LEAF INFECTION OF COTTON BY XANTHOMONAS MALVACEARUM (E.F.SM.) DOWSON

Xanthomonas malvacearum spread more rapidly along vascular tissue than into mesophyll when inoculated to the main veins of susceptible cotton leaves. The extent of spread varied with the concentrations of inocula, tissue age and cotton variety.
Increasing concentrations of inocula accelerated the initial spread of disease.
Bacteria spread more rapidly in young leaves than in old—increasing age greatly decreased disease in the mesophyll. The initial invasion was quicker in young leaves of young plants than in young leaves of old plants.
Three types of behaviour, according to the host's reaction, distinguish Knight's resistance factors: ( a ) where X. malvacearum spread extensively along veins and into mesophyll of plants containing factors B₃ and B₅; ( b ) where it was restricted to the point of inoculation in plants containing B ₄, B₉ and combinations with B _6m; and ( c ) where it spread along veins but not appreciably into mesophyll in varieties containing B ₂ and B ₂ B ₃.
From this and four other different types of tests, factors B ₂ and B ₃ seem to increase mesophyll resistance but only B ₂ gives appreciable vascular resistance. Further, the vascular bundles in varieties with B ₂ seem to be surrounded by an additional 'barrier' which resists X. malvacearum.     

STEM INFECTION OF COTTON BY XANTHOMONAS MALVACEARUM (E. F. SM.) DOWSON

Varying the position of stem inoculation, the concentration of inoculum and the age of plant affected the reaction of cotton, Gossypium sp., to infection with Xanthomonas malvacearum (E. F. Sm.) Dowson.
The extent of stem discoloration, internal and external, and the probability of disease ocurring in leaves by bacteria moving within the plant increased ( a ) the nearer the point of stem inoculation was to the apex, and ( b ) the higher the concentration of inoculum. The leaf symptoms were not the angular spots typical of primary leaf infection. Instead, bacteria seemed to lodge in, discolour and blacken sections of leaf veins. Then tissue next to the affected veins became water-soaked and leaf sectors dependent upon these veins died and dried. These symptoms usually developed 14 to 55 days after inoculation in the expanding leaves.
The amounts of stem discoloration and the probabilities of leaf symptoms developing were less when hypocotyls of old plants were inoculated than when hypocotyls of young plants were inoculated. The probabilities of leaf symptoms developing were similar, however, when young tissues in young and old plants were inoculated.
American cotton, Gossypium hirsutum , was less affected by stem inoculation than Egyptian cotton, G. barbadense. Of the resistance factors against primary leaf infection only B_6m gave appreciable stem resistance.     

BACTERIAL BOLL ROT OF COTTON (XANTHOMONAS MALVACEARUM (E. F. SMITH) DOWSON)

Two inoculation techniques were compared for their value in assessing resistance of cotton to bacterial boll rot. In the first method, bacterial suspensions were applied with a fine brush to the outsides of young bolls immediately after corolla drop. In the second, suspensions were inoculated into the wall tissue of bolls 3–4 weeks old with a fine needle. The second method is the simpler and produces infections in all weather conditions; other advantages are that bolls are inoculated after the period of natural shedding and the circular lesions are easily measured, but a disadvantage compared with the brush method is that the puncture method does not satisfactorily indicate damage to the lint.
Results from the two methods of inoculation suggest that resistance lies in some component of the boll-wall tissue that affects bacterial growth and not in a physical factor that prevents the bacteria entering the boll. Variability in resistance occurs in local strains of cotton, and this could probably be exploited to give high resistance without the need of a large crossing programme to introduce new genes.     

STUDIES IN BACTERIOSIS, XXVII FACTORS INFLUENCING INFECTION BY CORYNEBACTERIUM FASCIANS (TILFORD) DOWSON

Laboratory experiments showed that gram ( Cicer arietinum ) could be infected by Corynebacterium fascians. Parallel tests on sweet peas and gram confirmed the existence of host specificity among strains of the pathogen, and of differences in host susceptibility towards a given strain. Adventitious root formation appeared as a new, though rare, sign of infection. Inoculation of aerial dormant buds invariably caused infection whereas cotyledonary bud inoculation often failed. Sporing bacteria antagonistic to C. fascians in culture media were isolated from soil, but they failed to exert their influence in infection experiments in sand.     

ANTIBACTERIAL SUBSTANCES IN SEED COATS AND THEIR ROLE IN THE INFECTION OF SWEET PEAS BY CORYNEBACTERIUM FASCIANS (TILFORD) DOWSON

Antibacterial substances active against Corynebacterium fascians have been shown to be present in the coats of various seeds. There were considerable differences in activity between the seeds of different genera and species and between individual seeds of a single species.
C. fascians also showed strain variation in sensitivity to the antibacterial substances of the seeds of any one species. An inverse relationship was demonstrated between the sensitivity of a strain to the sweet-pea seed substances and its ability to infect sweet-pea seedlings under laboratory conditions.     

棉花病菌Xanthomonas campestris pv.malvacearum的一种具特异肽键专一性的胞外蛋白酶的纯化与鉴定

棉花病原体Xanthomonas campestris pv.malvacearum在酪蛋白(脱脂奶)存在下生长时产生胞外蛋白酶活性,其中至少包含3种蛋白酶,表观分子量分别为29(蛋白酶-1)、38和43kD。 蛋白酶-1被纯化,其最适pH在5.5～7.5之间。抑制研究表明蛋白酶-1可被Phosphoramidone、EDTA及1,10-邻二氮杂菲抑制,然后用锌离子温育重新激活,说明这是一个金属蛋白酶。发现蛋白酶-1特异地裂解肽链的天冬氨酸残基或半胱氯酸残基的氨基端侧,这种高度的肽键专一性预示这个酶在蛋白质链顺序分析中及由较大蛋白质制备特定多肽方面可能十分有用。     

中国细长蚁属系统分类研究(膜翅目,蚁科)

在中国记载细长蚁属Tetraponera F. Smith昆虫13种,其中在云南省描述5新种,报道中国1新纪录种.编制了工蚁的分种检索表.评论了该属中国种类的分类历史.13个已知种依次是红黑细长蚁T.rufonigra(Jerdon),凹唇细长蚁T.concava sp.nov.,宾氏细长蚁T.binghami(Forel),狭唇细长蚁T.attenuata F.Smith,显赫细长蚁T.notabilis Ward,光亮细长蚁T.nitida(F.Smith),隆背细长蚁T.convexa sp.nov.,榕细长蚁T.microcarpa Wu et Wang,叉唇细长蚁T.furcata sp.nov.,尖唇细长蚁T.protensa sp.nov.,飘细长蚁T.allaborans(Walker),无缘细长蚁T.amargina sp.nov,平静细长蚁T.modesta(F.Smith).显赫细长蚁T.notabilis Ward为中国新纪录种.