The exploitation of genetic resources of Brassica oleracea in breeding for resistance to clubroot (Plasmodiophora brassicae)

Summary About 1000 Brassica oleracea accessions were evaluated in glasshouse tests for response to Plasmodiophora brassicae (clubroot). Resistance was confirmed in some north and west European kales and cabbage. A new source of resistance in cabbage, from Eire, is reported. Most other accessions were highly susceptible but lower levels of susceptibility were observed in open pollinated Brussels sprouts and forms of south European cabbage, cauliflower and broccoli. Modern breeding (as in the production of hybrid cultivars) appears to have resulted in increased susceptibility in several crop types. The implications of these results for the exploitation of germplasm are discussed.     

Geographic distribution of insect resistance in potatoes

Potato germplasm accessions representing 92 Solanum species and associated with known coordinates of latitude, longitude, and elevation were rated for resistance to one or more of the following potato insect pests: green peach aphid, Myzus persicae (Sulzer); potato aphid, Macrosiphum euphorbiae (Thomas); Colorado potato beetle, Leptinotarsa decemlineata (Say); potato flea beetle, Epitrix cucumeris (Harris); and potato leafhopper, Empoasca fabae (Harris), in Minnesota field trials (1966–1986). Chi-square tests were used to determine if the proportion of resistant accessions differed from expected among altitude classes, small geographic quadrants (4° latitude by 4° longitude), and larger geographic regions (Mexico-USA, Colombia-Ecuador, Peru, Bolivia, and Argentina). Resistant potatoes were not evenly distributed throughout North and South America. Fourteen quadrants were identified that had greater or fewer resistant accessions than expected. The Mexico-USA potatoes as a group had more resistance than expected to all insects except Colorado potato beetle. Potatoes from Colombia and Ecuador were less resistant than expected to all but green peach aphid. Potatoes from Peru were more resistant than expected to green peach aphid. Potatoes from Bolivia were less resistant than expected to potato aphid, but more resistant than expected to Colorado potato beetle, potato flea beetle, and potato leafhopper. Potatoes from Argentina were more resistant than expected to Colorado potato beetle and green peach aphid, but less resistant than expected to potato aphid and potato leafhopper. Potatoes from North America and collected at or below 2,500 m were more resistant than expected to green peach aphid, Colorado potato beetle and potato flea beetle. Potatoes from South America and elevations greater than 3,000 m were more resistant than expected to green peach aphid and potato aphid and those collected at or below 3,000 m were more resistant than expected to Colorado potato beetle, potato flea beetle and potato leafhopper.     

Identification of high levels of resistance to cabbage root fly, Delia radicum, in wild Brassica species

Wild Brassica species and associated breeding lines were evaluated for their resistance to Delia radicum, the cabbage root fly, in the field in 1993 and in the field, glasshouse and laboratory in 1996. High levels of antibiosis resistance were discovered in the field in 1993 in Brassica fruticulosa, B. incana, B. villosa and B. spinescens and confirmed in the field in 1996 while two B. oleracea accessions and the susceptible control Brussels sprouts variety, ‘Oliver’, were highly susceptible. No D. radicum pupae were found in the soil around the roots of B. fruticulosa and B. spinescens at the end of the season. All the Brassica species were attractive to egg-laying by D. radicum in the field and in a laboratory experiment and therefore lacked antixenosis resistance. In a series of glasshouse experiments, Brassica species and breeding lines were inoculated with D. radicum eggs supplied from a laboratory culture and the effects of larval feeding on plants recorded. Brassica incana, B. fruticulosa and B. spinescens were highly resistant, most plants surviving, whilst B. macrocarpa and B. villosa were moderately resistant as were two F1 lines bred from a cross between B. macrocarpa and B. oleracea. This revised version was published online in August 2006 with corrections to the Cover Date.     

Intertribal somatic hybridization between rapid cycling Brassica oleracea L. and Camelina sativa (L.) Crantz

Black spot, caused by Alternaria brassicae and A. brassicicola, is an important disease in all Brassica oleracea vegetables. Sufficient resistance to the pathogen is not found within the species, nor in species that readily cross to B. oleracea. Camelina sativa (false flax) is highly resistant to Alternaria spp. and has, in addition, other desirable characters for the improvement of B. oleracea. Protoplast fusions were performed between rapid cycling B. oleracea (tribe Brassiceae), which has good regenerability, and C. sativa (tribe Sisymbrieae) by polyethylene glycol (PEG) treatment. The B. oleracea fusion partner was inactivated by treatment with iodoacetate. C. sativa has poor regenerability; hence, no pretreatment was needed for this species. The protoplasts were cultured using a feeder layer system. A total of 2903 calli were isolated from the fusions. Fourteen of these initiated shoots, i.e., 0.5% regeneration frequency. Approximately 110 shoots were excised from 6 of these calli and transferred to rooting medium. Rooted plantlets grew vigorously in vitro and flowering was frequently observed. However, establishment of rooted shoots in soil was unsuccessful. Hybrid identity was confirmed by intermediate shoot morphology, RAPD marker analysis, and flow cytometric estimation of nuclear DNA content. This revised version was published online in August 2006 with corrections to the Cover Date.     

有毛野生甘蓝(Brassica incana)抗蚜虫特性研究

甘蓝(Brassica oleracea var.)是重要的十字花科芸薹属蔬菜,但生产中常遭受蚜虫危害,鉴定抗虫资源并了解其抗虫机制是抗虫育种的重要基础。课题组前期征集到1份周身覆盖浓密表皮毛的野生甘蓝(B.incana),为调查该材料是否具有蚜虫抗性,并明确其抗性是否与表皮毛有关,本研究利用该有毛野生甘蓝与1份无毛芥蓝(B.alboglabra)杂交,对双亲及其F2:3家系中有毛和无毛家系进行室内蚜虫接种发现,蚜虫在无表皮毛甘蓝上的平均产卵数(36.7枚)和存活天数(22.2 d)均显著高于有表皮毛甘蓝(平均产卵8.1枚,平均存活13.1 d)。为进一步明确该野生甘蓝对蚜虫是否具有化学毒杀或排拒作用,采用有毛和无毛甘蓝叶片的浸提液对蚜虫进行胃杀、触杀和拒食性调查发现,2种浸提液对蚜虫均无胃杀和触杀作用,但有毛甘蓝浸提液对蚜虫存在一定的趋避作用。表明野生甘蓝B.incana对蚜虫的抗性一方面源于其表皮毛的物理阻碍,另一方面与其体内化学物质的趋避作用有关。     

Genetic control of resistance to the aphid Brevicoryne brassicae in the wild species Brassica fruticulosa

Initial studies have shown variable resistance in Brassica fruticulosa to the aphid Brevicoryne brassicae The aim of this work was to fix high levels of resistance to B. brassicae in true breeding lines of B. fruticulosa and obtain data on the genetic control of resistance. Plants from initially variable B. fruticulosa accessions were selfed to produce inbred resistant and susceptible lines that were studied in three separate experiments to determine the extent to which resistance to B. brassicae had been fixed. Results from three experiments using successive generations of resistant and susceptible inbred lines showed that continued selection resulted in resistant inbred lines that supported an average of three aphids per plant compared with an average of 96 aphids per plant for susceptible inbred lines. Data collected from an experiment determining the resistant phenotype of lines including the selfed progenies and the F₁ and F₂ progeny of a cross between resistant and susceptible individual plants indicated that the resistance was not controlled by a single gene.     

山东高粱品种资源农艺性状及营养品质分析

对山东省现有的1223份高粱地方品种资源的农艺性状和部分材料的抗逆性、抗病虫性以及籽粒的蛋白质含量、赖氨酸含量和单宁含量进行了分析,结果表明:农艺性状中株高以高秆品种最多,其次是特高秆品种,生育期集中在106～120d,千粒重以小粒品种和中粒品种最多,分别占34.59%、43.34%;穗长集中在20.1～35cm,穗粒重集中在30.1～70g;穗型以散穗最多,粒色以红粒为主,壳色以黑壳最多。高粱抗性中,已经鉴定的材料有2份耐盐性为1级,96.09%材料的耐盐级别为4、5级,有4份材料抗旱为1级,有2份材料对黑穗病免疫,多数材料不抗螟虫和蚜虫,但有9份材料抗螟性为1、2级;在已经测定的种质资源中有79.16%的材料蛋白质含量低于12.5%,有7份材料的蛋白质含量超过15%,有81.54%的材料赖氨酸含量在0.21%～0.40%之间,有4份材料赖氨酸含量超过0.45%,单宁平均含量0.645%,基本成正态分布,有101份材料含量低于0.1%。总之,山东省地方品种资源农艺性状、抗性、籽粒品质变异类型丰富,可以为高粱育种提供良好的种质资源。     

番茄野生种L.pennellii核心种质抗虫性初步评价

以番茄属中近源野生种L.pennellii的16份核心种质为试材,开展对红蜘蛛和蚜虫抗虫特性的鉴定和评估。结果表明,16份核心种质中除LA1920高感红蜘蛛外,其余15份均对红蜘蛛表现出明显的抗性。15份抗红蜘蛛的材料中,1份表现免疫,12份表现高抗。试验还表明,16份材料对蚜虫均表现出很高的抗性,野生材料单株上的蚜虫数均明显少于栽培番茄,其中9份材料对蚜虫表现免疫,7份表现高抗。     

Combination of resistance to Verticillium longisporum from zero erucic acid Brassica oleracea and oilseed Brassica rapa genotypes in resynthesized rapeseed (Brassica napus) lines

Resynthesized (RS) forms of rapeseed (Brassica napus L.; genome AACC, 2n = 38) generated from interspecific hybridization between suitable genotypes of its diploid progenitors Brassica rapa L. (syn. campestris; genome AA, 2n = 20) and Brassica oleracea L. (CC, 2n = 18) represent a potentially useful resource to introduce resistance against the fungal pathogen Verticillium longisporum into the gene pool of oilseed rape. Numerous cabbage (B. oleracea) accessions are known with resistance to V. longisporum; however, B. oleracea generally has high levels of erucic acid and glucosinolates in the seed, which reduces the suitability of resulting RS rapeseed lines for oilseed rape breeding. In this study resistance against V. longisporum was identified in the cabbage accession Kashirka 202 (B. oleracea convar. capitata), a zero erucic acid mutant, and RS rapeseed lines were generated by crossing the resistant genotype with two spring turnip rape accessions (B. rapa ssp. olerifera) with zero erucic acid. One of the resulting zero erucic acid RS rapeseed lines was found to have a high level of resistance to V. longisporum compared with both parental accessions and with B. napus controls. A number of other zero erucic acid RS lines showed resistance levels comparable to the parental accessions. In the most resistant RS lines the resistance and zero erucic acid traits were combined with variable seed glucosinolate contents. Erucic acid‐free RS rapeseed with moderate seed glucosinolate content represents an ideal basic material for introgression of quantitative V. longisporum resistance derived from B. oleracea and B. rapa into elite oilseed rape breeding lines.     

Resistance in wheat to a new North American–Russian wheat aphid biotype

The Russian wheat aphid (RWA), is a serious threat to wheat production worldwide. The identification of a new RWA biotype in the USA virulent to all commercially grown winter wheats poses new challenges to wheat breeders. Wheat germplasm was evaluated to identify accessions resistant to the new virulent RWA isolate (biotype 2). Eleven biotype 1‐resistant wheats and one susceptible check were challenged with RWA biotype 2. Two resistant wheat entries were identified (one highly resistant and one moderately resistant). This information is useful to wheat breeders searching for sources of resistance to the new RWA biotype to incorporate into their breeding programmes.     

First steps towards a rational use of African rice, Oryza glaberrima, in rice breeding through a ‘contig line’ concept

The inheritance of resistance to clubroot, caused by Plasmodiophora brassicae, in Brassica oleracea was studied in the F₁, F₂and backcross progenies of four crosses between resistant and susceptible doubled haploid lines. The disease severity was scored visually on a 0–3 scale of symptom grades. These were analyzed qualitatively and quantitatively. The qualitative analysis involved the conversion of symptom grades to a classification as resistant or susceptible, and segregation ratios were used to test several simple genetic models. The quantitative analysis was based on a threshold model, in which symptom grades are considered to arise from splitting a continuous response range into disjoint intervals. This analysis was based on the maximum likelihood method, and several genetic models were evaluated.Of the four resistances studied, one was shown to be largely determined by two complementary genes. Two other resistances were also shown to be probably controlled by two genes, but the mode of inheritance was not determined unambiguously. The fourth resistance appeared to be determined by more than two genes.     

利用人工合成甘蓝型油菜建立白菜—甘蓝附加系

采用白菜子房培养和甘蓝胚培养方法得到了带有标记性状的白菜和甘蓝种间杂种，并将这些人工合成甘蓝型油菜回交于白菜，得到３１个白菜－甘蓝单体附加系（２ｎ＝２１），和１８个双体附加系（２ｎ＝２２），为进一步对附加染色体上的所载基因定位奠定了基础。此外，还研究了附加甘蓝染色体对雄笥和雌性育性的影响，结果表明，白菜中附加甘蓝染色体可明显降低育性，特别是可显著降低附加系的自交和杂交结实率。     

The Effect of A Genome Substitution on the Resistance of Brassica napus to Infection by Leptosphaeria maculans

Six accessions belonging to four subspecies of Brassica rapa, including three accessions of B. rapa subsp. sylvestris, were crossed with B. oleracea subsp. alboglabra in order to develop a series of synthetic B. napus lines with a common C genome but contrasting A genomes. Different A genomes had significant effects on the efficiency of B. napus resynthesis and the sexual compatibility of the synthetic lines with oilseed rape cultivars. The synthetic lines were used to investigate the effect of A genome substitution on the resistance of B. napus to infection by Leptosphaeria maculans, and to explore the potential for the use of wild forms of B. rapa in oilseed rape breeding programmes. Synthetic lines derived from two wild accessions of B. rapa, and their F₁ hybrids with oilseed rape cultivars, expressed high levels of resistance to L. maculans in glasshouse experiments. One of these lines also expressed high levels of resistance in field experiments in England and Australia when exposed to a genetically diverse pathogen population. All other synthetic lines and cultivars were highly susceptible in both glasshouse and field experiments. F₁ hybrids between oilseed rape cultivars and synthetic lines derived from B. rapa subsp. chinensis were significantly more susceptible than either parent.     

Genome-wide detection of genetic loci associated with soybean aphid resistance in soybean germplasm PI 603712

Soybean aphid (Aphis glycines Matsumura) has become one of the major pests of soybean [Glycine max (L.) Merr.] in North America since 2000. At least four biotypes of soybean aphid have been confirmed in the United States. Genetic characterization of new sources of soybean aphid resistance will facilitate the expansion of soybean gene pool for soybean aphid resistance and thus will help to develop soybean aphid resistant cultivars. To characterize the genetic basis of soybean aphid resistance in PI 603712, a newly identified resistant germplasm line, 142 F₂ plants derived from the cross ‘Roberts’ × PI 603712 and their parents were evaluated for soybean aphid resistance in the greenhouse, and were genotyped with BARCSoySNP6K Illumina Infinium II BeadChip. A genome-wide molecular linkage map was constructed with 1495 polymorphic SNP markers. QTL analysis revealed that PI 603712 possessed two major loci associated with soybean aphid resistance, located on chromosome 7 and 16, respectively. The locus on chromosome 7 was dominantly expressed and positioned about one Mega-base-pair distant from the previously identified resistance locus Rag1. The locus on chromosome 16 was positioned near the previously identified resistance locus Rag3 and expressed partially dominance or additive effect. Interestingly, two minor loci were also detected on chromosomes 13 and 17 but the alleles from PI 603712 decreased the resistance. In developing soybean aphid resistant cultivars through marker-assisted selection, an appropriate combination of resistance loci should be selected when PI 603712 is used as a donor parent of resistance.     

Evaluation of French Brassica oleracea landraces for resistance to Plasmodiophora brassicae

A total of 240 kale, 38 cabbage and 126 winter cauliflower French landraces from the B. oleracea genepool of INRA were assessed for resistance to clubroot caused by Plasmodiophora brassicaeWoron. Two French isolates of the pathogen (K and SJ) were used in the experiments under controlled conditions. The reaction of the 126 cauliflower accessions to naturally occurring clubroot was also evaluated in field trials. Kales exhibited considerable variation for expression of disease resistance and high levels of resistance were found in several accessions. In this group, single resistant plants were observed in most of the morphological types and from quite different geographical origins. Cabbage accessions were moderately to highly susceptible to both isolates. All cauliflower populations proved to be highly susceptible to K isolate and moderately susceptible to SJ isolate. In field trials, cauliflowers were also severely infected. Two lines selected from a resistant kale population were highly resistant against a large range of pathotypes of the pathogen. These lines presented a sufficient level of resistance to be directly useful in the breeding program in order to develop cauliflower and broccoli hybrids resistant to clubroot. This revised version was published online in July 2006 with corrections to the Cover Date.     

Screening and identification of resistance to bacterial soft rot in Brassica rapa

Mist-chamber, field, and detached leaf inoculation procedures identified plants resistant to bacterial soft rot [Erwinia carotovora subsp. carotovora, (Ecc)] in Brassica rapa and related species. The mist-chamber seedling inoculation provided the best correlation of mean disease severity ratings with the field plant inoculation (r = 0.67^**) and was used to identify resistant materials. The optimum mist-chamber incubation conditions to distinguish the resistance of accessions were 23 ^°C and 100% RH and were used for primary screening. A total of 752 accessions of B. rapa and related Cruciferae were screened. In general, accessions of B. oleracea were more resistant than accessions of B. rapa. Within B. rapa, subspecies pekinensis and chinensis were more susceptible than other subspecies. No completely resistant material was found. In species of B. rapa, only 7% of accessions showed some degree of resistance with plant-to-plant variation within the accessions. G30444, G30449, and AVRDC2837 were identified as the most resistant materials in B. rapa by both mist-chamber and field inoculations. The resistance was correlated between an USA isolate (Geneva-1) and two Chinese isolates (RL4-1 and RL-19) of Ecc. This revised version was published online in July 2006 with corrections to the Cover Date.     

Antibiosis and antixenosis to Rhopalosiphum padi among triticale accessions

Tests for antibiosis and antixenosis resistance to Rhopalosiphum padi L., the bird cherry-oat aphid, were conducted among four wheat (Triticum aestivum L.) and eight triticale (XTriticosecale Wittmack) accessions. Tests for antibiosis included measuring R. padi-population growth over 13 days, number of days to reproduction of individual R. padi, and number of aphid progeny produced in the first 7 days of adulthood. Antixenosis was measured in no-choice nymphiposition tests and in choice tests of host selection by winged R. padi. Three of seven triticale accessions limited R. padi populations relative to control accessions. Lower R. padi-population growth on N1185 and Okto Derzhavina could be explained partially by increased developmental times. Lower R. padi-population growth on triticale accessions N1185, N1186 and Okto Derzhavina could be explained at least partially by fewer aphid progeny on these accessions. Developmental time of R. padi on N1185 and Okto Derzhavina was greater than that on Stniism 3 triticale, identified previously as resistant to R. padi. There were less R. padi progeny on N1185 than on Stniism 3, and comparable numbers of R. padi progeny among N1186, Okto Derzhavina, and Stniism 3. None of the accessions limited nymphiposition by R. padi. Choice tests revealed heterogeneity in host selection by R. padi but an overall trend that triticale accessions Okto Derzhavina, N1185, N1186 and Stniism 3 were less preferred hosts than Arapahoe wheat. Relatively strong resistance in these triticale accessions warrant consideration of their future use in breeding programs for cereal-aphid resistance.     

Unveilingsources of stripe rust resistance in diverse wheat (<Emphasis Type="Italic">Triticum Aestivum</Emphasis> L.) germplasm using narrow down methodology: a proof of concept

Stripe rust of wheat caused by the fungal pathogen is a destructive foliar disease of wheat. Thus, it is crucial step to characterize the resistant germplasm for stripe rust in a diverse germplasm pool for their ultimate utilization in efficient crop rust resistance breeding. In the present study, we followed two pronged strategies involving integrated phenotypic and molecular characterization of 440 diverse wheat germplasm lines for rust resistance. The germplasm panel was extensively evaluated in field epiphytotic conditions during two consecutive years. After rigorous screening, 72 accessions were successfully revealed as resistant to moderately resistant to stripe rust. Subsequently, entries were then evaluated for their field agronomicperformances, considering prerequisites for serving as a donor germplasm,particularly for yield and 33 potential rust-resistant accessions were identified. Furthermore, to detect the sources of resistance, accessions were molecular characterized for potential race-specific resistance genes Yr5, Yr10,Yr15, and effective adult plant resistance (APR) gene Lr34/Yr18/pm38. We identified the 22 accessions possessing one or more single resistance genes and two accessions were observed with at least three of them. Moreover, Lr34/Yr18/pm38 was determined to confer resistance when observed along with any of the race-specific genes. Thus, the study not only provides proof of concept methodology to identify candidate resistant sources from large germplasm collections but simultaneouslyconfirmed the contribution of combining race-specific andnon-specific APR genes. The finding could further assist in the potential deployment of resistant genes directly into the stripe rust breeding program by involving marker-assisted approaches.     

Resistance to Rhopalosiphum padi (Homoptera: Aphididae) in Hordeum vulgare subsp. spontaneum and in hybrids with H. vulgare subsp. vulgare

Summary Accessions of Hordeum vulgare subsp. spontaneum, the progenitor of cultivated barley, were screened in field and glasshouse trials for resistance to the aphid Rhopalosiphum padi. A few selected lines were furthermore hybridized with a modern barley variety and the resulting populations evaluated. High levels of resistance were found among some of the spontaneum accessions resulting in lower aphid growth rates (maximum reduction 57%). Segregation patterns among siblings in F2 populations were continuous, indicating the presence of several genes with possibly additive effects. The usefulness of H. vulgare subsp. spontaneum for breeding aphid resistant barley is discussed.     

Components of variation,heritabilities and correlations for indices of sprouting tolerance and seed dormancy in Triticum spp.

Summary RFLPs were used to study the genetic relationships of 31 Portuguese coles (Brassica oleracea L.) representing the different ecotypes or landraces grown in Portugal. Other cole crops such as Jersey kale, Chinese kales, common cabbages, broccolis and cauliflower, two nine-chromosome wild species, and one accession of turnip also were included to determine the evolutionary relationships of Portuguese coles to other related coles. Principal coordinates and cluster analyses were conducted using a package of computer programs and RFLP data from 55 nuclear DNA probes, detecting 291 polymorphic restriction fragments. The results showed that the 48 accessions clustered into five groups: (a) a dispersed group with turnip and the wild brassicas; (b) Chinese kales; (c) broccolis and cauliflower; (d) a disperse group including Algarve and Jersey kales, thousand head kale, cabbages, and savoy cabbage; (e) a large and compact group containing all Portuguese tronchuda cabbages and kales. This unique and closely related group containing Portuguese tronchuda cabbages and kales could be further divided into five subgroups corresponding to the major areas of cultivation. The phenetic groupings of Portuguese tronchuda cabbages and kales based on RFLP data corresponded more with their geographic origins (collecting sites) than with their morphological similarities. A mechanism involving geographic isolation and frequent intercrossing within local areas is proposed to explain genetic relationships among Portuguese tronchuda cabbages and kales.