BROWN ROOT ROT OF TOMATOES

Population counts and nutritional grouping of bacteria from a tomato-sick soil showed that steaming greatly reduced the population and the percentage of group I bacteria (i.e. those able to use inorganic nitrogen). The numbers subsequently increased, and by the time tomatoes were planted, the distribution of nutritional groups approximated to that in unsteamed soil. Rhizosphere and root-surface population numbers did not differ widely in steamed and unsteamed soils. The nutritional groups in soil before planting differed much more between samples from steamed soil with a changing population, than from soil unsteamed for 3 years. Groups I and II (bacteria requiring amino acids) were higher in unsteamed, cropped soil than in steamed soil, and were dominant in rhizosphere and root-surface populations. Group I increased on the root surface in unsteamed soil from July to October, whereas group II increased on root surfaces in steamed soil. Group V (bacteria requiring soil extract) was less frequent on the root surface than in soil from plots unsteamed for 1 year, but more frequent on the root surface than in soil unsteamed for 3 years.     

BROWN ROOT ROT OF TOMATOES: II. THE FUNGAL FLORA OF THE RHIZOSPHERE

The fungal populations of soil and of the rhizosphere of tomatoes in steamed, fallowed and unsteamed plots were compared. Steaming greatly reduced the numbers of fungi in the soil, but fallowing had little effect. Soil bacteria were greatly reduced by steaming but increased to the level in the unsteamed plots after heavy watering. Outer rhizosphere fungal populations in unsteamed plots in July were larger than in the steamed plots, but by October this difference had disappeared, although roots in the unsteamed soil showed the greater development of disease.
Root surface counts indicated that the populations on actively growing roots in July in steamed and unsteamed plots reached similar levels, and there was a slight fall in numbers in both types of plot in October. Fungal infection of roots increased noticeably in unsteamed plots between July and October, although root surface numbers showed a decrease.
Of the fungal species isolated Colletotrichum atramentarium showed a distribution between soil and root surface which suggested that it was a root inhabiting fungus. Cephalosporium spp. were also found on the root surface and in roots, especially those from steamed soil.     

海南非洲菊根腐病病原的分离与鉴定

从海南省五指山市非洲菊苗圃,儋州市兰花基地非洲菊苗圃的腐烂病根上采集分离到9个疫霉菌株,经鉴定属于隐地疫霉Phytophthoracryptogea。     

喀麦隆芋艿根腐病病原菌鉴定

从采自喀麦隆不同地区的芋艿(Xanthosoma mafaffa L.)病根及田土中分离菌株,分别从雅温得(Yaound(?))和巴马约(Mbalmayo)分离到的腐霉菌株XPMY和XPMM1,根据其形态学及生理学特征鉴定为群结腐霉Pythium myriotylum,用上述腐霉菌株的游动孢子悬液或菌丝体片断悬液人工接种,表现叶黄化及根腐等典型症状。用经常伴随群结腐霉的立枯丝核菌Rhizoctonia solani及茄镰孢Fusarium solani人工接种后均未表现症状。研究结果表明:群结腐霉Pythium myriotylum Drechsler是喀麦隆芋艿根腐病的致病菌。     

THE EFFECT OF CERTAIN SOIL TREATMENTS ON DIDYMELLA STEM ROT OF TOMATOES PART I. GLASSHOUSE EXPERIMENTS

When tomatoes were planted in steamed soil inoculated with spores of Didymella lycopersici Kleb., a large proportion became infected, but very few became infected in unsteamed soil similarly inoculated. In soil treated with formalin and subsequently inoculated the number of diseased plants was about half that in steamed soil. Reinfecting steamed soil with soil micro-organisms before inoculation with D. lycopersici reduced the amount of disease. Covering steamed soil with a layer of maiden loam filtered out a large proportion of D. lycopersici spores applied in water suspension and reduced the amount of disease. Addition of stable manure either before or after steaming did not affect the number of diseased plants. Steamed soil remained susceptible to infection by D. lycopersici for 4 months. D. lycopersici survived in a glasshouse soil over the winter, but the number of diseased plants was small. Cultivation may lessen the amount of disease by burying most of the infected surface layers of the soil. The peak of infection under glass occurred in May. The amount of disease and the yield were correlated, but with severe infection the yield varied with the time of infection and the distribution of diseased plants.     

RELATION OF DL-HOMOCYSTEINE,DL-METHIONINE,AND METHYL DONORS TO THE APHANOMYCES ROOT ROT OF PEAS

Davey , C. B., and G. C. Papavizas . (Crops Res. Div., ARS, USDA, Beltsville, Md.) Relation of dl -homocysteine, dl .-methionine, and methyl donors to the Aphanomyces root rot of peas. Amer. Jour. Bot. 50(1): 67–72. 1963.—dl -Homocysteine, a compound lacking a methyl (CH₃) group, completely prevented Aphanomyces root rot of peas, whereas several CH₃ donors (betaine, choline, dimethyl-β-propiothetin chloride, S-methylmethionine) did not. dl -Homocysteine was taken up by pea plants from nutrient solution and converted to methionine. The methylation of dl -homocysteine in pea tissue occurred without an exogenous source of labile CH₃ groups. More d - than l -methionine was taken up by the plants and more methionine of both forms was taken up when methionine served as the sole sulfur source than when it was supplemented with sulfate. dl -Methionine sulfoxide but not dl -methionine sulfone was converted to methionine in pea tissues. Methionine derived from dl -methionine sulfoxide was proportionately more abundant in the aerial portions of the plants.     

光照和温度对根田鼠褐色脂肪组织产热能力的影响

测定了根田鼠在室内驯化2周后褐色脂肪组织（BAT）的蛋白含量、线粒体蛋白含量和细胞色素C氧化酶活性的变化。动物进行如下4种处理:23℃,16L:8D;23℃,8L：16D;5℃,16L：8D和5℃,8L:16D.。结果表明,短光照可刺激根田鼠的BAT线粒体细胞色素C氧化酶的活性增加;低温驯化可导致根田鼠的BAT线粒体蛋白含量增加;短光照加低温可进一步促进酶的活性增加。结合个体水平的产热特点,说明根田鼠在产热能力的季节驯化过程中,光周期是一主要的季节调节信号,环境温度进一步增强光照的作用,环境温度和光周期共同作用以诱导其产热能力等方面的生理调节。研究结果支持了环境温度和光周期共同作用以调节动物产热变化的学说。     

DIDYMELLA STEM-ROT OF OUTDOOR TOMATOES

In studies on Didymella stem-rot of outdoor tomatoes several possible modes of introduction of the disease were investigated, together with methods of avoiding them. The pathogen was found to invest and penetrate the seeds in diseased fruit without destroying their viability and methods were devised of ridding the seeds of infection. It was not, however, possible to demonstrate the infection of mature plants from infected seed. It was found that the disease could be introduced on contaminated canes, in potting soil and from plant debris from the previous season's crop. The spread of the disease was encouraged by overhead irrigation.
Tests of strains of various species of Lycopersicon showed that one line of L. hirsutum was highly resistant to stem and root infection although another line was highly susceptible.