Interspecific Hybrid Cultivars Research Articles

Nuclear DNA Markers to Distinguish between Salix caprea, Salix gracilistyla, and Their Interspecific Hybrids

The Salix genus of the Salicaceae family has advantages such as rapid initial growth, a high germination rate, and asexual reproduction; therefore, it is used as a short-rotation energy crop for biomass production. The National Institute of Forest Science created new interspecific hybrid cultivars with superior biomass production by artificially interbreeding Salix caprea L. and Salix gracilistyla Miq. Identifying these hybrids during the seedling stage is challenging because their separate reproductive and vegetative growth stages necessitate prolonged observation of their morphological characteristics. Consequently, a reliable identification method is required to overcome these limitations. This study aimed to develop nuclear DNA markers to distinguish between S. caprea, S. gracilistyla, and their interspecific hybrids. An evaluation of 35 nuclear simple-sequence repeat (nSSR) markers in the Salix genus revealed two markers that distinguish these parent species and their hybrids. A sequence analysis confirmed the presence of insertion-deletion (InDel) regions within the nSSR markers that differed between S. caprea and S. gracilistyla. To effectively identify hybrids, a primer set comprising the InDel region, which exhibited only interspecies differences and no intraspecies differences, was developed. The results of this study will facilitate the genetic resource management of interspecific hybrids between S. caprea and S. gracilistyla, thus allowing for early identification and improved management of hybrids.

Environmental and energy issues in biodiesel production using palm oil from the interspecific hybrid OxG and Elaeis guineensis: a case study in Colombia

In Colombia, in the last decade, the interspecific hybrid cultivar OxG, generated by a cross between American palm and African palm, has increased due to its tolerance to bud rot caused by Phytophthora palmivora. This study aimed to evaluate and compare the energy balance and environmental indicators of biodiesel production chains for both cultivars in Colombia. For this, an energy analysis was carried out to determine how energy is used in each process, as well as the palm energy per hectare. Also, a comparative analysis “cradle-to-gate” was made to verify the environmental performance of the genotypes studied. The functional unit was defined as 1.0 MJ of energy produced, and impacts were modeled using SimaPro v.8.0.3 software and quantified using the Impact 2002+ method. The results showed biodiesel from hybrid OxG reduced 6.2% the overall efficiency indicator of the system compared to biodiesel from E. guineensis. Life cycle CO2eq emissions of E. guineensis biodiesel were 12.5 g MJBD-1 (excluding carbon sequestration). In contrast, the CO2eq emissions of OxG hybrid biodiesel were 13.8 g MJBD-1. The life cycle efficiency indicators for biodiesel produced from OxG and E. guineensis showed a reduction in the fossil energy index of 26.9% and 19.7%, respectively.

A MADS-Box Gene-Based InDel Marker Discriminating Sex in Actinidia arguta

Gene-based markers are valuable tools in breeding programs due to their direct linkage to traits of interest. In dioecious plants, such as kiwifruit (Actinidia spp.), sex-discriminating markers can shorten the breeding cycle by enabling the selection of preferred sexes at the juvenile stage. To develop a gene-based sex-discriminating marker, resequencing was conducted on female and male A. arguta accessions, and insertion and deletion (InDel) variations within sex-related genes were explored. A total of 203,116 InDels were detected between female and male A. arguta accessions, and 118,865 InDels were heterozygous between the two accessions. Sequence similarity between thirty-seven sex-related genes from seven dioecious species and the kiwifruit reference genome was investigated, revealing that ten genes exhibited similarities ranging from 59 to 79%. Among the 118,865 InDels, seven InDels were located on four sex-related genes encoding agamous-like MADS-box genes and hypothetical proteins. A 20 bp insertion in male A. arguta located in the agamous-like MADS-box gene was converted into an InDel marker, which clearly discriminates female and male A. arguta accessions and the interspecific hybrid cultivar. The InDel marker was designated CBk25id01 and produced approximately 350 bp amplicon only in the male A. arguta. The CBk25id01 linked to the agamous-like MADS-box gene involved in floral organ development may help understand sex differentiation and accelerate the breeding of kiwifruits.

Hybrid Vitis Cultivars with American or Asian Ancestries Show Higher Tolerance towards Grapevine Trunk Diseases.

Grape production worldwide is increasingly threatened by grapevine trunk diseases (GTDs). No grapevine cultivar is known to be entirely resistant to GTDs, but susceptibility varies greatly. To quantify these differences, four Hungarian grape germplasm collections containing 305 different cultivars were surveyed to determine the ratios of GTDs based on symptom expression and the proportion of plant loss within all GTD symptoms. The cultivars of monophyletic Vitis vinifera L. origin were amongst the most sensitive ones, and their sensitivity was significantly (p < 0.01) higher than that of the interspecific (hybrid) cultivars assessed, which are defined by the presence of Vitis species other than V. vinifera (e.g., V. labrusca L., V. rupestris Scheele, and V. amurensis Rupr.) in their pedigree. We conclude that the ancestral diversity of grapes confers a higher degree of resilience against GTDs.

Effects of Nighttime Applications of Germicidal Ultraviolet Light upon Powdery Mildew (Erysiphe necator), Downy Mildew (Plasmopara viticola), and Sour Rot of Grapevine.

Nighttime applications of germicidal ultraviolet were evaluated as a means to suppress three diseases of grapevine. In laboratory studies, UV-C light (peak 254 nm, FWHM 5 nm) applied during darkness strongly inhibited the germination of conidia of Erysphe necator, and at a dose of 200 J/m2 germination was nil. Reciprocity of irradiance and duration of exposure with respect to conidial germination was confirmed for UV-C doses between 0 and 200 J/m2 applied at 4 or 400 seconds. When detached grapevine leaves were exposed during darkness to UV-C at 100 J/m2 up to 7 days before they were inoculated with zoospores of Plasmopara viticola, infection and subsequent sporulation was reduced by over 70% compared to untreated control leaves, indicating an indirect suppression of the pathogen exerted through the host. A hemicylindrical array of low-pressure discharge UV-C lamps configured for trellised grapevines was designed and fitted to both a tractor-drawn carriage and a fully autonomous robotic carriage for vineyard applications. In 2019, in a Chardonnay research vineyard with a history of high inoculum and severe disease, weekly nighttime applications of UV-C suppressed E. necator on leaves and fruit at doses of 100 and 200 J/m2. In the same vineyard in 2020, UV-C was applied once or twice weekly at doses of 70, 100, or 200 J/m2, and severity of E. necator on both leaves and fruit was significantly reduced compared to untreated controls, and twice-weekly applications at 200 J/m2 provided suppression equivalent to a standard fungicide program. None of the foregoing UV-C treatments significantly reduced the severity of P. viticola on Chardonnay vines compared to the untreated control in 2020. However, twice-weekly applications of UV-C at 200 J/m2 to the more downy mildew-resistant Vitis interspecific hybrid cultivar Vignoles in 2021 significantly suppressed foliar disease severity. In commercial Chardonnay vineyards with histories of excellent disease control in Dresden, NY, E. necator remained at trace levels on foliage and was nil on fruit following weekly nighttime applications of UV-C at 200 J/m2 in 2020, and after weekly or twice-weekly application of UV-C at 100 or 200 J/m2 in 2021. In 2019, weekly nighttime applications of UV-C at 200 J/m2 also significantly reduced the severity of sour rot, a decay syndrome of complex etiology, on fruit of the Vitis interspecific hybrid cultivar 'Vignoles', but not the severity of bunch rot caused by Botrytis cinerea. A similar level of suppression of sour rot was observed on Vignoles vines treated twice-weekly with UV-C at 200 J/m2 in 2021. Nighttime UV-C applications did not produce detectable indications of metabolic abnormalities, phytotoxicity, growth reduction, or reductions of fruit yield or quality parameters, even at the highest doses and most frequent intervals employed.

An assessment of the genetic diversity of pear (Pyrus L.) germplasm resources based on the fruit phenotypic traits

Germplasm resources are an important basis for genetic breeding and analysis of complex traits, and research on genetic diversity is conducive to the exploration and creation of new types of germplasm. In this study, the distribution frequency, coefficient of variation, Shannon–Wiener index, and variance and cluster analyses were used to analyze the diversity and trait differences of 39 fruit phenotypic traits from 570 pear accessions, which included 456 pear accessions from 11 species and 114 interspecific hybrid cultivars that had been stored in the National Germplasm Repository of Apple and Pear (Xingcheng, China). The comprehensive evaluation indices were screened by correlation, principal component and regression analyses. A total of 132 variant types were detected in 28 categorical traits of pear germplasm fruit, which indicate a rich diversity. The diversity indices in decreasing order were: fruit shape (1.949), attitude of calyx (1.908), flesh texture type (1.700), persistency of calyx (1.681), russet location (1.658), relief of area around eye basin (1.644), flavor (1.610) and ground color (1.592). The coefficient of variation of titratable acidity in the 11 numerical traits of pear germplasm fruit was as high as 128.43%, which could more effectively reflect the differences between pear accessions. The phenotypic differentiation coefficient Vst (66.4%) among the five cultivated pear species, including Pyrus bretschneideri (White Pear), P. pyrifolia (Sand Pear), P. ussuriensis (Ussurian Pear), P. sinkiangensis (Xinjiang Pear), and P. communis (European Pear), was higher than the within population phenotypic differentiation coefficient Vst (33.6%). The variation among populations was the main source of variation in pear fruit traits. A hierarchical cluster analysis divided the 389 accessions of six cultivated pear species, including P. pashia (Himalayan Pear), into six categories. There were certain characteristics within the populations, and the differences between populations were not completely clustered by region. For example, Sand Pear cultivars from Japan and the Korean Peninsula clustered together with those from China. Most of the White Pear cultivars clustered with the Sand Pear, and a few clustered with the Ussurian Pear cultivars. The Ussurian Pear and European Pear cultivars clustered separately. The Xinjiang Pear and Himalayan Pear did not cluster together, and neither did the cultivars. Seventeen traits, three describing fruit weight and edible rate (fruit diameter, fruit length and fruit core size), five describing outer quality and morphological characteristics (over color, amount of russeting, dot obviousness, fruit shape, and stalk length), and nine describing inner quality (flesh color, juiciness of flesh, aroma, flavor, flesh texture, flesh texture type, soluble solid contents, titratable acidity, and eating quality) were selected from the 39 traits by principal component and stepwise regression analyses. These 17 traits could reflect 99.3% of the total variation and can be used as a comprehensive evaluation index for pear germplasm resources.

Chromosome-level genome sequence assembly and genome-wide association study of Muscadinia rotundifolia reveal the genetics of 12 berry-related traits.

Vitis has two subgenera: Euvitis, which includes commercially important Vitis vinifera and interspecific hybrid cultivars, and Muscadinia. Of note, the market for Muscadinia grapes remains small, and only Muscadinia rotundifolia is cultivated as a commercial crop. To establish a basis for the study of Muscadinia species, we generated chromosome-level whole-genome sequences of Muscadinia rotundifolia cv. Noble. A total of 393.8Mb of sequences were assembled from 20 haploid chromosomes, and 26 394 coding genes were identified from the sequences. Comparative analysis with the genome sequence of V. vinifera revealed a smaller size of the M. rotundifolia genome but highly conserved gene synteny. A genome-wide association study of 12 Muscadinia berry-related traits was performed among 356 individuals from breeding populations of M. rotundifolia. For the transferability of markers between Euvitis and Muscadinia, we used 2000 core genome rhAmpSeq markers developed to allow marker transferability across Euvitis species. A total of 1599 (80%) rhAmpSeq markers returned data in Muscadinia. From the GWAS analyses, we identified a total of 52 quantitative trait nucleotides (QTNs) associated with the 12 berry-related traits. The transferable markers enabled the direct comparison of the QTNs with previously reported results. The whole-genome sequences along with the GWAS results provide a new basis for the extensive study of Muscadinia species.

A Novel Pear Scab (Venturia nashicola) Resistance Gene, Rvn3, from Interspecific Hybrid Pear (Pyrus pyrifolia × P. communis).

Asian pear scab is a fungal disease caused by Venturia nashicola. The identification of genes conferring scab resistance could facilitate the breeding of disease-resistant cultivars. Therefore, the present study aimed to identify a scab-resistance gene using an interspecific hybrid population ((Pyrus pyrifolia × P. communis) × P. pyrifolia). Artificial inoculation of V. nashicola was carried out for two years. The segregation ratio (1:1) of resistant to susceptible individuals indicated that resistance to V. nashicola was inherited from P. communis and controlled by a single dominant gene. Based on two years phenotypic data with the Kruskal–Wallis test and interval mapping, 12 common markers were significantly associated with scab resistance. A novel scab resistance gene, Rvn3, was mapped in linkage group 6 of the interspecific hybrid pear, and co-linearity between Rvn3 and one of the apple scab resistance genes, Rvi14, was confirmed. Notably, an insertion in pseudo-chromosome 6 of the interspecific hybrid cultivar showed homology with apple scab resistance genes. Hence, the newly discovered Rvn3 was considered an ortholog of the apple scab resistance gene. Since the mapping population used in the present study is a pseudo-BC1 population, pyramiding of multiple resistance genes to pseudo-BC1 could facilitate the breeding of pear cultivars with durable resistance.

Ion-specific Limitations of Sodium Chloride and Calcium Chloride on Growth, Nutrient Uptake, and Mycorrhizal Colonization in Northern and Southern Highbush Blueberry

Excess salinity is becoming a prevalent problem for production of highbush blueberry (Vaccinium L. section Cyanococcus Gray), but information on how and when it affects the plants is needed. Two experiments, including one on the northern highbush (Vaccinium corymbosum L.) cultivar, Bluecrop, and another on the southern highbush (V. corymbosum interspecific hybrid) cultivar, Springhigh, were conducted to investigate their response to salinity and assess whether any suppression in growth was ion specific or due primarily to osmotic stress. In both cases, the plants were grown in soilless media (calcined clay) and fertigated using a complete nutrient solution containing four levels of salinity [none (control), low (0.7–1.3 mmol·d−1), medium (1.4–3.4 mmol·d−1), and high (2.8–6.7 mmol·d−1)] from either NaCl or CaCl2. Drainage was minimized in each treatment except for periodic determination of electrical conductivity (EC) using the pour-through method, which, depending on the experiment, reached levels as high as 3.2 to 6.3 dS·m−1 with NaCl and 7.8 to 9.5 dS·m−1 with CaCl2. Total dry weight of the plants was negatively correlated to EC and, depending on source and duration of the salinity treatment, decreased linearly at a rate of 1.6 to 7.4 g·dS−1·m−1 in ‘Bluecrop’ and 0.4 to 12.5 g·dS−1·m−1 in ‘Springhigh’. Reductions in total dry weight were initially similar between the two salinity sources; however, by the end of the study, which occurred at 125 days in ‘Bluecrop’ and at 111 days in ‘Springhigh’, dry weight declined more so with NaCl than with CaCl2 in each part of the plant, including in the leaves, stems, and roots. The percentage of root length colonized by mycorrhizal fungi also declined with increasing levels of salinity in Bluecrop and was lower in both cultivars when the plants were treated with NaCl than with CaCl2. However, leaf damage, which included tip burn and marginal necrosis, was greater with CaCl2 than with NaCl. In general, CaCl2 had no effect on uptake or concentration of Na in the plant tissues, whereas NaCl reduced Ca uptake in both cultivars and reduced the concentration of Ca in the leaves and stems of Bluecrop and in each part of the plant in Springhigh. Salinity from NaCl also resulted in higher concentrations of Cl and lower concentrations of K in the plant tissues than CaCl2 in both cultivars. The concentration of other nutrients in the plants, including N, P, Mg, S, B, Cu, Fe, Mn, and Zn, was also affected by salinity, but in most cases, the response was similar between the two salts. These results point to ion-specific effects of different salts on the plants and indicate that source is an important consideration when managing salinity in highbush blueberry.

감초 종간교잡 육성품종 ‘다감’의 재배 및 품질특성

Background: Licorice is an important medicinal plant, but climate conditions can hinder seed production. Because it is difficult to produce the seeds, Korea mostly depends on the imported product. In addition, when grown domestically, the standard ingredients do not comply with those of the Korean Pharmacopoeia (glycyrrhizin 2.5% and liquritigenin 0.7%). Therefore, it is necessary to develop licorice variety suitable for the domestic environment.<BR>Methods and Results: A new interspecific hybrid cultivar designated ‘Dagam’, was developed from Glycyrrhiza glabra × G. uralensis (G. korshinskyi Grig.) and is regarded as a high-yielding and high-quality licorice by Rural Development Administration. On average the yield for ‘Dagam’ was recorded 431.5 ㎏/10a. The cultivar displayed strong brown spot disease and lodging resistance. Additionally, the glycyrrhizin and liquiritigenin contents of ‘Dagam’ (3.0 and 0.7%, respectively) met, the Korean Pharmacopoeia standard. This cultivar can widely adapt to most cultivation areas in Korea except Jejudo, Gangwondo, and the mountain-alpine regions. Furthermore, ‘Dagam’ was not showed any cytotoxicity and high cell viability compared to ‘G. uralensis’.<BR>Conclusions: The interspecific hybrid cultivar ‘Dagam’ will contribute to the stability of domestic cultivation of licorice in Korea.

A Diverse Virome of Leafroll-Infected Grapevine Unveiled by dsRNA Sequencing.

Quebec is the third-largest wine grape producing province in Canada, and the industry is constantly expanding. Traditionally, 90% of the grapevine cultivars grown in Quebec were winter hardy and largely dominated by interspecific hybrid Vitis sp. cultivars. Over the years, the winter protection techniques adopted by growers and climate changes have offered an opportunity to establish V. vinifera L. cultivars (e.g., Pinot noir). We characterized the virome of leafroll-infected interspecific hybrid cultivar and compared it to the virome of V. vinifera cultivar to support and facilitate the transition of the industry. A dsRNA sequencing method was used to sequence symptomatic and asymptomatic grapevine leaves of different cultivars. The results suggested a complex virome in terms of composition, abundance, richness, and phylogenetic diversity. Three viruses, grapevine Rupestris stem pitting-associated virus, grapevine leafroll-associated virus (GLRaV) 3 and 2 and hop stunt viroid (HSVd) largely dominated the virome. However, their presence and abundance varied among grapevine cultivars. The symptomless grapevine cultivar Vidal was frequently infected by multiple virus and viroid species and different strains of the same virus, including GLRaV-3 and 2. Our data show that viruses and viroids associated with the highest number of grapevines expressing symptoms included HSVd, GLRaV-3 and GLRaV-2, in gradient order. However, co-occurrence analysis revealed that the presence of GLRaV species was randomly associated with the development of virus-like symptoms. These findings and their implications for grapevine leafroll disease management are discussed.

Cryo-scanning electron microscopy reveals that supercooling of overwintering buds of freezing-resistant interspecific hybrid grape ‘Yamasachi’ is accompanied by partial dehydration

Dormant compound buds of grapevines adapt to subfreezing temperatures through a freezing avoidance mechanism. One still-unclear question, however, is whether supercooled water in primordial cells of dormant grape buds are partially dehydrated under subfreezing temperatures. In this study, we used differential thermal analysis (DTA) and cryo-scanning electron microscopy (cryo-SEM) to look for partial dehydration of primordial cells of the freezing-resistant interspecific hybrid cultivar ‘Yamasachi’. According to DTA, the freezing temperature of supercooled water in primary buds was not significantly affected by cooling rates between 2 and 5 °C/h; however, maintaining the bud temperature at −15 °C for 12 h followed by cooling at a rate of 5 °C/h depressed the freezing temperature. As revealed by cryo-SEM observation, many wrinkles were present on inner surfaces of walls and outer surfaces of plasma membranes of leaf primordial cells in dormant buds frozen to −15 °C. These results suggest the existence of partial dehydration in dormant-bud primordial cells under subfreezing temperatures. The apparent absence of extracellular ice crystals in bud primordial tissues under subfreezing temperatures suggests that Yamasachi dormant buds adapt to subfreezing temperatures by extraorgan freezing. When we coated primary buds with silicone oil to inhibit freeze dehydration of primordial cells, the freezing temperature of buds was slightly but significantly increased. This result suggests that the partial dehydration of cells promotes bud supercooling capability and has an important role in the freezing adaptation mechanism of grapevines.

Disease incidence and genetic variability of economically important grapevine viruses in Nova Scotia

Several virus diseases cause damage to Vitis vinifera L., but information on their incidence and impact on hybrid cultivars is scarce, particularly under cool-climate conditions. In Nova Scotia (NS), the wine industry is based predominantly on interspecific hybrid cultivars. To understand the occurrence of major grapevine viruses in NS, surveys were conducted in 2016, 2017 and 2018. A total of 965 composite five-vine samples, collected from 35 hybrids and 18 V. vinifera vineyard blocks, were tested for grapevine leafroll-associated virus 1 (GLRaV-1), GLRaV-2, GLRaV-3 and GLRaV-4, grapevine fanleaf virus (GFLV), grapevine red blotch virus (GRBV) and grapevine Pinot gris virus (GPGV) by PCR/RT-PCR. Overall, 3.4% of the samples were positive for GLRaV-1, 22.8% for GLRaV-3, 0.9% for GFLV, 4.6% for GRBV and 3.2% for GPGV. None of the 575 samples collected in 2016 and 2017 tested positive for GLRaV-2 or GLRaV-4. Mixed infections by more than one virus occurred in 3% of the composite samples. Of 671 hybrid and 294 V. vinifera samples tested, 38.3% and 27.6% were positive for at least one of the viruses (GLRaV-1, −3, GFLV, GRBV and GPGV), respectively. Phylogenetic analysis of GLRaV-1, −3, GFLV and GPGV revealed the presence of global variants. Complete genome characterization and phylogenetic analysis of nine GRBV isolates grouped three into clade I and six into clade II, indicating the presence of two variants. These findings, along with preliminary reports of insect vectors, establish the first epidemiological framework of the major viral diseases in NS, highlighting the need for long-term management strategies.

Malate Content in Wild Vitis spp. Demonstrates a Range of Behaviors during Berry Maturation

Wild <i>Vitis</i> spp. and their interspecific hybrids are known to have high malate concentrations at sugar maturity as compared to domesticated <i>Vitis vinifera</i>, but it is unknown if differences in malate at harvest among species arise from differences in malate accumulation or degradation. Over two years, fruit from <i>Vitis riparia</i> and <i>Vitis cinerea</i> accessions along with commercial <i>V. vinifera</i> and interspecific hybrid cultivars were collected at multiple time points. In contrast to the well-known biphasic behavior of malate in <i>V. vinifera</i> (preveraison accumulation, postveraison degradation), we observed a range of behaviors for malate in wild species. On average, <i>V. riparia</i> accessions had malate per berry comparable to <i>V. vinifera</i> just prior to veraison, but degraded malate to a much lesser extent. <i>V. cinerea</i> accessions had lower malate prior to veraison than other species but showed an increase in malate from pre- to postveraison. Variation in postveraison malate behavior appears related to diminished malate degradation in the mesocarp of wild <i>Vitis</i> spp. Our results indicate that studies of malate behavior in <i>Vitis</i> spp. and their hybrids should include both pre- and postveraison time points.

삽주 육성품종 뿌리의 항산화 및 항염증 효과 비교

삽주 육성품종 뿌리의 항산화 및 항염증 효과 비교

삽주 육성품종 간 생육특성 및 유효성분 분석

삽주 육성품종 간 생육특성 및 유효성분 분석

Evaluation of Poinsettia Cultivars for Resistance to Pythium Root Rot Caused by Pythium aphanidermatum

Pythium aphanidermatum is the predominant species causing pythium root rot of commercially grown poinsettia (Euphorbia pulcherrima) in North Carolina. Pythium root rot is primarily managed with strict sanitation practices and preventative fungicide applications. To determine if host resistance could play a role in the integrated management of pythium root rot, information on the susceptibility of commercial poinsettia cultivars is needed. Commercially available poinsettia cultivars were inoculated with P. aphanidermatum 3 weeks after transplant and evaluated for resistance to pythium root rot 2 months later. Thirty-four cultivars were evaluated for resistance in 2014 and 58 cultivars were evaluated in 2015, for a total of 62 cultivars evaluated. Twenty-nine cultivars were evaluated in both years. Most cultivars were susceptible to pythium root rot and none were completely resistant. However, several cultivars demonstrated partial resistance to pythium root rot. Interspecific hybrid cultivars, including Luv U Pink, had a higher level of partial resistance when compared with conventional cultivars. Partial resistance varied across bract color, response time, and plant vigor groupings. Overall, 6 of 13 partially resistant cultivars identified in 2015 had red bracts. These results indicate that growers should be able to choose among several red bract cultivars that have higher-level partial resistance to pythium root rot than others.

Reactive Oxygen Species Production and Alternative Hosts of Spring Dead Spot–Causing Fungi

Three fungi in the genus Ophiosphaerella,—O. herpotricha, O. korrae, and O. narmari—are the causal agents of spring dead spot of bermudagrass. The extent to which Ophiosphaerella spp. can colonize and infect other plant hosts and the mechanism by which they render host cells necrotic remain unknown. In other plant–pathogen interactions, it has been shown that the hypersensitive response (HR), initiated by the formation of reactive oxygen species (ROS) in the host, can promote the infection of necrotrophic fungi. The objectives of these studies were to investigate the formation of ROS during infection of plant cells and to characterize the host range of Ophiosphaerella spp. To assess ROS production, roots of three bermudagrass cultivars—Tifway 419, Midlawn, and U3—were each inoculated with an isolate of either O. herpotricha or O. korrae. The roots were stained with 2′,7′‐dichlorofluorescein diacetate at 4 to 74 h after inoculation. Staining of root cells indicated formation of ROS in response to fungal infection. The cultivar U3, which is tolerant to spring dead spot, is more likely to form high levels of ROS than the interspecific hybrid cultivars Midlawn and Tifway 419. To determine the potential host range of O. herpotricha and O. korrae, several warm‐season grasses, cool‐season grasses, and dicotyledonous plants were evaluated for colonization at 2 to 14 d after inoculation. The colonization process was similar for O. herpotricha and O. korrae on most plant species tested. Grass plant roots were readily colonized, and some showed symptoms of necrosis. The dicot plants evaluated were nonhosts. Significantly higher ROS production by the tolerant bermudagrass cultivar U3 suggests that root necrosis caused by Ophiosphaerella spp. is independent of HR associated with plant‐generated ROS. Colonization studies show that these fungi have a broad monocotyledonous host range.

Differential effects of elevated air humidity on stomatal closing ability of Kalanchoë blossfeldiana between the C3 and CAM states

High relative air humidity (RH≥85%) impairs stomatal functionality, attenuating plant capacity to cope with abiotic stress. Previous studies were limited to C3 species, so the RH effect on stomatal physiology of CAM plants remains unexplored. We addressed the topic through comparisons of C3 and CAM states in a facultative CAM species. These states were validated by diel measurements of net assimilation rate and malate level. In the first two experiments, three Kalanchoë interspecific hybrid cultivars were exposed to moderate (60%) or high (90%) RH. Both leaves that expanded at high RH and leaves that had expanded at moderate RH and were subsequently exposed to high RH (for nine days) showed increased stomatal conductance. In the third experiment, both C3 and CAM state plants of one K. blossfeldiana cultivar were exposed to low (40%), moderate (60%) or high (90%) RH. Plant transpiration during night-time was inversely related to ambient RH in either state, whereas during day-time a significant effect was only noted at 90% RH. Kalanchoë leaves showed a very effective control of water loss upon water deprivation, especially in the CAM state. Following a single week exposure to 90% RH, detached leaves showed increased rates of water loss during desiccation in C3 state plants. No effect of high RH on stomatal response to desiccation was noted in leaves detached from plants in CAM-state. It is concluded that the negative effect of either growth or one-week exposure to high RH is restricted to the C3 state in Kalanchoë.

Biological Characteristics and Vegetative Propagation of a New Camellia Cultivar Maozi

Camellia flowers are highly prized for their beauty worldwide and are strongly symbolic in many cultures. A new interspecific hybrid cultivar, Camellia ‘Maozi’, generated by crossing Camellia pubipetala with C. japonica ‘Dahong Mudan’, exhibits strong hybrid vigor and has small flowers with a rare light tone of purple. In southwest China with a subtropical monsoon climate, young Camellia ‘Maozi’ trees flush shoots three times in spring, summer, and autumn, with an average annual growth of 12.9 cm. Adult trees flush once a year. Floral bud formation occurs in late April and early May. Camellia ‘Maozi’ flowers are sterile with no fruits and seeds produced. While an individual flower wilts 4–8 days after opening, the blossom can last 1–3 months. Frost damage can be found in young leaves when temperature drops to 4–7 °C. Under direct sunlight with temperatures of 37–39 °C lasting for more than 2 days, young leaves can turn yellow on their edges. Its primary diseases include sooty mold, shoot tip blight, and peony leaf tip blight. Its primary insect pests are tea green leafhopper (Jacobiasca formosana) and tea aphid (Toxoptera aurantii). Rooting of stem cuttings occurs directly from stems, mostly without callus development. Two hours of treatment with 500 mg·L−1 indole-3-butyric acid and rooting in a mix of latosolic red soil and vermiculite (2:1 v/v) resulted in high rooting rate and quality of aboveground growth. Grafting can be carried out from May to September, while survival rate and new shoot length are highest in July. The most compatible rootstock is C. oleifera, followed by C. polyodonta. The results of this study are of value for understanding the reproductive biology of Camellia ‘Maozi’ and further disseminating it as a new cultivar for camellia collection.