摘要:

SUMMARYA satisfactory method of collecting samples ofThrips nigropilosuswas developed in which only the mature leaves were collected, and a number of plants were sampled across several rows of the plot. This give a reproducible and representative estimate of the population within the plot.Despite the development of this technique, very great differences remained between counts on plots of a Latin square experimental design. The use of covariance analysis considerably reduced the residual variance when populations were increasing arithmetically or at only slightly increased rates. When the increase became more rapid, the value of covariance diminished rapidly while simultaneously positional effects became more significant, suggesting that restraining influences were operating unequally in different parts of the experimental area. It is considered that this phenomenon is widespread in populations ofT. nigropilosusand that, as expanding populations are the most likely to be subject to experiment, a more complex design, probably of the incomplete block type, should be used in future.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb07862.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYChanges in populations ofHeterodera goettingianaLiebs. were studied in microplots containing three kinds of soil. Starting with an artificially uniform population, varieties of pea which matured quickly induced smaller numbers of cysts and eggs than later‐maturing varieties although there was ample time for completion of the life cycle on the former. Field bean was comparable with the late‐, and broad bean with the early‐maturing pea varieties.When one variety of pea was grown on all plots of a group, yield decreased in proportion to the density of the population before planting. The relationship between yield and initial population over a narrow population range was expressed equally well by the simple equationsY=a+bxorY=a+blogx, whereY= yield,x= the number of eggs,a= theYintercept andbthe regression coefficient. For plots with a wide range of initial populations (4–359 eggs/g. soil), neither equation was adequate and the relationship was best fitted by a sigmoid curve.In two sets of plots, the influence of two population levels, nitrogen versus no nitrogen, and light versus heavy soil, was tested. Soils and populations affected yield significantly; nitrogen was ineffective on light soil but increased yield on the heavy soil. Only soil type affected the final population, that in the heavy soil which gave the greater yield being twice as large.When peas were grown, the final population rose to a ceiling level independent of the initial population size. In the plots with widest initial population range, the ceiling level was determined by the number of females (new cysts) formed. Their number was almost constant over the whole initial population range and they produced on average 129 eggs/cyst which was the maximum theoretically possible rate of increase under the conditions of the experiment. At small initial egg densities (4 eggs/g.) about 50% of the eggs became female and at great densities (359 eggs/g.) only 1% or less.Final populations in the microplots bore no relationship to yield of peas. It is suggested that the size and form of the central part of the root system determines how many females the roots can support and that root size is one of the factors that determines ceiling levels.Nematicides used to decrease numbers of cyst‐nematode eggs or larvae in soil tend to remove only those surplus to the carrying capacity of root systems. Nematicides or enemies able to kill established females before they produce eggs would control reproduction more ef

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb07863.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYWhen 200 ml. dispersed soil is sedimented from an obliquely rising water current in a simple compartmented tank about three‐quarters of the nematodes are extracted. About 95% of the nematodes in the concentrated suspension can be separated finally from mineral and heavy organic particles by centrifugal notation. When mobile nematodes were finally separated from soil particles by paper tissue, this sedimentation method extracted as many nematodes from sand and loam as Seinhorst's two‐flask and elutriation methods, but in one test extracted fewerTylenchorhynchusfrom clay and in another fewerParatylenchusfrom clay than the elutriation method. The method is quicker (4 or 6 instead of 30–45 min.) and easier.Mobile nematodes can be extracted from 300 ml. soil spread out on paper tissue in 23. 33 cm. trays of 8 mesh/cm. phosphor‐bronze gauze, just resting on shallow water. The suspension obtained after 24 hr. at 16–18°C. was concentrated to 10–15 ml. without loss by sedimentation in two tapered cylinders, one of 8 cm. bore, the other of 2.6 cm. bore. This method usually extracted significantly more nematodes than the sedimentation, two‐flask and elutr

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb07864.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYA detailed examination has been made of the natural infection in two field experiments with sweet peas. Common pea mosaic virus (CPMV) and pea enation mosaic virus (PEMV) accounted for infection in most of the plants.In the first experiment, evidence was found of differences in ‘field resistance’ of fifteen varieties to PEMV but not to CPMV.The second experiment indicated that, though soil application of granular systemic insecticides rendered the plants toxic to aphids, it did not significantly reduce the spread of CPMV. The insecticides had no effects on the growth or flowering of the plants.Incidence of CPMV infection was significantly correlated with trap catches ofAcyrthosiphon pisum, Myzus persicaeandAphis fabaeand PEMV infection withAcyrthosiphon pisumandMyzus persicae.CPMV was not transmitted mechanically by flower cutting but the rate of infection was increased when the plants were layered.The epidemiology of CPMV and PEMV in relation to sweet peas is discus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb07865.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYKinetin stimulated production of tomato aucuba mosaic virus in detached tobacco leaves kept at 18 and 28°C., both in newly infected leaves and in those infected a week previously. Kinetin counteracted the ageing effect of exposing leaves at 28°C. In attached leaves kinetin either stimulated or inhibited virus synthesis, depending on the quantity applied and the age of the leaves. Kinetin increased fresh weights, soluble proteins and chlorophyll content of leaves.In an individual comparison of leaves treated with kinetin and with water, infectivity of extracts and ribonuclease activity were correlated in leaves treated differently at the same temperature, but not otherwis

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb07866.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYOnly a small percentage of tomato plants became infected when grown in soil that contained TMV‐infected debris from a previous crop, whether they were set out into this soil or into a layer of partially sterilized soil overlying it. In one experiment, half the plants were infected when grown in sand containing infected tomato debris, and treating the sand–debris mixture with metham‐sodium greatly increased the proportion of plants infected. When shoots were separated from each other virus was not transmitted from adjacent infectors through roots of plants growing in uninfested soil.When roots were inoculated with TMV, virus was detected in young shoots after periods varying from 3 weeks in seedlings to 6 months in older plants, the average periods being between 10 and 16 weeks. Virus was detected in the roots of many plants, but not in their shoots, when experiments ceased 4–6 months after root inoculation. Plants infected in their roots often showed severe fruit defects in the lower trusses several weeks before mosaic showed in the

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb07867.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYHouse sparrows (Passer domesticusL.), confined in a cage with separate groups of TMV‐infected and healthy tomato plants, infected fifty of the 262 healthy plants by flying between the groups and perching on the plants. None of 191 healthy plants in an adjoining or the same cage without birds was infected. Thus birds could possibly spread TMV within crops and from one crop to anothe

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb07868.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYTomato fruit bronzing occurs in green fruits and produces variable symptoms in ripe fruits. The bronzing is caused by brown necrosis of the fruit wall, mainly at the calyx end of the fruit, which is also the most severely affected part. Field observations and experiments showed that bronzing is closely associated with infection of the plant with tobacco mosaic virus (TMV) and some other factors, notably rank or ‘soft’ growth. Symptoms occur within a short time of infection with TMV and affected fruits are produced over a relatively short period on any one plant. The symptoms in a particular fruit remain constant and do not get progressively worse. Plants systemically infected with TMV do not subsequently produce bronzed fruits. This disease can be distinguished from some other tomato fruit disorders such as blotchy ripening and appears to be similar to a disorder in the U.S.A. called internal browning.A second type of bronzing in green fruits is less common but symptoms are more severe. In this case the necrosis of the fruit wall is not particularly associated with the calyx end and it gets progressively worse so that the fruit is often unsaleable; a characteristic symptom is a series of dark lines radiating from the stylar end of the fruit. Affected fruits are produced on a particular plant over a long period of time and are not associated with infection of plants with TMV.A histological examination of both types of bronzing is repor

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb07869.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYChitin applied to soil naturally infested withF. oxysporumf.pisigreatly lessened the severity of wilt in Onward peas, sown at the time the chitin was applied to the field. In the glasshouse, different pea varieties sown in the field soil 8 months after the chitin was applied were protected equally against infection by any of the three races of the fungus. The severity of wilt decreased with increasing amounts of chitin added to the soil.Applying chitin to artificially inoculated soil a month before pea seedlings were planted in pots also greatly diminished the severity of wilt.Adding chitin to soil decreased the population ofFusariumand increased the number of actinomycetes. Many of the actinomycetes were antagonistic towardsFusarium.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb07870.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

SUMMARYThe production of bulbiformin byBacillus subtilishas been observed on the seed coats, spermatosphere and rhizosphere of bacterized pigeon‐pea seeds sown in sterile and unsterile soils. The importance of different nutrients as a base for bacterization in enhancing the antibiotic production has been established. Maximum antibiotic activity was observed in the treatments where bacterization had been made in molasses solution supplemented with groundnut cake. The rate of antibiotic production reached a peak after 15–18 days. Relatively less antibiotic was synthesized under natural unsterile soil conditions.It is shown that the antibiotic produced as a result of bacterization becomes systemic in plant tissue and provides a protective zone around the roots of pigeon‐pea seedlings. Appreciable reduction in the incidence of pigeon‐pea wilt has been obtained through seed bacter

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1965.tb07871.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY