Seed Coat Thickness Research Articles

English

Seed germination capability of Adonis distorta, Androsace mathildae , Aquilegia magellensis and Campanula fragilis subsp. cavolinii endemic species of the Central Apennines in Italy were analyzed. Seed traits varied significantly among the considered species. In particular, seed volume was the largest in Ad. distorta (91.642 ± 16.851 mm 3 ) and the lowest in C. fragilis subsp. cavolinii (0.029 ± 0.008 mm 3 ). The seed coat thickness ranged from 31 ± 10 µm in Ad. distorta to 9 ± 1 µm . in C. fragilis subsp. cavolinii. Seed coat was brown colored in An. mathildae , dark brown in Aq. magellensis , light brown in Ad . distorta and cream colored in C. fragilis subsp. cavolinii . Pre-treatments were carried out to improve seed germination. Seed germination did not happen in Ad. distorta and An. mathildae in response to the applied treatments (i.e., 0, 250, 500 ppm gibberelic acid, GA3) and cold-wet stratification. A 65 % increase of germination was observed after the pre-treatment with 500 ppm GA3 in Aq. magellensis which could be justified by an endogenous non-deep physiological dormancy. The final germination percentage increased by 26% in Aq. magellensis and decreased by 89% in C. fragilis subsp. cavolinii after the cold-wet stratification treatment. The obtained results may be used to define a germination protocol in reinforcement projects of the wild populations as a mean of reducing the extinction risk of these endemic species.

Studies on Resistance Discrepancy in Seeds of Local and Exotic Lentil (Lens culinarisMedikus) Genotypes AgainstCallosobruchus analisL. (Coleoptera: Bruchidae)

The bruchid, Callosobruchus analis L., is a common storage insect pest of leguminous pulses including lentil (Lens culinaris Medikus). This study was conducted to document relative resistance and susceptibility differences among the eight lentil genotypes against C. analis. Feeding preference, weight lost after feeding, frass weight obtained, reproduction and development time of the bruchid pest, thickness of the outer seed coat and percentage germination were measured to determine the reaction of lentil genotypes. The results showed that none of the genotypes screened was completely free from bruchid infestation. Seeds of genotype AEL-49/20 were least infested and displayed relatively tolerant response; conversely, genotype AEL-23/40 harboured the maximum infestation and was highly susceptible. The remaining six genotypes, Matiary-S, AEL-57/50, M-85, ICARDA-8, AEL-28/40 and M-93 were categorized as intermediate (moderate resistant or moderate susceptible) to the attack of bruchids. Significant (P ≤ 0.05) variations existed among the lentil genotypes with respect to seed coat thickness (from 19 to 39 µm), playing an important role in imparting resistance. Germination test of tolerant genotype AEL-49/20 showed 91 % emergence potential. The results emphasize the importance of resistance development to maximize the protection of L. culinaris against C. analis.

Evaluation of the Performance of Different Maize Varieties against Sitophilus Zeamais Motsch ( Coleoptera , Curculionidae ) : Infestation in the Niger Delta Region of Nigeria

The performance of different maize varieties aginst Sitophilus zeamais infestation was evaluated in a laboratory. Seventeen maize varieties comprising fourteen hybrids (ACR.97 TZL COMP.1-W, ACR.8328 BNC7, TZL COMP.4C2, OBA SUPER 1 and 2, SINE 9449-SR, IWD SYN C3F2, TZL COMP.1SYN STR-Y, TZSR White and Yellow; 95TZEE-W, MASYN VAR-3 F2, ADV.NCRE-STR and BG 97 TZE COMP.3XL) and three local cultivars (Akparike, Bende and Ogbia muno) were screened to ascertain their level of susceptibility to S. zeamais in the study area. Number of adults that emerged from the 17 varieties differed significantly (P ≤ 0.05) and ranged from 2.00 for the improved variety ADV.NCRE-STR to 62.0 in the local cultivar Bende. Significantly higher weight losses were recorded on local cultivars. Heavier males emerged from the local cultivars Akparike and Bende and lighter (P ≤ 0.05) weights were recorded on Oba super 1, TZL Comp.4C2, TZSR White, ADV.NCRE-STR and MASYN VAR-3F2. Grain hardness test showed that the hybrid variety MASYN VAR-3F2 (275.12N) was the hardest followed by TZSR-Y (259.42N) and the softest were local varieties Akparike (116.62N) and Bende (91.65N). Seed coat thickness result indicated that the local variety Akparike (0.38mm) had the highest value of seed coat thickness followed by MASYN VAR-3F2 (0.22mm) and the least seed coat thickness was BG 97 TZE COMP.3XL (0.03mm). Results indicated that the local cultivars commonly cultivated in the Niger Delta (Bende, Akparike and Ogbia muno) supported higher S. zeamais adult progeny than the improved varieties which had harder seeds and thicker coats. The fact that Akparike which has thick testa was susceptible shows that physical factors alone are not responsible for the observed resistance.

Seed Performance of Selected Bottle Gourd (Lagenaria siceraria (Molina) Standl.)

Aims: Bottle gourd is a useful crop to include in climate change adaption strategies for agronomy. However, diversity in plant and seed forms makes it difficult to predict performance under field management. There is a dearth of knowledge on the relationship between seed morphology and seed performance, namely, germination and early establishment of seedlings. This led to a need to evaluate seed morphology of different bottle gourd landraces and its effect on seed quality as defined by germination and vigour. Methodology: Six mature fruits of different bottle gourd landraces were collected from subsistence farmers and seeds from each fruit were morphologically characterized. Standard germination test, root: shoot ratio, seedling fresh mass, seedling dry mass, germination velocity index (GVI) and electrical conductivity were used to establish seed quality and vigour. Results: Although all traits were significantly different, most of them were not good indicators of seed quality. Seed coat thickness isolated varieties by provenance and was inversely proportional to root: shoot ratio as a measure of seedling establishment. Conclusion: It is concluded that Lagenaria siceraria seed morphology could be a useful trait for selection of planting material in the context of seed germination as a trait.

Contrasting Selective Pressures on Seed Traits of Two Congeneric Species by Their Main Native Guilds of Dispersers on Islands

Many fleshy-fruited plants from the Mediterranean and Macaronesian islands are dispersed through endozoochory. In mainland Mediterranean areas, reciprocal adaptations have been found between plants and animals, although evidence is scarce. On small isolated oceanic islands, such reciprocal adaptations might well be more prevalent due to intrinsic island traits. Here we evaluate the existence of selective pressures exerted by two different disperser guilds (lizards and birds) on two seed traits (seed coat thickness and seed germination pattern) of two congeneric species present on Mediterranean and Macaronesian islands. In the continental Balearic Islands, Rubia peregrina has evolved mostly with birds, although frugivorous lizards are present in some of these islands and are known to eventually consume its fruits. By contrast, R. fruticosa, endemic to the Macaronesian archipelago, has evolved mostly interacting with lizards and only recently with birds. We hypothesized that R. fruticosa would be especially adapted to saurochory, with thicker seed coats and higher germination proportion, whereas R. peregrina would be more adapted to ornithocory, with thinner seed coats and showing a lower germination percentage after being ingested by lizards. Captivity experiments of seed ingestions by natural and non-natural dispersers (i.e., frugivores that have not evolved with those plants) were conducted. Results suggest that dispersers did not exert any strong enough selective pressure to induce changes in germination patterns. We attribute this to the fact that the Rubiaceae is an ancestral family in the Mediterranean (both on continent and islands) and thus probably interacted with lizards in the past. Lastly, although we hold that the seed coat structure of R. fruticosa is probably associated with its evolutionary success after a long interaction with insular lizards, our findings support the idea that the relationship between endozoochorous plants and the guild of dispersers with whom they evolved is rather unspecific.

Milling Performance and Other Quality Traits Affected by Seed Shape in Isogenic Lines of Desi Chickpea (Cicer arietinum L.)

Milling of pulses generally involves removal of the seed coat and splitting of the cotyledons to produce splits or ‘dhal’. The aim of this research was to investigate whether seed shape affected seed quality using two sets of near-isogenic lines differing by a single allele at the seed shape locus (Rd/rd). Seed shape had a profound effect on milling quality: rounded seeds produced 7% more dhal than their angular counterparts. There were also significant effects on other quality parameters attributable to seed shape: rounded seeds had less seed coat content because it was thinner, a more intense seed coat colour, faster water absorption but lower hydration capacity and a slightly longer dhal cooking time. This study shows that seed shape is more important than seed coat thickness from a milling perspective and suggests that breeding programs should select for rounder shaped desi chickpeas to maximise dhal yields and profitability for the splitting industry.

Modeling the dynamics and emergence of a multispecies weed seed bank with species traits

Models quantifying the effects of cropping systems on weed life-cycles, in interaction with environmental conditions, are invaluable tools to evaluate and design integrated cropping systems. In the past, we have developed such a model called AlomySys for a single grass weed species. The objective of the present paper was to extend the monospecific emergence model to a multi-specific weed flora, by removing a few non-generic processes (e.g. maternal effects on dormancy and germination) and by adapting the germination sub-model to a larger diversity of species.The model is based on a daily simulation of weed seedbank mortality, seasonal dormancy variations, germination and pre-emergent growth until seedling emergence, in interaction with cropping systems and environmental conditions. In order to parameterize the model for numerous and contrasting species, we developed an innovative approach consisting in estimating 25 parameters from easily accessible species traits or from empirical expert knowledge. Relationships were established between seed traits (e.g. seed coat thickness, mass or shape) and seed mortality rates, dormancy levels, speed of germination as well as pre-emergent mortality. Base temperature for germination and dates of dormancy variations were related to usual dates of the species emergence in fields, obtained from expert knowledge. The generic model structure and the trait–parameter relationships make it possible to simulate a wide diversity of weed species and to predict their response to a large range of cropping systems. Thanks to a daily time-step and the integration of the interactions with soil and climatic conditions, FlorSys permits to optimize the choice of cultural techniques for weed management, as a function of field characteristics and previous technical operations. For instance, the model was used to compare the emergence of different weed species depending on tillage, in interaction with the preceding technical operations.

The Bsister MADS-box proteins have multiple regulatory functions in plant development

Abstract B sister MADS-box proteins are a group of recently characterized MADS family transcription factors. The genes encoding these proteins have a close relationship with the male-organ-expressed class B floral homeotic genes, but are predominantly expressed in female organs. B sister MADS-box proteins display important regulatory functions in seed coat development, fruit development, and proanthocyanidin biosynthesis. Therefore, genes encoding B sister MADS-box proteins are potentially useful in genetic engineering of crop plants to reduce seed coat thickness and condensed tannin content. In this review, recent progress on biochemical, molecular and functional aspects of plant B sister MADS-box proteins is discussed.

Standardizing germination protocols for diverse raspberry and blackberry species

Most blackberry and raspberry (Rubus) seed exhibit delayed or poor germination because of a deep double dormancy. The objective of this study was to improve seed scarification and germination protocols for the diverse Rubus species in two subgenera often used for breeding improved cultivars. We also defined the germination potential of freshly collected seed and the seed characteristics of 17 Rubus species in three subgenera. Only four of 17 species had ≥50% germination of immediately-germinated, non-scarified seed, indicating primary seed dormancy. Seed-coat thickness was better correlated with seed size (R=0.82) than was hardness (R=0.71). Dry seed of three species each in the subg. Idaeobatus and Rubus were scarified with concentrated sulfuric acid (98% H2SO4) or sodium hypochlorite (14% NaOCl) followed by germination treatments of deionized water (DI), smoke gas solution, gibberellic acid (2.03mg/L GA3) with potassium nitrate (34mg/L KNO3) or GA3 alone. Germination after H2SO4 scarification was significantly better than NaOCl for four of the six species despite equal reduction in the seed coat by the scarification treatments. H2SO4-scarified seed had maximum germination in 6–8 months compared to 12 months for NaOCl-scarified seed. Scarification treatments were not uniform for the subgenera. Increased H2SO4 scarification durations monitored by viability testing with 2,3,5 triphenyl tetrazolium chloride (TZ) were very effective in determining optimal scarification timing. R. georgicus and R. occidentalis H2SO4-scarified seed treated with GA3+KNO3 or smoke germinated significantly better than the other treatments; GA3+KNO3, smoke and DI water were equally effective for the other four species.

Seed-coat anatomy and proanthocyanidins contribute to the dormancy of Rubus seed

Rubus seed has a deep double dormancy that restricts germination due to seed coat structure and chemical composition. Improved germination of diverse Rubus species required for breeding improved blackberry and raspberry cultivars is partly dependent on the seed coat structure. This study evaluated the seed coat structure of three species with thin ( R. hoffmeisterianus Kunth & C. D. Bouché), medium ( R. occidentalis L.) and thick ( R. caesius L.) seed coats. The three species exhibited distinctive seed-coat cell composition. The very thin testa (0.086 mm) of R. hoffmeisterianus had little exotesta (surface) reticulation; with the meso- and endotesta composed of sclereids of homogenous shape and size. R. occidentalis had a thick testa (0.175 mm) and a highly reticulate exotesta; the meso- and endotesta were composed of several diverse types of sclereids. R. caesius had the thickest seed coat (0.185 mm) but only moderate exotesta reticulation; the meso- and endotesta were composed of large, irregular, loosely arranged sclereids. R. occidentalis, a medium size seed, was the most heavily lignified with seed-coat thickness similar to R. caesius, the largest seed. Proanthocyanidins (PAs) from dry seed of six Rubus species were extracted and quantified by high performance liquid chromatography. R. hoffmeisterianus, a thin only slightly hard seed, had half the PA (0.45 μg/seed) of R. occidentalis with a thick, extremely-hard seed coat and diverse sclereids (1.07 μg/seed). PA content and sclereid composition both appear contribute to seed coat hardness and resulting seed dormancy. The effectiveness of sulfuric acid for Rubus seed scarification is likely due to degradation of PAs in the testa.

Optimized scarification protocols improve germination of diverse Rubus germplasm

Seed collections of the wild relatives of cultivated blackberry and raspberry ( Rubus species) are maintained at the National Clonal Germplasm Repository, Corvallis, OR. Information on wild species germination requirements is rarely available, and germination may be poor or slow, making it difficult for scientists to use them for breeding improved cultivars. Eight diverse Rubus species in 6 of the 12 Rubus subgenera from seed stored at −20 °C for 1–23 years were studied. Seed weight, seed-coat thickness and hardness varied widely. Scarification with sulfuric acid (98% H 2SO 4) or sodium hypochlorite (14% NaOCl) was followed by germination treatments of deionized water (DI), smoke gas or a combination of gibberellic acid (2.03 mg/L GA 3) and potassium nitrate (34 mg/L KNO 3) during stratification. The commonly used scarification protocols were not effective for many species; but effective scarification exposure was established based on the amount of embryo damage seen with 2,3,5 triphenyl tetrazolium chloride (TZ) viability testing. H 2SO 4 scarification followed by a treatment with KNO 3 and GA 3 during stratification was highly effective for the most species. Two species in subgenus Anoplobatus had a hilar-end hole that allowed rapid germination of unscarified seed. Some species with extremely hard seed coats had little or no germination, and longer scarification times are suggested based on seed size, seed-coat thickness and hardness and viability testing.

Effects of seed traits on the success of direct seeding for restoring southern Thailand’s lowland evergreen forest ecosystem

The success of direct seeding, as a low-cost approach to forest restoration, varies with tree species and seed characteristics. A system to predict which tree species are likely to be suitable for direct seeding would therefore be useful for improving forest restoration projects. Therefore, this study aimed to determine the effects of seed traits on the success of direct seeding to restore tropical forest in southern Thailand. Seeds of 19 indigenous lowland tropical forest tree species were collected, from both the east and west sides of the Thailand peninsular and the following parameters measured: seed size, shape, coat thickness and moisture content. Field trials were established to determine seed germination rates and to calculate a “direct seeding suitability score” for each species, which combined seedling establishment and growth rates. Seed size, shape and moisture content were associated with germination percentage. Species with higher seedling survival tended to have large or intermediate-sized seeds, round or oval seeds and seeds with low or medium moisture content. Only seed coat thickness was significantly correlated with the suitability score (r = 0.65, p 0.4 mm coincided with higher rank suitability score. These conditions successfully predicted the success or failure of direct seeding for 15 out of 19 species tested. Eight tree species are recommended as suitable for restoring lowland evergreen forest ecosystems in southern Thailand, by direct seeding.

Seed morphology and anatomy of the Mediterranean pentamerous species of Erica (Ericaceae)

The species of the "Pentapera group" are distinguished from the rest of the European and Mediterranean Erica L. species by having 5 corolla lobes and sepals instead of 4, and 10 stamens instead of 8. The genus Pentapera Klotzsch was proposed for these taxa but recent studies regards it as part of Erica. Two species are recognised: Erica sicula Guss. and E. bocquetii (Peşmen) P.F.Stevens, and 3 subspecies have been described within E. sicula. This taxonomic treatment is still under discussion and relationships with other species have been poorly discussed. Seed morphology of the 2 species and the 3 subspecies was studied by means of scanning electron microscope techniques. Characters concerning size and shape of seeds, and primary and secondary ornamentation were observed and measured. Anatomy of the seed coat was analysed in 2 populations of E. sicula subsp. libanotica (C.Barbey) P.F.Stevens using a light microscope, and seed coat thickness and cell junctions were measured. Seeds range from 0.45 to 0.8 mm; shape is ellipsoid, oblong, or obovoid with a lateral wing; primary ornamentation is striate while secondary ornamentation shows smooth outer anticlinal walls and indented or smooth outer periclinal walls. Clear differences were found for the studied taxa. The seeds of E. bocquetii have the lowest values for size and lack an indented surface; this is shared with E. sicula subsp. libanotica. E. sicula subsp. sicula has an indented surface and E. sicula subsp. cyrenaica Brullo & Furnari has smaller, rounder seeds. Compared to the rest of the northern Erica species, seed coat sections reveal similarities with E. arborea L. and E. australis L, and seed morphology relate this group with E. ciliaris L. but most of all with E. arborea

Composition of seed soluble carbohydrates and ultrastructural diversity of testa in lupins from the mediterranean region

This article present a comparison of soluble sugar levels in seeds of <em>Lupinus atlanticus</em>, <em>Lupinus cosentinii</em>, <em>Lupinus palaestinus</em> and <em>Lupinus pilosus</em>, <em>Lupinus hispanicus</em> subsp. <em>hispanicus</em> and <em>Lupinus luteus</em> of Juno variety. Considering that sugars are accumulated in embryos, only the embryonic tissues were used for biochemical analyses. Additionally, the share of testa and embryo in seed tissues was evaluated. The seed-coat thickness was measured using scanning electron microscopy. The seed coat had the largest share in seeds of <em>Lupinus pilosus</em> and <em>Lupinus palaestinus</em>, and the least share in seeds of <em>Lupinus hispanicus</em> subsp. <em>hispanicus</em> and <em>Lupinus luteus</em> of Juno variety. In the seed of <em>Lupinus pilosus</em> the thickness of the seed coat was 1100 µm, while in <em>Lupinus luteus</em> it was 300 µm. The analysed <em>Lupinus</em> seeds accumulated from 73 mg/g d.m. (dry matter of seed embryo) to 155 mg of soluble sugars/g d.m. The highest quantity of oligosaccharides of the raffinose series was found in seeds of <em>Lupinus luteus</em>, while the lowest amount in seed of <em>Lupinus palaestinus</em>. Galactosyl cyclitols appeared in largest amount in seeds of <em>Lupinus palaestinus</em> and <em>Lupinus pilosus</em>, appropriately 41.93 and 33.75 mg/g dm. The lowest amount of galactosyl cyclitols appeared in <em>Lupinus atlanticus</em>, <em>Lupinus cosentinii</em> and <em>Lupinus hispanicus</em>.

Physiological-biochemical parameters and characteristics of seed coat structure in lupin seeds subjected to long storage at different temperatures

Seed vigour, viability, the contents of soluble carbohydrates, total protein, albumins, and globulins, as well as seed coat structure, were analysed in yellow lupin (<em>Lupinus luteus</em> L.) cv. Iryd seeds stored for 20 years at -14<sup>o</sup>C, 0<sup>o</sup>C or at room temperature (approx. +20<sup>o</sup>C). Seed storage at room temperature reduced viability (to 2%) and increased seed leachate electroconductivity. Determinations of total proteins showed that protein content was significantly reduced in seeds stored at +20<sup>o</sup>C compared to the other storage regimens. Raffinose family oligosaccharides were the main soluble carbohydrates in seeds stored at 0<sup>o</sup>C and -14<sup>o</sup>C, whereas sucrose dominated in seeds stored at room temperature. Scanning electron microscopy (SEM) of seed surface and seed coat sections revealed appearance of an amorphic layer on the surface of seeds stored at room temperature (not observed in other seeds) and distinct shrinking of macrosclereid layer in seeds stored at -14<sup>o</sup>C. Macrosclereids layer in all seeds was 100 um thick and accounted for 60% of seed coat thickness. The obtained results suggest that for long term storage of lupin seeds at 0<sup>o</sup>C is the most advisable temperature if both costs of storage and seed storability are considered.

Seed morphology and endosperm structure of selected species of Primulaceae, Myrsinaceae, and Theophrastaceae and their systematic importance

Seed size and shape, seed coat surface pattern, seed coat thickness, and endosperm structure were investigated in Androsace septentrionalis, Cortusa matthioli, Hottonia palustris, Primula elatior, Soldanella carpatica (Primulaceae), Anagallis arvensis, A. minima, Cyclamen purpurascens, Glaux maritima, Lysimachia nemorum, L. vulgaris, Trientalis europaea (Myrsinaceae), and Samolus valerandi (Theophrastaceae). Three seed size categories were distinguished on the basis of biometric measurements. Almost all seeds examined were found to be small with an angular shape classified as sectoroid or polyhedral. A new type of seed shape, suboval, was identified for H. palustris. Cyclamen purpurascens seeds differed from seeds of all other species examined because of their large size, subglobose shape, and concave hilar area. Despite the different shape types, the length/width ratio of the seeds examined was constant, while their hilum length/width ratio was a highly variable feature. Three types of seed surface patterns were observed: (1) reticulate, (2) tuberculate with secondary striations, and (3) poroid-alveolate with the presence of a spongy outer layer. For seeds of Anagallis arvensis, A. minima, Cortusa matthioli, Lysimachia nemorum, and Soldanella carpatica, secondary seed sculpture was described. The seed coats of all species examined were two-layered, and great differences in testa thickness were found (9.9–128.6 μm). In general, seeds of the Myrsinaceae species were more often characterized by thick testa. Different proportions in thickness of the inner and outer testa layers were observed. In seeds with reticulate seed patterns, the inner testa layer was twice to several times thicker than the outer layer, while the opposite proportions were observed in seeds with the tuberculate or poroid-alveolate seed sculpture pattern. In seeds of all species examined, oxalate crystals were present on the surface of the inner testa layer. Thus, the presence or absence of oxalate crystals in testa is not a feature distinguishing species with angular or subglobose seeds. Four types of endosperm structure were identified according to the thickness of the endosperm cell walls and the relief of their inner surface: (1) with evenly thickened and smooth cell walls, (2) with evenly thickened cell walls and circular or helical thickenings on their inside surfaces, (3) with very thick, but not evenly thickened cell walls with constrictions (“pitted”), and (4) with very thin papery and undulate cell walls. There is no rule concerning the seed shape, type of the seed sculpture, testa thickness, or endosperm structure that corresponds to the family affiliation of the species examined.

Integration of invasive Opuntia spp. by native and alien seed dispersers in the Mediterranean area and the Canary Islands

The success of many alien plant species depends on mutualistic relationships with other species. We describe the assemblage of seed dispersers on three species of alien Opuntia invading Mediterranean and Macaronesian habitats, and examine the quality of such plant-animal interactions. We identified vertebrates consuming O. maxima, O. dillenii and O. stricta fruits by direct observation and collecting droppings and pellets. Phenology of the alien species, as well as that of coexisting native species, was monitored for an entire year. Germination tests of ingested and non-ingested seeds were performed both in the greenhouse and in the field. Seed coat thickness and viability were also measured for all treatments. A great variety of taxa, including reptiles, birds and mammals actively participate in the seed dispersal of Opuntia. Phenology of Opuntia fruits in Menorca and Tenerife overlaps with only a few native fleshy-fruited plants present in the study areas, which suggests an advantage for the invader. Most seeds germinated during the second year of the experiment, independently of the effect produced by the dispersers’ guts. We found great variation in the germination percentage of Opuntia after gut passage and in the effects of ingestion on seed coat thickness. Seed viability was somewhat reduced after gut passage compared to manually depulped seeds. Our results show how different Opuntia species are integrated into native communities by means of mutualistic interactions, with both native and alien dispersers. Although with heterogeneous effects, either type of disperser potentially contributes to the spread of these alien cacti in the recipient areas.

Seed mortality in the soil is related to seed coat thickness

AbstractModels that quantify the effects of cropping systems on weed dynamics are useful tools for testing innovative cropping systems. In these models, seed mortality in the soil is a key parameter to account for the cumulated effect of cropping systems over time via the soil seed-bank. Since seed mortality is difficult to measure, our objective was to develop a method to estimate it from easily accessible information. Seeds of 13 weed species were buried 30 cm deep in fields and were recovered regularly for 2 years to measure their viability. Seed mass, dimensions, shape, and protein and lipid contents as well as coat thickness were measured. To estimate seed mortality of species not included in the study, we searched for relationships between mortality rates and seed traits. Seed viability mainly decreased during the second year of burial, with mortality rates ranging from 0.01 to 0.63 seeds·seeds− 1·year− 1, depending on the species. Seed mortality decreased with increasing seed coat thickness. No correlation was found with other measured traits or with seed persistence data in the literature. These results were confirmed when the effects of phylogenetic relatedness with phylogenetically independent contrasts were included. The thickness of the seed coat, which varied between 17 and 231 μm over the range of species studied, can protect the seed from external attacks in the soil and slow down seed decay. This trait can be easily measured via X-ray images and could be used to estimate the seed mortality rate for a wider range of species.

Pengaruh Variasi Ukuran Biji Terhadap Perkecambahan Acacia Fauntleroyi (Maiden) Maiden and Blakely

The aim of this study was to investigate to what extent are germination of A. fauntleroyi affected by seed size. Does pre-treatment improve germination? Under what temperature regime does most seed germinate? Three seed size classes (small, medium and large) were chosen. Seeds were pre-treatments either at ambient, 50°C, 75°C or 100°C and incubated at 15°C or 30°C. Then, number of seed that germinate and speed of germination were measure. Five seeds representing each of small, medium and large seed sizes were also selected and the seed coat thickness measured. Seed size, pre-treatment temperature and incubation temperature all affected the number of seed that germinated. Pre-treatment temperature affected germination more than incubation temperature. Incubation temperature affected germination more than seed size. The interaction of seed size and pre-treatment temperature was stronger than that between seed size and incubation temperature. Small seeds produce less germination than medium or large seeds, however small seed germinated sooner. Seed coat thickness varied among seed sizes. Thinner seed coats occur in smaller than larger seeds.

Genetic analysis of agronomic traits in a wide cross of chickpea

A genetic map composed of 10 linkage groups (LGs) covering 848.1 cM was constructed from a recombinant inbred line population from the cross Cicer arietinum (ICCL81001) × Cicer reticulatum (Cr5-9). The lines were genotyped with random amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR) and sequence tagged microsatellite site (STMS) markers, and phenotyped with respect to flowering time, flower colour, growth habit, seed size, seed coat reticulation, seed coat thickness and reaction to infection by two races of fusarium wilt. Segregation distortion was observed for 35% of markers, mainly clustered on LG4, LG7 and two unassigned linkage groups. Rs/ rs (seed coat reticulation) together with a quantitative trait locus (QTL) accounted for >50% of the variation for seed coat thickness. Both Hg/ hg (growth habit) and a flowering time QTL mapped to LG3A. The STMS marker TA142 was closely linked to this QTL. Two QTL for seed size were detected—one on LG4 linked to STMS markers GAA47 and STMS11, and the other on LG2 linked to STMS TA110. Two tightly linked QTL on LG2 closely linked to STMS marker TA59 controlled the resistance to both races of the pathogen causing fusarium wilt.