Horticulture Research International Research Articles

Control of root aphid (Pemphigus bursarius L.) in witloof chicory culture (Cichorium intybus L. var. foliosum)

Pemphigus bursarius L. is a serious pest of the witloof chicory (Cichorium intybus L. var. foliosum) during its growing phase in the field. Trials investigating many ways of improving control of this aphid were carried out, including improved knowledge of the pest's life cycle and of beneficial insects, tests of biological and chemical insecticides, impact of plants' growing conditions in the field (water stress) and research for resistance in different chicory families. The work showed that the winged flights of P. bursarius should be monitored in Northern France according to the temperature-based model established at Horticulture Research International, Wellesbourne (now Warwick Crop Center). An insecticide spray with spirotetramat during the fundatrigeniae migration strongly reduced the wingless colonies in summer. Beneficial insects also contributed to limiting the populations of P. bursarius, particularly several species of a genus of a fly (Thaumatomyia spp.) whose larvae are able to predate on about 100 wingless aphids on the root chicory. The use of an insecticide has been authorized based partly on efficacy results obtained in these reported trials. Italian chicories were more resistant than witloof chicories (“Belgian endive”) and could be used in breeding programs. Data on the life cycle of some species of the genus Thaumatomyia have been recorded and will be useful for biological management programs in the future.

Performance of Jonagold, McIntosh and Novaspy on three new semi-dwarf apple rootstocks in eastern Canada

Experiments were conducted in the provinces of Ontario (ON), New Brunswick (NB), and Nova Scotia (NS), all of which differ in growing regime, to determine the performance of Jonagold (Wilmuta strain), McIntosh and Novaspy on three new size-controlling apple [Malus × domestica (Borkh.)] rootstocks AR86-1-20, CG.008, and G.30 compared with a standard (M.26EMLA). For most response variables, rootstock performance differed in each location. Irrespective of cultivar, trees on AR86-1-20 were consistently more vigorous than those on M.26EMLA, while trees on G.30 were more vigorous in four of six experiments, and trees on CG.008 were similar to those on M.26EMLA in five of six experiments. G.30 and CG.008 were significantly more yield-efficient in four of the six experiments and show promise as replacements for rootstocks in this size category. CG.008 could be a good choice for a productive, well-anchored semi-dwarf rootstock between M.26EMLA and M.7 in vigour control, and CG.30 is likely a suitable replacement for M.7. The Horticulture Research International (HRI) rootstock AR86-1-20 is well adapted to wide soil and climate differences and may replace other rootstocks in the semi-dwarf vigour category. The results of this study provide a comprehensive look at comparable field performance of some new rootstocks for three of the five apple growing regions of Canada.

Verticillium albo‐atrum and V. dahliae on hop

<i>Verticillium albo‐atrum</i> and <i>V. dahliae</i> on hop

The Export Model for Local Vegetable Production and Poverty Reduction

"The Export Model for Local Vegetable Production and Poverty Reduction." The Journal of Horticultural Science and Biotechnology, 80(2), p. 161 Additional informationNotes on contributorsJill LennéJill LennéJill Lenne has 28 years’ experience in tropical agricultural research with B.Agr.Sci. (Hons), Ph.D. and D.Agr.Sci. degrees from the Faculty of Agriculture, University of Melbourne, Australia. She has held positions as Principal Plant Pathologist, ClAT, Colombia; Programme Leader (Strategy), DFID-Crop Protection Programme; Director, Crop Protection Division and Deputy Director General - Research, ICRISAT, India; and non-Executive Director, Board of Horticulture Research International, UK. Jill has authored/edited more than 150 research publications, and is currently Co-Editor-in-Chief, Field Crops Research and a consultant with strong interest in horticultural development in East Africa.

Determination of (in)compatibility genotypes of Hungarian sweet cherry (Prunus avium L.) accessions by PCR based methods

Sweet cherries (Prunus avium L.) are generally self-incompatible and pollinator cultivars are needed in orchards for reliable yield. In Hungary, choosing the appropriate cross-compatible cultivar pairs has so far been based on traditional test-crosses in the field. In recent years PCR-based methods that allow the identification of the S-alleles responsible for compatibility have been elaborated. We have determined the S-allele constitution of 24 cultivars and four selections important to Hungarian growers and breeders using PCR-based methods developed at Horticulture Research International, East Malling. The 28 accessions had various pairs of 9 alleles including one new allele, Sr. They could be assigned to 12 of the existing incompatibility groups or to a new group (S4S12) for which the designation 'Group XXVII' is proposed. The cultivars `Krupnoplodnaja' and 'Rita' had novel genotypes, S5S9 and S5Sx, respectively and can be placed into group 0 that holds universal pollen donors. The genotype of the cultivar ‘Hedelfingeni óriás' grown in Hungary was found to be S3S4 and therefore different from the cultivar `Hedelfingen' that is widespread in Western Europe.

Management of basal rot - the narcissus disease

Gordon Hanks and John Carder of Horticulture Research International (HRI) describe the methods being used to manage basal rot, the main fungal disease of this important ornamental crop.

Controlling cavity spot of carrot

Geoff White formerly of Horticulture Research International at Wellesbourne in the UK discusses the most serious disease affecting carrot production worldwide.

WHAT'S GOING ON IN THE WORLD OF RUBUS BREEDING?

WHAT'S GOING ON IN THE WORLD OF RUBUS BREEDING?

Control of sclerotial pathogens in horticulture

John Clarkson and John Whipps from Horticulture Research International at Wellesbourne, Warwick, UK, outline the wide variety of methods which are available for the control of sclerotial pathogens in horticulture, including the use of biological and integrated control methods.

Susceptibility of cabbage root fly Delia radicum, in potted cauliflower (Brassica oleracea var. botrytis) to isolates of entomopathogenic nematodes (Steinernema and Heterorhabditis spp.) indigenous to the UK

AbstractThe susceptibility of larvae of the cabbage root fly (Delia radicum) to ten isolates of entomopathogenic nematodes was examined in a glasshouse experiment using cauliflower (Brassica oleracea var. botrytis) as the host plant. Steinernema affine Horticulture Research International (HRI) code 179 provided the highest level of control, killing approximately 46% of the cabbage root fly within 28 days. Two Heterorhabditis isolates (HRI code K122 and UK211) and Steinernema E1 and F1 (HRI code 194 and GWE63) did not give any significant control. In a second experiment, S. affine was applied against cabbage root fly larvae at 8000 to 64 000 nematodes per pot, and its performance was compared to identical dose applications of Nemasys®, a commercial formulation of S. feltiae. Averaged over the four dose rates, S. affine controlled significantly more cabbage root fly (36%) than Nemasys® (10.4%).

Outbreak of Tomato spotted wilt virus in Tomato in Kenya.

Tomato spotted wilt virus (TSWV) of the genus Tospovirus, family Bunyaviridae (1), causes an economically important virus disease in tomato in several parts of the world. The virus has a wide host range that includes numerous crops and weeds and is transmitted by at least seven species of thrips. Tomato crops in the Subukia, Bahati, and Kabazi areas of the Nakuru District in Kenya were affected by a disease suggestive of TSWV infection during the November 1999 to March 2000 tomato-growing season. Farmers reported up to 80% losses of their potential yields. Characteristic symptoms were noticed on fruits, especially when they were green. Distinct concentric rings on fruits, which later turned into brown, uneven ripening, were the most visible symptoms. Foliage did not develop pronounced symptoms, but mild bronzing was observed in a few cultivars. However, foliage senesced prematurely, starting with older leaves. Foliar symptoms were mistaken for blight infection, and as a result, excessive fungicides were applied that failed to manage the disease. To test for TSWV infection, tomato leaf samples collected from the fields were tested initially with a TSWV test kit (HortiTech, Horticulture Research International, Wellesbourne, UK), and the results were confirmed by double-antibody sandwich-enzyme-linked immunosorbent assay with antibodies from Agdia Inc. (Elkhart, IN). Further molecular characterization was done using reverse transcription-polymerase chain reaction (RT-PCR). Total RNA was extracted from symptomatic leaves of tomato cv. Money Maker using the RNeasy mini kit (Qiagen Inc., Valencia, CA). Using primers 5' TTAAGC AAGTTCTGTGAG 3' and 5' ATGTCTAAGGTTAAGCTC 3' specific to the nucleoprotein (N) gene of TSWV, the N gene was amplified by RT-PCR (2). A 777-bp product of the expected size was obtained from symptomatic plants, whereas no amplification was obtained from noninfected tomato. The PCR product was cloned into pGEM-T Easy (Promega, Madison, WI) and sequenced. A search of GenBank revealed a sequence identity of 95 to 99% with the N genes of known TSWV isolates. To our knowledge, this is the first report TSWV infection of tomato in Kenya. Considering its wide host range, future surveys should be directed toward estimating its incidence in tomato and other TSWV-susceptible crops, such as Irish potatoes, pepper, peanut (groundnut), beans, and a wide variety of ornamental cut flowers in Kenya.

The current state of plant virus taxonomy

The current state of plant virus taxonomy

The role of ethylene and cell wall modifying enzymes in raspberry (Rubus idaeus) fruit ripening

This study focuses on four raspberry (Rubus idaeus) genotypes from two different genetic backgrounds: cvs Glen Prosen and Glen Clova, bred at the Scottish Crop Research Institute (SCRI) and genotypes bred at Horticulture Research International (HRI), East Malling (EM), EM 4997 and EM 5007. The ripe fruit of each genotype pair were characterised subjectively by raspberry breeders as relatively firm or soft, respectively. Different stages of fruit development from each genotype were used to quantify fruit firmness, rates of ethylene evolution and ripening rate. Penetrometry data confirmed suspected firmness differences. Firmness correlated with rates of ethylene evolution. Rates of ethylene production also correlated with receptacle size. Storage of green fruits in 20 μl l−1 ethylene reduced fruit firmness, enhanced respiration rate and colour (anthocyanin) development and stimulated the development of cell wall hydrolase activities. However, during natural ripening in the field, fruit respiration rate declined, which indicates a non‐climacteric ripening pattern. In drupelets, the activities of polygalacturonase (PG), pectin methylesterase (PME), Cx‐cellulase (Cx) and β‐galactosidase (β‐gal.) increased substantially as ripening progressed. More detailed studies with ripe fruit of cv. Glen Clova indicated major isoforms of PG at pIs 3.3, 8.6 and 10.1; of PME at pIs 7.2, 8.5, 8.7, 8.8; of Cx at pI 2.4; and of β‐gal. at pIs 6.3 and 6.7.

The Identification and Exploitation of Resistance in Carrots and Wild Umbelliferae to the Carrot Fly, Psila rosae (F.)

Partial plant resistance to the carrot fly, Psila rosae, has been identified in several Nantes varieties of carrot, Daucus carota, which reduces larval damage to the roots and the number of pupae remaining in the soil after cropping by 50%. The resistance of the Nantes variety 'Sytan' was found to be consistent at 12 sites in 5 European countries over two seasons. The resistance has been shown to be based on antibiosis and correlated with concentrations of chlorogenic acid in the roots. The resistance complements cultural and chemical methods for controlling P. rosae. Thus, in field experiments over two seasons it was shown that carrots could be left in the ground for a longer period providing a greater sowing/harvesting interval with a resistant variety than a susceptible one because of the reduction in damage and the delayed development of insects on the resistant variety. In two seasons at two sites a partially-resistant variety required only one-third of the dose of insecticide to provide a marketable crop compared with a susceptible carrot variety. In a breeding programme involving the variety 'Sytan', male sterile lines, inbreds and selections with improved levels of resistance were developed. Much higher levels of resistance were identified in certain wild Daucus species and 15 years of crossing and selection produced lines with significantly higher levels of resistance than exists in the variety 'Sytan'. A range of resistant carrot material bred at Horticulture Research International has been released to seed companies for use in the production of improved carrot varieties. The partially-resistant variety 'Flyaway' was made available to amateur gardeners in 1993 and to commercial growers in 1995 as a result of this research.

Orchard comparisons of `Cox's Orange Pippin' grown on selections of the apple rootstock M.9

SummaryTwenty four selections (clones) of M.9 were compared as rootstocks for the apple cv. Cox's Orange Pippin in three orchard trials planted on similar sites at Horticulture Research International (HRI)-East Malling between 1980 and 1987. Rootstock clone effects on maiden tree quality were inconsistent in two of the trials, and appeared to be associated more with nursery conditions at the time of raising the trees than with the clone of rootstock used. Shoot growth following planting in the orchard was related positively to tree size (maiden tree height and feathering) at the time of planting and no differences in initial tree vigour were attributable to rootstock clone. Tree size differences at maturity were variable between trials, were small (10% to 30%), and in most instances not statistically significant. Nevertheless, the scion weights of trees on the Dutch T.337, the French INRA 71/0 and Lancep (Pajam 1) rootstock clones were 10% to 30% smaller than trees on the EMLA clone when the trials were terminated. None of the clones had any consistent effect on the precocity of flowering, the numbers of floral buds produced by the trees, or the efficiency of fruit set. In two of the three trials, annual yields and cumulative yields per tree were very similar for trees on all the M.9 clones, even when adjusted for differences in tree size at planting. Estimates of yield efficiency in each year (yield in kg cm22 trunk cross sectional area) also showed no statistically significant differences between any of the M.9 clones in these two trials. In a third trial, yield precocity in the first three cropping years was much lower than average for trees on the Belgian clone Nic.29, the French clone INRA 71/0 and the German clone SP.1 (719), even after adjustments to take account of differences in tree size at planting. Trees on the Dutch selection T.340, the Belgian selections Nic.16 and Nic.19 the German selection SP.18 (751) and M.9A also showed reduced yield efficiency compared with trees on the EMLA clone in two of these three years. No differences were recorded in the mean fruit size at harvest or the yield of fruits in the highest quality grades in this third trial.

The use of measurements of soil mineral N in understanding the response of crops to fertilizer nitrogen in intensive cropping rotations

The effects on succeeding crops of nitrogen in residues returned to the soil of brassica vegetable crops (Brassica oleracea) were studied on a nitrogen-retentive silt loam soil at Horticulture Research International, Kirton, Lincolnshire, UK. A sequence of four crops was started in 1988 and again in 1989. In the first sequence, two successive cauliflower crops (Brassica oleracea cv. botrytis L.), crops 1 and 2 in the first year, were followed by Brussels sprouts (Brassica oleracea cv. Gemmifera D.C.), crop 3, in the second and spring barley (Hordeum vulgare), crop 4, in the third year. The second sequence, started in spring 1989, was on an area adjacent to the first, but with spring wheat (Triticum aestivum) as crop 4. The sites followed an unfertilized, 1-year grass ley (1987) or spring barley (1988) with 73 and 107 kg N/ha soil mineral nitrogen (SMN, NH4+NO3) in the 0–90 cm soil profile at the start of each sequence. The marketable yield of the first cauliflowers in both sequences increased with fertilizer nitrogen up to 240 or 300 kg/ha. The response of the second cauliflower crop to fresh N declined with increasing amounts of SMN (0–90 cm) at planting, with no response when SMN exceeded c. 270 kg N/ha. Crop 3 apparently responded to fresh N in sequence 1 but not in sequence 2 even though SMN at planting ranged up to c. 400 kg N/ha. This difference in response was largely explained by the amount and distribution of SMN in the 0–30 and 30–60 cm layers when the sprouts were planted. Soil mineral N to 90 cm when the cereals were sown was only c. 100 kg N/ha, which did not reflect the large amounts of N applied to the previous crops. In spite of this, barley yield without any fresh fertilizer N did vary with the amounts of N applied to the previous crops. The results showed that SMN was a useful predictor of fertilizer response in some, but not all, situations. To use SMN more generally requires interpretation using dynamic simulation models.

Localised insecticide treatment for the control of vine weevil larvae ( Otiorhynchus sulcatus) on field-grown strawberry

Three field experiments at Horticulture Research International (HRI), Efford, in 1992, 1994 and 1995, showed that the incorporation of controlled-release chlorpyrifos granules (78–208 g a.i. m −3) into the compost of the propagation modules of strawberry plants gave significant control of vine weevil larvae in the field. Better control (approximately 90%) was achieved when field planting was in early August so that the root system was small at the time of egg infestation, than following planting in mid-May (approximately 50% control) where a much larger root system had grown. Control was as good where the treated modules had a compost volume of 80 ml as where the volume was 230 ml. Better control occurred when eggs used for artificial infestation were placed close to the crown of the plant than when placed 15 cm away. In a replicated field experiment at Hinton Admiral, Hampshire, in 1994, pre-planting spot, band or whole-bed soil treatment of raised-bed, polythenemulched plants (planted as bare-root runners) with the chlorpyrifos granules (at 52 or 104 g a.i. m −3) did not reduce the numbers of larvae significantly. In a further field experiment at HRI East Mailing in 1994, treatment of a 15 cm diameter by 15 cm deep cylinder of soil round each plant (at 104 g a.i. m −3) did not significantly affect larval numbers. Pre-planting spot treatment with imidacloprid granules (125 g a.i. ha −1) or a curative drench (at the same dose) was not efficacious, though good control was achieved with a standard curative drench of chlorpyrifos (13.1 kg a.i. ha −1). The survival of vine weevil eggs and of young larvae was low (less than 9%), circumstantial evidence pointing to soil type and condition as being important determining factors. Lighter soils with a structure allowing easy movement of larvae appeared to be more favourable for the survival of the pest. Where adults were caged round strawberry plants with the surrounding surface soil replaced by sand in the field, most eggs (more than 79%) occurred in the top 0–1 cm of sand, 50% being found on or close to the surface (0 – 0.2 cm depth) in one experiment. Eggs were aggregated weakly round a single non-mulched plant, but there was little evidence of such aggregation round plants grown in polythene-mulched, raised beds. Survival to the semi-mature larval stage from eggs placed on, or 2 cm below, the soil surface 15 cm from the crown of the plant was as great as for eggs placed on, or 2 cm below, the surface adjacent to the crown. Larvae were shown to migrate towards the crown of the plant during their development. Implications for the optimum placement of insecticide granules are discussed.

Sweet cherry rootstock studies: Comparisons ofPrunus cerasusL. andPrunushybrid clones as rootstocks for Van, Merton Glory and Merpet scions

SummarySixteen Prunus species and hybrid clones were tested as potential dwarfing rootstocks for the sweet cherry scion cvs Van, Merton Glory and/or Merpet. The trials were grown without irrigation on light loam soils at Horticulture Research International, East Mailing, UK. Although several of the rootstocks produced fully dwarfed trees, only one, a clone of P. mugus, showed good nursery budtake and tree longevity. Trees on another dwarfing rootstock, Gisela 1 (Gi.172/9), grew very poorly on this site and several of the trees died before the completion of the experiment. Trees on Gi.202/2 and MxM 39 both showed poor graft compatibility. Although not fully dwarfing, several other rootstocks tested showed great promise by inducing excellent yield precocity and productivity. Amongst the most promising rootstocks were Weiroot 10, Gi.195/4 and Gisela 6 (Gi.148/1).

Spatial and temporal population structure of Brevicoryne brassicae

AbstractAllozymes from individual aphids were used as markers to examine the structure of Brevicoryne brassicae colonies collected from field experiments at Horticulture Research International, Wellesbourne, during the summers of 1991, 1992 and 1993. Eighteen enzyme systems were examined using cellulose acetate electrophoresis, but only 6‐phosphogluconate dehydrogenase (6‐PGDH) showed polymorphism (three alleles) in the samples. There were significant differences in gene frequencies between populations at some sites within 1 kilometre and between times of sampling, with an increase in the proportion of the most common genotype AA later in the season, possibly due to selection during the summer of the best adapted clones. These changes in gene frequency might produce biased results in trials screening brassica crops against aphids.

An investigation of the resistance to cabbage aphid in brassica species

SummaryFifteen Brassica species and subspecies, as well as accessions of Arabidopsis thaliana and Eruca sativa, were evaluated for their resistance to the cabbage aphid, Brevicoryne brassicae, in the field and laboratory at Horticulture Research International (HRI) Wellesbourne in 1992. In the laboratory, aphid performance was measured in terms of pre‐reproductive period, reproductive period, population increase and insect survival. Using these parameters it was possible to identify brassicas possessing antibiosis resistance. In the field B. brassicae attack was assessed in terms of numbers of insects and it was possible to determine aphid preferences for alighting on different species. High levels of antixenosis and antibiosis resistance were discovered in accessions of Brassica fruticulosa and B. spinescens, in a Brassica juncea breeding line and in Eruca sativa. Partial resistance was found in several other Brassica species. The potential of these various sources as donors of resistance genes to be bred into cultivated brassicas is discussed.