Growing season climate affects phenological development, seed yield and seed quality of dill (Anethum graveolens)

Dill seed production was investigated over two seasons, comprising a spring growing cycle (SGC) and an autumn growing cycle (AGC). The effects of growing cycle on phenological traits, yield and quality of dill seeds formed on different umbels of the mother plant were investigated. Significant differences were noted in the flowering period, seed yield and quality parameters. The SGC resulted in a shorter time from sowing to bolting and flowering initiation compared with the AGC. Plant height, number of umbels/plant, number of umbelets/umbel, umbel diameter, umbel length and seed weight/plant increased in the AGC. In contrast, decreased germination at 20/30°C and at 13°C, and increased mean germination time at 20/30°C in AGC indicated lower seed quality compared with SGC. Primary umbels produced the best yield and higher quality seeds, followed by the secondary umbels while tertiary umbels gave poor yield and quality seeds in both SGC and AGC. In conclusion, AGC was advisable for higher seed yield, but SGC resulted in higher seed quality compared with the AGC. This highlights the need to select a suitable growing cycle to guarantee high seed yield and quality for each seed production environment.

Editorial: Seed Science and Technology. Volume 49 Issue 3 (2021)

This issue of Seed Science and Technology is a good reflection of the wide scope of the field of study. Species of interest include major cultivated crops as well as wild and native species. Likewise, research topics span a wide array of subjects relevant to those interested in basic seed biology, production, testing, ecology, conservation and biodiversity. Understanding basic mechanisms of seed dormancy and germination remains a major topic of interest. Seed quality and its attributes are also of particular interest, as evidenced by research articles on seed vigour, health, genetic purity and physical characterisation.

Quality requirement for seed production in the Nigerian seed industry

Greater attention is always being given to quantity of seeds produced rather than the inherent quality when issues related to seed requirements are discussed. However, seed production should not be limited to production of crops with high yielding potential, but also of high quality seeds with good economic potential that can give good crop establishment and yields in a wide range of production environments. This requires good knowledge of seed production and the establishment of an economically functional seed system with serviceable strategies. This underscores the importance of seed quality assurance systems strengthened with seed law enforcement strategies to assure production of good quality seeds of preferred varieties. This paper discusses those strategies put in place to ensure a successful production of quality seeds in the Nigerian seed industry and how the setups operate to achieve this objective.

The radicle emergence test and storage longevity of cucurbit rootstock seed lots

A study was carried out to test whether a single count of radicle emergence (RE test) would correlate with the storage potential of seed lots of cucurbit (C. maxima × C. moschata) rootstock cultivars. The RE test was performed by counting radicle emergence percentage between 26 and 100 hours of germination. Seed longevity was determined by storage at 75% relative humidity at 35°C over 100 days, with seed survival curves constructed based on normal germination percentages. Ki (estimated initial viability in probits), σ (standard deviation of the normal distribution of seed death in time) and p50 (time for viability to fall to 50%) were determined through probit analysis. Correlation analysis showed that RE counts particularly between 30 and 34 hours were highly (P < 0.01) correlated with normal germination percentage, Ki and p50. It can be concluded that RE tests can be used as an indicator of subsequent seed lot longevity in cucurbit rootstock seed cultivars.

Germination characteristics of plump and shriveled seeds of Tamarix ramosissima matured in different seasons

Tamarix ramosissima has bi-seasonal flowering and fruiting. Although the basic germination characteristics of T. ramosissima seeds have been evaluated, there is a lack of information about the effects of seed plumpness on germination. Effects of seed plumpness and season of maturity and light conditions on germination were tested. Plump seeds matured in spring or summer had similar size and pappus length. The size of plump seeds was significantly larger than that of shriveled seeds. Both types of seeds matured in summer germinated better than seeds matured in spring. Germination percentage of plump seeds was significant higher than that of shriveled seeds, especially for seeds matured in spring. Darkness significantly decreased the germination of seeds matured in summer. This study provides comprehensive information about the seed germination requirements of T. ramosissima and the results can be used in restoration of desert lands.

Effects of brassinosteroids and gibberellin on water uptake and performance of soya bean seeds under different temperatures

Low temperature has negative effects on seed performance and seedling growth in soya bean, reducing stand establishment. It was hypothesised, that seed treatment with plant hormones could improve seed imbibition and performance at low temperature. Therefore, the effects of 24-epibrassinolide (EBL) and gibberellic acid (GA3) on soya bean seed germination were studied. Seeds of 'CM60' and 'CM0701-24' were imbibed with 0.25 or 0.50 ppm EBL, 50 or 100 ppm GA3, or distilled water at 10, 15, 20 and 25°C. The seed imbibition patterns of the two soya bean varieties followed a similar trend. Low temperature delayed seed imbibition resulting in longer time to reach the end of phases 1 and 2 of seed germination as compared with high temperature. Soya bean seeds treated with 50 or 100 ppm GA3 showed increased germination index, shoot and root length and reduced mean germination time. Thus, 50-100 ppm GA3 could be used as a pre-soaking seed treatment to improve soya bean seed and seedling performance under low temperature.

Seed germination of Leersia perrieri (Poaceae), a rare crop wild relative from Madagascar

Madagascar is home to a diversity of aquatic grasses. One of these is a rare rice relative, Leersia perrieri (known as Ahitsiriry or Tsingirifiry in the Malagasy language), which is found in a restricted area around the Mahajanga wetlands. A germination test was carried out on two types of local substrate and a control with randomised selected seeds. Seed germination on the control and clay substrates reached 50% while on the organic substrate germination failed to reach 40% during 22 days of observation. The GLM analysis of the final germination showed significant differences between the three treatments. The germination percentage (GP%) was higher in the control and significantly decreased on the clay and organic substrates. Our results help explains our field observations where L. perrieri tends to form monodominant stands on clay substrate, and dispersed multispecies assemblages with fewer individuals on organic soils. This work will be of direct benefit to our panned conservation activities and eventually germplasm availability for crop improvement research.

Hydrotime model to evaluate the effects of a set of priming agents on seed germination of two leek cultivars under water stress

Water deficit is one of the main constraints of germination for many cultivated species. Among the techniques used to promote germination, seeds priming has been found to play a key role. In the present study, a set of different priming agents (KCl, KH2PO4, CaCl2 and PEG 8000) was tested on seeds of two leek (Allium ampeloprasum L.) cultivars (“Lungo della riviera” and “Monstrueux de Carentan”) to assess the effects on germination performances both in optimal hydration condition (Ψw = 0 MPa) and under water deficit (−0.3 and −0.6 MPa). Germination percentage of “Lungo della riviera” was improved by PEG and KCl at −0.3 MPa and −0.6 MPa, respectively, whereas CaCl2 improved germination of “Monstrueux de Carentan” at −0.6 MPa. Osmopriming was beneficial in terms of germination rate although to different extent depending on genotype and priming agent. The hydrotime model showed that the effects of priming on germination rate was mostly due to a lowering of the predicted hydrotime constant (θH), whereas median base water potential Ψb(50) tended to increase following treatments albeit with some exception. In this study, hydrotime model proved to be a useful tool to test the effectiveness of different priming treatments on leek seeds and the intraspecific variability in germination capability and speed under water stress.

Mycoflora impact on germination and vigour of bottle gourd (Lagenaria siceraria) seeds and its management through different plant protectants

Bottle gourd is an important cucurbitaceous crop. The impact of 14 species from eight fungal genera on bottle gourd seeds was studied through in vitro tests. Bottle gourd seeds were inoculated with each isolate separately and subjected to various germination tests. Maximum germination inhibition was upto 69.3% due to Fusarium proliferatum. Inoculation of seeds with F. proliferatum significantly reduced the germination speed index to 2.69. The seedling vigour index I for seeds inoculated with F. proliferatum and F. incarnation-equiseti (species complex) was 860 and 861, respectively, significantly different from that of non-inoculated seeds having a vigour index of 1791. The seedling vigour index II of seeds inoculated with F. proliferatum was 1818, significantly lower than the control (4631), indicating that the F. proliferatum isolate was highly virulent among all the isolates. Amongst seven plant protectants evaluated for their efficacy as seed dressers against F. proliferatum, propioconazole (25% EC), copper oxychloride (50% WP) and Mancozeb (75% WP) were effective in reducing infection. Germination percentage was highest for seeds treated with the bioagent Trichoderma harzianum 1% WP.

Impacts of high temperature on embryonic growth and seed germination of dill (Anethum graveolens)

Temperature is the main exogenous factor that determines the growth, development and productivity of agricultural plants, including seed germination. In this work, we studied the thermosensitivity of heterogeneous dill seeds (Anethum graveolens). The study aimed to study the short-term (1-5 days) effect of high temperature (40°C) on the growth of the embryo and germination of dill seeds formed on different umbels of the mother plant. The growth of the embryo had a significant effect on seed germination (r = 0.976; P < 0.001). Seeds collected from primary umbels have a more developed embryo and can overcome the effects of thermal stress. We also found that the duration of heat exposure at 40°C, leading to a decrease in viability, can vary from 1-5 days for seeds from primary umbels, to 1-2 days for seeds from secondary umbels, which, in our opinion, is due to the heteromorphism. The influence of the place of seed formation on the mother plant and the high temperature during germination is critical for embryo growth and dill seeds’ germination.