Observations on the effects of browning (Polyspora Lini Laff.) of flax on seed production

An account is given of observations made on the effects on seed production of the incidence of the browning phase of the disease of flax caused by Polyspora Lini Laff. The work was carried out during three seasons.
Disinfection of seeds before sowing exercises an effect on the average weight of the well-developed seeds harvested, and the results obtained show that the intensity of the attack of browning in crops is inversely correlated with the weight of 1000 well-developed seeds. When poorly developed seeds are separated from the remainder at harvest, evidence obtained in one year suggests that the percentage number of such seeds may be directly related to the incidence of browning in the crop. It was found in each of two years that more of the poorly-developed than of the well-developed seeds were contaminated with P. Lini. Evidence available for one year suggests that the viability of well-developed seeds is not related to the incidence of browning.     

Black scurf and stem canker of potato (Corticium Solani Bourd. & Galz.): Further field studies on the use of clean and contaminated seed potatoes and on the contamination of crop tubers

Black scurf and stem canker of the potato were investigated in field trials in contaminated soil at Warburton, Cheshire, to determine the effect of planting clean and contaminated seed (vars. Arran Banner and Majestic) on crop yield and on the contamination of the crop tubers.
Black-scurf contamination was prevalent on crops grown from clean seed and was not significantly different from that occurring on plots planted with contaminated seed. It was severe on early-dug tubers, but was more severe on late-dug tubers. Produce grown with and without stable manure was heavily contaminated.
Contaminated seed caused a check to tuber formation and an appreciable increase in stem canker and in the number of primary shoots killed. Nevertheless, the yields from the manured, contaminated seed plots were satisfactory and were not lower than those from the clean-seed plots. There was no relation between the yield and the amount of black scurf on the produce.
The results of a trial made in a field which had been in grass for at least 43 years, suggested that the soil contained little, if any, Corticium Solani. Heavy contamination occurred on tubers grown under relatively dry soil conditions.
In all the trials misses and wilted shoots caused by Corticium were rare and there was no premature yellowing or death of the haulms on the clean or contaminated seed plots.
The evidence obtained in the four seasons from 1941 to 1944 indicates that in this country satisfactory yields of early maincrop and maincrop varieties may be obtained despite the prevalence of C. Solani in the soil and on the seed, provided the soil and cultural conditions are reasonably good.     

A study of the longevity of the seed-borne parasites of flax in relation to the storage of the seed

From 1939 to 1947 observations were made on the longevity of Colletotrichumlinicola Pethybr. & Laff., Polyspora Lini Laff., Botrytis cinerea F t ., and Phoma sp. occurring to different extents as seed-borne parasites of naturally contaminated samples of flax seed held under ordinary conditions of storage. The results obtained, together with the germination capacity of the seed estimated on different occasions during storage, are given and show that the longevity of the fungi considered varies within the following limits: Colletotrichum linicola , 26–69 months, Polyspora Lini , 16–55 months, Botrytis cinerea , 16–40 months and Phoma sp. 27–43 months. The data provide grounds for suggesting that the higher the percentage number of seeds contaminated with Polyspora Lini the longer will be the time taken for the death of the parasite to occur. As the time taken for the deactivation of the parasites is normally much longer than that for which flax seed for sowing purposes can be safely stored, prolonged storage of the seed does not commend itself as a likely method for securing the control of the diseases caused by seed-borne fungi. The germination capacity of the seed was normally found to be seriously impaired by the time all the parasites had died.     

Black scurf and stem canker of potato (Corticium Solani Bourd. & Galz.)

Black scurf and stem canker of the potato was investigated in field trials on infected soil at Warburton, Cheshire, to study the effect of planting clean and contaminated seed, and the relation between the dates of planting and lifting and the contamination of the crop tubers.
Black scurf was prevalent on crops grown from clean seed but was more severe on crops raised from contaminated seed. Under conditions favourable for the disease the yields from clean and contaminated seed were satisfactory and were not significantly different. Young shoots of plants from contaminated seed were severely attacked and tuber formation was checked; these results were not obtained on clean seed plots.
More black scurf occurred on late-dug crops; on early-dug plots the disease, although almost absent in 1941, was prevalent in 1942. Late planting failed to reduce appreciably the amount of black scurf.
Variety trials included Arran Banner, Kerr's Pink (two vigorous varieties), King Edward and Majestic (two less vigorous varieties). All were heavily infected and each recovered well from an attack on the young shoots.
Inoculation of the seed at planting time did not affect the results; in all trials, misses and wilted shoots caused by Corticium were rare and there was no relation between the yield and the amount of black scurf on the crop tubers.
The results indicate that the disease causes little, if any, loss under farm conditions.     

Detection of Seed-Transmitted Brome Mosaic Virus by ELISA, Radial Immunodiffusion and Immunoelectroblotting Tests

The extent of contamination of wheat seedlots by brome mosaic virus (BMV), and the possible transmission of the virus through seed, were investigated by radial immunodiffusion (RID), enzyme linked immunosorbent assay (ELISA), and enzyme-assisted immunoelectroblotting (IEB) tests. BMV was purified from seed washings, and from plants grown from contaminated seed. All three serological tests proved of value in detecting contaminated seeds, while ELISA and IEB were especially useful in detecting virus in infected plants grown from such seed. Rhopalosiphum padi aphids were shown to increase the incidence of BMV infectLon in seedling batches containing a few seed-infected plants. The implications of these findings for wheat breeding schemes are discussed.     

The role of seed-tuber and stem inoculum in the development of gangrene in potatoes

To determine the relative importance of seed tubers and stems as sources of inoculum for potato gangrene in progeny tubers, different levels of inoculum of Phoma exigua var. foveata were established in field experiments by planting rotting or contaminated seed tubers and by inoculating stems shortly before haulm desiccation. The pathogen was only occasionally detected by isolation from inside green stems in June and July on plants growing from contaminated but unrotted seed. The incidence of pycnidia on desiccated stems increased with increasing concentration of inoculum contaminating seed tubers and with increasing time interval between desiccation and harvest. Stem infection was probably derived from inoculum on seed tubers spreading via the soil to the stem bases. Stem inoculation of plants growing from uninoculated or uncontaminated seed greatly increased both the gangrene potential of progeny tubers (defined as % wounds with gangrene after uniformly damaging tubers and storing them at 5°C for 12 wk), and tuber contamination (defined as % wounds with gangrene after spreading tuber-borne soil onto test tuber slices and storing them at 5°C for 8 wk). However, when stems of plants growing from rotting or contaminated seed were cut at ground level and removed before desiccation, gangrene potential of progeny tubers was only slightly less than that of tubers from untreated plots. There was no evidence that soil inoculum or aerial spread played a significant role in disease development. Gangrene potential and contamination of progeny tubers were related to Contamination levels on seed tubers. Some transmission also occurred from rotted seed tubers to progeny. Inoculum levels around progeny tubers increased rapidly after desiccation even in plots where stems had previously been cut at soil level and removed to eliminate pycnidial development above ground as a source of inoculum. Both gangrene potential and contamination of progeny tubers were greater on cv. Ulster Sceptre than on cv. Pentland Crown. The results showed that the inoculum on seed tubers, whether from rots or surface contamination, contributed more to the contamination of progeny tubers at harvest than did the inoculum from pycnidia on stems following desiccation of the haulm.     

The extent and survival of contamination of potato stocks in Scotland by Erwinia carotovora var. carotovora and E. carotovora var.atroseptica*

The following results were obtained when fifty-seven bulk and crate-stored commercial seed potato stocks from the East of Scotland were examined in 1966-8 for contamination by pectolytic Erwinia spp. (1) Most tubers of all the cultivars and stocks examined, irrespective of whether they were obtained from blackleg-infected or blackleg-free crops, were contaminated with E. carotovora; (2) some 80% of the Erwinia isolates obtained were identified as var. atroseptica, the rest being var. carotovora; (3) the organisms survived in and on tubers for 6–7 months of bulk storage over the winter and up to planting time the following spring; (4) contrary to what is generally thought, the high incidence of contamination of all stocks, while suggesting that the seed itself is the major source of E. carotovora for the growing crop, emphasizes that other factors affect manifestation of blackleg in the field and soft rot in store.     

Studies on the seed-borne phases of dark leaf spot Alternaria brassicicola and grey leaf spot Alternaria brassicaeof brassicas

Tests in Britain on samples of basic and commercial Brassica oleracea seed between 1976 and 1978 showed that many lots were infected with Alternaria brassicicola. A. brassicae was uncommon in basic seed in these years and in commercial seed harvested in 1976 and 1977 but was frequent in seed harvested in 1978. Most affected seeds were contaminated by surface-borne spores and mycelium of A. brassicicola but many were internally infected by the fungus situated within the seed-coat and in some seeds in the embryo tissues. Superficial contamination by the fungus declined rapidly after 2 yr in cabbage seeds stored at 10 °C, 50% r.h. but internal infection persisted for up to 12 yr. In some samples, internal infection was commonly associated with small shrivelled seeds. Surface contaminated and internally infected seeds transmitted the disease but seedling infection was more closely correlated with the latter.     

Hydrocarbon Tolerance Correlates with Seed Mass and Relative Growth Rate

The abundance and vegetation cover of plant species with different seed masses growing on crude oil contaminated and uncontaminated field plots were examined. In addition, seedling mass and relative growth rate of eight plants in four seed mass classes were compared in contaminated and uncontaminated soils. Species producing seed in the second largest seed class (1.0 to 9.9 mg) were more common on contaminated than uncontaminated field plots. Species with seed in the smallest seed class (< 0.1 mg) were less common on contaminated than uncontaminated plots. Species with seed masses between 1.0 and 9.9 mg formed 15% more vegetation cover, and those with masses between 0.1 and 0.9 mg formed nearly 15% less vegetation cover on contaminated compared to uncontaminated field plots. In the growth chamber, species with larger seeds produced approximately 25% less seedling mass and exhibited a 32% reduction in relative growth rate, when grown in contaminated compared to uncontaminated soil. Small-seeded species had reductions of 95% in seedling mass and 72% in relative growth rate. Species with the highest relative growth rates in uncontaminated soil had the lowest seedling mass in contaminated soil. Seed mass and relative growth rate were negatively correlated (r = 0.866).     

国家库贮藏20年以上种子生活力与田间出苗率监测

对34种作物1.4万多份的国家库贮存种子进行了生活力监测,结果表明,贮存20年后,92.9%被监测种子的发芽率仍保持在85%以上,但有155份种子（占被监测份数的1.1%）出现了明显的下降（发芽率从80%以上降至70%以下）。发芽率显著下降的作物包括蚕豆、红小豆、黄麻、蓖麻、甜菜、西瓜、烟草、牧草。小麦等8种作物2078份种子的田间出苗率调查表明,所有种质均有出苗,但有8份种质的出苗率低于10%。出苗率与入库初始平均发芽率存在差别,平均出苗率最高的作物为普通菜豆86.2%,比该批入库初始发芽率平均值低9.3%;平均出苗率最低作物为谷子39.2%,比该批种子的入库初始发芽率平均值低51.3%。总体而言,国家库内保存的作物种子中,多数可安全保存20年以上,尤其是水稻等禾谷类作物种子,但对于蚕豆、红小豆等平均监测发芽率出现显著下降的作物种子需要增加监测频率,以确保种子的长期安全保存。     

The performance of carrot seeds in relation to their viability

The germination and emergence characteristics, and early seedling growth, of carrot seeds cv. Chantenay red-cored from different sources with a range of germination from 54–94%, was compared. Seeds from protected crops (mean temperature of growth 21°C, r.h. 45–70%) gave higher percentage germination than those from crops grown outdoors (mean temperature 15°C, 70–100% r.h.). Germination was also higher from mature (seed moisture content at harvest 20% or lower) than immature seed (seed moisture content at harvest between 20 and 60%). High percentage germination (>90%) was associated with low mean germination times and low spreads of germination times whilst the reverse was true for low percentage germination. Similar relationships were found for seedling emergence characters in the field although a lower proportion of the viable seeds produced seedlings from slowly than rapidly germinating seed lots. In general, seed lots having a low percentage germination gave greater variability in plant weight than those of higher percentage germination. There was no effect of seed source on radicle or shoot relative growth rates or on post-emergence seedling growth rates.     

林木种子园花粉污染与防治措施

林木种子园花粉污染是影响种子园种子遗传品质的重要因子,由于野生同种花粉进入种子园而增加遗传损失。本文综述了国内外林木种子园花粉污染研究的概况、污染水平、影响污染水平的因子和减少污染的措施。研究表明：DNA分子标记在分析种子园交配动态和种子园管理效果方面非常有效（例如,cpDNA、RAPD和SSR）;种子园污染水平比预期的更高;花粉产量好像对污染水平没有影响;空间和生殖隔离也没有产生预期的效果。目前,人工辅助授粉和疏伐是减少花粉污染的两种有效措施。为了改善种子园林木的亲本平衡,人工处理技术的使用,例如：赤霉素A4/7处理技术和无性繁殖技术在种子园很受欢迎。污染程度其他方面的研究工作仍在继续,本文提到的基因流的研究。并对我国种子园花粉污染研究和花粉管理提出建议：当分析种子园花粉污染时,涉及到花粉基因型自然的（花粉扩散）、生理（开花时间）和花粉生活力等因素都应该被考虑。     

The prevention of seed-borne diseases of flax by seed disinfection II. Comparison of the dusting, short wet and fixation methods of treatment

Suitable organo-mercury preparations applied by the short wet method of seed treatment and organo-mercury powders, of the type used for treating cereal seeds, fixed to the seed with water by the fixation method of treatment, gave as satisfactory control of seedling blight and better control of stem break and browning than a proprietary dry fungicide containing tetra-methyl thiuram disulphide (Nomersan) applied at the rate of 12 oz./cwt. of seed.
Treatment of seed heavily infected with Polyspora Lint using an efficient fungicide resulted in highly significant increases in crop and fibre yields, while in the case of seed heavily infected with Colletotrichum Lini similar treatments significantly increased the yield of fibre but not the crop yield. Some treatments significantly increased the crop and fibre yields even when the seed used was only slightly contaminated with P. Lini and C. Lini. The results presented support the suggestion that effective treatment of the seed may produce an increase of fibre not directly attributable to the prevention of seedling blight or stem break and browning but which may be explained by a general beneficial effect due to seed disinfection.
The results obtained suggest that no treatment consistently affected crop establishment in the field.     

A simple, sensitive, and rapid method for detecting seed contaminated with highly virulent Leptosphaeria maculans.

A primer-directed DNA amplification polymerase chain reaction assay for detection of seed contaminated with highly virulent Leptosphaeria maculans was developed. The primers were derived from a 5,238-bp repetitive sequence present only in the highly virulent isolates of the fungus. A procedure for isolating DNA from organisms infesting germinating seed was also developed. Seeds were added to liquid fungal minimal medium, and the culture was incubated for 3 days at room temperature with shaking. The organisms were collected from the cultures by centrifugation and lysed with a combination of sodium dodecyl sulfate and proteinase K. The DNA was extracted with organic solvents and with a high-salt-cetyltrimethylammonium bromide solution. It was also precipitated with a low-salt-cetyltrimethylammonium bromide solution. The extensive treatments used for minimizing polysaccharide contamination greatly improved the reliability of the assay. The minimum contamination level (2 of 1,000 seeds) that was tested was successfully detected with this DNA isolation procedure. The reliability of the assay was 96% at the 1 to 2% level of seed contamination. The described method is less laborious and requires only 4 to 5 days for completion in comparison to the 11 to 22 days required for the currently employed methods. In addition, large sample sizes can be easily handled, thus reducing the probability of contaminated seed escaping detection.     

The Influence of the Inoculum Source of Rhizoctonia solani on Development of Black Scurf on Potato

Rhizoctonia solani, the causal agent of stem canker and black scurf on potato, survives as sclerotia on tubers, in soil and in plant residues. The objective of the present study was to evaluate the importance of inoculum source on disease development. Disease‐free minitubers and seed tubers contaminated with low levels of R. solani were planted in fumigated or artificially inoculated growth mixture in greenhouse experiments. Black scurf incidence and severity were significantly higher when the inoculum was present in both seed tubers and soil, compared with either of them separately. The severity of disease symptoms on the subterranean parts of the plant also were significantly higher in plots where both seed tubers and soil were contaminated, compared with plots where the inoculum source was either the seed tubers or the soil. Thus, both major sources of inoculum, seed tubers and soil, are important in disease development. However, when both sources are present, black scurf incidence and severity are increased, leading to economical damage to tuber yield and quality. Additional results from field trials support these findings. Disease incidence and severity on daughter tubers were correlated with levels of contamination in seed tubers and soil. When seed tubers and soil were heavily infested, the levels of black scurf incidence and severity on daughter tubers were very high; when seed tuber and soil infestation were very low, black scurf incidence and severity on progeny were also lower. Disease levels were reduced by in‐furrow fungicide treatment, but were less effective when the initial levels of the fungus on the seed tubers and in the soil were high.     

THE SPREAD OF BEET YELLOWS AND BEET MOSAIC VIRUSES IN THE SUGAR-BEET ROOT CROP I. FIELD OBSERVATIONS ON THE VIRUS DISEASES OF SUGAR BEET AND THEIR VECTORS MYZUS PERSICAE SULZ. AND APHIS FABAE KOCH

A survey of aphids and virus diseases of sugar-beet root crops in eastern England was made between 1940 and 1948. Prior to 1943 the observations were made on fertilizer experiments; from 1943 onwards they were made on commercial fields selected for position in relation to beet and mangold seed crops. The incidence of beet yellows increased with increasing numbers of Myzus persicae , but not of Aphis fabae. The relation with M. persicae was sufficiently close to suggest that it is the most important, possibly the only important, vector of beet yellows virus. Beet mosaic virus also increased with increasing numbers of M. persicae , but the relation was not close enough to exclude the possibility of other vectors.
Numbers of A. fabae on sugar beet were slightly, but consistently, depressed by the use of salt as a fertilizer. Other fertilizers had variable effects. Neither aphids nor virus are likely to be greatly affected by fertilizers.
Beet yellows is most prevalent in areas where seed crops are grown, but within these areas nearness to individual seed crops did not appear to increase its incidence. M. persicae were more numerous on sugar beet in seed-crop areas than elsewhere, and this alone might account for the prevalence of yellows. Beet mosaic virus is more closely associated with seed crops than is beet yellows. It is most prevalent near to seed crops within the seed-crop areas.     

油菜对3种作物种子萌发和幼苗生长的化感作用

油菜是我国重要的绿肥作物,除增加土壤肥力外,对后茬作物也有一定的化感作用。本文研究了不同浓度油菜浸提液(0.025、0.05和0.1 g·mL^-1)对3种作物(燕麦、玉米和向日葵)种子萌发、幼苗生长及生理生化的影响。结果表明: 油菜浸提液对3种作物种子发芽率的影响不显著,但对燕麦有“低促高抑”的趋势,对向日葵有抑制的趋势。油菜浸提液高浓度处理对燕麦幼苗根和茎长、玉米幼苗茎长以及向日葵幼苗根长起抑制作用,低浓度处理对玉米幼苗根茎长起促进作用。燕麦和向日葵幼苗在浸提液浓度为0.05 g·mL^-1时蛋白质含量最大,玉米在0.025 g·mL^-1时蛋白质含量最大,显著高于对照。3个浓度下,向日葵脯氨酸含量均显著降低,玉米脯氨酸含量在浓度为0.05 g·mL^-1时显著高于对照。玉米过氧化物酶(POD)活性在浸提液浓度为0.05 g·mL^-1时最大,向日葵POD活性在浓度为0.025 g·mL^-1时最大,与对照有显著差异,其余浓度处理与对照无显著差异。油菜浸提液浓度为0.025 g·mL^-1时显著降低了燕麦超氧化物歧化酶(SOD)活性,3种作物幼苗过氧化氢酶(CAT)活性与对照均无显著差异。加入油菜浸提液后,向日葵幼苗丙二醛(MDA)含量在浓度为0.1 g·mL^-1时显著增加,玉米幼苗MDA含量在不同浓度处理下均显著低于对照。综合分析,油菜浸提液对向日葵的化感抑制作用最强,其次为玉米、燕麦。     

A study of the relationship between seedling characters and rate of germination within a seed lot

The relationship between seedling characters and germination rate within a seed lot was studied in cauliflower, leek and onion seeds. Newly germinated seeds were selected after successive days of imbibition at 20°C and placed on slope tests to assess early seedling growth. In all three species seedling length decreased and the coefficient of variation of those seedling lengths increased with increasing number of days of imbibition required for germination. Slow germinating seeds in all three species produced fewer normal healthy seedlings than faster germinating seeds. The relevance of these results to pre-germinated seed sowing techniques is discussed.     

Chelator-buffered nutrient solution is ineffective in extracting Ni from seeds of Alyssum

Hyperaccumulator species of the genera Alyssum can accumulate 100 times more Ni than normal crops and are therefore used for phytomining and phytoextraction of nickel contaminated soils. Basic studies on the physiology and metal uptake mechanisms of these plants are needed to increase efficiency and uptake capacity of Nickel (Ni) by hyperaccumulators. Recent attempts to disclose if those hyperaccumulator species require higher Ni level than normal plants failed because of the high Ni content in the seeds (7000-9000 microg g(-1)). In this study, we attempted to use chelator buffered nutrient solution to deplete Ni from the seed/seed coat and to obtain low Ni seedlings of Alyssum cultivars to be used in physiology studies. HEDTA-buffered nutrient solution did not deplete Ni from the seeds, perhaps because Ni was mainly localized within the seedling embryonic tissues with greatest Ni enrichment in the cotyledons and hypocotyls. We could not observe any positive correlation between seed fitness and germination capacity with seed Ni content. Investigation of nickel localization in Alyssum seeds using synchrotron X-ray microfluorescence (micro-SXRF) showed that nickel is localized in the embryonic tissues with greatest Ni enrichment observed in the cotyledons and hypocotyl.     

The combined effects of a newly designed dibber drill, irrigation and seed covering treatments on lettuce and calabrese establishment

A comparison was made between seedling establishment following sowing with the Mk2 dibber drill and a conventional coulter drill at three sowing occasions with both lettuce and calabrese. Different seed covering materials used to cover dibber-drilled seed were also compared. With lettuce, the rate and uniformity of seedling emergence and the numbers of seedlings emerging were greater following sowing with the dibber drill than with the coulter drill. Seedling establishment was further improved with irrigation especially when seeds were sown with a small quantity of the hydrophillic polymer, Alcosorb, which avoided associated problems of increased soil impedance. Alcosorb was a more effective seed cover than a peat and vermiculite mix and better suited for mechanical metering. Results indicate that the dibber drill can be considered as a realistic and cheaper alternative to transplanting for establishing later-season lettuce crops. With calabrese, however, percentage seedling emergence on all dibber-drilled plots was lower than that on plots sown with the coulter drill. This result may have been due to seed-coat damage caused as seeds are plunged into the soil during sowing with the dibber drill.