is the simplest and quickest approach to dispose of wheat straw and also improve soil quality. The study determined whether MS-DDSR after wheat straw returning could obtain a high yield and whether early nitrogen (N) application could compensate for the negative effects caused by returned wheat straw. Field experiments were performed in a split-plot design. Main plots were comprised without wheat straw returning (S0) and wheat straw returning (S1). Split plots consisted of three plots with early N application treatment: 65 (N1), 95 (N2), and 125 (N3) kg N ha−1 at 0 and 20 days after sowing. S1 reduced yield, N uptake, and biomass accumulation in MS-DDSR compared to S0 because S1 negatively affected the seedling roots growth, seedling establishment, and tillering capacity of MS-DDSR. The positive interaction between wheat straw returning and early N on yield, biomass accumulation, and N uptake was likely related to the positive interaction on spikelet number per panicle, total spikelet number, and biomass accumulation after the stem elongation stage. These findings demonstrate that wheat straw returning led to poor seedling establishment and yield loss for MS-DDSR, but these negative effects could be compensated for by an appropriate increase in early N application, based on the locally recommended N application protocols.

Growth of Deciduous and Evergreen Species in Two Contrasting Temperate Forest Stands in Korea: An Intersite Experiment.

Poor seedling establishment and growth can be a result of the limitation of light and soil resources in the forest understory. Here, we investigate the interacting effects of stand and soil characteristics on the seedling growth of deciduous species (Fraxinus rhynchophylla and Zelkova serrata) and evergreen species (Pinus koraiensis) through a 3-year intersite experiment in two contrasting forest stands. Seedlings were grown in both oak and pine stands using two different soil types, i.e., gray-brown forest soil (GB) and red-yellow forest soil (RY). Soil physicochemical properties, light intensity, tree-seedling height, root-collar diameter (RCD), and biomass growth were analyzed between two stands and/or soil types. Light availability was generally more abundant in the pine stand (mean: 1074.08 lx or 20.25%) than the oak stand (mean: 424.33 lx or 9.20%) throughout the year. The height and RCD growth of fast-growing and deciduous F. rhynchophylla and Z. serrata were higher in the pine than in the oak stand, particularly in GB soil. The growth of the slow-growing and evergreen P. koraiensis was not affected by the forest stand, except for its higher root growth in the oak stand and RY soil. Therefore, abundant light availability can enhance the growth and seedling establishment of F. rhynchophylla and Z. serrata in the pine-stand understory. Contrarily, P. koraiensis may be planted in the understory regardless of light condition, but with a slower growth rate.

Changes on Sugar and Starch Contents during Seed Development of Synergistic Sweet Corn and Implication on Seed Quality

Synergistic sweet corn equipped with multiple-recessive genes encoding sugar synthesis is proposed through hybrid breeding to improve the balance eating quality including flavor, texture, and aroma. However, the drawback on seed quality occurs such as low germination and poor seedling vigor. This study aimed to investigate the changes of carbohydrate contents on seed quality of five sweet corn genotypes differing in the number of equipped recessive genes during seed development. Seeds were sampled at 4-day intervals from 18 to 46 days after pollination (DAP) and analyzed for seed germination, sugar, water-soluble polysaccharide, and starch. Then, their relationships were analyzed by using time series regression analysis. Although there were significant differences among 5 corn genotypes in their seed germination and carbohydrate contents, some genotypes showed responses in similar patterns. The optimal time to harvest seeds was genotype-dependent, which were 38 DAP for triple-recessive gene (btbtsh2sh2wxwx) and single-recessive genes (BtBtsh2sh2WxWx and Sh2Sh2susuWxWx) and 42 DAP for double-recessive genes (BtBtsh2sh2wxwx). The regression analysis revealed that seed germinability could be predicted by total starch content in synergistic sweet corn lines during seed development stages; however, this prediction seemed to be negligible in sweet corn genotypes equipped with a single-recessive gene. Implications and further suggestions for establishing an effective seed production technique and seed quality of synergistic sweet corn are discussed.

Two New Bacterial Pathogens of Peanut, Causing Early Seedling Decline Disease, Identified in the Texas Panhandle.

Peanut (Arachis hypogaea L.) is cultivated in tropical and subtropical regions of the world as an important source of oil and protein. Until now, bacterial wilt, caused by Ralstonia solanacearum, was the only known bacterial disease of peanut. In 2020, widespread incidence of poor stand establishment was observed in multiple production fields planted to the Spanish-type peanut varieties in the Texas Panhandle. The observed symptoms included seed rot, pre- and postemergence damping-off, poor seedling vigor, poorly developed root systems with little or no nodule formation, and death. Subsequent diagnosis of symptomatic seedlings recovered two bacterial species identified by BLAST using 676- and 661-bp 16S rRNA fragments as a Ralstonia sp. and a Pantoea sp., respectively. To investigate a possible causative role of these bacteria in the observed peanut disease, the pathogenicity of the two isolates was evaluated under greenhouse conditions relying on Koch's postulates. Cell suspensions of the two bacteria, separately and in combination, were used to inoculate seeds of a Valencia-type peanut variety with no history of the disease and found to be pathogenic on the resultant seedling plants. Symptoms that developed on the inoculated plants were similar to the symptoms initially observed in the field, including seed rot, pre- and postemergence damping-off, poor seedling vigor, and root establishment. The two bacteria were also successfully recovered from inoculated and symptomatic plants, thus satisfying Koch's postulates. Given the early onset of symptom development on affected seeds and seedlings, a seedborne origin of the disease, described here as early-decline bacterial disease of peanut, was investigated in the same batches of peanut seeds that were planted, as well as seeds later harvested in some of the affected fields. Identical bacterial species, on the basis of 16S rRNA identity, were recovered from all of the seeds evaluated indicating that the bacteria are both seedborne and seed-transmissible. Multilocus sequence analysis involving six genes (dnaK, fumC, gyrB, murG, trpB, and tuf) showed that these new strains are most closely related to R. pickettii and Pantoea dispersa, but also phylogenetically distinct. The two bacteria were designated Ralstonia sp. strain B265 and Pantoea sp. strain B270. Losses from the disease in affected fields in 2020 averaged 50% (US$1.12 million) from a total of nine production fields. Findings from this study provide evidence for two new bacterial pathogens of peanuts capable of infecting Spanish and Valencia peanut varieties.

Seedball technology enhances pearl millet yield in a Sahelian subsistence production system

Pearl millet (Pennisetum glaucum (L.) R.Br.) is the major staple crop produced by subsistence farmers in the West African Sahel, but its panicle yield is low because of poor seedling establishment in low-nutrient soils. Seedball is a cheap seed-pelleting technique that combines sand, loam, seeds and optionally wood ash or mineral fertiliser as an additive to enhance early growth of pearl millet under infertile soil conditions. The aim of this study was to investigate the effects of seedball technology on pearl millet crop establishment and panicle yield on-farm under Sahelian subsistence conditions. Over 2000 on-farm (2015–18) trials were conducted in 65 villages of the Maradi region in Niger. Conventionally sown and seedball-derived pearl millet crops were grown by using ‘farmer-optimised’ simple split-plot designs with three treatments: (i) farmers’ practice as control; and seedballs (2.0 cm diameter, made from 80 g sand + 50 g loam + 25 mL water + 2.5 g seeds as standard recipe) that contained either (ii) 3 g wood ash or (iii) 1 g mineral fertiliser (nitrogen, phosphorus, potassium; NPK) as effective nutrient compounds. In 2016–18, participating farmers could opt for one of the seedball treatments. Panicle as well as stover yield data were collected and compared with respect to seedball type (wood ash vs NPK), sowing depth (shallow vs deep), sowing time (wet vs dry), weed management (complete vs partial), local soil type (texture range sand to loamy sand), cropping system (sole vs mixed), and farmer. Results showed that seedballs do not suppress seedling emergence. Seedball treatments produced fewer but longer and denser panicles. Wood ash-amended seedballs showed a higher panicle yield increase relative to their site controls than NPK-amended seedballs. However, the average panicle yield of NPK-amended seedballs was higher than that of the wood ash-amended seedballs. The treatment factors wet sowing, partial weeding, sole cropping and farmers showed higher panicle yield. The seedball technology increases pearl millet panicle yield by ∼30% in the Sahel; it is simple and based on local materials.

Salicylic acid seed priming boosts germination in Brassica rapa ssp pekinensis under cold stress

In Korea, the seeds of Brassica rapa ssp. pekinensis are sown in the winter and spring months. Cold stress can result in irregular seed germination and poor seedling establishment in some cases. Priming seeds with salicylic acid (SA) can reduce the likelihood of poor seedling establishment when exposed to cold stress conditions, which is beneficial for many plant species. The present study was carried out to determine the effectiveness of seed priming with SA on seed germination and seedling establishment in B. rapa ssp. pekinensis under cold stress conditions. Seeds were soaked in different SA concentrations (0.5 and 1.0 mM) for 12 and 24 hours, respectively, and then both primed and unprimed seeds germinated at 5 oC. Using SA treatment, seed germination was improved, as was root and shoot length, which were both longer in SA primed seeds than in unprimed seeds. Based on the findings, it is possible to use SA priming as one of the most effective ways to maintain productivity in B. rapa ssp. pekinensis while it is exposed to low temperatures.

Reproductive biology of Ophiorrhiza caudata C.E.C.Fisch. (Rubiaceae), an endemic and endangered creeping perennial herb of the Western Ghats, India

Ophiorrhiza caudata is a creeping, perennial herb distributed along wet and shady areas. The species is distylous with two distinct floral morphs: pin and thrum. Flowering usually occurs during the monsoon season. No particular difference was noticed in the flowering phenology of the two morphs. Presently the species is self-incompatible, however, it shows a tendency towards intramorph compatibility. Fruit set is above 60% in open pollination and intermorph pollination. Bees and butterflies are the major pollinators. The pollen flow between the two floral morphs varies depending upon floral morphology and pollinators. Fruit is a bi-valved capsule which dehisces by a splashing drop mechanism. The seeds are very minute. The rate of seed germination and seedling establishment in the wild condition is very poor due to adverse climatic factors. Ophiorrhiza caudata is struggling for survival in its natural habitat, where habitat fragmentation, climatic factors and poor seedling establishment could account for its narrow distribution.