摘要:

SummarySpeed of emergence of juveniles from cysts in potato root diffusate (PRD)in vitrodiffered betweenGlobodera rostochiensisandG. pallidaand between populations within each species. Early emergencein vitrowas slower in most populations ofG. pallidathan in most populations ofG. rostochiensis. FewerG. rostochiensisjuveniles emerged from 4 or 6 month old than from 4 yr old cysts.MoreG. rostochiensisemerged in solutions of sodium metavanadate at concentrations of 10‐2and 10‐3M than in PRD and as manyG. pallidaemerged in the same solutions as in PRD. In plots of bare fallowed sandy loam, emergence ofG. pallidawas stimulated by 10‐‐3M sodium metavanadate. The emergence of two populations ofC. pallidain PRD was stimulated by the addition of benomyl at 0.1 ppm (3.4 × 10‐‐7m). In microplots, cv. Cara potatoes grown for 8 wk decreased four populations ofG. pallidaby up to 93%. During a 4 wk period in PRD, more than 20 juveniles per gravid female emerged from five of 25 populations ofG. pallida. In root observation boxes in which cv. Désirée was grown, oxamyl applied to the top 15 cm of a peaty loam soil greatly increasedG. pallidain soil 1545 cm deep. In another peaty loam, but not in a sandy loam, the same treatment appeared to increase the nematode in soil 15–30 cm deep. Oxamyl incorporated in the uninfested top 15 cm of all three soils largely prevented nematode increase from juveniles migrating upwards from untreated heavily infested soil 15–30 cm deep.These experiments suggest that inadequate control ofG. pallidaincrease on susceptible potatoes by an oximecarbamate nematicide of short persistence, such as oxamyl, is primarily due to the slow rate of juvenile emergence in most populations ofG. pallida, with a second generation and the upward migration of juveniles from deeper untreated soil later in the growing season as potential co

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb04907.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryReproduction of artificially selected near isogenicMeloidogyne incognitalineages virulent and avirulent against theMiresistance gene of tomato was assessed on host and resistant lines and cultivars of pepper. Egg mass production following inoculation of individual potted seedlings with second‐stage juveniles was studied in experiments conducted in controlled environment. Artificially selected Mi‐virulent nematode populations were unable to develop on resistant pepper lines PM 217 and PM 687. This suggests that the genetic systems governing resistance to root‐knot nematodes are differently expressed in tomato and pepper, in spite of the very close phylogenetic relationships and structural genomic homologies occurring between these two vegetable crops. Moreover, these artificially selected nematode populations were also found unable to develop on the susceptible pepper cultivars California Wonder and Doux Long des Landes, while their pathogenicity was not significantly affected on susceptible tomatoes. Due to the existence of naturally virulentMeloidogynepopulations, these results enhance the need for a better understanding of the mechanisms involved, in order to develop new forms of management of plant resistance to root‐knot ne

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb04908.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryTomato and lettuce plants were exposed to vapour of the herbicide [14C‐phenyl] 2,4‐D iso‐octyl at concentrations in the range 0–450 pg litre‐1for periods of 6, 24 and 72 h in separate experiments using a flowing‐air system. The rate of uptake, as indicated by plant content of radiolabel, was both linear with respect to the vapour concentration and independent of the duration of exposure. The uptake rate of tomato was greater than that of lettuce at any given vapour concentration. Uptake by the apical leaves of lettuce was higher than by the older leaves expressed on an area basis; tomato showed no effect of leaf position. Visible symptoms of phytotoxicity were shown by both species 40 days after exposure to the highest doses. Advantages of using the low‐volatile ester (iso‐octyl) of 2,4‐D to reduce vapour drift damage are discussed in term

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb04909.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummarySomaclonal lines of linseed from the parent cultivar Norlin were produced from a callus‐basedin oitroregeneration system (the R0generation). In field trials conducted over two seasons, 47 R1(plants produced from the R0generation) and 20 R2somaclonal lines (plants produced from the R1generation) were compared to the parent cultivar Norlin for quantitative characters. Irrespective of the genotype, traits in R1's and R2's were assessed on the basis of regression analysis as showing heritabilities of between 28% and 64%. Generally, the somaclonal variation assessed during these early generations revealed some detrimental traits, e.g. lower seed yield than the parent (control) cultivar and reduced 1000 seed weights, but a few lines were identified which had early or late flowering dates, improved seed yield and increased 1000 seed weights. It is concluded that somaclonal variation could be of value as an adjunct to classical breedin

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb04910.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThree controlled environment experiments were conducted at different temperatures to determine the relation between temperature and leaf development and growth in the potato (cv. Maris Piper). Developmental stages are defined for the appearance and duration of leaf extension in the potato and comparisons made with other temperate zone crops.The rate of leaf appearance was linear over the temperature range (9–25°C) and above 25°C there was no further increase in the rate. The temperature coefficient for the rate of appearance of leaves was 0.032 leaves (degree days)‐1using a base temperature of 0°C. The duration of extension of an individual leaf decreased with increase in temperature up to 25°C such that the thermal duration was constant at 170 degree days using a base temperature of 0°C for leaf positions 4–10 on the main stem. At higher leaf positions the thermal duration was similar or greater. The advantages and limitations of controlled environment work as a parallel to field experimentation are

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb04911.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryStudies on the floral morphology of macabo cocoyam (Xanthosoma sugittifolium(L.) Schott) indicated that it required 50 to 70 days for flower formation while fruit maturity took 40 to 60 days after pollination. Among the three types of cocoyams (“white”, “red” and “yellow”), male flowers were more sterile in the “red” and “yellow” types. The spadix consisted of three parts, a bottom pistillate section, a central constricted region with sterile flowers separating the pistil from a third staminate section. The fruiting head formed as a result of hybridisation, is dome shaped and is comprised of a dense cluster of berries. Mean number of berries per fruiting head was 244 ± 40 while the weight of each head was 16.15 ± 6.38 gm. There were an average of 15 ± 6 seeds per berry with 100 seeds weighing 0.0266 ± 0.0048 gm. The longitudinally shaped seed is ridged and grooved like a pumpkin pod when observed under hi

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb04912.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryIn an analysis of leaf development of leek plants grown in the field in 1988, successive leaves initiated, appeared (tip and ligule) and senesced at equal intervals of accumulated temperature/thermal time. These intervals corresponded to a plastochron of 92°C days and phyllochrons of 135 (tip) and 233 (ligule) °C days. The rate of appearance of ligules was exactly equal to the rate of leaf senescence, with the result that the number of fully‐expanded leaves per plant remained constant at 1.4. These data, which were compatible with results from previous seasons, were used to develop a model of the interrelationships between primordium initiation at the shoot apex and subsequent events in the development of individual leaves. Primordium initiation is considered to be the primary controlling event in the life of a leaf, and the processes of tip appearance, ligule appearance and death can be predicted from knowledge of the number of primordia which have been initiated, without reference to the environment. A model of canopy expansion, based on the central role of the shoot apex, was developed using the temperature relations of primordium initiation and additional data on leaf expansion and leaf dimensions. Leaf area indices computed in this way provided a satisfactory simulation of the thermal‐time course of leaf area index observed in a previous season,

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb04913.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe response of potato cultivars to water salinity was studied under field conditions in sandy loessial soil in the arid desert of Southern Israel. The potatoes were drip‐irrigated with water of three different salinities: water commonly used for irrigation (1.0–1.4 dS m‐1); saline water from a local well (6.1–6.9 dS m‐1); and a mixture of the two (3.84.3 dS m‐1). Salinity retarded plant emergence, enhanced haulm senescence and reduced growth of both haulms and tubers. Increasing the salinity progressively reduced tuber yields. Application of the saline water well after plant establishment (Expt A) decreased tuber yields by 615% and 22–31% in the intermediate and the high salinities, respectively. When irrigation with saline water was started soon after planting (Expt B), tuber yields were decreased by 0–17% and 21–79% in the intermediate and the high salinities, respectively. When the tubers emerged in salinised soil, tuber yields were decreased by 21–54% and 42–59% in the intermediate and the high salinities, respectively. A differential response of various cultivars to salinity was observed. None of the potato cultivars or clones exhibited exceptional tolerance to severe salinity. The earlier maturing cvs Atica and Désirée were the least susceptible to the moderate salinity imposed throughout the entire growing season; however, no association was noted between maturation time and t

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb04914.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThirty‐six groundnut gentoypes of varied origin were evaluated for their yield, crop growth rates (C), and partitioning to reproductive sinks (p) in three trials. In the trials irrigation and sowing date were used to vary the amount of water available either throughout the crops' life, or through the grain filling phase. Genotype performance across the five environments for these attributes showed that although differences in C existed, differences in the stability of the partitioning were the dominant attribute of genotypes adapted to the drought prone Sahelian region. Data suggested that these differences were more attributable to tolerance to temperature and/or humidity than water stress. Over all treatments canopy temperatures relative to air (CATD) were strongly correlated with the C observed, but not so with yield; and differences between genotypes in the relationship between C and CATD were not statistically significan

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb04915.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SummaryThe effect of micronutrient supply on the growth and seed production of guayule (Parthenium argentatumGray) was investigated. A deficiency of boron, but no other trace element, significantly reduced the growth, seed production and the percentage of seeds that germinated. The optimum concentration of B for seed production was between 20 and 100 μM. Results indicate that guayule may benefit from B fertilisation

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1992.tb04916.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY