Some effects, especially on yield, of artificially defoliating sugar beet

The effects of completely defoliating sugar beet at different dates from May to October were examined in four years. In each year there were plots given the usual nitrogen fertiliser application to the seedbed, and also in two of the years plots given no nitrogen. At harvest in mid-November, minimum root weights followed defoliation in July or August, but defoliation in August or later gave minimum sugar contents. When nitrogen was applied to the seedbed sugar yields were smallest after August defoliation; in the absence of nitrogen, July defoliation gave the lowest sugar yields, root yield being smaller but sugar content usually greater than with nitrogen. Up to 40% of the sugar yield was lost by July or August defoliation and late defoliation increased some of the impurities in the root juice. Yields, and recovery from defoliation, were greater with nitrogen than without. Partial defoliation in May had relatively little effect on yield. Defoliation affected the incidence of virus yellows differently in different years.     

Carbohydrates and resistance to <Emphasis Type="Italic">Phytophthora infestans</Emphasis> in potato plants

Plants generally deal with biotic or abiotic stresses by altering components as for example cell wall constituents and metabolites. Infection by Phytophthora infestans, the causal agent of late blight, constitutes a stress condition for the plants and they react to it with changes arising in their metabolism depending on the resistance level of the plants. The present work compares two potato hybrids differing in their level of horizontal resistance to late blight. Carbohydrate content in stems and leaves of infected and uninfected plants was determined by HPLC. Some carbohydrates accumulated in the stems of the resistant hybrid infected by P. infestans, whereas they remained unchanged in the susceptible hybrid. On the other hand, in the leaves, these carbohydrates accumulated only in the infected susceptible hybrid.     

Variability of nectar production and composition in Linaria vulgaris (L.) Mill. (Scrophulariaceae)

 We studied nectar characteristics during the long flowering period (late June to end of November) in two populations of Linaria vulgaris (L.) Mill. spontaneously growing in the Botanical Gardens of Siena University (Tuscany, central Italy). The two populations were close to each other but they differed in blooming period. Plants of population 1 sprouted in May and flowered from the end of June to the end of September. Population 2 sprouted at the end of August and flowered from September to the end of November. Differences in nectar production and composition were found between and within populations. Flowers of population 1 produced a very small amount of nectar (not collectable) that remained on the nectary surface. The quantity of nectar increased in late September, when each flower produced 2–3 μl of nectar that flowed into the spur. Total sugar concentration was 175.8 mg/ml in young flowers. Flowers of population 2 produced 5–8 μl of nectar with a total sugar concentration of 200.9 mg/ml in the young stage. In bagged senescent flowers nectar volume decreased in both populations and nectar sugar concentration decreased down to 11.6 mg/ml in population 2 and increased up to 289.6 mg/ml in population 1. For both populations, the decrease in nectar volume in bagged flowers may have been due to water loss by evaporation. In population 2, the decrease in sugar concentration may have been due to nectar reabsorption that was never observed in population 1. Nectar variability is discussed in relation to insect visits and seed set. Received August 14, 2002; accepted December 17, 2002 Published online: June 2, 2003     

THE EFFECT OF SUCROSE SPRAYING ON SYMPTOMS CAUSED BY BEET YELLOWS VIRUS IN SUGAR BEET

When leaves of sugar-beet plants infected with beet yellows virus were sprayed daily with 10% sucrose solution, yellowing symptoms were intensified. When glasshouse plants were shaded so that the light intensity was reduced to less than half of full daylight, yellowing symptoms were suppressed more completely on un-sprayed than on sprayed plants. Spraying with 2–5 % sucrose solution had similar, but slightly smaller effects.
Spraying with sucrose solution increased the carbohydrate content of the leaves, and the effects on symptom intensity and carbohydrate content were closely correlated. The regression coefficients of symptom score on total sugar content were nearly the same for shaded and unshaded plants. As the severity of symptoms was increased by supplying carbohydrate without change in the light conditions, it is concluded that light intensity affects symptom expression by varying the carbohydrate content of the leaves through its influence on photosynthesis.
Sucrose spraying increased the yield of roots of healthy and infected plants, and most of the increase was sucrose. This shows that sprayed sugar was translocated to the roots from the leaves of both healthy and infected plants.
Measurements of changes in carbohydrate content between evening and morning samplings confirmed that movement of carbohydrate out of infected leaves is not stopped by infection.     

Reproduction of sugar beet mosaic and tobacco mosaic viruses in anthocyanized beet plants

During our studies on the interaction of anthocyanins and plant virus diseases, reproduction of sugar beet mosaic (SBMV) and tobacco mosaic viruses (TMV) was investigated. Experiments were carried out in leaves of sugar beet,Beta vulgaris cv. Dobrovicka N and its spontaneous anthocyanized mutant. SBMV induces a systemic infection while TMV is responsible for primary local symptoms in sugar beet leaves only. Our quantitative analyses onAmaranthus caudatus L. andChenopodium quinoa Wilid. showed a significant decrease in concentration of SBMV in juice extracted from anthocyanized beet plants as compared with extracts from normal green infected plants. Significant differences were also obtained when SBMV — containing juice was tested in mixtures with healthy extracts from anthocyanized and normal green plants. Also the intensity of TMV symptoms in beet leaves was considerably decreased in leaves of antho-eyanized plants.     

The Relationship between Sugar and Amino Acid Export to the Phloem in Young Wheat Plants

The relationship between amino acid and sugar export to thephloem was studied in young wheat plants (Triticum aestivumL. ‘Pro-INTA, Isla Verde’) using the EDTA-phloemcollection technique. Plants grown with a 16 h photoperiod showeda rapid decrease in the concentration of sugars and amino acidsin the phloem exudate from the beginning of the dark period.When plants grown with a 16 h photoperiod were kept in the darkfor longer than 8 h the free amino acid content in leaves andexudate (on a dry weight basis) increased continually throughoutthe 72 h of darkness. During the first 24 h of darkness thesugars in the phloem exudate decreased to 30% of the initialvalue, and returned to the control level when plants were returnedto light. When plants grown under low light intensity for 10d were transferred to high light intensity, they showed an increasein leaf sugar content (dry weight basis) after 3 d but therewere no differences in leaf free amino acid content (dry weightbasis) compared to low-light plants. The sugar concentrationin the phloem exudate was increased by higher light intensities,but there was no difference in the amino acid concentrationof the phloem exudate, and thus the amino acid:sugar ratio inthe phloem decreased in the high-light plants. The present resultssuggest that amino acids can be exported to the phloem independentlyof the export of sugars. Copyright 1999 Annals of Botany Company Sugar exudation, amino acid transport, nitrogen, phloem, transport, wheat, Triticum aestivum L.     

Changes in a Heterodera rostochiensis population through the growing season

Changes in the numbers of all stages of Heterodera rostochiensis in plants and soil were studied in a potato crop growing on infected land. Hatching and invasion occurred early in the season, when plants were very young and temperatures were below those considered necessary for hatching and invasion in Long Island, U.S.A. More larvae hatched from cysts nearer than away from potato roots. Males were abundant during June and July, when fertilization probably occurs. Many new cysts appeared during late June and early July. In May/June, there were many larvae in the roots of young plants but later there were few; a slight increase during August probably indicated a small second generation. The larvae for this second invasion may have come from the most recently formed cysts, which may have been stimulated to hatch either by root exudates or by substances from other soil organisms.     

Powdery mildew of tobacco (Erysiphe cichoracearum DC.)

In water culture experiments, tobacco plants of Hicks variety were supplied with factorial combinations of high and low concentrations of nitrogen, phosphorus and potassium. Incidence of powdery mildew and growth and chemical composition of infected and healthy plants were compared.
There was more disease when all elements were supplied at the higher of two concentrations, but the increase in infection was less than the increase in growth. Plants grown in media containing a low ratio of potassium to nitrogen produced the least susceptible leaves; their disease indices were up to 30 times less than those of plants that received the full nutrient treatment. Potassium-deficient leaves had thinner cell walls, larger water content, smaller sugar and potassium contents, and greater amino nitrogen and magnesium contents, compared with those of plants grown in any of the other media. The possible relation between these characteristics and susceptibility to Erysiphe cichoracearum DC. are discussed.     

Development of Ramularia Leaf Spot on Sugar Beet as Influenced by Temperature and the Age of the Host Plant

A method of inoculating sugar beet plants (Beta vulgaris L.) with Ramularia beticola Faut. & Lamb, is described. Following inoculation, disease development in relation to temperature and plant age was studied for more than a month. The incubation period was 18 days at 10°C compared to 14 days at 17°C. At 25°C no symptoms appeared. Both temperature and plant age significantly influenced disease level and rate of disease development. Plants incubated at 17°C were more severely diseased 33 days after inoculation than plants incubated at 10°C. Young plants (3 weeks at inoculation) Were more susceptible than older plants (5 and 8 weeks at inoculatson) under growth chamber conditions. In the field, symptoms of Ramularia leaf spot appear relatively late in the season and young leaves are rarely attacked. The inconsistency of these observations is discussed.     

Juice,sugar, and bagasse response of sweet sorghum (Sorghum bicolor (L.) Moench cv. M81E) to N fertilization and soil type

The objective of this research was to determine the optimum nitrogen fertilizer rate for producing sweet sorghum (a promising biofuel crop) juice, sugar, and bagasse on silt loam, sandy loam, and clay soils in Missouri. Seven nitrogen fertilization rates were applied, ranging from 0 to 134 kg N ha^?1. Regardless of the soil and year, the juice content of sweet sorghum stalk averaged 68.8% by weight. The juice yield ranged from 15.2 to 71.1 m³ ha^?1. Soil and N rate significantly impacted the juice yield (P < 0.0001). The pH and the density of the juice were not affected by the soil or N. The sugar content (Brix) of the juice varied between 10.7% and 18.9%. N fertilization improved the sugar content of the juice. A negative correlation existed between the sugar concentration and the juice yield. In general, the lowest sugar content was found in the clay soil and the impact of the N fertilization on juice sugar content was most pronounced in that soil. The juice sugar yield ranged between 2 and 9.9 Mg ha^?1, with significant differences found between years, N rates, and soils. N fertilization always increased the sugar yield in the clay soil, whereas in loam soil, a significant sugar response was recorded when the sweet sorghum was planted after corn. The average juice water content was 84% by weight. The dry bagasse yield fluctuated between 3.2 and 13.8 Mg ha^?1 with significant difference found with N rate, soil, and year. When sweet sorghum was grown after soybean or cotton, its N requirement was less than after a corn crop was grown the previous year. In general, a minimum of 67 kg N ha^?1 was required to optimize juice, sugar, and bagasse yield in sweet sorghum.     

Sympatric Epichloë species and chemotypic profiles in natural populations of Lolium perenne

The distribution of different Epichloë species within eight natural populations of Lolium perenne was studied. In total, 40.2% of the asymptomatic plants were infected by Epichloë festucae var. lolii or by Epichloë typhina. Both species occurred in sympatry in seven grass populations, and some plants had dual infections by both taxa. No hybrid taxa such as Epichloë hybrida were detected. Epichloë festucae strains were classified into two morphotypes, M1 and M3, according to culture characters, both morphotypes occurred in sympatry in seven populations. Plants bearing stromata produced by Epichloë typhina were observed, but asymptomatic plants infected by this species also occurred in seven populations. The alkaloid profile of Lolium perenne plants was related to the morphotype of their infecting strains: most plants infected by M3-strains were characterized by lolitrem, and those with M1-strains contained either ergovaline or lolitrem. Plants infected by Epichloë typhina were characterized by high peramine content.     

Application of enzyme-linked immunosorbent assay to the detection of potato leafroll virus in potato tubers

Factors affecting the detection of potato leafroll virus (PLRV) by enzyme-linked immunosorbent assay (ELISA) in tubers of field-grown potato plants with primary or secondary infection were studied. The reactions of extracts of virus-free potato tubers were minimised by pre-incubating the extracts at room temperature and by careful choice of the dilution of enzyme-conjugated globulin. PLRV was reliably detected in tubers produced by secondarily infected plants of all six cultivars tested. PLRV concentration was greater in heel-end than in rose-end vascular tissue of recently harvested tubers but increased in rose-end tissue when tubers stored at 4°C for at least 5 months were placed at 15–24°C for 2 wk. PLRV occurred at greater concentration in tubers from plants of cv. Maris Piper with natural or experimentally induced primary infection than in tubers from secondarily infected plants; again PLRV concentration was greater in heel-end than in rose-end vascular tissue. Plants whose shoots were infected earliest in the growing season were invaded systemically and produced the greatest proportion of infected tubers; plants infected late in the season also produced infected tubers but PLRV was not detected in their shoot tops. PLRV concentration in tubers from the earliest-infected plants was less than in tubers from later-infected plants. PLRV was detected reliably by ELISA in tubers from progenies that were totally infected but was not detected in all infected tubers from partially infected progenies. ELISA is suitable as a routine method of indexing tubers for PLRV, although the virus will not be detected in all infected tubers produced by plants to which it is transmitted late in the growing season.     

Self-interactions of Meloidogyne hapla and of Heterodera schachtii on Beta Vulgaris

Double inoculations of sugar beet with larvae of Meloidogyne hapla resulted in a higher galling incidence in only one treatment than did a single inoculation using the same number of larvae. Double inoculations with larvae of Heterodera schachtii, however, resulted in three- to five-fold more cysts in most cases than did single inoculations using the same number of larvae. In general, plants died more quickly after double inoculations than after single inoculations of the same total number of either nematode. Ratios of total soluble carbohydrates to reducing carbohydrates were lower in multiple inoculated treatments than in other treatments. Plants infected with M. hapla had lower quantities of B, K, and P in leaf tissue than noninoculated plants, but no differences were correlated with type of inoculation. Plants inoculated with H. schachtii had lower quantities of B, K, and Mg than noninoculated plants. Also, quantities of Mn, Cu, and Zn were much lower in plants inoculated twice with H. schachtii larvae than in plants inoculated with the same total number of larvae in a single dose.     

Phenology and life cycle of the annual, <Emphasis Type="Italic">Chamaesyce maculata</Emphasis> (L.) Small (Euphorbiaceae), with multiple overlapping generations in Japan

The phenology of germination, vegetative growth and sexual reproduction in the annual Chamaesyce maculata (L.) Small (Euphorbiaceae) were investigated in a natural population in western Japan. Seedlings emerged from mid-June to early October, with three peaks: mid-June, late July and late August. Plants that emerged in June commenced sexual reproduction from late July, and thereafter both vegetative growth and sexual reproduction occurred together until early November, the plants showing no switching from vegetative growth to sexual reproduction. Seedlings that emerged in June and July suffered high mortality, but most seedlings that emerged from August onward survived until the reproductive stage. The minimum size for reproduction was largest for plants that emerged early in the season, and it decreased with a delay in seedling emergence. The late emergence of seedlings that resulted in low reproductive output may be to some extent compensated for by the increased probability of survival in the seedling stage. A transplant experiment clarified that C. maculata can repeat a maximum of three overlapping generations within a year. Multiple generations per year were attained by non-dormant seeds produced in the first and second generations and clearly resulted in an increased reproductive output per year. The life cycle with multiple overlapping generations may have been acquired in habitats where unpredictable disturbance results in temporally unsuitable conditions for germination, vegetative growth and sexual reproduction of annual plants, but where suitable conditions frequently continue over a period longer than the single generation time of annual plants.     

Effect of prevention of iron chlorosis on the quality of sugarcane grown on vertisols

Results of a field experiment comprising various sources of sulphur and iron showed that band application of sulphur @ 500 kg/ha significantly increased the mean sugar content by 5.6%, recovery of sugar by 5.8% and purity of sugarcane juice by 0.8% on account of increased leaf sulphur content as compared with that under control. The application of Fe-EDDHA or gypsum had little effect on the quality of sugarcane juice. Effect of ferrous sulphate was intermediate between that of sulphur and gypsum. A study of the relationship between sulphur content of leaves and juice characteristics showed that every 1% increase in sulphur content of leaves increased sugar content in cane juice by 0.038%, recovery of sugar by 0.038% and purity of juice by 0.033%.     

Two low-cost food attractants for capturing Toxotrypana curvicauda (Diptera: Tephritidae) in the field

Adults of the papaya fruit fly, Toxotrypana curvicauda Gerstaecker, living in wild vegetation in Yautepec, Morelos, Mexico, were captured using McPhail traps baited with pineapple juice or brown sugar. Maximum capture peaks occurred during August and November in the afternoon. Baits were most effective when aged over a 4-d period. Traps baited with brown sugar captured the highest number of adults, and both baits were more attractive to females than males. Potential use of these baits for pest management and research is discussed, considering that this is the first report of pineapple juice being attractive to the papaya fruit fly.     

Spread of raspberry bushy dwarf virus by pollination, its association with crumbly fruit, and problems of control

Raspberry bushy dwarf virus (RBDV) was transmitted to raspberry seed both through the pollen and through the ovule and it infected plants pollinated with infected pollen. It did not infect plants prevented from flowering, and transmission through pollen seems to be the only method of spread in the field; in the proximity of infectors, most plants became infected during the first two or three flowering seasons. Plants containing RBDV showed no obvious symptoms, but healthy or infected flowers pollinated with infected pollen produced ‘crumbly’ fruit, containing a high proportion of aborted drupelets. RBDV was difficult to eliminate from infected raspberry by heat therapy. Raspberry cultivars that fail to become infected naturally were also immune to infection by grafting. Use of immune cultivars offers the only method of control and, because infected plants may produce crumbly fruit, future cultivars should if possible possess immunity to RBDV.     

Effect of virus yellows on yield of some monogerm cultivars of sugar beet

The yield of plants of monogerm cultivars of sugar beet artificially infected with both beet yellows and beet mild yellowing viruses was, on average, depressed 2–7% for every 100 ‘infected plant weeks’, equivalent to c. £25/ha at 1976 prices. The cv. Vytomo, previously recommended to growers as being tolerant of infection by virus yellows, had a high sugar content and abundant foliage but in field trials its actual yield of sugar was no greater when infected, and lower when virus-free, than that of some other monogerm cultivars.     

中国石榴品种资源经济性状研究

本文测定了34个中国石榴主栽品种的单果重、可溶性固形物含量、糖酸比等9个经济性状,根据测定结果对各品种果实品质进行了模糊综合评判.结果表明,皖榴3号、皖榴2号、皖榴1号、大笨子等品种品质最佳;提出了评判结果等级划分的方法;各品种经济性状的相关与回归分析结果显示,果实百粒重与出汁率,可溶性固形物含量、可溶性糖含量与糖酸比,出汁率与糖酸比,糖酸比与可溶性糖含量均呈极显著正相关(α=0.01,F＞F0.01);出汁率与果皮光洁度呈极显著负相关(a=0.01,F＞0.01);主成分分析结果表明,前5个主成分累积方差贡献率达到87.67%,基本概括了全部9个性状的主要信息.