Secondary Gene Pool Research Articles

Pyramiding white mould resistance between and within common bean gene pools

Singh, S. P., Schwartz, H. F., Terán, H., Viteri, D. and Otto, K. 2014. Pyramiding white mould resistance between and within common bean gene pools. Can. J. Plant Sci. 94: 947–954. White mould caused by Sclerotinia sclerotiorum (Lib.) de Bary is a severe disease of common bean (Phaseolus vulgaris L.) in North America and similar production regions. Low to high levels of white mould resistance exist in cultivated and wild common bean and the secondary gene pool. But, cultivars with high levels of resistance are not yet available. The objectives of this study were: (1) to combine or pyramid high levels of resistance from multiple-parent populations between and within gene pools, and (2) to compare the response of pyramided breeding lines (PBL) to four isolates of the white mould pathogen with that of known sources of resistance. Two Andean PBL each derived from an Andean intra-gene pool and inter-gene pool, four Middle American pinto bean PBL from one inter-gene pool multiple-parent population, their seven resistant parents, and susceptible pinto, Othello, were inoculated in the greenhouse with pathogen isolates ARS12D and ND710 at University of Idaho, Kimberly in 2012, and isolates CO467 and NY133 at Colorado State University, Fort Collins in 2013. The percentage of resistant plants for the PBL ranged from 62.5 to 81.9, and mean white mould score from 4.0 to 4.6. The respective values for the white mould resistant parents ranged from 3.1 to 57.0 for the percentage of resistant plants and from 4.8 to 7.5 for the mean white mould score. Furthermore, PBL SE154-1 inoculated with isolate ARS12D, and SE152-6 with isolates ARS12D and ND710 had 100% resistant plants. But, only SE153-1 and SE155-9 inoculated with isolates CO467 and NY133 had significantly (P ≤0.05) higher levels of resistance than the most resistant parents A 195 and VA 19. The pinto bean PBL SE153-1, SE153-6, and SE153-7, and Andean types SE152-6 and SE155-9 were the most resistant among all genotypes inoculated with the four isolates of the white mould pathogen in both greenhouses.

Introgressing White Mold Resistance from Phaseolus coccineus PI 439534 to Common Pinto Bean

ABSTRACTWhite mold [caused by Sclerotinia sclerotiorum (Lib.) de Bary] is a devastating disease of common bean (Phaseolus vulgaris L.) in cool‐ to moderate‐temperature and wet‐production regions worldwide. Use of resistant cultivars is crucial for effective and economical white mold control. Partial resistance exists in cultivated and wild common bean and Phaseolus species of the secondary gene pool. The objectives were to (i) develop highly resistant breeding lines (BL) from a recurrent interspecific backcross of common pinto bean ‘UI 320’ with P. coccineus PI 439534, and (ii) compare their response with known sources of resistance. Five pinto BL derived from UI 320 × 2/PI 439534 interspecific backcross population, the two parents, nine known sources of resistance, and susceptible pinto ‘Othello’ were screened in the greenhouse. Sclerotinia sclerotiorum isolates ARS12D and ND710 were used at the University of Idaho, Kimberly, in 2012 and isolates CO467 and NY133 at Colorado State University, Fort Collins, in 2013. All five interspecific pinto BL (VC13‐1, VC13‐3, VC13‐4, VC13‐5, VC13‐6) in Idaho and three (VC13‐4, VC13‐5, VC13‐6) in Colorado exhibited significantly (P ≤ 0.05) higher levels of resistance than PI 439534. Their resistance was either similar to (in Colorado) or higher (in Idaho) than the highest levels available in other interspecific BL (92BG‐7, I9365‐31, VCW 54, VRW 32) derived from the secondary gene pool thus far, as well as medium‐ (USPT‐WM‐1) and small‐ (‘ICA Bunsi’) seeded Middle American and large‐seeded Andean dry (G 122) and green (NY 6020‐4) beans. The effectiveness of the five interspecific pinto BL for controlling white mold with and without fungicides and other disease management strategies should be performed. Genetics of resistance and tagging and mapping of new resistance genes and/or quantitative trait loci should be performed. Also, high levels of resistance from the five interspecific pinto BL should be pyramided across Phaseolus species and/or transferred into cultivars.

Trifolium interspecific hybridisation: widening the white clover gene pool

White clover (Trifolium repens) is adapted to moist, fertile soils in temperate zones. Despite its heterozygous allotetraploid nature, it lacks useful genetic variation for survival and growth in semi-arid, infertile soils. Although white clover is apparently genetically isolated in nature, 11 other taxa have so far been found that can be artificially hybridised into the wider gene pool. These species range from annuals to long-lived, hardy perennials with adaptations to stress environments, and they potentially provide new traits for the breeding of more resilient varieties of white clover. The delineation of the secondary, tertiary and quaternary gene pools is described, along with a review of interspecific hybrids achieved to date. The results of large breeding programs to integrate traits from T. nigrescens and 4x T. ambiguum are reviewed, and schemes introduced for the use of T. uniflorum, T. occidentale, T. pallescens, 2x T. ambiguum and 6x T. ambiguum. Interspecific hybrid breeding of white clover has the potential to enable the development of resilient perennial clovers for seasonally dry, infertile grassland environments in many parts of the world.

Highly Fertile Intersectional Blueberry Hybrids of Vaccinium padifolium Section Hemimyrtillus and V. corymbosum Section Cyanococcus

The primary gene pool of Vaccinium species used by blueberry breeders has traditionally been the North American Vaccinium species of section Cyanococcus. Blueberries in commercial production represent three primary Vaccinium species and two ploidy levels. Significant use has been made of the secondary gene pool of Vaccinium, especially in the development of southern highbush blueberry (Vaccinium ×corymbosum) cultivars. Section Hemimyrtillus species are distantly related and are best considered part of the tertiary gene pool of Vaccinium. Vaccinium padifolium, a member of section Hemimyrtillus and native to the Madeira Islands, Portugal, has features of notable value to conventional blueberry development, among these: upright structure, strong growth, abundant flowering and fruiting, good self-fertility, inflorescence structure suited to mechanical harvesting, and indeterminate/repeat flowering. Our objective was to incorporate germplasm from this section into cultivated materials and transfer the desirable traits these species possess for commercial production. We used V. padifolium as a female in crosses with V. corymbosum and generated two highly fertile hybrids. These hybrids are intermediate in morphology, phonological, and their hybridity has been confirmed through DNA testing. These hybrids were used in further crosses to a variety of section Cyanococcus selections and have generated numerous second-generation hybrids. We have also determined by flow cytometry the ploidy levels of the hybrids and several previously unevaluated section Hemimyrtillus species.

Breeding Common Bean for Resistance to White Mold: A Review

ABSTRACTUnder favorable weather conditions white mold causes 100% loss of yield and quality of susceptible common bean (Phaseolus vulgaris L.) cultivars. The disease is endemic and widespread in North and South American countries including the United States, Canada, Argentina, and Brazil. Our objective was to review progress achieved in identifying sources of resistance in Phaseolus species, genetics, and breeding for resistance to white mold. We also describe an integrated genetic improvement strategy for resistance to the pathogen with germplasm enhancement and cultivar development using multiple‐parent crosses and gamete selection methods of breeding. Substantial progress has been made in understanding pathogenic variation in the white mold fungus, developing screening methods, identifying sources of resistant germplasm, genetics of resistance, and introgressing resistance from the secondary gene pool, and breeding for resistance to white mold. Also, molecular marker‐assisted selection for partial resistance is practiced. However, development of white mold resistant common bean cultivars in most market classes has been slow and localized. Breeding strategies for simultaneous and integrated genetic improvement of qualitatively and quantitatively inherited resistances to white mold and cultivar development are briefly described.

Molecular and morphological diversity of on-farm hazelnut (Corylus avellana L.) landraces from southern Europe and their role in the origin and diffusion of cultivated germplasm

Hazelnut (Corylus avellana L.) is a traditional nut crop in southern Europe. Germplasm exploration conducted on-farm in five countries (Portugal, Spain, Italy, Slovenia, and Greece) identified 77 landraces. The present work describes phenotypic variation in nut and husk traits and investigates genetic relationships using ten simple sequence repeat (SSR) markers among these landraces, 57 well-known references cultivars, and 19 wild accessions. Among the 77 landraces, 42 had unique fingerprints while 35 showed a SSR profile identical to a known cultivar. Among the 42 unique landraces, morphological observations revealed high phenotypic diversity, and some had characteristics appreciated by the market such as nut round and caliber. Analysis of genetic relationships and population structure allowed investigation of the origin and spread of the cultivated germplasm in southern Europe. Our results indicate the existence of three primary centers of diversity in the Mediterranean basin: northwestern Spain (Tarragona) and southern Italy (Campania) in the West and Black Sea (Turkey) in the East. Moreover, the data suggest the existence of secondary gene pools in the Iberian (Asturias) and Italian (Liguria and Latium) Peninsulas, where local varieties were recently domesticated from wild forms and/or from introduced ancient domesticated varieties.

Interspecific hybridization betweenCajanus cajan(L.) Millsp. andC. lanceolatus(WV Fitgz) van der Maesen

Cultivated pigeonpea has a narrow genetic base. Wild relatives play an important role in the efforts to broaden its genetic base. In this report, we present a successful wide-cross between the cultivated pigeonpea andCajanus lanceolatus, a wild relative from the secondary gene pool, native to Australia, with desirable traits such as frost and drought resistance. A range of F1progeny were obtained and the resultant F1hybrid plants set mature pods and seeds. The hybrids had intermediate morphology, sharing the traits of both the parents. All the F1hybrids flowered profusely. Some of the hybrids were completely male sterile and some were partially fertile with pollen fertility ranging from 35 to 50 %. Meiotic analysis of the fertile F1hybrids revealed a high degree of meiotic chromosome pairing between the two parental genomes. Meiotic analysis of the sterile F1hybrids revealed that the breakdown of microsporogenesis occurred at the post-meiotic stage after the formation of tetrads. Fertile plants formed regular bivalents with normal disjunction, except for occasional asynchrony at meiotic II division.

Elucidation of Genetic Relationships in the Genus Cajanus Using Random Amplified Polymorphic DNA Marker Analysis

In this present investigation, a total of 27 RAPD primers were used to elucidate the genetic relationships between cultivated Cajanus cajan cultivars and 10 allied species of primary, secondary and tertiary gene pool, including C. cajanifolius, C. scarabaeoides, C. platycarpus, C. albicans, C. volubilis, C. sericeus, C. acutifolius, C. lineatus, C. lanceolatus and C. reticulates. All primers showed polymorphism at species level and produced 215 unequivocal polymorphic bands, with an average of 7.96 bands per primer. These polymorphic primers exhibited variation with regard to average band informativeness, resolving power, and showed high polymorphism information content value. No single primer was able to distinguish between all the two cultivars of C. cajan and ten allied species of Cajanus, but several species specific amplified fragments were observed. The pair wise Jaccard’s similarity coefficient values revealed high level of inter-specific genetic variation in the genus Cajanus. Cluster analysis exhibited the grouping of two C. cajan accessions with C. cajanifolius in one cluster, while except C. platycarpus, all the nine wild Cajanus species belonging to the secondary and tertiary gene pool form another cluster. The present analysis more or less agreed with the sectional classification of the genus Cajanus, and it has been hypothesized that cultivated pigeonpea has evolved through multi-genomic interaction through C. cajanifolius, and it has experienced minor genomic reorganization during its divergence. Again, identification of species specific amplification pattern substantiated the utility of RAPD markers on selection of suitable species to transfer the desirable trait into cultivated C. cajan, through marker aided breeding for its genetic augmentation, and also for the effective management of genetic resources of C. cajan.

Conventional and Molecular Approaches towards Genetic Improvement in Pigeonpea for Insects Resistance

Pigeonpea [Cajanus cajan (L.) Millspaugh] is an important food legume of the semi-arid tropics (SAT) sustaining livelihood of millions of people. Stagnant and unstable yield per hectare all over the world is the characteristic feature of this crop. This is primarily ascribed to its susceptibility/sensitivity to a number of biotic and abiotic factors. Among biotic factors, insects such as pod borer (Helicoverpa armigera), pod fly (Melanoagromyza obtusa) and spotted borer (Maruca vitrata) substantially damage the crop and result in significant economic losses. Management of these insects by genetic means has always been considered environment friendly approach. However, genetic improvement has always been impeded by limited genetic variability in the primary gene pool of pigeonpea. Wild species present in the secondary and tertiary gene pools have been reported to carry resistance for such insects. However, transfer of resistance through conventional backcrossing has not been much successful. It calls for gene introgression through marker assisted backcrossing (MABC) or advanced backcross breeding (AB breeding). In this review, we have attempted to assess the progress made through conventional and molecular breeding and suggested the ways to move further towards genetic enhancement for insects resistance in pigeonpea

Molecular characterization of ZzR1 resistance gene from Zingiber zerumbet with potential for imparting Pythium aphanidermatum resistance in ginger

Soft rot disease caused by the oomycete Pythium aphanidermatum (Edson) Fitzp. is the most economically significant disease of ginger (Zingiber officinale Rosc.) in tropical countries. All available ginger cultivars are susceptible to this pathogen. However a wild ginger relative viz., Zingiber zerumbet L. Smith, was identified as a potential soft rot resistance donor. In the present study, a putative resistance (R) gene designated, ZzR1 was isolated and characterized from Z. zerumbet using sequence information from Zingiber RGCs identified in our earlier experiments. Analysis of the 2280bp segment revealed a 2157bp open reading frame (ORF) encoding a putative cytoplasmically localized protein. The deduced ZzR1 protein shared high homology with other known R-genes belonging to the CC-NBS-LRR (coiled coil-nucleotide binding site-leucine rich repeat) class and had a calculated molecular weight of 84.61kDa. Real-time PCR analysis of ZzR1 transcription in Z. zerumbet following pathogen infection demonstrated activation at 3hpi thus suggesting an involvement of ZzR1 in Z. zerumbet defense mechanism. Although many R-genes have been characterized from different taxa, none of them will help in the development of resistant ginger cultivars owing to the phenomenon of “Restricted Taxonomic Functionality” (RTF). Thus ZzR1 gene characterized from the resistant wild Zingiber accession represents a valuable genomic resource for ginger improvement programs. This first report on R-gene isolation from the Zingiber secondary gene pool is pivotal in designing strategies for engineering resistance in ginger, which is otherwise not amenable to conventional improvement programs owing to sexual reproduction barriers.

White Mold–Resistant, Interspecific Common Bean Breeding Line VRW 32 Derived from Phaseolus costaricensis

The interspecific breeding line VRW 32 (Reg. No. GP‐287, PI 665037) of common bean (Phaseolus vulgaris L.), which is resistant to white mold [caused by Sclerotinia sclerotiorum (Lib.) de Bary], was jointly developed at the University of Idaho Kimberly Research and Extension Center, Kimberly, ID; Colorado State University, Fort Collins, CO; and CIAT, Cali, Colombia. The Idaho Agricultural Experiment Station released VRW 32 on 7 Dec. 2011. VRW 32 is the first white mold–resistant interspecific breeding line derived from P. costaricensis Freytag & Debouck, a member of the secondary gene pool of common bean. VRW 32 was derived from recurrent backcrossing between the small‐seeded (100‐seed weight < 25 g) tropical black common bean cultivar ICA Pijao and the small‐seeded wild P. costaricensis germplasm accession G 40604 (100‐seed weight < 19 g). ICA Pijao has an indeterminate upright growth habit Type II, purple flowers, and resistance to Bean common mosaic virus and tolerance to Bean golden mosaic virus. G 40604 has an indeterminate climbing growth habit Type IV and deep reddish‐purple magenta flowers. VRW 32 has growth habit Type II, white flowers, grayish‐brown seed, and white mold resistance with a score of 2.7 in the field and 4.3 in the greenhouse in Idaho and 5.5 in the greenhouse in Colorado compared with 5.7, 5.8, and 6.6, respectively, for the recurrent parent, ICA Pijao. VRW 32 matures in approximately 100 d in southern Idaho. VRW 32 may be used to study the interaction between the pathogen and different sources of white mold resistance and for pyramiding resistance from across Phaseolus spp. and introgressing higher levels of resistance into common bean cultivars.

Screening of wild and cultivated lentil germplasm for resistance to stemphylium blight

Lens culinaris Medik. ssp. culinaris is the only cultivated species in the genus Lens. Intensive selection pressure to develop new cultivars, a narrow genetic base, co-evolution of pathogens to partially resistant cultivars and other factors have accelerated susceptibility to different fungal diseases in this species. Few sources for resistance to stemphylium blight (SB) caused by Stemphylium botryosum Wallr. exist among commercial lentil cultivars. A total of 70 accessions were selected from seven species of the genus Lens to screen for SB resistance. The L. culinaris accessions were screened in four different environments, and the accessions of Lens ervoides, L. culinaris ssp. orientalis, Lens tomentosus,Lens nigricans, Lens odemensis and Lens lamottei in growth chamber or greenhouse experiments to identify resistance sources for potential use in lentil breeding. A highly aggressive isolate of SB was used as an inoculum to screen them under controlled conditions. Lentil cultivars ‘Eston’ (resistant) and ‘CDC Glamis’ (susceptible) were used as checks with consistent results in all experiments. Most of the L. culinaris accessions were susceptible to SB, whereas more than 70% of the wild lentil accessions had disease severity scores equal to or significantly lower than that of the SB-resistant check ‘Eston’. Some wild species accessions previously identified with resistance to anthracnose (Colletotrichum truncatum) and ascochyta blight (Ascochyta lentis) were also highly resistant to SB. The highest frequency of resistance to SB was found in L. lamottei followed by L. ervoides of the secondary gene pool. These sources can potentially be used to develop new commercial cultivars with multiple or single disease resistance.

Pollen Tube Growth After Intergeneric Pollinations of iap‐Homozygous Sorghum

ABSTRACTHybridization within sorghum [Sorghum bicolor (L.) Moench] has been the primary means of creating genetic diversity for improvement. While considerable variation exists within S. bicolor, traits such as biotic stress tolerance could be improved if secondary and tertiary germplasm pools were accessible through hybridization. Sorghum germplasm possessing the inhibition of alien pollen (iap) allele has enhanced the ability to make successful wide hybridizations between secondary and tertiary gene pools. However, the range of this efficacy has not been tested. Pollen from Miscanthus Andersson, Pennisetum Rich., Sorghastrum Nash, and Zea L. was transferred to the stigmas of S. bicolor lines Tx3361 (with the iap allele) and ATx623 (without the iap allele). Pollen of all genera exhibited tube growth, but the frequencies of germination and growth rates varied among species and accessions within a genus. Significantly more pollen germinated and grew into the pistils of Tx3361 than ATx623. Pollen grains were noticeably more numerous on stigmas of Tx3361, implying that factors within Tx3361 may also affect pollen adhesion. The results indicate that the potential for intergeneric hybridization of S. bicolor via Tx3361 will vary based on the individual species and accessions within a species that are used as pollinators.

Potential to improve oilseed rape and canola breeding in the genomics era

With 2 figures and 1 tableAbstractHigh‐throughput genomics technologies today offer unprecedented possibilities for gene discovery, complex trait analysis by genome‐wide association studies, global gene expression analyses, genomic selection and predictive breeding strategies. Dissection of the complex Brassica napus genome using mapping‐by‐sequencing techniques provides a powerful bridge between genetic maps and genome sequences. The completed sequence of the Brassica rapa A genome and the expected forthcoming publication of the C genome (Brassica oleracea) will greatly accelerate the release of public reference sequences for B. napus (genome AC). Dramatically falling DNA costs for targeted or genomic resequencing and the availability of a new, high‐density B. napus single‐nucleotide polymorphism (SNP) array open the way for considerably more efficient mining and exploitation of genetic variation within the primary and secondary gene pools of B. napus. In this review, we outline some of the most significant recent advances in high‐throughput genomics of Brassica crops and their potential impact on germplasm development and breeding of oilseed rape and canola in the coming years and decades.

VACCINIUM SPECIES OF SECTION HEMIMYRTILLUS - THEIR VALUE TO CULTIVATED BLUEBERRY AND APPROACHES TO UTILIZATION

The primary gene pool of Vaccinium species used by breeders has traditionally been the North American Vaccinium species in section Cyanococcus. Blueberries in commercial production represent several Vaccinium species and ploidies. Moreover, significant use has been made of the secondary gene pool of Vaccinium, especially in the development of southern highbush cultivars. Section Hemimyrtillus represents species that are part of the tertiary gene pool of Vaccinium. Two species of section Hemimyrtillus, native to the Portuguese islands of Madeira (Vaccinium padifolium Smith) and the Azores (Vaccinium cylindraceum Smith), have features of notable value to conventional blueberry development such as upright structure, strong growth, abundant flowering and fruiting, good self-fertility, acceptable fruit quality, inflorescence structure suited to mechanical harvesting, and repeat flowering. Vaccinium cylindraceum is deciduous, whereas V. padifolium is evergreen. Vaccinium arctostaphylos L., a native of the Caucasus region, is closely allied to V. padifolium, hybridizes freely with it, and has many similar characters, but with the valuable addition of greater cold hardiness. Initial progress has been made at incorporating these species into forms compatible with Vaccinium corymbosum L. based blueberry cultivars, and further evaluations are being made of both parental material and the derived hybrids.

Vacciniumspecies of sectionHemimyrtillus: their value to cultivated blueberry and approaches to utilization1This article is part of a Special Issue entitled “A tribute to Sam Vander Kloet FLS: Pure and applied research from blueberries to heathland ecology”.

The primary gene pool of Vaccinium species used by breeders has traditionally been the North American Vaccinium species in section Cyanococcus. Blueberries in commercial production represent several Vaccinium species and ploidies. Moreover, significant use has been made of the secondary gene pool of Vaccinium, especially in the development of southern highbush cultivars. Section Hemimyrtillus represents species that are part of the tertiary gene pool of Vaccinium. Two species of section Hemimyrtillus, native to the Portuguese islands of Madeira (Vaccinium padifolium Smith) and the Azores (Vaccinium cylindraceum Smith), have features of notable value to conventional blueberry development such as upright structure, strong growth, abundant flowering and fruiting, good self-fertility, acceptable fruit quality, inflorescence structure suited to mechanical harvesting, and repeat flowering. Vaccinium cylindraceum is deciduous, whereas V. padifolium is evergreen. Vaccinium arctostaphylos L., a native of the Caucasus region, is closely allied to V. padifolium, hybridizes freely with it, and has many similar characters, but with the valuable addition of greater cold hardiness. Initial progress has been made at incorporating these species into forms compatible with Vaccinium corymbosum L. based blueberry cultivars, and further evaluations are being made of both parental material and the derived hybrids.

Photosynthate remobilization capacity from drought-adapted common bean (Phaseolus vulgaris L.) lines can improve yield potential of interspecific populations within the secondary gene pool

Interspecific lines obtained from crosses between common bean (Phaseolus vulgaris L.) and other species from its secondary gene pool have a tendency for excessive vegetative growth and low grain yield. Contrariwise, drought-adapted common bean lines have been observed to produce high yields despite low shoot biomass production. This was attributed to greater remobilization of photosynthates to grain development. The objective of the present study was to investigate whether F2-families derived from crosses between an interspecific line and drought-adapted P. vulgaris lines have improved ability to remobilize greater proportion of photosynthate from shoot biomass to grain yield and subsequently obtain higher yield potential. Seven F2-progenies derived from crosses of an interspecific hybrid line of P. vulgaris × Phaseolus dumosus with seven drought-adapted lines reflecting a range of photosynthate remobilization and partitioning were evaluated under irrigated and rainfed field conditions along with their eight parent lines and one drought-tolerant check at the International Center of Tropical Agriculture (CIAT) at Palmira, Colombia. Although no single parent trait led to higher yield potential in progenies, the mean yield potential of the progenies, as well as mean yield under drought was significantly higher than yields of the interspecific parent, indicating that crosses with drought-adapted bean lines with greater plant efficiency constitute a promising breeding approach for yield improvement of interspecific crosses in both drought stressed and favorable environments.

Field evaluation of resistance to Colletotrichum truncatum in Lens culinaris, Lens ervoides, and Lens ervoides × Lens culinaris derivatives

Anthracnose, caused by Colletotrichum truncatum, is a major disease of lentil ( Lens culinaris Medik.). Resistance to the more virulent race Ct0 of the pathogen is extremely rare within the cultivated L. culinaris gene pool and is limited to partial resistance. The secondary gene pool of L. culinaris, especially Lens ervoides, is a source of resistance. Previously, a population of interspecific recombinant inbred lines was developed between susceptible L. culinaris line Eston and resistant L. ervoides L-01-827A; both resistant and susceptible stable lines were then identified in the population. A multi-year field trial in two different disease nurseries was conducted with the objectives of assessing relative resistance levels in the field and to evaluate the usefulness of field-nurseries for selecting resistance. A sub-set of the interspecific lines and L. culinaris and L. ervoides lines were evaluated which included eight resistant, eight partially resistant and four susceptible lines using a randomized complete block design with four replications per site over two years. Results confirm that disease control can be obtained using L. ervoides-derived resistance gene(s) as under high disease pressure, some interspecific lines were significantly more resistant than the most resistant L. culinaris lines. Resistance ratings from disease nurseries were significantly correlated (0.69–0.90) with inoculations of both the virulent race Ct0 of C. truncatum and the less virulent race Ct1 on the interspecific lines suggesting that field nurseries could effectively be used for selecting for resistance within a lentil breeding program.

Hybridisation of Australian chickpea cultivars with wild Cicer spp. increases resistance to root-lesion nematodes (Pratylenchus thornei and P. neglectus)

Australian and international chickpea (Cicer arietinum) cultivars and germplasm accessions, and wild annual Cicer spp. in the primary and secondary gene pools, were assessed in glasshouse experiments for levels of resistance to the root-lesion nematodes Pratylenchus thornei and P. neglectus. Lines were grown in replicated experiments in pasteurised soil inoculated with a pure culture of either P. thornei or P. neglectus and the population density of the nematodes in the soil plus roots after 16 weeks growth was used as a measure of resistance. Combined statistical analyses of experiments (nine for P. thornei and four for P. neglectus) were conducted and genotypes were assessed using best linear unbiased predictions. Australian and international chickpea cultivars possessed a similar range of susceptibilities through to partial resistance. Wild relatives from both the primary (C. reticulatum and C. echinospermum) and secondary (C. bijugum) gene pools of chickpea were generally more resistant than commercial chickpea cultivars to either P. thornei or P. neglectus or both. Wild relatives of chickpea have probably evolved to have resistance to endemic root-lesion nematodes whereas modern chickpea cultivars constitute a narrower gene pool with respect to nematode resistance. Resistant accessions of C. reticulatum and C. echinospermum were crossed and topcrossed with desi chickpea cultivars and resistant F4 lines were obtained. Development of commercial cultivars with the high levels of resistance to P. thornei and P. neglectus in these hybrids will be most valuable for areas of the Australian grain region and other parts of the world where alternating chickpea and wheat crops are the preferred rotation.

Screening new Arachis amphidiploids, and autotetraploids for resistance to late leaf spot by detached leaf technique

Cultivated groundnut is susceptible to late leaf spot (LLS) caused by Phaeoisariopsis personata [(Berk. & M.A. Curtis) Aex] and resistance is low to moderate in the primary gene pool of groundnut. Closely related wild species in the secondary gene pool are highly resistant to the disease. All the closely related Arachis species are diploid and cultivated groundnut is a tetraploid. Utilization of diploid Arachis species to transfer LLS resistance is time consuming and cumbersome. New sources of Arachis hypogaea (also called synthetic groundnut) were developed at ICRISAT. These are tetraploids and the present investigation has shown that they are resistant to LLS.