EFFECT OF TETRACHLORONITROBENZENE ON THE SPROUTING AND CROPPING OF POTATO TUBERS

Potato tubers dusted with a preparation containing 3% tetrachloronitrobenzene (TCNB) and kept in a nearly closed container in the laboratory showed reduced sprouting. The reduction was greater the lower the temperature and the earlier the application of the dust; it was less marked with tubers lying on a moist substratum. After long exposure, and especially at higher temperatures, sprouts of treated tubers tended to show a 'witch's-broom' appearance. The repressive effect of TCNB on growth rate disappeared as soon as the tubers were brought into ordinary air. To a certain extent the action of TCNB was antagonized by treatment of the tubers with ethylene chlorhydrin.
Replicated field experiments over three seasons, with four potato varieties, gave a measure of the check to bulking of the crop which is brought about by winter storage of seed tubers in presence of TCNB. This check was eliminated by airing the tubers before planting, the time necessary for this depending on conditions. An airing period of about 6 weeks, in an unheated greenhouse (apart from sun- heat) was found to be sufficient for this purpose.
The speed of emergence of the variously treated batches was closely correlated with the yields produced, especially in the earlier liftings.
The average number of shoots per plant was significantly increased by the dust treatment and this was reflected in a higher seed/ware ratio in the mature or late-lifted crop.
There was no evidence that the delay in sprouting brought about by TCNB was due to an effect on the respiration rate of the dormant tubers.
The concentration of active principle was materially diminished in treated clamps after the period ( c. 5 months) of winter storage. Estimates were also made of the persistence of TCNB on exposed surfaces in still and in moving air.     

THE USE OF TETRACHLORONITROBENZENE ISOMERS ON POTATOES

In laboratory and field experiments from 1952 to 1955, 2:3:5:6-tetrachloro-I-nitrobenzene (tecnazene) delayed the development of sprouts on treated potato tubers, and 2:3:4:6-TCNB retarded sprout development in two laboratory experiments. At the usual commercial rates of application the 2:3:4:5 isomer had no effect on sprout development and very little effect at higher rates. The crop from 2:3:5:6-TCNB-treated seed tubers usually contained a higher proportion of small tubers than that from untreated or 2:3:4:5-TCNB-treated seed. Marketable yield from 2:3:5:6-TCNB-treated seed was sometimes below that from untreated seed, but when this happened the yield from 2:3:4:5-TCNB-treated seed was higher.
Both isomers produced good control of dry rot, Fusarium caeruleum (Lib.) Sacc., on five varieties of potatoes, but did not produce a commercial control on Doon Star. To achieve control, the isomers had to be present at the time of infection. There was some evidence that the development of disease symptoms was delayed in treated, infected tubers. Since 2:3:4:5-tetrachloro-1-nitrobenzene has no sprout depressant action it merits further trial as a fungicidal treatment for seed potatoes.     

The effect on gangrene incidence of dusting seed potatoes with benomyl at time of planting

In 1 out of 2 years' field trials benomyl applied as a dust treatment at time of planting seed potatoes resulted in an increase in potato gangrene in the progeny of both gangrene-free tubers planted in land contaminated with Phoma exigua var. foveata and gangrene-diseased tubers planted in clean land. Gangrene-infected seed tubers treated with benomyl also produced more stems infected with var. foveata than untreated tubers. Two hypotheses are presented to account for this increase in gangrene which does not occur in seed potatoes treated shortly after lifting. In all cultivars tested an organo-mercury dip-treatment increased total numbers of tubers in the seed and chat-size grades without increasing total weight whereas benomyl dust increased the numbers in these grades in Majestic only. The treatment of gangrene-diseased seed with benomyl dust affected neither total weight nor total number of tubers.     

THE INFLUENCE OF PLANTING DATE AND MANURING ON THE INCIDENCE OF VIRUS DISEASES IN POTATO CROPS

Field experiments with Majestic potatoes were made over six years at Rothamsted to test the effects of varying date of planting and manuring on the yield of tubers and the incidence of the aphid-transmitted leaf roll and Y (rugose mosaic) viruses. Yield was increased by early planting, and by all the manures, especially dung. Early planting also usually increased the incidence of virus disease. Different manures had different effects on disease incidence; the average results from all comparisons showed the largest increase in incidence of both viruses from the use of dung; sulphate of ammonia increased the incidence of leaf roll, and muriate of potash that of rugose mosaic. Counts in two years showed that aphid populations were highest on the earlier planted potatoes, and were increased by dung, sulphate of ammonia and superphosphate, but were reduced by muriate of potash.     

ON THE BACTERIA RESPONSIBLE FOR SOFT ROT IN STORED POTATOES, AND THE REACTION OF THE TUBER TO INVASION BY BACTERIUM CAROTOVORUM (JONES) LEHMANN & NEUMANN

Bacterium carotovorum (Jones) Lehmann & Neumann and Pseudomonas syringae van Hall were the only two species of Gram-negative bacteria isolated from rotting potatoes collected from clamps in England in 1945-7. Both were found capable of producing a rot under known conditions, and both were isolated on plates of a pectate-gel medium which is liquefied by these bacteria. Ps. syringae has not been recorded before as causing a rot of stored potatoes. In a slightly different type of rot which was ropy or gassy and often pink in colour, Gram-positive spore-forming bacilli were found, generally associated with Bacterium carotovorum. These bacilli proved to be anaerobes–species of Clostridium –one of which, when inoculated together with Bacterium carotovorum, produced a gassy rot pink in colour.
On infection by Bad. carotovorum the tuber reacts to form a barrier of suberized cells, the extent and efficiency of which depend on temperature and relative humidity. Low temperatures and a low humidity favour the formation of the barrier and eventually of periderm; high temperatures favour the multiplication of the bacteria the advance of which is limited by humidities not reaching saturation. Fluctuations of temperature or humidity may promote a succession of barriers.     

Mint essential oil can induce or inhibit potato sprouting by differential alteration of apical meristem

Sprouting of potatoes during storage, due to tuber dormancy release, is associated with weight loss and softening. Sprout-preventing chemicals, such as chlorpropham (CIPC), can negatively impact the environment and human health. Monthly thermal fogging with mint (Mentha spicata L.) essential oil (MEO) inhibited sprouting in eight potato cultivars during large-volume 6-month storage: the tubers remained firm with 38% lower weight loss after 140 days of storage. The sprout-inhibitory action may be nullified: treated tubers washed with water resumed sprouting within days, with reduced apical dominance. MEO application caused local necrosis of the bud meristem, and a few weeks later, axillary bud (AX) growth was induced in the same sprouting eye. MEO components analysis showed that 73% of its content is the monoterpene R-carvone. Tubers treated with synthetic R-carvone in equivalent dose, 4.5 μl l⁻¹, showed an inhibitory effect similar to that of MEO. Surprisingly, 0.5 μl l⁻¹ of MEO or synthetic R-carvone catalyzed AX sprouting in the tuber. To the best of our knowledge, this is the first report of an essential oil vapor inducing early sprouting of potato tubers. R-carvone caused visible damage to the meristem membrane at sprout-inhibiting, but not sprout-inducing doses, suggesting different underlying mechanisms. After 5 days’ exposure to R-carvone, its derivatives transcarveol and neo-dihydrocarveol were found in buds of tubers treated with the inhibitory dose, suggesting biodegradation. These experiments demonstrate the potential of MEO vapor as an environmentally friendly alternative to CIPC in stored potatoes and as a research tool for the control of sprouting in plants.     

Control of potato tuber dormancy and sprouting by expression of sense and antisense genes of pyrophosphatase in potato

Inorganic pyrophosphate (PPi) is an enzyme involved in sugar metabolism in potato tubers. In our previous study, we isolated an inorganic pyrophosphatase (PPase) gene from potato and obtained the transgenic potato plants transformed with the sense and antisense PPase genes respectively. In the present experiment, the physiological indexes, tuber dormancy, and sprouting characteristics of the transgenic potatoes were analyzed and evaluated. The result showed that the PPase activity and the inorganic phosphate content of tubers were lower in the antisense transgenic plant lines but were higher in the sense transgenic plant lines, compared with wild-type tubers. Soluble sugars, such as glucose, fructose and sucrose increased in transgenic plants that had overexpression of the sense PPase gene, but decreased in the antisense transgenic plant lines, compared with wild-type tubers. Tuber sprouting time of the antisense transgenic plants were delayed for 2 and 3 weeks and reached the 100 % sprouting rate only after 14 and 16 weeks storage compared with the wild-type when tubers are stored under 25 and 4 °C, respectively. In contrast, tuber sprouting time of the sense transgenic plants was earlier by approximately 2 weeks than that of wild-type tubers under these storage temperatures.     

Effects of treating seed potatoes with trace elements on sprouting and microbial spoilage during storage under tropical conditions

Attempts were made to extend the storage life of seed potatoes by treating them with trace elements as antimicrobial and antisprouting agents. In tests to measure the growth of Fusarium oxysporum, and Erwinia carotovora pv. carotovora it was found to be decreased more by iron, copper and zinc than by boron, manganese and molybdenum. Dipping seed tubers in aqueous solutions of trace element salts decreased both sprouting and microbial spoilage during storage at ambient conditions. Field testing at the end of storage proved that treating seed potatoes with ferrous sulphate did not decrease the yield of tubers or increase their iron content. It is suggested that trace elements may be used to extend the storage life of seed potato tubers, in tropical conditions.     

The Metabolism of Fructose Polymers in Plants: II. EFFECT OF TEMPERATURE ON THE CARBOHYDRATE CHANGES AND MORPHOLOGY OF STORED TUBERS OF HELIANTHUS TUBEROSUS L.

It is confirmed that the change in optical rotation of extractsobtained from tubers during dormancy is correlated with theconversion of fructosan to oligosaccharides of lower molecularweight, and that there is an associated increase in the combinedglucose content. Storage at 2° C. both accelerated and greatlymagnified this process; storage at 20° C. considerably depressedit. The change is not initiated or controlled by the dormantbuds. Tubers kept at 20° C. throughout the dormancy periodsprouted to give daughter tubers; new plants did not develop,even after some months. Normal sprouting was induced by keepingthe dormant tubers at 2° C. for 7 weeks.     

EXPERIMENTAL STUDIES ON THE SITE OF PROPAGATION OF THE FERTILIZATION-WAVE IN THE SEA URCHIN EGG

Although the fertilization-wave in the sea urchin egg is generally considered to propagate over the egg surface, there has been no definite evidence to show the site of propagation. The possibility that the wave passes through the endoplasm, not over the egg surface, has not been denied.
A drop of paraffin was injected into an egg, so that the endoplasm was divided into 2 parts by the paraffin drop, the 2 parts being connected only by the egg cortex. When spermatozoa were added to one side of the egg, the fertilization membrane was formed first on this part of the egg and then on the opposite part. This indicates that the egg surface or the egg cortex is the site of propagation of the fertilization-wave and the endoplasm has no direct influence on the propagation.     

DRY-ROT DISEASE OF THE POTATO

A study has been made of the incidence of dry rot in seed potatoes in relation to commercial handling methods, and it has been shown that infection following grading by mechanical reciprocating riddles fitted with bare wire screens is more serious than that following normal handling at harvest or during transport. Hand picking, hand riddling and the use of rubber-spool graders or rubber-coated screens reduced infection by varying amounts. The higher incidence of the disease in 'transported' as against 'home-saved' seed is regarded as being due to machine grading of such stocks some months prior to planting.
Contamination of stores or boxes has not been found to play any material part in the spread of infection under commercial conditions unless tubers are roughly handled during storage. As contact infection has been found to be rare, it is considered that the practice of 'picking over' stocks during the winter to remove diseased tubers is unnecessary and may lead to further infection.
In addition to wounds, lesions of both blight and powdery scab, but not common scab, have been found to be a means of infection.     

应用酶联免疫吸附试验检测马铃薯卷叶病毒

以辣根过氧化物酶标记马铃薯卷叶病毒抗体,采用双抗体夹心ELISA方法鉴定了马铃薯和洋酸浆的茎、叶、根及马铃薯块茎中的马铃薯卷叶病毒(Potato Leafroll Virus,PLRV),结果表明,对提纯的PLRV可测出的最低浓度为25ng/ml,当包被抗体浓度为40μg/ml、酶标记抗体稀释度为1/120时,可测出马铃薯茎、叶和根汁液中的PLRV,感染PLRV的洋酸浆茎、叶和根汁液的消光值,均比无病对照者高二倍以上,虽然感染PLRV的马铃薯休眠块茎维管束组织汁液的消光值高于无病毒对照,且脐部维管束组织消光值高于顶端,但测定打破休眠的感病块茎顶端维管束组织的阳性结果更为可靠和明显。     

REGULATION OF BUD REST IN TUBERS OF POTATO SOLANUM TUBEROSUM L.: I. EFFECT OF GROWTH SUBSTANCES ON EXCISED POTATO BUDS

Excised plugs containing buds from potato tubers were treatedwith 5-µliter droplets of a number of growth-regulatingsubstances. Gibberellin A₃ stimulated sprouting over a widerange of concentrations. Gibberellins A₃, A₄, A₅, and A₇ stimulatedsprouting, and A₆, A₈, and A₉ either had no effect or slightlyinhibited. Extracts of gibberellinlike substances from potatopeelings promoted sprouting. NAA and IAA both promoted sproutingslightly at low concentrations (4 x 10^–8M) but inhibitedsprouting at 4 x 10^–5M. Leaching of plugs resulted indelayed sprouting, and gibberellin restored total sproutingpotential. Plug size influenced rate of sprouting: small plugs(8 mm in diameter) sprouted faster than large (23 mm) plugs,and gibberellin stimulated sprouting slightly faster in thelarger than in the 8 mm plugs. None of the presumed componentsof ß, including cinnamic, chlorogenic, and caffeicacids, and coumarin, convincingly inhibited sprouting; in fact,they stimulated sprouting at almost all concentrations tested.5- Fluorouracil (5-FU) inhibited sprouting only slightly; andgibberellin completely or partially promoted sprouting in plugspreviously treated with 5-FU. Failure of 5-FU to inhibit sproutingwas considered to be the result of slow penetration of the inhibitorinto the potato bud. The potato "eye" bioassay is deficient in certain aspects, especiallyin view of the inconsistent rates of sprouting between experimentsand of nonspecificity. The results of this study, however, donot obviate the use of potato buds as a bioassay for inhibitorsof sprouting. ¹This research was supported in part by United States PublicHealth Service Grant EF-61. ²Present address: Department of Botany, Hebrew University, Jerusalem,Israel. ³Present address: U.S.D.A.-A.R.S., Department of Agronomy, Universityof California, Davis, California, U.S.A.     

Dry rot of potato [Fusarium caeruleum (Lib.) Sacc.]. Investigation on the sources and time of infection

Inoculation with soil samples proved that the fungus causing dry rot is frequently present in field soils in Cheshire and in soil adhering to imported seed tubers. The fungus was viable in soils having a wide range of p H values and in fields which had not grown potatoes for 5-6 years. Other sources of infection include lofts, used sacks, seed boxes, diseased tubers, and knives used for cutting seed potatoes.
Bruised tubers stored in heavily contaminated boxes developed much dry rot; far less disease occurred in unbruised tubers. In boxes containing own-saved seed, healthy tubers in contact with diseased ones remained sound. Bruised tubers in contact with, or contaminated by, diseased tubers contracted dry rot. Cutting seed with a contaminated knife increased the disease seven-fold.
Inoculation of tubers attached to the parent plant showed that little or no infection occurred before lifting. In field trials severe dry rot developed in several varieties 6-8 weeks after lifting.
The results are discussed in relation to seed treatment.     

Persistence of Phoma exigua xar. foveata and Polyscytalum pustulans in dry soils from potato stores in relation to reinfection of stocks derived from stem cuttings

The incidence of Phoma exigua var. foveata and Polyscytalum pustulans in dry soil and dust from potato stores was assessed at 10 farms in Scotland producing virus-tested stocks of seed potatoes derived from stem cuttings (VTSC). Samples were collected on three occasions during 1976: during the storage period (February-March), soon after the potatoes were planted (May) and just before the new crop was lifted and stored (August-October). Both pathogens were detected at all three sampling times but P. exigua var. foveata was more frequently detected at the last one than P. pustulans. Soil and dust from various sites within the stores, such as floors, ledges, graders and boxes, were contaminated by these pathogens. Propagules of both pathogens remained airborne for at least 12–17 min after the floors were swept. P. exigua var. foveata remained viable for at least 16 months in dry soil from tuber surfaces stored at 4–6°C. When VTSC tubers were dusted before planting with a dry store soil contaminated by P. exigua var. foveata the gangrene potential of the progeny tubers was much greater than that from untreated tubers or from tubers treated with an uncontaminated soil. The role of inoculum surviving in dry soil is discussed in relation to reinfection of VTSC stocks.     

Tissue distribution and change in potato starch phosphorylase mRNA levels in wounded tissue and sprouting tubers.

Starch phosphorylase has been cloned from a lambda gt10 cDNA library of potato tuber mRNA. Selected recombinants have been used to demonstrate that phosphorylase mRNA is most abundant in tubers but is also detectable in stolon, root, stem and leaf tissue. The level of phosphorylase mRNA was greatly reduced in wounded stem and tuber tissue. The wounding-induced decrease in phosphorylase mRNA levels is not reversed in the presence of sucrose or mannitol. Regional differences are described in the levels of phosphorylase and patatin mRNA in different parts of the tuber and in the shoot of sprouting potatoes.     

EFFECTS OF ENVIRONMENT OF PARENT AND GRANDPARENT GENERATIONS ON TUBER PRODUCTION BY POTATOES

Went , F. W. (Missouri Botanical Garden, St. Louis.) Effects of environment of parent and grandparent generations on tuber production by potatoes. Amer. Jour. Bot. 46(4): 277–282. Illus. 1959.—Potato tubers have very different potentialities of producing tubers on plants of the next generation, according to the growing conditions of the parent plants. When these were grown at cool temperatures, the tuber yield not only of these plants, but also of the following generations, was much higher than when they were grown under warm conditions. Differences in morphology and taste of the tubers as a result of differential temperature treatment of the parent generation are described as well.     

Temperature and Light Requirements for the Sprouting of Chilled and Unchilled Tubers of the Purple Nutsedge, Cyperus rotundus

Mature and immature tubers of purple nutsedge (Cyperus rotundus L.) chilled at 0°C in dry and wet conditions, were sprouted along with fresh, unchilled tubers over a range of temperatures (10°C-45°C) in light and darkness. Fresh immature tubers showed a high sprouting percentage at all temperatures between 20°C and 40°C, while the mature ones did so only at 30°C and 35°C. Chilling of dry tubers stimulated early sprouting and increased the maximum sprouting percentage of both the mature and immature tubers. Dry chilling also lowered the limit of favourable temperatures to 15°C in the case of mature tubers. Chilling of wet tubers had a depressing effect and no sprouting occurred below 30°C. At all temperatures, light apparently favoured the sprouting of both the mature and immature tubers (except mature wet-chilled ones at 35°C and 40°C). Immature tubers showed relatively higher sprouting percentage than the mature ones, both in light and darkness. Alteration of temperature requirements due to dry and wet chilling of the tubers is regarded as significant and functional in relation to the ecology of the species.     

FIELD TRIALS OF THE EFFECT OF ALDRIN ON CLUBROOT OF SUMMER CABBAGE

Field experiments were carried out from 1956 to 1958 on the effect of soil applications of aldrin on clubroot disease of summer cabbage. In the first two seasons the compound was applied either as a dust, broadcast and worked into the soil, or as an emulsion watered round the plants. Results in 1956 were inconclusive and the same plots were used again in 1957, the same quantities of aldrin being re-applied. In this season increasing doses of the compound gave increasing control of the disease. The treatment of individual plants with emulsion was more successful than the application of dusts.
In 1957 half of each plot received a heavy dressing of ground limestone. Lime alone gave a control equal to that given by the highest aldrin treatment. Lime and aldrin together gave a further reduction in clubbing.
In 1958 increasing doses of emulsion were tested. These gave increasing control of disease but the higher doses caused some phytotoxicity which was reflected in a delay in maturation of the crop.
A reduction of clubbing from 'severe' to 'moderate' caused a marked increase in crop, but further reductions in clubbing did not result in any corresponding increase in crop weight.     

Potato coiled sprout in relation to seed tuber storage treatment and to infection by Verticillium nubilum Pethybr

Inoculation of seed potato tubes with Verticillium nubilum produced infection on the underground stem bases to subsequent growth in the form of brown lesions, often accompanied by longitudinal or transverse cracking. Some inoculation tests provided further evidence of a causal relationship between infection with V. nubilum and coiled sprout, but it was not possible to define the conditions in which the fungus gave rise to coiling. Seed tubers sprouted in light before planting produced more coiling than unsprouted or desprouted tubers. Sprouting had this effect whether V. numbilum was present or not and coiling induced by sprouting and that induced by V. nubilum occurred independently. The increased coiling of stem bases from sprouted tubers was often accompanied by fasciation, whereas this symptom was not usually associated with the coiling from unsprouted or desprouted seed tubers inoculated with the fungus. Brown lesions associated with V. nubilum were readily distinguishable from those of Rhizoctonia solani but not from those caused by Oospora pustulans. Neither of these fungi was found to cause coiling. Different varieties of potatoes showed differences in the incidence of coiling in response to sprouting treatment. There was no apparent differences in varietal response to infection by V. nubilum.