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Achieving the optimum moisture content for long-term seed storage usually requires that seeds be dried after receipt at a genebank. Soybean (Glycine max L.) seeds were dried using four procedures: over concentrated H2S O4, over silica gel, at 15% relative humidity (RH), or in an oven at temperatures of 30, 35 and 40C. Following dying seeds were stored at 40C for 10 days and at 5C for one yr. Seeds were evaluated for germination and vigor (root length, dehydrogenase, and leachate conductivity). Initial moisture content (mc) was reduced from 8.3% to between 6.6% (24 hr at 30C) and 4.6% (H2S O4, 30 days). Germination and vigor of seeds was essentially unchanged immediately following the drying treatments. Storage for 10 days at 40C reduced germination by up to 12% while storage for one yr at 5C had a similar effect (14% maximum loss) for most treatments. The treatments having the lowest drop in germination after one yr of storage treatment were the silica gel and the 30C oven treatments, which dropped only 3% in germination. Drying at 15% RH, also resulted in a lower loss in germination. In all three tests, vigor of seeds after storage at 40C was higher than controls for the the silica gel and 15% RH treatments as well as for the 30C and 35C oven treatments. Storage at 5C gave similar results for all three vigor assessments.
Seed moisture content (MC) has been considered the most important factor controlling physiological reactions in seeds, and MC changes with relative humidity (RH) and temperature (T). This relationship is revealed by studying the interaction of RH and T at equilibrium. Cucumber (Cucumis sativus L.), lettuce (Lactuca sativa L.), maize (Zea mays L.), onion (Allium cepa L.), pea (Pisum sativum L.), and watermelon (Citrullus lanatus M. & N.) seeds were equilibrated over sulfuric acid (1% RH) and various saturated salt solutions (5.5% to 93% RH) at temperatures from 5 to 50 °C. Best-fit subset models were selected from the complete third-order model MC = β0 + β1 *RH + β2 *T + β3 *RH2 + β4 *T2 + β5 *RH*T + β6 *RH3 + β7 *T3 + β8 *RH*T2 + β9 *RH2*T, using Mallows' minimum Cp as the selection criterion. All six best subset models (R 2, 0.98 to 0.99) had the same functional form, MC = β0 + β1 *RH + β2 *T + β3 *RH2 + β5 *RH*T + β6 *RH3 + β9 *RH2*T. Coefficients had essentially the same respective values among all species except onion and pea, for which some coefficients were statistically different from those of the other species (P ≤ 0.05). All models indicated that seed MC increased as RH increased and decreased as T increased; but RH had the greater influence. The inverse relationship between seed MC and T, although slight, was evident in the response surfaces. The interaction effect of RH and T on MC was significant at P ≤0.001. These results suggest that orthodox seed species respond similarly to T and RH. This in turn suggests that a common model could be developed and used for optimizing seed storage environments.
Seed hydration and dehydration affects many physiological reactions, including priming, accelerated aging, and desiccation intolerance. Maize grains were repeatedly imbibed and desiccated, or imbibed and held for periods of time to identify the role of each of these factors. Grains were equilibrated to 12% moisture content (mc) and subjected to cycles (up to 14) of hydration (2 hours) and immediate dryback, or one hydration of 2 to 12 hours and dryback. Germination and vigor (root length and leachate conductivity) were determined after each cycle. Grains adjusted to three levels of hydration (27%, 34%, and 40%) were held for up to 10 days in a sealed desiccator. Each day samples were taken and either dried to the original mc prior to evaluation, or evaluated immediately as above. With each cycle of 2 hours of imbibition, seed mc increased (22% to 39%). Root lengths increased (priming effect) during the early cycles of imbibition and dryback. Decline in germination after eight cycles was a result of either accelerated aging or desiccation intolerance. Based on the results of the holding study, both factors contributed to deterioration, but desiccation intolerance was only observed when mc was above 27%. Conductivity of grain leachates was not correlated with loss of germination or vigor in whole grains, but appeared to reflect deterioration in isolated embryos.
The primary objective of this research was to study the female fertility of the odd-tetraploid cultivar Honesty of Lilium containing one set of Longiflorum chromosomes and three sets of Asiatic chromosomes (LAAA) to open a new approach to Lilium breeding. To assess its female fertility, ‘Honesty’ was hybridized with four autotetraploid Asiatic lily cultivars. The results showed that the fruit of all ‘Honesty’ × tetraploid (4x × 4x) combinations developed well, and viable seedlings could be obtained, suggesting that ‘Honesty’, despite being male-sterile, has considerable female fertility. Genomic in situ hybridization showed that the progenies of the 4x × 4x hybridizations were aneuploid. Considering that lily is vegetatively propagated and aneuploids often demonstrate considerable phenotypic variation, odd-tetraploid lilies such as ‘Honesty’ may be useful maternal parents for breeding new lily cultivars.
Three kinds of expression vectors of a pollen-S determinant were constructed to provide a reference for molecular breeding of self-compatible (SC) Prunus species. An S-haplotype-specific F-box (SFB) protein gene from the ‘Xiaobaixing’ apricot (Prunus armeniaca) was cloned by reverse transcription polymerase chain reaction (RT-PCR) and 3′-rapid-amplification of cDNA ends (3′-RACE). A 1136-bp sequence complementary to the 3′-end of the cDNA (GenBank accession number KP938528.2) with a 912-bp complete open reading frame (ORF) was obtained. The deduced amino acid sequence contained an F-box domain, two variable regions, and two hypervariable regions with structural characteristics similar to SFB in other Rosaceae plants. Sense, antisense, and RNA interference (RNAi) vectors for SFB were constructed by enzyme restriction. The target fragment was restricted using the corresponding restriction enzyme and then directionally inserted between the 35S cauliflower mosaic virus promoter and the nopaline synthase terminator (NOS-ter) of the expression vector pCAMBIA-35S-MCS-NOS-NPTII. The intron-containing hairpin RNA (ihpRNA) was obtained by fusion PCR. The constructed vectors were transferred into Agrobacterium tumefaciens strain LBA4404 by freezing/thawing. The RNAi vector of SFB was also transformed in tobacco (Nicotiana tabacum). The successful construction of these three expression vectors provides a basis for transforming ‘Xiaobaixing’ apricot and the breeding of SC Prunus cultivars.
The characterization of aroma of the 14 main apricot (Prunus armeniaca L.) cultivars in Xinjiang was evaluated using high-performance solid-phase microextraction (HP-SPME) with gas chromatography-mass spectroscopy (GC-MS). A total of 208 volatiles that include 80 esters, 25 aldehydes, 15 terpenes, 21 ketones, 39 alcohols, 27 olefins, and 1 acid were identified from these cultivars. The compounds propyl acetate, 3-methyl-1-butanol acetate, (Z)-3-hexen-1-ol acetate, d-limonene, β-linalool, hexanal, hexyl acetate, butyl acetate, β-myrcene, ethyl butanoate, and β-cis-ocimene were the major compounds responsible for aroma in these cultivars. GC-MS results showed that Kuchexiaobaixing, Guoxiyuluke, and seven other cultivars were characterized by a high level of esters and were considered to be fruity apricot aroma. ‘Luotuohuang’ and ‘Heiyexing’ accumulate high levels of terpenes and exhibited an outstanding floral aroma. Higher levels of alcohols and aldehydes were observed in ‘Danxing’, ‘Sumaiti’, and ‘Kumaiti’. The latter are considered green aroma cultivars. These three types of cultivars with different aroma characteristics can be significantly differentiated by using the principal component analysis (PCA) method. The contributions of volatiles to the apricot aroma were assessed by using the partial least squares regression (PLSR) model. Esters, terpenes, and C6 components were shown to be responsible for the fruity, floral, and green character of fresh apricots, respectively.