Development of a New Cold-Tolerant Maize (<i>Zea mays</i> L.) Germplasm Using the <i>ICE1</i> Gene from <i>Arabidopsis thaliana</i>

To develop cold-tolerant maize germplasms and identify the activation of INDUCER OF CRT/DRE-BINDING FACTOR EXPRESSION (ICE1) expression in response to cold stress, RT-PCR was used to amplify the complete open reading frame sequence of the ICE1 gene and construct the plant expression vector pCAMBIA3301-ICE1-Bar. Immature maize embryos and calli were transformed with the recombinant vector using Agrobacterium tumefaciens-mediated transformations. From the regenerated plantlets, three T1 lines were screened and identified by PCR. A Southern blot analysis showed that a single copy of the ICE1 gene was integrated into the maize (Zea mays L.) genomes of the three T1 generations. Under low temperature-stress conditions (4°C), the relative conductivity levels decreased by 27.51%–31.44%, the proline concentrations increased by 12.50%–17.50%, the malondialdehyde concentrations decreased by 16.78%–18.37%, and the peroxidase activities increased by 19.60%–22.89% in the T1 lines compared with those of the control. A real-time quantitative PCR analysis showed that the ICE1 gene was ectopically expressed in the roots, stems, and leaves of the T1 lines. ICE1 positively regulates the expression of the CBF genes in response to cold stress. Thus, this study showed the successful transformation of maize with the ICE1 gene, resulting in the generation of a new maize germplasm that had increased tolerance to cold stress.     

<i>In vitro</i> Evaluation of Seed Germination in Twelve Alfalfa Cultivars under Salt Stress

Alfalfa (Medicago sativa L.), when exposed to abiotic stress such as salinity, suffers significant losses in yield and productivity. The present study evaluated the salinity tolerance of 12 alfalfa cultivars in vitro using five concentrations of sodium chloride (NaCl), ranging from 0 to 250 mmol L⁻¹ . The results obtained in the current study revealed that the Saudi cultivars, Kasimi and Hassawi, and the German cultivar (Berlin) had the highest salinity tolerance in terms of germination percentage (GP), corrected germination rate index (CGRI), days to reach 50% germination (GT50), and ability to form cotyledonary and true leaves. Under mmol L⁻¹ NaCl, the Saudi cultivar Kasimi cultivar showed GP, CGRI, and GT50 of 55.20%, 123.15, and 3.77 days, respectively. Similarly, the German cultivar (Berlin) showed GP, CGRI, and GT50 of 50.06%, 86.61, and 5.17 days, respectively. These findings might reveal a pivotal aspect in salt tolerance in alfalfa. Our results will help to select salt-tolerant alfalfa cultivars that could thrive in arid and semi-arid areas with salinity problems.     

Phenotype Analysis and Fine Mapping of the Male Sterile Mutant <i>ms10</i> in Rice (<i>Oryza sativa</i> L.)

There is a positive correlation between fertility and yield, and the decrease of fertility is bound to a greatly reduced crop yield. Male sterile mutants can be used in hybrid rice. Therefore, rice male sterility has an important value in research and application, and the study of related mutants is also very vital. The mutant ms10 (male sterile 10) reported in this study was induced by ethyl methane sulfonate (EMS) in the indica maintainer line Xinong 1B. There was no significant difference between the ms10 and wild type in the vegetative growth stage. However, in the reproductive growth stage, ms10 showed that the plant became shorter, the anther became smaller and the color became lighter, and finally showed the phenotype of male sterility in comparison to the wild type. I₂-KI staining showed that the pollen was malformed and only a little was active. Scanning electron microscopy observation showed that the exine waxy layer of the ms10 anther decreased, suggesting that the protective effect on pollen was decreased. This may be one of the reasons leading to the phenotype of male sterility. Finally, the pollen showed shrinkage and collapsed, and the structure of germinating pore cover disappeared. This may be the result of sterility. Genetic analysis showed that the male sterility phenotype of the mutant was controlled by a single recessive nuclear gene. MS10 was mapped between the molecular markers IND37 and IND51 on chromosome 4, with a physical distance of 178.6 kb. These results lay the foundation for further studies on MS10.     

Physiological Responses of <i>Dendrobium officinale</i> under Exposure to Cold Stress with Two Cultivars

This study aimed to explore the cold tolerance of two cultivars of Dendrobium officinale (MG1, MG2) grown in different regions of China. Under -2°C incubation, cultivar MG1 remained active after 3 d, and continued to grow after returning to room temperature. However, MG2 could only maintain its activity after 2 d treatment at −2°C, and the seedlings died with the low temperature treatment time. Investigation of the characteristics of the plants grown in the south (Hangzhou) or north (Zhengzhou) of China indicated that the leaves of MG1 also had reduced stomatal density, the highest thickness, and a compact microstructure. The contents of proline and soluble sugars were higher in MG1 than those in MG2. The cultivar MG1 had higher SOD enzyme activity than MG2, while CAT and POD activities in samples from Zhengzhou were higher than those from Hangzhou. The contents of polysaccharides and alkaloids in stems of in MG1 were higher than those in MG2, while the content of flavonoids in the Zhengzhou samples was higher than that in the Hangzhou samples. In addition, plant heights, stem diameters, and chlorophyll content were higher in MG1. Overall, MG1 had better cold resistance than MG2. MG1 is a cold tolerant cultivar with thick leaves and reduced stomatal density, higher contents of soluble sugars, proline, CAT, POD, polysaccharides, flavonoids and alkaloids, which together make it more adaptable to low temperatures. Thus, the cultivar MG1, with its demonstrated cold tolerance, can accordingly be grown on a large scale in cold regions, thereby expanding the available planting area for this important traditional medicinal plant to meet the increasing commercial demand for it.     

Microalgae Improve the Photosynthetic Performance of Rice Seedlings (<i>Oryza sativa</i> L.) under Physiological Conditions and Cadmium Stress

The aim of this study was to assess the impact of the microalgae Chlorella vulgaris on the rice seedlings at physiological conditions and under cadmium (Cd) stress. We examined the effects of C. vulgaris in the nutrient solution on rice seedlings grown hydroponically in the presence and the absence of 150 μM CdCl₂, using the low (77 K) temperature and pulse amplitude modulated (PAM) chlorophyll fluorescence, P700 photooxidation measurements, photochemical activities of both photosystems, kinetic parameters of oxygen evolution, oxidative stress markers (MDA, H₂O₂ and proline), pigment content, growth parameters and Cd accumulation. Data revealed that the application C. vulgaris not only stimulates growth and improves the functions of photosynthetic apparatus under physiological conditions, but also reduces the toxic effect of Cd on rice seedlings. Furthermore, the presence of the green microalgae in the nutrient solution of the rice seedlings during Cd exposure, significantly improved the growth, photochemical activities of both photosystems, the kinetic parameters of the oxygen-evolving reactions, pigment content and decreased lipid peroxidation, H₂O₂ and proline content. Data showed that the alleviation of Cd-induced effects in rice seedlings is a result of the Cd sorption by microalgae, as well as the reduced Cd accumulation in the roots and its translocation from the roots to the shoots.     

Comparison of Morphological and Anatomical Characteristics of <i>Taxus chinensis</i> var. <i>mairei </i>Seedlings Root under Waterlogging Stress in Different Substrates

Four different ratios of river sand, ceramic pellets, vermiculite and perlite (1:1), and field soil were selected as the substrates in this experiment, and four gradient levels of root waterlogging, half waterlogging, full waterlogging and normal were set to investigate the effects of different gradients of waterlogging stress on the root morphology of Taxus chinensis var. mairei seedlings under different substrates. In this study, the root anatomical structure of Taxus chinensis var. mairei under different waterlogging stress was observed by the paraffin section method. The roots of T. chinensis var. mairei were diarch, with no pith and resin canals. There was a large number of tannins in the pericycle of the aerial adventitious roots of seedlings adapted to waterlogging. Also, the endodermis has obvious casparian strip thickening, and there were 4-5 layers of large parenchymatous cells in the close to the inner side of the pericycle in the vascular cylinder, which could increase the storage capacity, and transport capacity of the root. Under the treatment of root waterlogging stress, the development of plant roots in the mixed substrate of vermiculite and, perlite was the earliest. Under half waterlogging stress, T. chinensis var. mairei seedlings treated with various substrates all could better adapt to the environment of waterlogging stress. Under the stress of fully waterlogging, the roots of seedlings planted in river sand substrate developed secondary growth.     

Exploration of Distinct Physiological and Biochemical Alterations in Chickpea (<i>Cicer arietinum</i> L.) under Varying Organic Materials,Drought and Proline Application

Chickpea yield is decreasing day by day due to drought stress, which could be an immense risk for future food security in developing countries. Management practices could be the most excellent approach to diminish loss due to this abiotic factor. The current research work was designed to explore the tolerance reaction of chickpea genotypes against management practices, through morphological and biochemical parameters and evaluate yield performance across drought prone location of Bangladesh. Four genotypes BD-6048, BD-6045, BD-6090, BD-6092 and eight management practices, e.g., severe water stress (SWS), i.e., without irrigation, 10 cm thick mulching with rice straw (MRS), 10 cm thick mulching with water hyacinth (MWH), organic amendment through compost (OAC) @ 3 t ha⁻¹, organic amendment through cow dung @ 5 t ha⁻¹ (OACD), organic amendment through poultry manure @ 2 t ha⁻¹ (OAPM), inorganic amendment through proline application (IAPA) as foliar spray and 16 h hydro-priming (HP). The study revealed that the genotypes BD-6048 showed excellent performance because of the highest chlorophyll, carotenoids, phosphorus, potassium, proline and protein content. The highest pod number plant⁻¹ also increased seed yield in BD-6048. Considering management practices, IAPA increased relative water content, carotenoids, leaf phosphorus and potassium compared to other management practices and severe water stress. Finally, BD-6084 was selected as best genotype because of a significant increase in chlorophyll a and b, carotenoids, and relative water content with IAPA. Identified top performing genotypes can be used for releasing variety and cultivated for sustainable production in drought prone area of Bangladesh.     

Doubled Haploid Production Using an Improved Anther Culture Protocol for Sorghum [<i>Sorghum bicolor</i> (L.) Moench]

Sorghum [Sorghum bicolor (L.) Moench] can benefit from accelerated breeding and release of improved varieties through doubled haploid technology. The technology has been used in speeding up the breeding of other major cereals such as wheat, maize and rice, for which generally widely applied optimised protocols exist. A reproducible protocol for the crop, that can overcome genotype dependency and other species-specific challenges such as phenolic exudation is however lacking. This study aimed at sorghum doubled haploids production thereby contributing to the development of an improved protocol. From the 28 hybrid genotypes, both F₁ registered- and experimental hybrids involved, this study successfully produced haploids from five genotypes and subsequently, four confirmed doubled-haploid lines on W14mf medium or its modification with 1.0 gl⁻¹ L-proline, 1.0 gl⁻¹ L-asparagine and 1.0 gl⁻¹ KH₂PO₄. Medium 190-2Cu was used for regeneration and rooting, which occurred successfully, if the calli were transferred on to it less than 7 days after induction, and temperature was maintained at 25˚C under light condition. Genotype dependency was not wholly overcome; however, sorghum’s high tillering ability and abiotic stress tolerance were observed to contribute to attainment of haploid plantlets. Spontaneous diploids producing seeds at rates of upto 80.5% were obtained, therefore eliminating the need for colchicine duplication.     

Conventional Breeding and Molecular Markers for Blast Disease Resistance in Rice (<i>Oryza sativa</i> L.)

Monogenic lines, which carried 23 genes for blast resistance were tested and used donors to transfer resistance genes by crossing method. The results under blast nursery revealed that 9 genes from 23 genes were susceptible to highly susceptible under the three locations (Sakha, Gemmeza, and Zarzoura in Egypt); Pia, Pik, Pik-p, Piz-t, Pita, Pi b, Pi, Pi 19 and Pi 20. While, the genes Pii, Pik-s, Pik-h, Pi z, Piz-5, Pi sh, Pi 3, Pi 1, Pi 5, Pi 7, Pi 9, Pi 12, Pikm and Pita-2 were highly resistant at the same locations. Clustering analysis confirmed the results, which divided into two groups; the first one included all the susceptible genes, while the second one included the resistance genes. In the greenhouse test, the reaction pattern of five races produced 100% resistance under artificial inoculation with eight genes showing complete resistance to all isolates. The completely resistant genes: Pii, Pik-s, Piz, Piz-5 (=bi2) (t), Pita (=Pi4) (t), Pita, Pi b and Pi1 as well as clustering analysis confirmed the results. In the F₁ crosses, the results showed all the 25 crosses were resistant for leaf blast disease under field conditions. While, the results in F₂ population showed seven crosses with segregation ratio of 15 (R):1 (S), two cross gave segregated ratio of 3 R:1 S and one gave 13:3. For the identi- fication of blast resistance genes in the parental lines, the marker K3959, linked to Pik-s gene and the variety IRBLKS-F5 carry this gene, which was from the monogenic line. The results showed that four genotypes; Sakha 105, Sakha 103, Sakha 106 and IRBLKS-F5 were carrying Pik-s gene, while was absent in the Sakha 101, Sakha 104, IRBL5-M, IRBL9-W, IRBLTACP1 and IRBL9-W(R) genotypes. As for Pi 5 gene, the results showed that it was present in Sakha 103 and Sakha 104 varieties and absent in the rest of the genotypes. In addition, Pita-Pita- 2 gene was found in the three Egyptian genotypes (Sakha 105, Sakha 101 and Sakha 104) plus IRBLTACP1 monogenetic. In F2 generation, six populations were used to study the inheritance of blast resistance and specific primers to confirm the ratio and identify the resistance genes. However, the ratios in molecular markers were the same of the ratio under field evaluation in the most population studies. These findings would facilitate in breeding programs for gene pyramiding and gene accumulation to produce durable resistance for blast using those genotypes.     

Arbuscular Mycorrhizal Fungal Diversity Associated with <i>Olea europaea</i> L. Growing in Yunnan Province,Southwestern China

Olive (Olea europaea L.) is one of the most important and widely cultivated fruit trees, with high economic, ecological, cultural and scientific value. China began introducing and cultivating olive in the 1960s, and Yunnan Province is one of the main growing areas. Improving the cultivation and productivity of this tree crop species is an important challenge. Olive is a typical mycotrophic species and the potential of arbuscular mycorrhizal fungi (AMF) for this plant is well recognized; nevertheless, studies of olive AMF in China are still very limited. Roots and rhizosphere soils of olive were sampled from five representative growing sites in the Yunnan Province of China to investigate the AMF colonization status in the root systems, the AMF community in the olive orchards and the edaphic factors influencing the arbuscular mycorrhizal (AM) parameters. Root samples of olive trees from different growing sites generally showed AMF colonization, suggesting that autochthonous AMF manifest a high efficiency in colonizing the roots of olive plants. The spore density on the five sites ranged from 81.6 to 350 spores per 20 g soil. Twenty-three AMF species from 9 genera were identified in total, and Glomeraceae was the dominant family. The findings of our study suggested a high AMF diversity harbored by olive growing in different areas of the Yunnan Province, Southwestern China. Furthermore, the hyphal colonization in roots positively correlated with soil pH and EC. The arbuscule colonization in olive roots negatively correlated with soil pH, EC, OM, TN, TP and AN. The spore density positively correlated with OM, TN, AN, AP and sand content. Finally, the Shannon index of AMF in the rhizosphere soil positively correlated with the clay content, but negatively correlated with soil pH, TN and silt content. The high diversity of autochthonous AMF in Yunnan is promising for screening AMF isolates for utilization in the efficient cultivation of this crop.     

Distribution,Etiology, Molecular Genetics and Management Perspectives of Northern Corn Leaf Blight of Maize (<i>Zea mays</i> L.)

Maize is cultivated extensively throughout the world and has the highest production among cereals. However, Northern corn leaf blight (NCLB) disease caused by Exherohilum turcicum, is the most devastating limiting factor of maize production. The disease causes immense losses to corn yield if it develops prior or during the tasseling and silking stages of crop development. It has a worldwide distribution and its development is favoured by cool to moderate temperatures with high relative humidity. The prevalence of the disease has increased in recent years and new races of the pathogen have been reported worldwide. The fungus E. turcicum is highly variable in nature. Though different management strategies have proved effective to reduce economic losses from NCLB, the development of varieties with resistance to E. turcicum is the most efficient and inexpensive way for disease management. Qualitative resistance for NCLB governed by Ht genes is a race-specific resistance which leads to a higher level of resistance. However, some Ht genes can easily become ineffective under the high pressure of virulent strains of the pathogen. Hence, it is imperative to understand and examine the consistency of the genomic locations of quantitative trait loci for resistance to NCLB in diverse maize populations. The breeding approaches for pyramiding resistant genes against E. turcicum in maize can impart NCLB resistance under high disease pressure environments. Furthermore, the genome editing approaches like CRISPR-cas9 and RNAi can also prove vital for developing NCLB resistant maize cultivars. As such this review delivers emphasis on the importance and current status of the disease, racial spectrum of the pathogen, genetic nature and breeding approaches for resistance and management strategies of the disease in a sustainable manner.     

Allelopathic Potential and Mechanism of Rosebay Willowherb [<i>Chamaenerion angustifolium</i> (L.) Scop.] Demonstrated on Model Plant Lettuce

Allelopathic plants are important resources for the discovery of bioherbicides. Rosebay willowherb [Chamaenerion angustifolium (L.) Scop. syn. Epilobium angustifolium L.] widely distributes in Western Asia, Europe, and North America, and behaves as a dominant species within the community due to the production of substances that restrict growth of other plants. This study aims at investigating the allelopathic potential of rosebay willowherb by evaluation of the effects of aqueous extracts from different parts on seed germination and seedling growth in lettuce (Lactuca sativa L.), as well as measuring the accumulation of reactive oxygen species and structural analysis of root tips via scanning electron and transmission electron microscopy. It was observed that the aqueous extracts from the leaves of rosebay willowherb had the strongest inhibitory effect on the germination index, germination energy and total germination of lettuce seeds, followed by capsular fruits and flowers, and the inhibition effect of stems was the weakest. All aqueous extracts (100 mg/mL) showed a significant inhibitory effect on radicle elongation of lettuce seedlings. Additionally, after treatment with the aqueous extract of rosebay willowherb leaves, accumulation of reactive oxygen species increased in columella cells, which correlated with disruption of root tip structure.