Hybrid Seedlings Research Articles

Production of allohexaploid Brassica hybrid between tuber mustard (Brassica juncea L. var. crassicaulis Chen &Yang) and Chinese kale (Brassica oleracea var. alboglabra Bailey)

Brassica is a key agricultural genus, containing oilseed and vegetable crops, which includes three major genomes (A, B and C), distributed in diploid (genomes: AA, BB and CC) and allotetraploid species (genomes: AABB, AACC and BBCC). Interspecific hybridization between Brassica species is an important way to combine valuable characters from the different species. In the present study, distant hybridization between inbred lines of tuber mustard (Brassica juncea var. crassicaulis Chen &Yang; AABB) and Chinese kale (Brassica oleracea var. alboglabra Bailey; CC) was conducted and allotriploid interspecific hybrids were identified. The hybrid seed set was improved by gibberellin treatment of the stigmas prior to pollination. Eight hybrid seedlings were obtained by bud pollination and ovary culture, and all seedlings were confirmed to be true hybrids by phenotypic analysis, cytological observation (27 chromosomes) and the use of parent-specific randomly amplified polymorphic DNA (RAPD) molecular markers. After tissue culture and colchicine-induced chromosome-doubling treatment, allohexaploid hybrids (AABBCC) were isolated and identified from the eight hybrids. The chromosomes of five plants were completely doubled, with a doubling rate of 5.68 %, and the number of chimeric plants was 24, at a rate of 27.27 %, when roots were immersed in 0.1 % colchicine solution. In comparison with the allotriploid hybrid, the synthetic hexaploid hybrids showed unique phenotypes with normal anthers, well-developed pods, larger flowers and petals, thicker stems than either parent and other phenotype types intermediate between the two parents. In the present study, synthetic tri-genomic Brassica vegetable germplasm, combining the A, B and C genomes, was created for use in vegetable breeding, as well as for a basis for further investigation of the mechanisms of Brassica evolution and adaptation. The current study is of great significance for the use of these allohexaploid plants to explore the heterotic effects of distant hybridization and for genetic improvement.

Early Establishment of Photosynthesis and Auxin Biosynthesis Plays a Key Role in Early Biomass Heterosis in Brassica napus (Canola) Hybrids.

Heterosis or hybrid vigor has been used widely for more than a decade in Canola (Brassica napus) production. Canola hybrids show heterosis in a variety of traits compared to parents, including increased biomass at the early stages of seedling establishment, which is a critical developmental step that impacts future plant growth and seed yield. In this study, we examined transcriptomes of two parental lines, Garnet (Gar) and NX0052 (0052), and their reciprocal hybrids, Gar/0052, at 4 and 8 days after sowing (DAS). In hybrids, early seedling biomass heterosis is correlated with earlier expression of genes in photosynthesis pathways relative to parents. The hybrids also showed early expression of genes in the auxin biosynthesis pathway, consistent with the higher auxin concentrations detected in hybrid seedlings at 4 DAS. Auxin is a key phytohormone that regulates plant development promoting cell expansion and cell proliferation. Consistent with the increased levels of auxin, hybrids have larger and more palisade cells than the parents at the same time point. We propose a possible mechanism of early biomass heterosis through the early establishment of photosynthesis and auxin biosynthesis, providing insights into how transcriptional changes in hybrids are translated into phenotypical heterosis. This finding could be utilized in future Canola breeding to identify hybrid combinations with the superior early seedling establishment and strong levels of hybrid vigor in later plant development.

Genetic basis of selection of stone fruit and other agricultural plants

Methods of creation, identification on marker signs and maintenance of the valuable genotypes used at creation of new grades, pure lines, interlinear hybrids of stone fruit plants are considered. The maintenance of valuable genotypes used in the creation of new cultivars, clean lines, interline hybrids of stone fruit plants. The laying of plantations of nectarine and peach by sowing seeds directly into the garden with subsequent budding in the form of reducing the cycle of cultivation of eyepieces, the entry into the period of full fruiting of trees, as well as accelerating the introduction into production of new breeding cultivars grown by non-transplanting method. This makes it possible to create for two years of vegetation productive mother-cuttings gardens up to 500 trees of each new cultivar. Significant importance is given to modem molecular genetic and biotechnological methods, as well as classical-hybridization, individual selection, acceleration of the breeding process (use of greenhouses for growing hybrid seedlings, as well as grafting seedlings of fruit plants). In nectarine, as well as endemic to China the peach of David and the peach of the world when self-pollinating interspecific hybrids F1 in inbred offspring sometimes there are sterile individuals of plants.

GROWING ONE AND HALF YEAR-OLD SEEDLINGS OF MULBERRY HYBRIDS IN THE CONDITION OF KASHKADARYA REGION

In the article the problem of growing one and half year old seedlings of hybrids of mulberry tree has been described in the condition of Kashkadarya region. It has been reported that in mid-salted gray soils of Karshi steppes under summer sowing levels in the second year plantings it was more useful to rejuvenate them by leveling system above the soil till the beginning of vegetation. Herein, mineral fertilizers are applied twice at the rate of 240 kg of nitrogen, 90 kg phosphorus, and 45 potassium per ha that allow to obtain more quantity of seedlings and nursery plants of mulberry free. KEYWORDS: Mulberry tree, seeds, seedlings, nursery plants, root crown, plantation, cultivation, irrigation, shoots, fertilizer, germination, hybrid, survival.

Cryphonectriaceae on Myrtales in China: phylogeny, host range, and pathogenicity.

Plantation-grown Eucalyptus (Myrtaceae) and other trees residing in the Myrtales have been widely planted in southern China. These fungal pathogens include species of Cryphonectriaceae that are well-known to cause stem and branch canker disease on Myrtales trees. During recent disease surveys in southern China, sporocarps with typical characteristics of Cryphonectriaceae were observed on the surfaces of cankers on the stems and branches of Myrtales trees. In this study, a total of 164 Cryphonectriaceae isolates were identified based on comparisons of DNA sequences of the partial conserved nuclear large subunit (LSU) ribosomal DNA, internal transcribed spacer (ITS) regions including the 5.8S gene of the ribosomal DNA operon, two regions of the β-tubulin (tub2/tub1) gene, and the translation elongation factor 1-alpha (tef1) gene region, as well as their morphological characteristics. The results showed that eight species reside in four genera of Cryphonectriaceae occurring on the genera Eucalyptus, Melastoma (Melastomataceae), Psidium (Myrtaceae), Syzygium (Myrtaceae), and Terminalia (Combretaceae) in Myrtales. These fungal species include Chrysoporthe deuterocubensis, Celoporthe syzygii, Cel. eucalypti, Cel. guangdongensis, Cel. cerciana, a new genus and two new species, as well as one new species of Aurifilum. These new taxa are hereby described as Parvosmorbus gen. nov., Par. eucalypti sp. nov., Par. guangdongensis sp. nov., and Aurifilum terminali sp. nov. Pathogenicity tests showed that the eight species of Cryphonectriaceae are pathogenic to two Eucalyptus hybrid seedlings, Melastoma sanguineum branches, and Psidium guajava and Syzygium jambos seedlings. The overall data showed that Chr. deuterocubensis is the most aggressive, followed by Par. eucalypti. Significant differences in tolerance were observed between the two tested Eucalyptus hybrid genotypes, suggesting that disease-tolerant genotypes can be selected for disease management in the Eucalyptus industry.

Hybridization and hybrid detection through molecular markers in finger millet [Eleusine coracana (L.) Gaertn.

ABSTRACTSelection of an appropriate hybridization method and use of molecular markers to study genetic purity of hybrids are important factors in crop improvement. In this study, our objective was to analyze two emasculation methods in finger millet and to present a strategy for the assessment of the genetic purity of F1 hybrids using molecular markers. Two parental lines of finger millet, PR 202 and IE 2606, were used for reciprocal crossing. Emasculation was performed with hot-water and hand methods; their efficiencies were compared. The hand method produced ~50-120 seeds per panicle and the hot-water method yielded ~30-90 seeds per panicle. The crossing efficiency was checked using molecular markers. The hot-water method was more efficient (52–80%) compared with the hand-emasculation method (16–40%). Simple sequence repeat (SSR), random amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) markers were used to analyze the genetic variation in the parental lines. Twelve out of 28 RAPD markers, 4 out of 20 ISSR markers and 21 out of 101 SSR markers showed polymorphism between parental lines. The genetic purity was 16–80% based on RAPD and SSR markers. This study suggested that molecular markers can be utilized to compare the efficiency of emasculation methods and are highly useful for the identification of true hybrid seedlings in the early stages of growth.

Features of the inheritance of fruit size in the hybrid families of prunus domestica

The aim of the research was to establish the features of the inheritance of the size of the fruit in the hybrid families of Prunus domestica. The objects of study were hybrid seedlings of plum selection of the Tatar research Institute of agriculture. Fruit sizes were estimated according to the methodology of the all-Russian research Institute of fruit crops selection. The analysis of the splitting of plum in hybrid families by the size of fruits showed that seedlings with small fruits dominated in the breeding gardens of the Tatar research Institute. The size of the plum fruit is controlled by polygens. All of the original parental forms are heterozygotes for the genes determining the size of the fruit. A small fruit is a dominant trait, a large fruit is a recessive trait. In most hybrid families, plum seedlings have a significant variability in the size of the fruit. Transgressive genotypes with large fruits are formed in hybrid families Eurasia 21 x Renklod Tenkovsky, Eurasia 21 x free pollination and Zyuzinskaya x free pollination. The varieties Eurasia 21 and Zyuzinskaya must be used as sources in breeding of plums for large-fruited.

Climate and water availability impacts on early growth and growth efficiency of Eucalyptus genotypes: The importance of GxE interactions

Predicting Eucalyptus plantation productivity in the face of climate change is a key challenge for intensively managed forest plantations around the world. Forest industry tree improvement and advanced silvicultural programs are charged with maximizing forest production but face challenging selection choices where Eucalyptus genotypes may be sensitive to genetic × environment interactions (GxE). Our study investigated the importance of GXE interactions by measuring the early (establishment to 2.6 years old) cumulative growth response of 30 selected genotypes of Eucalyptus globulus, E. nitens, E. badjensis, E. smithii, E. nitens × globulus and E. camaldulensis × globulus hybrid seedlings established across contrasting water availability conditions (High vs Low Irrigation). We compared the same genotypes at a low vapor pressure deficit (VPD) and clayey soil (North site) and a high VPD sandy soil (South site) in order to evaluate the stability of these genotypes across environmental gradients and thus evaluate the importance of genetic versus environmental impacts on growth. Stand growth was evaluated at 2.6 years when leaf area index (LAI) reached canopy closure in order to estimate a growth efficiency relationship (GE) with current annual increment (CAI). As expected, irrigation increased cumulative growth and LAI for all taxas, except for E. smithii at the North site. Genotypes showed large significant differences of performance within and across sites under each irrigation treatment. However, a strong relationship between North and South cumulative volume at age 2.6 years was observed for irrigated genotypes but not for non-irrigated genotypes. This suggests that a large GxE interaction may be expected under low water resource availability conditions associated with strong effects in ranking change of evaluated taxas and genotypes. Comparing taxas with at least two genotypes or more in our experiment, GE increased under High Irrigation for all taxas across sites. However, E. nitens × globulus hybrids showed small differences between High vs Low Irrigation treatments GE relationships compared to E. nitens and E. globulus genotypes. Our results suggest the need for strategic allocation of genotypes to contrasting drought risk environments and the need to assess our understanding of how particular genotypes interact with water stress conditions.

Alternative method of sowing canola hybrids using adhesive tape

ABSTRACT Canola, which has tiny oil-producing seeds, requires care during planting, so that there is an ideal number of plants. The aim of this study is to evaluate alternative method of sowing using adhesive tape and the influence it has on the emergence and vigor of the seedlings of different canola hybrids and define the best positioning of the adhesive tape for the formation of the experimental field. The study was carried out at the Seed Laboratory at the Universidade Federal de Goias. The tests were conducted with hybrid canola seeds (Hyola: 50, 61, 433, 571CL and 575CL). The seed characterization was performed in terms of physiological quality. They were then sown: without adhesive tape; seeds arranged on adhesive tape with the tape facing down, sideways and up, with a completely randomized experimental design, in a 5x4 factorial scheme. The evaluations were performed: emergence, speed of emergence index and first seedling emergence count in sand. The use of the adhesive tape did not interfere in the emergence of canola hybrids seedlings, with the Hyola 571CL characterized as having the best performance while the Hyola 50 and 61 had inferior performances.

Physio-biochemical analyses in seedlings of sorghum-sudangrass hybrids that are grown under salt stress under in vitro conditions

Abstract Objective This study was conducted to analyze the physio-biochemical responses of two sorghum-sudangrass (Sorghum bicolor × Sorghum Sudanese Stapf.) hybrid (“Aneto” and “Sugar Graze”) seedlings exposed to salt stress. Materials and methods Sorghum-sudangrass hybrid seeds sown in MS medium containing 50 and 100 mM NaCl. The activity of antioxidant enzymes (SOD, CAT, GR, APX), chlorophyll (a, b, and total), malondialdehyde (MDA), and proline levels measured in 14 days old seedlings. Results As a result of the study, the activity of antioxidant enzymes (CAT, SOD, APX, and GR), malondialdehyde (MDA), proline and chlorophyll contents of seedlings of cv. “Aneto” increased. On the other hand, SOD activity, proline, and chlorophyll content increased while CAT, APX, GR activity, and malondialdehyde (MDA) content decreased in seedlings of cv. “Sugar graze”. Conclusion Overall, the results showed that the cv. “Aneto” was less affected by the adverse effects of salt stress than the cv. “Sugar graze”. This study is essential for revealing biochemical responses of 14 days old Sorghum-Sudanese hybrid seedlings against salt stress. These study findings can use in breeding programs for sorghum plants.

Selection estimation of red currant hybrid family ‘Belaya Potapenko’ x SS 1426-21-80

Relevance.One of the priority trends in berry crop breeding is to create highly adaptive and resistant to biotic and abiotic environmental factors varieties with high commodity and consumer quality of berries, not inferior to the best Western European varieties.Material and methods.The research was conducted in 2017-2018 at VNIISPK (Orel) on the selection plot of red currants, planted in 2012, with a planting scheme 2.8 x 0.8 m. The research object was the selection red currant family 2466 (♀Belaya Potapenko x ♂SS 1426-21-80) of VNIISPK breeding in the amount of 66 hybrid seedlings. The parent forms of this family were selected as sources of valuable economical and breeding characters. The variety Belaya Potapenko has a dessert taste of berries, and the selected seedling 1426-21-80 was taken due to its productivity and long racemes. The economical and biological characters of the hybrid seedlings were studied according to the “Program and methods of fruit, berry and nut crops variety investigation”, section “Currants, gooseberry and their hybrids” (1999).Results.The progeny of the crossing combination Belaya Potapenko x SS 1426-21-80 is characterized by high adaptability to soil and climatic conditions of cultivation that provides good development of the seedlings and their high productivity. When crossing white-fruit Belaya Potapenko with redfruit SS 1426-21-80, seedlings with white berries are absent in the offspring, which indicates that the paternal original form is homozygous for the dominant gene that controls the red color of the berries. Hybridological analysis showed that with medium weight of berries of parental forms, the manifestation of this trait in the offspring increased, the share of large-fruited seedlings was 18-37%, depending on the year of the study. The taste estimation of the off-spring of this family showed that a great amount of the seedlings had an intermediate sweet and sour taste, part of hybrids inherited sour taste from the paternal original parent. The hybrid family is valuable for the output of highly productive large-fruited seedlings with long racemes. Re-hybridization of the best seedlings with sources of high taste of berries is necessary to improve the taste.

In vitro cultivation of the embryos of hybrid forms of early-ripening sweet cherry (Prunus avium L.) varieties

Russia does not possess as many highly adaptable, technological, early-ripening varieties of sweet cherry (Prunus avium L.) as would suffice to feel comfortable. Therefore, breeders are faced with the task of obtaining hybrid seeds as soon as possible. This task is not easy because of low field germination rates of hybrid seeds. The goal of our research was to select the best environments and ways to reduce infection while obtaining the largest number of full-fledged sweet cherry seedlings from intraspecific hybridization in vitro and to accelerate the selection process. Work on the in vitro cultivation of germs of intraspecific hybrids from four combinations of crosses of the promising varieties and sweet cherry donors ‘Valerij Chkalov’ × ‘Svithart’, ‘Krasnodarskaya Rannaya’ × ‘Krupnoplodnaya’, ‘Jaroslavna’ × ‘Sv ее thart’, ‘ Е iforiya’ × ‘Sv ее thart’ under the “early-ripening and large-fruited” program started with prebreeding and the selection of maternal and paternal forms of sweet cherries. In the course of research, the terms of taking fruits for planting in vitro culture have been determined, which correspond to the end of May and the beginning of June. The process of sterilization from saprophytic microflora of fruits, stone and seeds before cultivation has been optimized. Three modified media with macro- and microelements based on Murashige and Skoog, Prunus and Smirnova were tested and assessed for suitability for cultivation of cherry embryos. According to the results of the experiments, an agarized M4 artificial nutrient medium based on the Murashige and Skoog formulations with the addition of ascorbic acid and sucrose was proposed as the most optimal for germination and providing excellent nutrition. Mass germination from bud seedlings of these hybrid combinations of sweet cherry crosses, when applying the developed scheme, was noted in our experiments as early as in the first decade of July, i. e. about a month and a half after putting them into culture. The efficiency of growing hybrid seedlings of early-ripening sweet cherries with the use of embryo culture is indisputable, since it makes it possible to produce hybrids in the same year when the crosses are made.

Utility of ion-exchange substrates to grow potato seedlings under pot conditions

Present study reports the cultivation of potato seedlings on ionite substrates in pot culture. The possibility of using these substrates to preserve the qualitative characteristics of the potato genotype was studied. The research was conducted on hybrid seed potatoes produced in VNIIKH named after A. G. Lorch. During the growing season, the intensity of seedlings development in terms of stem height (every 2 weeks) was taken into account. At the end of the growing season, the number of leaves was analyzed, and after harvesting, the yield and its contributing components were taken into account. Dispersion analysis was performed to study the quantitative assessment of phenotypic factors. In peat soil, depending on their origin and year of cultivation, the percentage of seedling death varied from 26.0 to 41.6%. On ionite substrates, the survival rate of seedlings significantly increased - only 4.0-14.4% died when grown in cuvettes. After picking in pots, the full survival of seedlings was observed both in the control and in the experimental variants. The best of the experimental options for growing seedlings in pot culture was the substrate IS-2E, prepared on the basis of IS-2V and clinoptilolite in a volume ratio of 3:1. Growth and survival rate of seedlings on ionite substrates significantly increased by 19.3-30.2% over control and thus reduces percentage of seedlings elimination. Growing seedlings is one of the first and most important stages in the general scheme of potato breeding [1,2]. The pot culture of seedlings in greenhouses, which provides separate cultivation of genotypes, high planting density and the ability to eliminate the seasonality of this process, has acquired great importance [3]. However, the mixtures used as a substrate for growing plants do not provide optimal conditions for the growth and development of seedlings and the preservation of all genotypes [4,5]. Identifying optimal substrates and methods for obtaining hybrid seedlings of potatoes and improving the efficiency of selecting high-yielding genotypes at an early stage of selection is considered as an important researchable issue to increase the effectiveness of the entire selection process [6,7]. All this leads to strengthen the research in this direction, which has not yet developed and reported [8].

ЗАДАЧИ ПО УСКОРЕНИЮ ВНЕДРЕНИЯ НОВЫХ СОРТОВ ЯБЛОНИ В ПРОИЗВОДСТВО

As a rule, it takes on average 25 years to develop new apple cultivars and include them in the State Register of breeding achievements. Usually the same time is spent for the widespread introduction of a new cultivar into production. This does not suit the producers, as during this time, as a rule, the requirements for cultivars change and increase due to changes in the technology of cultivation of apple orchards. Breeders face a difficult task to accelerate the creation of apple cultivars and their rapid introduction into industrial and amateur gardens. The time of single breeders is over, and in order for new cultivars to meet the requirements, they must be with a certain habit, immunity to scab, precocity, regular and high yield; have fruits with a bright color (red, yellow or green) of certain weight and size. Winter cultivars should have durability of fruit, rich taste and high marketability. Only a large interdisciplinary team of researchers can solve the problem with such requirements. Besides breeders, these groups also should include gardeners, geneticists, cytoembriologists, physiologists, biochemists, phytopathologists and agronomists with the corresponding machinery equipment. Large hybrid funds, giving the opportunity to rigidly reject hybrid seedlings, are needed for constant updating of the assortment. The establishing of small production testing of varieties in the institution-originator already in the transfer of the varieties to the state test can seriously reduce the time of introduction of new varieties into production. Such well-coordinated interdisciplinary teams can create apple cultivars with a whole range of economic and biological characteristics that meet the high requirements of the production.

Intraspecific, interspecific and intergeneric hybridization of stone fruit plants

Aim. The aim to identify valuable source material from the number of intraspecific, interspecific and intergeneric hybrids of stone fruit plants to improve and expand the varietal composition of peach that meets the needs of industrial and amateur gardening. Methods. Program and methods of varietal study of fruit, berry and nut crops / Ed. G. A. Lobanov. Michurinsk, 1973. 492 p. Program and methods of selection of fruit, berry and nut crops / Ed. G. A. Lobanov. Michurinsk, 1980. 529 p. Program and methods of selection of fruit, berry and nut crops / Ed. Sedova and T. P. Ogoltsova. Orel: VNIISPK, 1999. 608 p. Results. New genotypes of peach, which are sources of cytoplasmic male sterility (CMS), were selected; large-fruited peach I4 970-89 was isolated, as a pollinator for genotypes with male sterility; in the population of hybrid seedlings F2 (peach of the world x David peach) we identified new genotypes of plants with absent characters in their original species; with resistance to powdery mildew and leaf curl, dwarf plant growth, forms with decorative double flowers, white, pink and purple-red color of the petals of the corolla, bell-shaped and rosy flower types, male sterility, pollen fertility and honey taste of the fruit inherited from his wild ancestor - David peach. Summary. Selected maternal genotypes of the original parental forms of apricot, with a character of CMS - 189-88, 249-81, 498-86. They are of breeding value for the development of new peach cultivars. Peach I4 970-89 of the Nikitsky Botanical Gardens’ breeding is a pollinator for hybrids of peach with common almond, characterized by male sterility. Valuable characters of David peach could be transferred to common peach and its cultivars as a result of natural hybridization due to their joint growth in the primary Chinese-Japanese genetic center. From wild ancestor, David peach common peach cultivars inherited such valuable characteristics as resistance to powdery mildew and leaf curl, dwarf growth of plants, shapes with decorative double flowers, white, pink and purple-red petals of the corolla campanulate and rose-like types of flower, male sterility, pollen fertility and the honey taste of the fruit.

Evaluation of Tactics for Management of Sugarcane Aphid (Hemiptera: Aphididae) in Grain Sorghum.

The invasive sugarcane aphid, Melanaphis sacchari (Zehntner), is a devastating new pest of grain sorghum. Studies were conducted utilizing an integrated approach of four management tactics: planting date, insecticidal seed treatment, a foliar-applied insecticide, and plant resistance. Experiments were conducted in 2016 and 2017 at Griffin, Tifton, and Plains Georgia, and in 2016 in Texas, Alabama, and Oklahoma, United States. Early planting was effective in reducing damage and increasing yields when compared to the late planting. Use of a resistant variety reduced cumulative aphid-days, plant injury and usually prevented significant yield loss. Foliar application of flupyradifurone when aphids reached an economic threshold, was an effective management tactic preventing aphid injury and yield loss. Use of clothianidin seed treatment also reduced aphid injury and yield loss of the susceptible hybrid but generally did not prevent injury and yield loss of the resistant hybrid. We conclude that an earlier planting date coupled with a resistant variety and judicious use of an efficacious foliar-applied insecticide can effectively manage sugarcane aphid on grain sorghum. An insecticide seed treatment also may be useful to reduce the risk of sugarcane aphid damage to seedlings of susceptible hybrids.

Reproductive ability of tetraploid cowberry (<i>Vaccinium vitis-idaea</i> L.)

Creation of allotetraploid cowberry-blueberry hybrids is a promising direction in Vacciniaceae breeding. However, obtaining such hybrids is difficult because of biological features of tetraploid cowberry. In this regard the aim of research was study of pollen viability of tetraploid cowberry, its crossing ability with different species and interspesific blueberry hybrid in various years, as well as based on the results obtained, selection of promising methods of growth stimulation of pollen tubes, hybrid seed setting and cultivation of hybrid seedlings.As a result of research it has been established that tetraploid cowberry is characterized by low productivity and pollen viability, although its viability may reach 10.7 % in some years. Hybrid seedlings gradually died off with growth. On the base of the data obtained it is proposed that a special technique be used to increase hybrid fruit setting (pollination of flowers by a mixture of pollen, pollination in different life spans of a flower, castration of flowers without removing a corolla, reciprocal crosses, spraying pollinated flowers by solutions of growth regulators and microelements) and cultivation of hybrid seedlings (in vitro culture).

Marker-trait associations and genomic predictions of interspecific pear (Pyrus) fruit characteristics

Interspecific pear (Pyrus spp.) hybrid populations are often used to develop novel cultivars. Pear cultivar breeding is a lengthy process because of long juvenility and the subsequent time required for reliable fruit phenotyping. Molecular techniques such as genome-wide association (GWA) and genomic selection (GS) provide an opportunity to fast-forward the development of high-value cultivars. We evaluated the genetic architecture of 10 pear fruit phenotypes (including sensory traits) and the potential of GS using genotyping-by-sequencing of 550 hybrid seedlings from nine interrelated full-sib families. Results from GWA suggested a complex polygenic nature of all 10 traits as the maximum variance explained by each marker was less than 4% of the phenotypic variance. The effect-size of SNPs for each trait suggested many genes of small effect and few of moderate effect. Some genomic regions associated with pear sensory traits were similar to those reported for apple – possibly a result of high synteny between the apple and pear genomes. The average (across nine families) GS accuracy varied from 0.32 (for crispness) to 0.62 (for sweetness), with an across-trait average of 0.42. Further efforts are needed to develop larger genotype-phenotype datasets in order to predict fruit phenotypes of untested seedlings with sufficient efficiency.

Enhancing the salt tolerance of commercial Eucalyptus hybrid seedlings in preparation for reclamation of inland salinity areas

Salinity is one of the primary issues causing a gradual reduction of fertile lands, especially in the arid and semiarid regions. With an increasing human population and demand for raw materials derived from tree species, it poses a threat for sustainability of such agricultural practices. Deep-rooted species like Eucalyptus can be used to reclaim such lands but seedling establishment in extremely saline conditions can be a challenge and an enhancement of salt tolerance is necessary through chemical treatment. This study attempts to quantify the effect of treating two commercially available Eucalyptus hybrid (H4 and H28) seedlings with chemicals, to increase their chances of survival in highly saline (40 dS m−1 of NaCl solution) inland environments of Thailand. This is most likely the first investigation of using chemicals to enhance the salt tolerance of Eucalyptus seedlings. After a month, no H28 seedlings could survive, while an average of 40% H4 seedlings survived. H4 seedlings treated with 30 μM selenium had the highest survival percentage (60%) along with the highest relative weight and lowest electrical leakage, suggesting a higher growth and low cell damage, or an increased salt tolerance under this chemical treatment. Prior to planting in salt-affected areas, application of selenium through root uptake is recommended, to increase the chances for seedling growth in the field.

Chestnuts bred for blight resistance depart nursery with distinct fungal rhizobiomes.

Restoration of the American chestnut (Castanea dentata) is underway using backcross breeding that confers chestnut blight disease resistance from Asian chestnuts (most often Castanea mollissima) to the susceptible host. Successful restoration will depend on blight resistance and performance of hybrid seedlings, which can be impacted by below-ground fungal communities. We compared fungal communities in roots and rhizospheres (rhizobiomes) of nursery-grown, 1-year-old chestnut seedlings from different genetic families of American chestnut, Chinese chestnut, and hybrids from backcross breeding generations as well as those present in the nursery soil. We specifically focused on the ectomycorrhizal (EcM) fungi that may facilitate host performance in the nursery and aid in seedling establishment after outplanting. Seedling rhizobiomes and nursery soil communities were distinct and seedlings recruited heterogeneous communities from shared nursery soil. The rhizobiomes included EcM fungi as well as endophytes, putative pathogens, and likely saprobes, but their relative proportions varied widely within and among the chestnut families. Notably, hybrid seedlings that hosted few EcM fungi hosted a large proportion of potential pathogens and endophytes, with possible consequences in outplanting success. Our data show that chestnut seedlings recruit divergent rhizobiomes and depart nurseries with communities that may facilitate or compromise the seedling performance in the field.