Volatile chemicals emitted from the flowers of globe amaranth (Gomphrena globosa) were collected using a dynamic headspace technique and analyzed using gas chromatography–mass spectrometry. Among the four globe amaranth cultivars analyzed, Fireworks was the highest producer of floral volatiles. The flowers of the other three cultivars, Las Vegas White, Las Vegas Pink, and Las Vegas Purple, emit less volatiles, both qualitatively and quantitatively, than ‘Fireworks’. ‘Fireworks’ was chosen for detailed characterization of regulation of floral volatile emission. A diurnal pattern of emission of floral volatiles was observed from the flowers of ‘Fireworks’. In addition, the emission pattern was not significantly affected by light, suggesting that the circadian clock plays a major role in the regulation of volatile emission. The emission of floral volatiles from ‘Fireworks’ flowers that were treated with several chemicals was also analyzed. The treatment with silver thiosulphate, an ethylene inhibitor, led to enhanced emission of total volatiles. In contrast, the treatments with salicylic acid and jasmonic acid led to enhanced emission of total floral volatiles at 4 h but reduced emission at 24 h after the treatment. Biochemical pathways leading to the production of the major floral volatiles of globe amaranth are proposed and partly validated by cluster analysis of floral volatiles emitted from ‘Fireworks’ flowers under various conditions. The implications of the results of this study to the understanding of the reproductive biology of globe amaranth and the breeding of novel globe amaranth cultivars are discussed.
Volatile chemicals emitted from the flowers of chinese wisteria (Wisteria sinenesis) and japanese wisteria (W. floribunda) were collected using a dynamic headspace technique and identified using gas chromatography–mass spectrometry; 28 and 22 compounds were detected from chinese wisteria and japanese wisteria flowers, respectively. These chemicals can be classified into four major classes, including fatty acid derivatives, benzenoids/phenylpropanoids, terpenoids, and nitrogen-containing compounds. Two monoterpenes, (E)-β-ocimene and linalool, belonging to the class of terpenoids, were the most abundant compounds emitted from both species. Despite strong similarity, the floral volatile profiles of the two species displayed variations in both quality and quantity. Chinese wisteria was selected as a model for further study of volatile emission from different parts of flowers, emission dynamics, and regulation of floral scent production. Although floral volatiles were detected from all flower parts, petals emitted the most. The emission of floral volatiles displayed a diurnal pattern with the maximal emissions occurring during the daytime. This rhythmic pattern was determined to be light-dependent. Regulation of floral volatile emission by exogenous chemicals, including silver thiosulphate (an ethylene inhibitor), salicylic acid, and jasmonic acid, also was analyzed. Generally, jasmonic acid promoted the emission of floral volatiles. In contrast, neither silver thiosulphate nor salicylic acid showed a significant effect on floral volatile emission. The results presented in this article suggest that wisteria can serve as a useful system for exploring novel biochemistry of floral scent biosynthesis. They also build a foundation for the study of the biological/ecological significance of floral volatiles on the reproductive biology of wisteria species.
Deep transcriptome sequencing allows for the acquisition of large-scale microsatellite information, and it is especially useful for genetic diversity analysis and mapping in plants without reference genome sequences. In this study, a total of 14,004 simple sequence repeats (SSRs) were mined from 10,511 unigenes screening of 63,608 nonredundant transcriptome unigenes in loquat (Eriobotrya japonica) with a frequency of 22 SSR loci distributed over 100 unigenes. Dinucleotide and trinucleotide repeat SSRs were dominant, accounting for 20.62%, and 42.1% of the total, respectively. Seventy primer pairs were designed from partial SSRs and used for polymerase chain reaction (PCR) amplification. Of these primer pairs, 54 exhibited amplification and 33 were polymorphic. The number of alleles at these loci ranged from two to 17, and the polymorphism information content values ranged from 0.24 to 0.89. We tested the transferability of 33 SSR polymorphic primer pairs in apple and pear, and the transferability rates in these two species were 90.9% and 87.9%, respectively. A high level of marker polymorphism was observed in apple [Malus ×domestica (66.7%)], whereas a low level was observed in pear [Pyrus sp. (51.5%)]. In addition, the PCR products from seven SSR primer pairs were selected for sequence analysis, and 89.2% of the fragments were found to contain SSRs. SSR motifs were conserved among loquat, apple, and pear. According to our sequencing results for real SSR loci, ≈12,490 SSR loci were present in these loquat unigenes. The cluster dendrogram showed a distinct separation into different groups for these three species, indicating that these SSR markers were useful in the evaluation of genetic relationships and diversity between and within the species of Maloideae in the Rosaceae. The results of our identified SSRs should be useful for genetic linkage map construction, quantitative trait locus mapping, and molecular marker-assisted breeding of loquat and related species.
The genetic base of commercial cucumber (Cucumis sativus L.) is extremely narrow (about 3%–8% polymorphism). Wide-based crosses within C. sativus [i.e., C. sativus var. sativus × C. sativus var. hardwickii (R.) Alef.] and interspecific hybridization attempts before 1995 have not substantially increased genetic diversity for plant improvement. However, in 1995, an amphidiploid (Cucumis hytivus Chen and Kirkbride) was derived from a C. sativus × Cucumis hystrix Chakr. mating. A derivative of this amphidiploid was used herein to broaden the genetic base of cucumber through backcross introgression [(C. sativus × C. hytivus) × C. sativus]. Initially, the combining ability of eight genetically diverse lines was investigated for days to anthesis (DA), sex expression (SEX), lateral branch number (LBN), fruit per plant (FP), fruit length:diameter ratio (L:D), and salt-processing ability [i.e., processed fruit color (exterior and interior), shape, and seed cavity characteristics]. Based on the combining ability, inbred backcross lines [IBL (BC2S3)] were developed from an original gynoecious determinate line WI 7023A [C. sativus (recurrent parent)] × monoecious indeterminate line WI 7012A (C. sativus × C. hytivus derived) mating, where 30 of 392 (8%) BC1 progeny were selected based on their diversity at 16 mapped marker loci. These progeny were used to develop BC2 progeny, which were then self-pollinated without further selection to produce 94 IBL. These IBL were genotyped and evaluated in the open field in two plantings in 2008 for DA, SEX, LBN, leaf size, FP, and L:D. The genetic distance (GD) between parental lines was 0.85, and the GD among IBL ranged between 0.16 and 0.75. Multivariate analyses indicated that IBL differed from parental lines and possessed considerable morphological and genotypic diversity that could be used to broaden the genetic base of commercial U.S. processing cucumber.
Camellia oleifera is an important woody tree species in China that produces edible oil. Although sterile male C. oleifera plants play an important role in hybrid breeding, the possible cytological characteristics of pollen abortion remain unknown. To characterize the pollen abortion process, a genic petaloid-type sterile male C. oleifera ‘X1’ plant was investigated using a cytological method. The results showed that in male-fertile plants, the anthers were full and butterfly shaped, the pollen viability was as high as 97.5%, and the development of the tapetum and anther vascular bundles was normal. However, in male-sterile C. oleifera ‘X1’, petaloidy in the anther was observed, and the pollen vitality was as low as 4.5%. Pollen abortion in sterile C. oleifera ‘X1’ anthers occurred from the microspore stage to the mature pollen period. Further cytological analyses revealed an abnormally enlarged tapetum and retarded tapetum degeneration, suggesting that insufficient nutrients were provided for microspore development. Moreover, the anther vascular bundles displayed hyperplasia, and the pollen sac area became increasingly smaller, causing most anthers to be sterile and to have few pollen grains. Taken together, the results indicate that petaloid-type male sterility in C. oleifera may be attributed to abnormal development of the tapetum and anther vascular bundles. The findings clarify the pollen abortion period and the cytological characteristics of petaloid-type cytoplasmic male sterility in C. oleifera, and lay a solid foundation for the male sterile line in C. oleifera hybrid breeding.
Loropetalum chinense, one of three species in its genus in China, is distributed primarily in Hunan and Jiangxi Provinces. By establishing a Loropetalum gene bank and reviewing research on its varieties, genetic traits, and genetic diversity, we hope to promote the full yet sustainable use of this valuable, regionally varied natural resource. Our results will help promote the development of a broader resource economy.
The embryo abortion rate of Ziziphus jujuba Mill. ‘Zhongqiusucui’ is high, which hinders cross-breeding. Research to identify the causes of embryo abortion is urgently required. To determine the embryo abortion pattern and create a foundation for further research, the embryo abortion characteristics of Z. jujuba Mill. ‘Zhongqiusucui’ were observed during this study. The results indicated that Z. jujuba Mill. ‘Zhongqiusucui’ was a cultivar with a high embryo abortion rate. Furthermore, there were some differences in the embryo abortion rates of jujube fruits in different batches. There was no significant difference between the first and second batches of jujube fruits. Large jujube fruits had a relatively low embryo abortion rate. Small jujube fruits had a relatively low kernel content rate and high embryo abortion rate. Most of the jujube fruits contained a single kernel, and some contained double kernels. The third batch of jujube fruits differed greatly from the first and second batches. The third batch had the highest degree of embryo abortion and all contained kernels were single. The embryo abortion degree of jujube fruits on the lignified bearing shoot was higher than that on the nonlignified bearing shoot, and the probability of jujube fruit with double kernels on the nonlignified bearing shoot was higher than that of the fruit on the lignified bearing shoot. The embryo abortion rates of jujube fruits with a smaller fruit shape index and larger fruit shape index were lower, and that of the medium (fruit shape index range, 1.30–1.60) was higher. The embryo abortion rates of globose, oblong globose, and long cylinder jujube fruits were lower, whereas that of cylindrical fruits was higher. Cracked jujube fruits did not contain normal seed kernels and their embryo abortion rate was 100%.