Current Germplasm Research Articles

PedigreeNet: a web-based pedigree viewer for biological databases.

Plant breeding aims to improve current germplasm that can tolerate a wide range of biotic and abiotic stresses. To accomplish this goal, breeders rely on developing a deeper understanding of genetic makeup and relationships between plant varieties to make informed plant selections. Although rapid advances in genotyping technology generated a large amount of data for breeders, tools that facilitate pedigree analysis and visualization are scant, leaving breeders to use classical, but inherently limited, hierarchical pedigree diagrams for a handful of plant varieties. To answer this need, we developed a simple web-based tool that can be easily implemented at biological databases, called PedigreeNet, to create and visualize customizable pedigree relationships in a network context, displaying pre- and user-uploaded data. As a proof-of-concept, we implemented PedigreeNet at the maize model organism database, MaizeGDB. The PedigreeNet viewer at MaizeGDB has a dynamically-generated pedigree network of 4706 maize lines and 5487 relationships that are currently available as both a stand-alone web-based tool and integrated directly on the MaizeGDB Stock Pages. The tool allows the user to apply a number of filters, select or upload their own breeding relationships, center a pedigree network on a plant variety, identify the common ancestor between two varieties, and display the shortest path(s) between two varieties on the pedigree network. The PedigreeNet code layer is written as a JavaScript wrapper around Cytoscape Web. PedigreeNet fills a great need for breeders to have access to an online tool to represent and visually customize pedigree relationships. PedigreeNet is accessible at https://www.maizegdb.org/breeders_toolbox. The open source code is publically and freely available at GitHub: https://github.com/Maize-Genetics-and-Genomics-Database/PedigreeNet. Supplementary data are available at Bioinformatics online.

Phenolic Content and Antioxidant Activity in Trifolium Germplasm from Different Environments.

Phenolics are important mediators in plant-environment interactions. The presence and concentration of phenolic compounds and their antioxidant activity were evaluated in leaves and flowers of a set of Trifolium species originating from contrasting environments encompassing lowland and mountain sites. The current germplasm proved a great reservoir of phenolic compounds, with different chemical structure and, possibly, diversified biological activity. Germplasm groups with specific phenolic composition were observed. In some cases, different patterns bore a taxonomic meaning. Lowland germplasm showed higher concentration of total phenolics in leaves than mountain accessions (50.30 vs. 34.19 mg/g dry matter (DM)), while the latter had higher concentration in flowers (114.16 vs. 57.44 mg/g DM). Outstanding concentration of isoflavones was observed in leaves of lowland germplasm (24.19 mg/g DM), and of both proanthocyanidins and flavonoids in flowers of mountain germplasm (53.81 and 56.62 mg/g DM, respectively). The pattern of phenolic composition in lowland and mountain germplasm was suggestive of different adaptive strategies. Three assays of antioxidant activity were tested, which were characterised by rather different reactivity towards phenolic composition. The scavenging activity was higher for leaf extracts of lowland germplasm, and for flower extracts of mountain germplasm. Besides identifying germplasm of interest, this study also suggested possible links between environmental factors and concentration and composition of phenolic compounds.

Diversity analysis and genome-wide association studies of grain shape and eating quality traits in rice (Oryza sativa L.) using DArT markers.

Microarray-based markers such as Diversity Arrays Technology (DArT) have become the genetic markers of choice for construction of high-density maps, quantitative trait loci (QTL) mapping and genetic diversity analysis based on their efficiency and low cost. More recently, the DArT technology was further developed in combination with high-throughput next-generation sequencing (NGS) technologies to generate the DArTseq platform representing a new sequencing tool of complexity-reduced representations. In this study, we used DArTseq markers to investigate genetic diversity and genome-wide association studies (GWAS) of grain quality traits in rice (Oryza sativa L.). The study was performed using 59 rice genotypes with 525 SNPs derived from DArTseq platform. Population structure analysis revealed only two distinct genetic clusters where genotypes were grouped based on environmental adaptation and pedigree information. Analysis of molecular variance indicated a low degree of differentiation among populations suggesting the need for broadening the genetic base of the current germplasm collection. GWAS revealed 22 significant associations between DArTseq-derived SNP markers and rice grain quality traits in the test genotypes. In general, 2 of the 22 significant associations were in chromosomal regions where the QTLs associated with the given traits had previously been reported, the other 20 significant SNP marker loci were indicative of the likelihood discovery of novel alleles associated with rice grain quality traits. DArTseq-derived SNP markers that include SNP12_100006178, SNP13_3052560 and SNP14_3057360 individually co-localised with two functional gene groups that were associated with QTLs for grain width and grain length to width ratio on chromosome 3, indicating trait dependency or pleiotropic-effect loci. This study demonstrated that DArTseq markers were useful genomic resources for genome-wide association studies of rice grain quality traits to accelerate varietal development and release.

Design and Cost Analysis of a Self-contained Mobile Laboratory for Commercial-scale Aquatic Species Cryopreservation.

Although aquatic species cryopreservation protocols have been studied around the world over the past 60 yr., germplasm repository development efforts and commercialization have begun only recently. The goal of this project was to develop a self-contained mobile laboratory for on-site high-throughput cryopreservation of aquatic species. The objectives of this study were to: (1) identify how a mobile laboratory would function in different operational scenarios, (2) customize an enclosed cargo trailer to function as a mobile laboratory, (3) evaluate the laboratory layout and ability of cryopreservation equipment to operate from generator power, and (4) document the investment costs for private and public groups to integrate a mobile laboratory into an existing cryopreservation facility at three levels of automation and estimate the total cost per trip based on hypothetical assumptions for two scenarios (aquaculture production and repository development). There were three operational designs identified for the mobile laboratory: (1) self-contained work inside the unit using generator power, (2) work inside the unit using external facility power, and (3) using the equipment inside of a host facility. The investment costs for a base-level mobile laboratory ranged between US$5670 and US$5787 for private groups and between US$5208 and US$5315 for public groups. With the addition of a range of automated processing equipment, total investment costs ranged from US$13,616 to US$103,529 for private groups and US$12,494 to US$94,891 for public groups. The total cost per trip to cryopreserve sperm of 59 blue catfish, Ictalurus furcatus, males to produce 6300 0.5-mL French straws was estimated to range from US$6089 to US$14,633 for private and between US$5703 and US$16,938 for public groups depending on the level of automation. Total cost per trip to cryopreserve sperm of 500 males of five different species in the genus Xiphophorus to produce 641 0.25-mL French straws was estimated to range from US$6653 to US$7640 for private and US$7582 to US$8088 for public groups depending on level of automation. Overall, a commercial-scale mobile laboratory was developed that can assist current germplasm activities and support future repository and industry development, and the layout information provided can help others to design and build comparable units.

Current germplasm conservation of camellias in China

Current germplasm conservation of camellias in China

Genome-Wide Association Study of Grain Architecture in Wild Wheat Aegilops tauschii.

Aegilops tauschii, the D-genome progenitor of Triticum aestivum, encompasses huge diversity for various traits of potential economic importance such as yield, biotic and abiotic stress tolerance, quality and nutrition. In the present study, variation for grain size in Ae. tauschii germplasm was studied and its genetic basis dissected using genome-wide association study (GWAS). Grain length, width, and weight evaluated in 177 Ae. tauschii accessions over 3 years showed near normal distribution with 1.74-, 1.75-, and 2.82-fold variation, respectively. These lines were genetically characterized using genotyping-by-sequencing (GBS) protocol that produced 11,489 single nucleotide polymorphic (SNP) markers. Genetic diversity analysis revealed the presence of two distinct subgroups (designated as lineage 1 and 2) in Ae. tauschii. Based on GBS markers, the genetic similarity was calculated between the accessions and GWAS was conducted using 114 non-redundant accessions and 5,249 SNP markers. A total of 17 SNPs associated with grain size traits distributed over all the seven chromosomes were revealed with 6D, 5D, and 2D harboring most significant marker–trait associations. Some of the chromosomal regions such as 6D_66.4–71.1 cM, 1D_143.5–156.7 cM, and 2D_89.9–92.5 cM had associations with multiple traits. Candidate genes associated with cell division and differentiation were identified for some of the associated SNP markers. Further efforts to validate these loci will help to understand their role in determining grain size and allelic diversity in current germplasm and its effect on grain size upon transfer to bread wheat background.

CUBAN BEAN DIVERSITY: Study could lead to new germplam sources, markets

CUBAN BEAN DIVERSITY: Study could lead to new germplam sources, markets

Crop wild relatives of pigeonpea [Cajanus cajan (L.) Millsp.]: Distributions, ex situ conservation status, and potential genetic resources for abiotic stress tolerance

Pigeonpea [Cajanus cajan (L.) Millsp.] is a versatile, stress-tolerant, and nutritious grain legume, possessing traits of value for enhancing the sustainability of dry sub-tropical and tropical agricultural systems. The use of crop wild relatives (CWR) in pigeonpea breeding has been successful in providing important resistance, quality, and breeding efficiency traits to the crop. Current breeding objectives for pigeonpea include increasing its tolerance to abiotic stresses, including heat, cold, drought, and waterlogging. Here we assess the potential for pigeonpea CWR to be further employed in crop improvement by compiling wild species occurrence and ex situ conservation information, producing geographic distribution models for the species, identifying gaps in the comprehensiveness of current germplasm collections, and using ecogeographic information to identify CWR populations with the potential to contribute agronomic traits of priority to breeders. The fifteen prioritized relatives of pigeonpea generally occur in South and Southeast Asia to Australia, with the highest concentrations of species in southern India and northern Australia. These taxa differ considerably among themselves and in comparison to the crop in their adaptations to temperature, precipitation and edaphic conditions. We find that these wild genetic resources are broadly under-represented in ex situ conservation systems, with 80% of species assessed as high priority for further collecting, thus their availability to plant breeders is insufficient. We identify species and highlight geographic locations for further collecting in order to improve the completeness of pigeonpea CWR germplasm collections, with particular emphasis on potential traits for abiotic stress tolerance.

Morphological Characterization of Cassava (Manihot esculenta Crantz) Accessions Collected in the Centre-west, South-west and West of Côte d'Ivoire

Cassava ( Manihot esculenta Crantz) is an important food crop in Cote d'Ivoire. Nonetheless, its production is facing many constraints including the abandonment of landraces, fires, pests and diseases. Such a pressure can cause an erosion of the genetic diversity of cassava and wild relatives. In order to overcome those constraints, collections of traditional varieties were carried out in the Centre-west, South-west and West of Cote d'Ivoire. A total of 159 accessions were used. These accessions were observed using morphological parameter. Morphological characterization was done through multivariate analyses on these 159 accessions to better manage germplasm. Accessions were clustered into three classes with 143 morphotypes and 16 duplicates. Class 1 or Type Sie, composed of 45 accessions, included the majority of accessions that had the least common modalities of collection (yellow flesh, white skin, yellowish phelloderm and orange stem). Analysis of similarity / dissimilarity showed that clusters known as Sie, Bassie djele4 and Djonan djonan of the current germplasm were close to different groups Cosca4, D14 and 256 of the existing collection.

Conservation implications of the mating system of the Pampa Hermosa landrace of peach palm analyzed with microsatellite markers.

Peach palm (Bactris gasipaes) is cultivated by many indigenous and traditional communities from Amazonia to Central America for its edible fruits, and is currently important for its heart-of-palm. The objective of this study was to investigate the mating system of peach palm, as this is important for conservation and breeding. Eight microsatellite loci were used to genotype 24 open-pollinated progenies from three populations of the Pampa Hermosa landrace maintained in a progeny trial for genetic improvement. Both the multi-locus outcrossing rates (0.95 to 0.99) and the progeny level multi-locus outcrossing rates (0.9 to 1.0) were high, indicating that peach palm is predominantly allogamous. The outcrossing rates among relatives were significantly different from zero (0.101 to 0.202), providing evidence for considerable biparental inbreeding within populations, probably due to farmers planting seeds of a small number of open-pollinated progenies in the same plot. The correlations of paternity estimates were low (0.051 to 0.112), suggesting a large number of pollen sources (9 to 20) participating in pollination of individual fruit bunches. Effective population size estimates suggest that current germplasm collections are insufficient for long-term ex situ conservation. As with most underutilized crops, on farm conservation is the most important component of an integrated conservation strategy.

Good Genes from Asia—Contributions and Opportunities of Asian Origin Crops to U.S. Horticulture: An Introduction to the Workshop

Asia is a region rich in plant biodiversity with many centers of origin for numerous horticultural crops. Plant germplasm from Asia is thus important for new crop development in North America. Globalization and increased immigration have opened up markets for many Asian horticultural crops that are not currently or widely cultivated in the United States or have not been included in past germplasm exchanges. Many of them have the potential to become niche market crops, increasing crop diversity and the economic sustainability for American farmers as well as benefiting consumers because of unique nutritional or medicinal values. In the past, several workshops have discussed use of indigenous Asian plants (Mou and Wang, 2012), plant exploration in Asia (Hummer, 2007; Volk and Richards, 2011), and germplasm exchange experiences with countries signed up for the Convention on Biological Diversity (Widrlechner, 2005). Some of these workshops were hosted by the Working Group of Asian Horticulture. As the group began planning for the 2012 workshop, the idea of reviewing and introducing interesting ornamental plants into U.S. landscapes was brought up at the working group business meeting in Waikoloa, HI. This was further developed into a colloquium proposal by expanding to pomology and vegetable crops. Five speakers, including one international speaker, renowned for their experiences in germplasm collection and introduction, were invited. Although we did not secure the colloquium, the speakers decided to contribute to this topic as a workshop, and the allocated time for the workshop was extended to accommodate the rich content it offered to the audience. The workshop location could not have been any more appropriate than Miami, FL, a state very rich in both indigenous and introduced plant germplasm, with many species introduced from Asia. The objectives of this workshop were to 1) review contributions of Asian germplasm to the development of important horticultural crops, including small berries, woody ornamentals, and vegetables; 2) discuss regulatory issues and other barriers that exist in using Asian germplasm resources; and 3) provide outlooks for future opportunities in introducing new crops with Asian germplasm. Dr. Richard Olsen, from the U.S. National Arboretum, Floral & Nursery Plants Research Unit in Washington, DC, presented the latest information on germplasm resources of Asian origin for woody ornamentals and current germplasm exchange climate and regulatory issues between Asian countries and the United States under the influence of the Convention on Biological Diversity and U.S. import regulations. Dr. James D. McCreight, from USDAARS, U.S. Agricultural Research Station in Salinas, CA, reviewed a wide range of valuable traits of melons and several other cucurbits that have been introduced or could be introduced to the United States as well as two important horticultural technologies that originated in Asia. Dr. Kim Hummer, from USDA-ARS, National Clonal Germplasm Repository in Corvallis, OR, discussed the evolution of the octoploid strawberry species, Asian genes and breeding traits of raspberry, and described several berry species indigenous to Asia that could be used to develop new berry crops in the United States. From the content discussed in the workshop, it was evident that Asian germplasm has enormous potential for North American horticulture. Although germplasm exchange activities have been affected by changes in international laws and national regulations, the contribution of Asian germplasm to U.S. horticulture will increase as researchers continue to use its rich gene pools to develop cultivars with superior qualities.

Yield stability for cereals in a changing climate.

The United Nations Food and Agriculture Organisation (FAO) forecasts a 34% increase in the world population by 2050. As a consequence, the productivity of important staple crops such as cereals needs to be boosted by an estimated 43%. This growth in cereal productivity will need to occur in a world with a changing climate, where more frequent weather extremes will impact on grain productivity. Improving cereal productivity will, therefore, not only be a matter of increasing yield potential of current germplasm, but also of improving yield stability through enhanced tolerance to abiotic stresses. Successful reproductive development in cereals is essential for grain productivity and environmental constraints (drought, cold, frost, heat and waterlogging) that are associated with climate change are likely to have severe effects on yield stability of cereal crops. Currently, genetic gains conferring improved abiotic stress tolerance in cereals is hampered by the lack of reliable screening methods, availability of suitable germplasm and poor knowledge about the physiological and molecular underpinnings of abiotic stress tolerance traits.

Breeding investigations into the gene action and agronomic performance of sunflower traits based on F1 top-cross hybrids

SUMMARY Information on the performance and gene action of sunflower traits is still scarce in southern Africa despite the crop’s increasing importance and the growing demand for adapted cultivars. To generate this information, 30 malesterile lines were cross-bred to a restorer line generating 30 experimental hybrids. The hybrids and three check varieties were evaluated in South Africa, Zambia and Zimbabwe. Data was analysed using REML procedure in Gen- Stat®. Significant differences (P<0.05) were observed for grain yield traits, oil content and days to 50% flowering. Grain yield ranged between 1700 kg ha -1 and 4278 kg ha -1 , 1000-seeds weight between 59.4 g and 89.3 g, oil content between 36.6% and 44.6%, and days to 50% flowering between 55.5 and 68.0 for the hybrids but going up to 70 for the control varieties. Five hybrids were ranked above the highest performing check variety for grain yield. Two hybrids, HV9120 and HV9132, significantly outperformed the highest check variety by up to 19.6% and the lowest check variety by up to 91.6%. Oil content showed similar trends with eight hybrids having up to 6.8% yield advantage over the highest check variety and 19.3% over the lowest check variety. The high yields were attributed to heterosis and indicated the high potential for grain yield and oil content from the current germplasm set. The presence of high yielding hybrids with shorter days to 50% flowering, such as HV9132, HV9127, HV9128 and HV9135, showed that it was possible to breed for the short growing season, characteristics of most southern African areas, without compromising grain yield. General combining ability (GCA) effects were significant for all the traits indicating the importance of additive gene action for the traits. Parental lines KP1235, KP1304 and KP1290 that showed desirable GCA effects for at least three of the important traits, were selected for inclusion in the breeding programme for cultivars adapted to the region.

Phenotypic Variation and Patterns of Linkage Disequilibrium Associated with Introduced Genes in Spring Wheat

ABSTRACTIntroduction of genes from outside a primary germplasm base has the potential to impact phenotypic diversity, genetic structure, and patterns of linkage disequilibrium (LD). Our goals were to monitor the introduction of key genes in a hard red spring wheat (Triticum aestivum L.) germplasm set using historical cultivars, to determine the impact of the introduced genes on phenotypic diversity in elite germplasm, and to assess the impact of selection history on LD. A superior allele for bread making was introduced early in the 20th century and quickly became fixed. An allele for solid stems introduced in the mid 20th century is the major source of variation in current germplasm. An introduced allele for photoperiod insensitivity is an important source of variation for heading date in current germplasm. The allelic introductions impacted patterns of LD. The unlinked loci for reduced height, RHT‐B1 and RHT‐D1, were in LD. Linkage disequilibrium for physically linked markers near introduced genes did not exceed previous estimates of genome‐wide LD. Our results showed a pattern of gene introductions into the spring wheat germplasm base that continues to have an impact on phenotypic diversity and patterns of LD.

Genotypic variation in domesticated and wild accessions of the tropical tuberous legume Vigna vexillata (L.) A. Rich.

Vigna vexillata is an underutilised perennial tuberous legume with several multipurpose uses. In a comparative study to identify sources of potentially useful genetic variation, six cultivated accessions from two regions in Bali, a var. macrosperma accession and 12 wild accessions from Africa, Australia and Indonesia were evaluated for selected morphological, agronomic and phenological traits. Measurements were made of qualitative and quantitative traits on plants grown over the spring–autumn period in large pots on benches outdoors at Townsville, Australia (19°19.7′S, 146°45.7′E). Variation among the genotypes was assessed between the three main groups of accessions, between provenances within groups, and between accessions within provenances. Large variation was observed for most traits, with clear differentiation evident between the three main groups of accession. There was minimal variation within the Bali accessions for all except tuber attributes, while within the wild accessions there were some small differences due to provenance. The Bali accessions and var. macrosperma shared many attributes often associated with domestication, distinguishing them from the wild accessions. For example, the Bali accessions and var. macrosperma had broad-ovate leaflets, uniform-coloured seed testa, and non-dehiscent pods, and larger pods and seeds, seed yield per plant and seed harvest index than the wild accessions. Nonetheless, there were distinct differences between the Bali accessions and var. macrosperma. The Bali accessions had a larger seed size but fewer seeds per pod than var. macrosperma and were unique in having more than twice as many flowers per peduncle and a much longer duration of seed development than either var. macrosperma or the wild accessions. Whereas the Bali accessions were photoperiod-sensitive and as a consequence, late flowering and vegetatively vigorous, var. macrosperma was early flowering, more bush-like in habit and had higher seed yield and seed harvest index, all traits associated with domestication. Across all the accessions, there were significant correlations between many pairs of traits. While the present study identified sources of potentially useful variation, it was concluded that the lack of variation within the Bali accessions, combined with the paucity of both cultivated and var. macrosperma accessions in current germplasm collections, pose constraints to the future genetic improvement of V. vexillata.

HORTICULTURAL GENETIC RESOURCES COLLECTIONS: THEIR CHARACTERISTICS, STRENGTHS AND WEAKNESSES

HORTICULTURAL GENETIC RESOURCES COLLECTIONS: THEIR CHARACTERISTICS, STRENGTHS AND WEAKNESSES

Genetic relationships among Chickpea (Cicer arietinum L.) genotypes based on the SSRs at the quantitative trait Loci for resistance to Ascochyta Blight

Breeding for resistance to ascochyta blight in chickpea has been challenged by several factors including the limited sources of good resistance. Characterization of a set of genotypes that may contain different genes for resistance may help breeders to develop better and more durable resistance compared to current cultivars. The objective of this study was to evaluate the genetic relationships of 37 chickpea germplasm accessions differing in reaction to ascochyta blight using Simple Sequence Repeat (SSR) markers linked to Quantitative Trait Loci (QTL) for resistance. The results demonstrated that ILC72 and ILC3279, landraces from the former Soviet Union, had SSR alleles that were common among the kabuli breeding lines and cultivars. A lower SSR allele diversity was found on LG4 than on other regions. No correlation was found between the dendrogram derived using SSRs at the QTL regions and the SSRs derived from other parts of the genome. The clustering based on 127 alleles of 17 SSRs associated with the QTL for ascochyta blight resistance enabled us to differentiate three major groups within the current germplasm accessions. The first group was the desi germplasm originating from India and cultivars derived from it. The second group was a mix of desi genotypes originating from India and Greece, and kabuli breeding lines from ICARDA and the University of Saskatchewan. The third and largest group consisted of landraces originating mostly from the former Soviet Union and breeding lines/cultivars of the kabuli type. Several moderately resistance genotypes that are distantly related were identified. Disease evaluation on three test populations suggested that it is possible to enhance the level of resistance by crossing moderately resistant parents with distinct genetic backgrounds at the QTL for resistance to ascochyta blight.

Tequila and other Agave spirits from west-central Mexico: current germplasm diversity, conservation and origin

Current germplasm diversity used in the production of Agave spirits in west-central Mexico is in danger of erosion due to an expansion in the cultivation of the clone A. tequilana Weber var. azul, used for the elaboration of the famous drink “Tequila”. In order to define critical areas of in situ conservation and to determine the role of local native and mestizo cultures in the generation and maintenance of diversity, an ethnobotanical exploration was conducted in the center and south of the state of Jalisco. Results situate the nucleus of greatest diversity at present in the south of Jalisco and indicate that this is a result of a continuous process of selection initiated by the indigenous population for the production of food and fermented drinks, which continued into the final years of the 16th century but with a new objective: distillation using the Filipino technology introduced to west-central Mexico through Colima. More than 20 variants were found to be cultivated by the traditional farmers, the majority relating to the A. angustifolia Haw. complex. We discuss the possibilities of in situ germplasm conservation and its legal protection.

Genetic markers for manganese efficiency in durum wheat

AbstractManganese (Mn) deficiency is a major constraint of alkaline soils around the world, particularly for cultivation of durum wheat, which is more intolerant of low Mn levels than either common wheat or barley. Genetic variation for Mn efficiency exists in the current germplasm of durum wheat. Several restriction fragment length polymorphisms (RFLPs) previously shown to be linked to the Mel1 locus for Mn efficiency on chromosome 4HS of barley were tested on 88 selected F2 plants of the durum cross, ‘Stojocri 2’ (Mn efficient) בHazar’ (Mn inefficient). The Mel1‐linked RFLP marker Xcdo583a was closely linked to the trait and explained over 42% of the total variation for Mn efficiency in the ‘Stojocri 2’/‘Hazar’ F2 progeny. This marker has the potential to provide a valuable tool for the marker‐assisted selection of Mn‐efficient durum progeny derived from crosses with ‘Stojocri 2’.

Sugarcane clones vary in their resistance to sugarcane whitegrubs

To determine the extent and type of resistance to sugarcane whitegrubs in clones of sugarcane and some of their wild relatives, pot trials and field trials were carried out. The pot trials tested 405 clones and estimated tolerance effects by differences in the yields of tops, roots, and stubble of infested and uninfested plants and estimated antibiosis effects by differences in the survival and final weights of larvae placed into the pots. Two field trials used a split-plot design, insecticide treated or untreated, to determine tolerance effects on yields of commercial cane and antibiosis/antixenosis effects through differences in the number of larvae in untreated plots. Comparison of pot trials and field trials allowed an estimate of the usefulness of pot trials in estimating resistance to whitegrubs under commercial farming conditions. Both pot and field trials showed that a range of tolerance and antibiosis resistance mechanisms to whitegrub feeding exists within the current sugarcane germplasm and close relatives. Tolerance effects were apparent in the growth of tops, roots, and stubble. Antibiosis effects were apparent on grub survival and grub growth. Some of these tolerance effects are partially correlated with the general vigour of clones, but there are a number of clones that depart from the general relationships for tolerance and antibiosis. These clones would be especially important in any future program to increase the levels of resistance within the breeding gene pool. There was reasonable repeatability of pot-based tolerance levels between pot trials and with results derived from field trials. These results would be best incorporated into the current sugarcane-breeding program through a specific subprogram targetting grub resistance and using recurrent selection with rapid generation turnover. This would require the development of an appropriate screening system and may require 2 stages. The first would need to handle large numbers of clones to discard the least resistant. This could be followed by a more intensive screening (e.g. our pot technique) to identify the most resistant clones. Those identified after the first cycle of selection would then be recombined to produce more progeny and the process repeated. It is likely that several cycles would be necessary to increase resistance to a level that provides an economic protection.