Resistant Potato Clones Research Articles

A breeding approach to enhance late blight resistance in potato

ABSTRACT A study was conducted at the Advanced Seed Research and Biotech Centre, ACI Limited from 2017 to 2020 for developing late blight (LB) resistant potato clones where BARI Alu 77 was used as the female parent and BARI Alu 53 was the male parent. Thirty-two potato clones out of 330 were selected based on plant vigour, tuber shape, size and colour. Finally, a putative clone, C2-5, was selected as a LB resistant, in which 0.4–0.5% foliage destruction was observed after 90 days of planting under artificial inoculation and natural infection of Phytophthora infestans. On an average, a maximum of 10.6 tubers/hill was recorded. Maximum 713.7 g of tubers per hill was found along with the highest yield potential of 59.5 metric tons per hectare, when no fungicide was applied. Besides, it was PCR positive for different LB-resistance genes/QTLs, such as Rpi-abpt1, R3b, R1, Rpi-sto1, Rpi-blb1, and Rpi-Smira1 from R2-F1R3, R3b-F4/R5, CosA, Ssto-448, 1521/518 and 45/XI primers, respectively. Therefore, this developed clone, C2-5, can be a potential candidate as a cultivar, as well as an elite germplasm for further LB resistance potato breeding programmes.

Performance of Solanum phureja-derived bacterial-wilt resistant potato clones in a field naturally infested with Ralstonia solanacearum in Central Brazil

ABSTRACT Bacterial wilt (BW), or brown rot, caused by the soil and seed borne bacterium Ralstonia solanacearum, is one of the most devastating diseases of potatoes cultivated in warmer regions of the world. There are no potato cultivars with a desirable level of BW resistance, although it has been recognized that resistance can be an outstanding component for disease management. However, the sources of resistance available lack agronomic traits required by potato growers, therefore being of little interest to breeders. The objective of this work was to evaluate the performance of 11 clones selected for BW resistance and improved for tuber traits upon selection in the last two decades. The clones under test were compared with susceptible and resistant clones and cultivars, in a completely randomized blocks design with three replications of single lines of 10 plants, in a field naturally infested with race 1, biovar 1, phylotype II of R. solanacearum. BW incidence was assessed 60-70 days after planting and total tuber yield in each plot was recorded 110 days after planting. All the evaluated clones presented higher levels of resistance to BW compared with the commercial varieties, not differing from the resistant, not commercial, controls. In a next step, these clones will be characterized for other desirable traits and those which combine high level of resistance and commercial characteristics will be recommended for breeders for enriching the genotypic background in the search for commercial varieties. We also confirmed that the cultivar BRSIPR Bel displays an intermediate level of resistance, what makes it an interesting genitor for its good agronomic characteristics. The findings of this work demonstrate that the improved potato clones selected under tropical conditions in the Embrapa’s pre-breeding project possess high and stable levels of resistance to bacterial wilt, being a valuable resource for breeders.

Selection of potato clones for heat tolerance and resistance to potato viruses X and Y for processing purposes

AbstractPotato (Solanum tuberosum L.) is one of the most important crops for human consumption worldwide, representing an essential component for the food security of several countries. However, yield and quality are negatively affected by biotic and abiotic stresses. In this sense, the selection of potato cultivars tolerant to heat and resistant to diseases is of great importance. Our goal was to select clones suitable for the chips industry, having heat tolerance and bearing the Rx1 and Ryadg alleles, which confer resistance to Potato virus X and Potato virus Y. We evaluated 491 clones originating from 31 biparental crosses under three different seasons in terms of heat stress (without heat stress [WHS], moderate heat stress [MHS], and high heat stress [HHS]). The evaluated traits were specific gravity (SG), dry matter yield (DMY), and proportion of physiological disorders (PD). After evaluation in the WHS and MHS seasons, the presence of the Rx1 and Ryadg alleles was investigated with the help of molecular markers in the 68 clones showing the best performance, which descended from the DGN2103 and DGN4002 parental clones. To gather the genotypic values for all traits in each season, the clones were ranked according to an index based on the genotype–ideotype distance. On average of all seasons, the top 10% selected clones by the index were 9 and 0.1% higher than the Atlantic cultivar for the traits DMY and SG, respectively, and 80% lower than Atlantic cultivar for PD. In conclusion, we report the selection of potato clones suitable for industrial processing.

Diallel Cross in Potato Cultivars (Solanum tuberosum L.) and Evaluation of Their Progenies Under Deficit Water Stress

This study was performed to assess superior potato clones for agronomic traits and water deficit stress tolerance in laboratory and greenhouse settings over 3 years (2016–2018). Four cultivars, ‘Satina,’ ‘Caesar,’ Savalan,’ and ‘Agria’ were used as parents and crossed by mutual hybridization based on a diallel cross using the Griffing III method. Of 279 successful crosses, 7,980 true potato seeds from 12 breeding populations were obtained, from which 2,313 seeds germinated and 244 hybrids were selected. The selected hybrids were cultured in triplicate in a splitplot based on a randomized complete block design. The main factor consisted of three levels of irrigation (100%, 80%, and 60% of available water) and a subfactor of 12 populations (♀‘Agria’ × ‘Satina’♂, ♀‘Agria’ × ‘Caesar’♂, ♀‘Agria’ × ‘Savalan’♂, ♀‘Satina’ × ‘Agria’♂, ♀‘Satina’ × ‘Caesar’♂, ♀‘Satina’ × ‘Savalan’♂, ♀‘Caesar’ × ‘Satina’♂, ♀‘Caesar’ × ‘Agria’♂, ♀‘Caesar’ × ‘Savalan’♂, ♀‘Savalan’ × ‘Satina’♂, ♀‘Savalan’ × ‘Agria’♂, and ♀‘Savalan’ × ‘Caesar’♂). In all three environmental conditions, the highest tuber yield and tuber weight per plant were related to ♀‘Agria’ × ‘Caesar’♂. The most general combining ability that produced positive and significant tuber yield in mild and severe stress conditions was in ‘Agria’ and ‘Caesar’ cultivars. Therefore, these cultivars can easily transfer these traits to offspring and increase the expression of these traits. The specific combining ability between potato cultivars had positive and significant effects on tuber yield under the growth conditions tested. These crosses can be used for the production of drought resistant potato clones.

Resistance of sweet potato clones to meloidogyne incognita races 1 and 3

The objective of this study was to evaluate sweet potato clones for resistance to root-knot nematode, Meloidogyne incognita races 1 and 3. For each nematode physiological race, a greenhouse experiment was set up in a randomized block experimental design with three replications and six plants per plot. Fifty-eight sweet potato clones from the UFVJM germplasm bank were evaluated, plus five commercial cultivars (Brazlândia Rosada, Brazlândia Branca, Palmas, Princesa and Coquinho), plus the cv. Santa Clara tomato (susceptible to Meloidogyne spp.). Stems were planted in 72-cell expanded polystyrene trays, filled with commercial substrate and inoculated with the pathogen thirty days after planting. Forty-five days after inoculation, the eggs were extracted, counted, and later evaluated. Resistance level classification was performed based on reproduction factor (RF) and reproduction index (RI). Among the 63 analyzed clones, a percentage of 78% were classified as resistant to M. incognita race 1.79% to race 3 and 67% showed multiple resistance to both M. incognita races.

Management of Bacterial Wilt [Rhalstonia solanacearum Yabuuchi et al., 1995] of Potatoes: Opportunity for Host Resistance in Kenya

This article gives a general overview of bacterial wilt of potatoes and its management. It also highlights the potential of host resistance as an important component of integrated management of bacterial wilt in Kenya. Bacterial wilt has spread to all potato growing areas in Kenya, affecting over 70% of potato farms and causing yield losses of between 50 to 100%. This disease has no effective means of control because crop protection chemicals are ineffective and expensive and biological control agents are ineffective. In addition, phytosanitary methods such as quarantine are either expensive or difficult to apply and cultural methods such as crop rotations are largely impractical because the farms are too small to allow effective rotation, the pathogen has a wide host range, and it persists for long in the soil. Development of resistant cultivars could therefore play an important role in managing the disease. More resistant potato clones have recently been identified by CIP scientists, and this resistance needs to be incorporated into the popular but susceptible Kenyan potato cultivars so as to increase potato production in Kenya. For better results, use of high resistant varieties may be coupled with use of disease-free tubers and clean fields.

RESISTANCE EVALUATION ON POPULATIONS OF CROSSES BETWEEN TRANSGENIC POTATO KATAHDIN RB AND NON-TRANSGENIC ATLANTIC AND GRANOLA TO LATE BLIGHT (Phytophthora infestans) IN CONFINED FIELD TRIAL

Late blight resistance gene (RB gene) isolated from Solanum bulbocastanum, is a broad resistance gene against all races of Phytophthora infestans. The gene was transformed into Katah-din event SP904 and SP951 using Agrobacterium tumefaciens and these transgenic plants have been crossed with susceptible potato cultivars Atlantic and Granola. Populations of the crosses have been molecularly characterized for the integration of the RB transgene. The study aimed to evaluate the resistance of the populations of crosses between transgenic Katahdin RB and susceptible non-transgenic parents (Atlantic and Granola) to late blight in a confined field trial at Pasir Sarongge, Cianjur, West Java. A total of 84 clones originated from four popula-tions were evaluated for resistance to late blight. These included 22 clones of Atlantic x transgenic Katahdin SP904, 16 clones of Atlantic x transgenic Katahdin SP951, 19 clones of Granola x transgenic Katahdin SP904, and 27 clones of Granola x transgenic Katahdin SP951. Observations of the late blight infection were conducted when late blight symptoms were detected, i.e. at 56, 60, 63, 70, and 77 days after planting (DAP). The result showed there were high variations in the resistance level of all the 84 clones tested. Clones of crosses between susceptible parents (Atlantic or Granola) and resistant parents (transgenic Katahdin SP904 or Katahdin SP951) showed a similar pattern based on the area under disease progress curve (AUDPC) value, i.e. 377.2 greater than the AUDPC of the resistant parents (180.1), but smaller than that of the susceptible parents (670.7). Observation at 77 DAP resulted four resistant potato clones having resistance score of 7.0-7.6, higher than the transgenic parents Katahdin SP904 (4.6) and Katahdin SP951 (6.8), i.e. clone B8 (Atlantic x transgenic Katahdin SP951) with resistance score of 7.6 and clones B26 (Atlantic x transgenic Katahdin SP951), C183 (Granola x transgenic Katahdin SP904), and D89 (Granola x transgenic Katahdin SP951) with resistance score of 7. These four transgenic potato resistant clones need to be further developed as promising potato clones to late blight.<br /><br />

Performance of a North American Field Population and a Laboratory Colony of the Potato Tuberworm,Phthorimaea operculella, on Foliage of Resistant and Susceptible Potato Clones

Foliar resistance of two potato clones was tested against a Columbia Basin field population (CBFP) and a Colorado laboratory colony (COLC) of the potato tuberworm, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae). The first clone was a cross of a cultivated potato, Solanum tuberosum L. (Solanales: Solanaceae), and a wild potato, Solanum berthaultii Hawkes (Q 174-2); the second clone was cv. Allegany, S. tuberosum L.. In no-choice assays, defoliation by P. operculella larvae of COLC and CBFP did not differ on Allegany and Q174-2. Larval weight and production of COLC and CBFP colonies were similarly reduced on Q174-2 compared to cv. Allegany, although larval weights and production of the CBFP population were slightly less affected by the host. Larval production by the COLC on Allegany was greater than that on Q174-2, while that of the CBFP on Allegany and Q174-2 did not differ. However, production of P. operculella larvae by the CBFP on Q174-2 during no-choice assays was greater than that in choice tests, indicating reduced host preference. Most of the larvae recovered from either host were fourth instars, followed by third instars. Although the levels of resistance expressed by Q174-2 potato clone to the two P. operculella populations differed in magnitude, nearly all of P. operculella performance criteria measured in this study were adversely affected by Q174-2 foliage compared to the commercial potato cultivar, cv. Allegany.

Superoxide dismutase isoelectric focusing patterns as a tool to differentiate pathotypes of Globodera spp.

Abstract Isoelectric focusing was used to separate proteins from cyst extracts of potato cyst nematode (PCN) populations. In a first set of assays, cyst extracts from standard populations of Globodera rostochiensis pathotypes Ro1, Ro2, Ro3, Ro2/3, Ro4, and Ro5, and G. pallida pathotypes Pa2 and Pa3, were loaded on isoelectric focusing gels. Gels were stained for superoxide dismutase (SOD), esterase, and glucose-6-phosphate isomerase (GPI). Twelve bands of SOD activity were detected, six (B1-B6) migrating towards the basic zone and the other six (A1-A6) migrating towards the acidic zone, starting from the loading point. A cluster analysis was carried out based on a data matrix that reported the presence or absence of SOD bands on the isozyme electrophoresis patterns (IEPs). Globodera spp. were clearly distinguished and, within G. rostochiensis, Ro2 and Ro4 shared a high level of similarity, respectively, with Ro3 and Ro5; moreover, Ro1 could be clearly distinguished from Ro2/3 and Ro4/5. Globodera pallida Pa2 and Pa3 also shared a high level of similarity. In contrast, esterase and GPI IEPs did not discriminate among G. rostochiensis standard pathotypes. Subsequently, 14 field populations of G. rostochiensis, five from Italy and nine from Venezuela, and three field populations of G. pallida, two from Italy and one from Chile, were assayed to obtain SOD IEPs. Italian populations had previously been identified at pathotype level by bioassays according to the generally accepted international test using different resistant potato cultivars and clones. The cluster analysis carried out on the SOD IEPs of all the populations tested formed four distinct groups within G. rostochiensis and only one within G. pallida. Pathotype identification of Globodera populations by SOD IEPs was not able to discriminate between bioassay standard couples Ro2/Ro3, Ro4/Ro5 and Pa2/Pa3. Therefore, three groups were assigned to Ro1, Ro2/3 and Ro4/5, and a fourth group to Pa2/Pa3. Four Venezuelan populations, not identified at pathotype level by bioassays, formed a distinct fifth group. By means of the method described herein, four additional unknown Venezuelan populations could be assigned to Ro1 group and one to Ro2/Ro3 group; one G. pallida population from Chile was assigned to Pa2/Pa3 group.

Evaluation of potato clones for resistance to stem canker and tuber black scurf in field studies following artificial inoculation with Rhizoctonia solani AG-3 in Maine*

Potato clones were evaluated for resistance to Rhizoctonia stem canker, stolon lesion and black scurf in field experiments during the 1997 and 1998 growing seasons. Seed pieces were inoculated with Rhizoctonia solani Anastomosis group 3 (AG-3) by dipping them in a slurry or suspension of inoculum. Uninoculated controls were also planted. Seed emergence was assessed beginning at two weeks after planting. After 60 days, incidence and severity (%) of stem and stolon cankers were assessed. The numbers of root and stolon lesions were also quantified. At harvest, the incidence of black scurf on tuber yield and numbers were also determined. Significant differences in emergence of potato seed pieces (%) were detected between inoculated and control treatments and the incidence of stem and root cankers differed among clones in both years. The incidence and severity of stem cankers and the numbers of stem and root lesions were not significantly correlated with the black scurf incidence on tubers. These studies suggest that various symptom types incited by Rhizoctonia can be important epidemiological factors in disease development.

Sistema de previsão de ocorrência de requeima em clones de batata suscetíveis e resistentes

Sistemas de previsão e cultivares resistentes à requeima são importantes ferramentas para reduzir a quantidade de fungicidas utilizados e os custos de produção da batata. O objetivo deste trabalho foi avaliar a utilização do sistema de previsão Blitecast e de clones suscetíveis e resistentes no manejo da requeima da cultura da batata na região produtora de Santa Maria, Rio Grande do Sul (RS). Os experimentos foram conduzidos na Universidade Federal de Santa Maria, na primavera de 2006 e no outono de 2007, sendo os dados meteorológicos medidos continuamente acima do dossel das plantas. Foram utilizados 10 tratamentos arranjados no delineamento inteiramente casualizado, com quatro repetições. Os tratamentos foram diferenciados pelos valores de severidade acumulados, calculados pelo sistema Blitecast, e pelos clones SMIJ461-1 e SMINIA793101-3, caracterizados como resistentes à requeima, e Macaca (suscetível). Verificou-se que o sistema Blitecast não foi eficiente para prever o momento de aplicação de fungicida no controle da requeima. Portanto, este deve sofrer ajustes para ser utilizado em clones suscetíveis. Nos clones considerados resistentes, a aplicação de fungicidas com base na utilização do sistema Blitecast não tem efeito sobre a severidade da requeima e a produtividade da cultura da batata.

Host resistance and influence of tuber surface on larval performance of potato tuberworm (Lepidoptera: Gelechiidae)

Potato tuberworm (PTW), Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), is one of the most important pests of potatoes in tropic and subtropic regions. Previous studies suggested that tuber periderm may limit larval penetration and establishment of PTW. Short term influence of parental host plant acclimatization, influence of tuber dormancy and influence of tuber periderm (the outer cork layer of tubers) on aspects of PTW biology were investigated on tubers of a susceptible commercial potato cultivar, cv. Allegany (Solanum tuberosum L.), and a resistant hybrid potato clone, Q174-2 (S. tuberosum × S. berthaultii Hawkes). Short-term parental host plant acclimatization did not affect numbers of PTW larvae on resistant and susceptible tubers. Numbers of larvae produced on tubers of Q174-2, and Allegany, were similar although larval weight was less on Q174-2 than on Allegany. Larval production increased with tuber age on both susceptible and resistant potato clones, suggesting that bud sprouts may enhance fitness by providing food and shelter for first instars prior to tuber entry. Removal of tuber periderm led to a significant increase in larval survival on Allegany and Q174-2, although proportional survival on Allegany and Q174-2 was similar to that on intact tubers, suggesting the involvement of internal rather than external periderm factors in tuber resistance of Q174-2. Weights of larvae reared on Q174-2 were consistently less than those of larvae reared on susceptible potato tubers in both intact and peeled tuber assays. Although the expression of periderm-mediated tuber resistance declines with tuber age, such resistance could significantly reduce preharvest field infestations by PTW and constitute an important component of sustainable PTW management, particularly for fresh market crops and for those potato crops stored for several months or less in the absence of refrigeration.

Foliar resistance to late blight in potato clones evaluated in national trials in 1997

Changes in the oomycetePhytophthora infestans in the United States and other parts of the world pose a significant threat to potato production. A continual evaluation of potato clones for resistance to late blight is necessary to identify clones with resistance and to monitor the stability of resistance in light of the emergence of new and more aggressive strains of this pathogen. Twentytwo potato clones (10 cultivars and 12 selections) were evaluated in 1997 for late blight resistance at seven U.S. locations. Seven late blight differentials (R1R2R3R4, R1R2R4, R1R3R4 R3, R8 R10, and Rmulti) were also included in the test at five of these locations. The US-8 strain of P.infestans was present at all locations. Percent infected foliage was recorded at approximately weekly intervals following the onset of disease. Area under the disease progress curve (AUDPC) was calculated. The nonparametric stability statistics mean absolute rank differences (Si(1)) and variances of the ranks (Si(2)) were used to analyze phenotypic stability. Although neither of these statistics was significant for individual clones, both of these statistics were significant when summed over clones, indicating the importance of genotype × environment interactions on the rankings of these clones across locations. The most late blight-resistant and susceptible clones were the most stable; clones in the intermediate ranges were most subject to rank changes due to genotype × environment interactions. The most late blight-resistant clones were AWN86514-2, B0692-4, B0718-3, and B0767-2. The most susceptible clones were B0811-13, B1004-8, Nor-Donna, and Krantz. AUDPC was very low for the late blight differentials R8 and Rmulti, moderately low for R10 and very high for the remaining differentials. This study is important in characterizing the reaction of potato clones to new strains of P.infestans.

Genetic Diversity in Diploid and Tetraploid Late Blight Resistant Potato Germplasm

An understanding of the genetic relationship within potato germplasm is important to establish a broad genetic base for breeding purposes. The objective of this study was to assess the genetic diversity of potato (Solanum tuberosum subsp. tuberosum Hawkes) germplasm that can be used in the development of cultivars with resistance to late blight caused by Phytophthora infestans (Mont.) de Bary. Thirty-three diploid and 27 tetraploid late blight resistant potato clones were evaluated for their genetic diversity based on 11 isozyme loci and nine microsatellites. A total of 35 allozymes and 42 polymorphic microsatellite fragments was scored for presence or absence. The germplasm was clustered based on the matrix of genetic similarities and the unweighted pair group means analysis of the isozyme and microsatellite data, which were used to construct a dendrogram using NTSYS-pc version 1.7. Twenty-three allozymes and DNA fragments were unique to the wild species. The diploid Solanum species S. berthaultii Hawkes and S. microdontum Bitter formed two distinct phenetic groups. Within S. microdontum, three subgroups were observed. The tetraploid germplasm formed another group, with S. sucrense Hawkes in one subgroup and the cultivated potato and Russian hybrids in another subgroup. Based upon the genetic diversity and the level of late blight resistance, S. microdontum and S. sucrense offer the best choice for strong late blight resistance from genetically diverse sources. This potato germplasm with reported late blight resistance should be introgressed into the potato gene pool to broaden the genetic base to achieve stronger and more durable resistance.

Short and long distance spread of potato leafroll luteovirus: effects of host genes and transgenes conferring resistance to virus accumulation in potato.

Potato leafroll luteovirus (PLRV) movement through phloem of PLRV-resistant potato clones was examined in experiments in which stem pieces were grafted either between infected rootstocks and virus-free susceptible scions or between infected scions and virus-free susceptible rootstocks. These test plants permitted either upwards or downwards virus movement into the susceptible tissue. Resistant potato clones had either host gene-mediated resistance (H-MR) or transgene-mediated resistance (T-NR, conferred by transformation with the PLRV coat protein gene) to PLRV accumulation. The rate of PLRV movement was similar whether stem tissue was taken from H-MR, T-MR or susceptible potato clones. Virus movement through two graft unions began around 7 days after grafting and was generally complete by about 14 to 16 days. Virus movement occurred soon after acquiring functional phloem continuity across grafts as demonstrated by tracing with 6(5)-carboxyfluorescein, a phloem-mobile dye. Most of the delay in virus detection after grafting probably resulted from the time necessary to develop new phloem strands across graft unions; subsequent movement of PLRV was rapid suggesting a passive process. PLRV infection was largely excluded from external phloem bundles in stem tissue of clones with either H-MR or T-MR. This trait was less pronounced as tissue aged. The mechanism limiting PLRV invasion of external phloem bundles of the T-MR clones appears to be similar to that operating in the H-MR clones. Results are discussed in the context of a proposed model of PLRV movement.

General resistance against potato virus Y introduced into a commercial potato cultivar by genetic transformation with PVYN coat protein gene

Transgenic cv. Folva potato plants expressing the coat protein gene of potato virus Y strain N (PVYN) were produced usingAgrobacterium tumefaciens mediated transformation. Forty independent transformants were selected for resistance screening. Four clones showed complete resistance to mechanical inoculation with all the five PVY isolates tested: the PVYN isolate from which the coat protein gene was derived, two PVYO isolates, and two PVYNTN isolates. Two of the fully resistant clones contained only one copy of the transgene, demonstrating that it is possible by genetic engineering to obtain highly virus resistant potato clones that can also be useful in future breeding programmes.

Inheritance of extreme resistance to potato virus Y in potato

Segregation for extreme resistance to PVY was evaluated in progenies derived from crossing two extremely resistant potato clones with parents differing in resistance. Resistance was evaluated after mechanical inoculation with PVYO and PVYN, and after graft inoculation with PVYO. Biological and serological tests (ELISA) were used for virus detection. The extreme resistance is governed by a single dominant gene, but observed segregations deviated from the expected ratios. Considerable modifying effects were detectable, depending on the potato genotype and virus isolate, for a significant excess of susceptible genotypes was observed in some progenies. Moreover, genotypes with non-parental types of resistance to PVY were observed.

Evaluation of diploid potato clones for resistance to tuber soft rot induced by strains ofErwinia carotovora subsp.atroseptica, E. carotovora subsp.carotovora andE. chrysanthemi

Tubers of clones from a diploid hybrid population ofSolanum phureja andS. stenotomum were screened for resistance to tuber soft rot caused by strains ofErwinia carotovora subsp.atroseptica (Eca),E. carotovora subsp.carotovora (Ecc) andE. chrysanthemi (Ech). Significant, positive correlations between resistance to the different strains and species were observed, indicating that screening for resistance to tuber soft rot could be accomplished by using just one of the three pathogens. Strains of Ecc and Ech were found to be much more virulent than strains of Eca. Inoculating with Ecc and Ech resulted in more distinct differences among susceptible, moderately resistant and resistant clones than inoculating with Eca.

Genotype by environment interaction in the assessment of tolerance of partially resistant potato clones to potato cyst nematodes

Summary Genotype by environment interactions in a number of field trials in different years are examined in relation to tolerance of potato cyst nematodes and the subsequent yield losses. A biplot technique is used to display the interaction effects graphically and facilitate identification of any patterns in the data. The results are assessed and discussed in relation to breeding strategies and the variation found between different nematode populations.

Integrated control of potato cyst nematodes using small amounts of nematicide and potatoes with partial resistance

SUMMARYThe control of potato cyst nematode (PCN) by less than approved amounts of nematicide combined with partially resistant potato clones was studied in a series of field experiments. On a site heavily infested with Globodera pallida only the most resistant clone (12380ac2) decreased the population density in untreated soil. With aldicarb at its full approved rate (3·36 kg ha‐1) numbers of PCN were decreased under all the genotypes, including the non‐resistant Maris Piper. Aldicarb at 1·68 kg ha‐1significantly decreased populations on all clones except 12380ac2. Aldicarb at 0·84 kg ha‐1still significantly decreased population densities and multiplication rates of G. pallida on two clones with intermediate resistance (12243acl and 11233ab22). At two G. rostochiensis sites with light infestations nematode multiplication rates were greater and the control given by aldicarb and partially resistant genotypes of potato was not as great as that at the site with G. pallida.Tuber yields were not increased by the application of aldicarb at the G. rostochiensis infested sites. However, at the site heavily infested with G. pallida the yield of the most intolerant genotype (12380ac2) was increased seven‐fold by the full rate of aldicarb (3·36 kg ha‐1) and four‐fold by the quarter rate (0·84 kg ha‐1)‐Yield of the most tolerant genotype (12243acl) was unaffected by the application of aldicarb.