Inheritance of resistance to race F of broomrape in sunflower lines of different origins

A new race F of broomrape overcomes all known resistance genes in cultivated sunflower, but recently, sources of resistance against race F have been developed. The objective of the present research was to study the inheritance of resistance to race F in crosses between 12 resistant sunflower breeding lines, derived from three different sources of resistance, and the susceptible male‐sterile line P‐21. Parental lines and F₁, F₂, F₃ and BC₁ generations were evaluated for broomrape resistance. Segregations in the F₂ and BC₁ to resistant parent approached resistant to susceptible ratios of 1: 15 and 1: 3, respectively, in most of the crosses, suggesting a double dominant epistasis. However, segregations of 3: 13 and 1: 1 for F₂ and BC₁, respectively, indicating a dominant‐recessive epistasis, were also found. The F₃ data confirmed these results. Owing to the recessive nature of this resistance, it must be incorporated into both parental lines for developing resistant hybrid cultivars.     

Screening for resistance to broomrape (Orobanche cernua) in cultivated sunflower

Racial evolution of sunflower broomrape (Orobanche cernua) has been very rapid in Spain during recent years, in which resistance has been overcome several times and there has been an important increase in areas infested with this parasitic angiosperm. In order to find resistance to a highly virulent population of sunflower broomrape that could be used directly in breeding programmes, three different sets of cultivated plant material composed of 429 entries were tested by artificial inoculation. All evaluated inbred lines from Moden, Canada, were fully susceptible. Out of the 240 P.I. accessions tested, only 10 segregated for resistance to broomrape, the rest being susceptible. From the 160 USDA breeding lines evaluated, 5% were resistant and 19% segregated for resistance to O. cernua. These lines traced back mainly to crosses of RHA 274 and RHA 801 with Russian, Turkish and Romanian hybrids. The origin of P.I. accessions that segregated for resistance were primarily derived from the former USSR and from Romania.     

Reproductive behaviour and broomrape resistance in interspecific hybrids of sunflower

Interspecific hybrids and backcross generations between the wild perennial species Helianthus resinosus, Helianthus paucifiorus, Helianthus laevigatus, Helianthus nuttallii ssp. nuttallii T. & G. and Helianthus giganteus, resistant to broomrape (Orobanche cernua) and susceptible inbred lines were obtained to study crossability to cultivated sunflower and the transmission and expression of resistance to this parasitic weed. Conventional crosses with all the species tested were successful except for the crosses with diploid H. giganteus, for which embryo rescue techniques were needed to overcome hybrid incompatibility. Pollen viability and seed set were highest for F₁ hybrids with hexaploid species and lowest for those with the diploid H. giganteus. We evaluated F₁, BC₁F₁, some BC₂F₁ plants and the wild and cultivated parents. The wild species and interspecific hybrids were resistant to broomrape infection except for H. nuttallii, which showed segregation, indicating that the resistance is dominant. The crossability and resistance of F₁, and back-cross generations of species with different ploidy levels indicate that the transfer of broomrape resistance to cultivated sunflower is feasible.     

R-41, a sunflower restorer inbred line, carrying two genes for resistance against a highly virulent Spanish population of Orobanche cernua

The inheritance of resistance to a highly virulent population of sunflower broomrape (Orobanche cernua) has been studied in R-41, a Spanish sunflower restorer inbred line. Using the cytoplasmic male-sterile inbred line HA-89 (cms; very susceptible to this population of broomrape) as a female parent, progenies of the cross with R-41, i.e. Fl, F2 and BC1 to both parents, as well as the parental lines, were analysed for their reaction to the broomrape population EC-94. The goodness of fit of the observed vs expected segregation ratios indicated that the inheritance of resistance to broomrape in line R-41 is conferred by two independent dominant genes.     

Sources of resistance to broomrape (Orobanche crenata Forsk.) in narbon vetch

Little is known about the levels of resistance to Orobanche crenata available in narbon vetch. A germplasm collection of 200 accessions of narbon vetch (Vicia narbonensis L.) originating from different countries was screened for resistance to crenate broomrape under field conditions. Thirteen accessions were selected for more detailed screening under controlled conditions and for additional field testing. Resistance to O. crenata was manifested by lower germination of broomrape seeds, reduced emergence of Orobanche shoots and fewer root attachments per narbon vetch plant. Differences in pod yield among narbon vetch accessions were also found in response to Orobanche infestation. Finally, eight accessions were selected and identified as new sources of narbon vetch resistant to broomrape.     

Inheritance of resistance to sunflower downy mildew races 1, 2 and 3 in cultivated sunflower

Sunflower downy mildew (SDM) caused by Plasmopara halstedii, is a major disease of sunflower. Eleven resistance genes have been identified, but allelic relationships among these genes are not clear. This study examined the inheritance and allelic relationships of genes conferring resistance to SDM races 1, 2 and 3 (virulence phenotypes 100, 300 and 700, respectively) and confirmed a twelfth resistance gene. Three USDA Plant Introductions, AMES 3235, PI 497250, and PI 497938, and three released lines, RHA 266, RHA 274 and DM‐2 were studied. RHA 266 has only the Pl₁ gene for race 1 resistance. Digenic inheritance of resistance was found in AMES 3235, PI 497250, and RHA 274. These lines have the Pl₁ and Pl₁₂ genes, conferring resistance to race 1, and the Pl₂ and Pl₁₁ genes, conferring resistance to race 2. DM‐2 and PI 497938 have Pl₁₂ (but not Pl₁ for resistance to race 1, the Pl₁₂ gene (but not the Pl₂) for resistance to race 2, and Pl₅ for resistance to race 3. These resistance genes will serve as a foundation for future gene designations and genetic diversity studies of resistance to SDM.     

Inheritance of resistance to race 330 of Plasmopara halstedii in three sunflower lines

Sunflower lines RHA‐274, HA‐61 and RHA‐325 were studied for their resistance to race 330 of downy mildew (Plasmopara halstedii). The same inbred line, with normal (HA‐89) or sterile cytoplasm (cmsHA‐89) was used in all the crosses as susceptible parent, and, in each cross, only one genotype of the resistant parent was studied. The resistant‐to‐susceptible ratios obtained in the BC₁ and F₂ progenies from the crosses of the lines RHA‐274 and HA‐61 to cmsHA‐89 and HA‐89, respectively, suggested that, in each resistant line, two dominant genes are responsible for resistance to this downy mildew race. One of the genes (A) is epistatic to the other (B), and the recessive allele b in homozygosity is also epistatic to aa, with plants carrying aabb genotypes being resistant. Resistance to race 330 seemed to be controlled by two complementary genes in the sunflower inbred line RHA‐325, the dominant allele of one of them being present in cmsHA‐89. In the genotypes HA‐89 or cmsHA‐89, the existence of genes that modify the expected segregations following the crosses with resistant parents is proposed. It is concluded that, although major genes have been described as responsible for monogenic resistance to downy mildew, other types of regulation of this character, such as complementarity and epistatic relationships, do occur.     

Inheritance of resistance to phomopsis (Diaporthe helianthi) in sunflower

The inheritance of resistance of sunflower to phomopsis (Diaporthe helianthi) was studied on 10 inbred lines representing a range of resistance and susceptibility levels, and 25 hybrids from a factorial cross of these lines. Analyses of observations over a 3-year period, of semi-natural infection (presence of stem lesions greater than 5 cm) on the hybrids indicated that additive gene control was predominant, with no significant interactions between parental effects. Correlations between infection of parental lines and the mean of their hybrids were not always significant, with certain inbreds which appeared quite susceptible giving hybrids with good levels of resistance. In order to predict hybrid values, it appears necessary to determine the general combining abilities of parental lines. Some inbreds gave very high levels of resistance, others gave very high levels of susceptibility. A test measuring the rate of extension of D. helianthi mycelium on leaves was significantly correlated with the results of natural infections. In particular, it permitted distinction of the most susceptible genotypes, and thus could be used in first generations of breeding to eliminate the most susceptible plants.     

Inheritance of reduced plant height in the sunflower line Dw 89

The objective of the present research was to study the inheritance of reduced plant height in the sunflower line Dw 89. Plants of the cytoplasmic male sterile version of this line, cmsDw 89 (mean plant height of 47.4 cm) were crossed with plants of the restorer line RHA 271 (mean of 120.9 cm). F₁ plants averaged 120.4 cm, which indicated dominance of standard over reduced plant height. F₂ plants followed a segregation pattern of 1 : 15 (reduced : normal height), suggesting that reduced plant height in Dw 89 is controlled by alleles at two loci, designated Dw1 and Dw2. Class assignment in the F₂ was confirmed through the evaluation of the F₃ generation. Backcrosses to Dw 89 segregated with 1 : 3 (reduced : normal height) ratios, which confirmed the digenic inheritance of the trait. The evaluation of plant height distributions in F₃ families suggested possible genetic interaction between the Dw1 and Dw2 loci.     

新疆阿勒泰地区和内蒙古乌拉特前旗抗列当向日葵品种(系)的鉴定

向日葵列当是向日葵生产中重要的寄生性杂草。新疆阿勒泰地区和内蒙古乌拉特前旗是国内向日葵列当发生的重灾区。为筛选并为抗列当育种工作提供优质抗性材料,从根本上防治向日葵列当,利用田间自然发生向日葵列当的田块,采用随机区组设计设置小区试验;通过寄生率、寄生程度2 个指标判定对列当的抗感性。于2012 年在新疆阿勒泰对56 个向日葵品种（系）,2013—2014 年在内蒙古乌拉特前旗分别对22 个品种（系）和20 个品种（系）,进行抗列当鉴定。结果表明：在新疆22 个油葵品（系）中‘陇葵杂1 号’、‘F08-1’、‘辽丰F53’、‘赤CY101’、‘S26’、‘MGS’、‘S31’等16 个品种,34 个食葵品种（系）中‘JK106’品种,表现为免疫;在内蒙古乌拉特前旗2013—2014 年24 个油葵品种（系）中,‘赤CY102’、‘F08-1’等2 个品种表现为免疫,‘MSG’、‘新葵杂5 号’、‘赤029×115R’、‘赤128A×116R’等4个品种（系）表现为高抗,而18 个食葵品种（系）中,没有免疫品种,只有‘JK103’和‘JK106’表现为抗列当,其余16 个品种（系）均表现为感病和高度感列当。其中油葵品种‘赤CY102’在新疆和内蒙古抗列当鉴定中均表现免疫。在2 个不同地区进行向日葵品种抗列当鉴定,新疆地区表现免疫和高抗的品种较内蒙古地区多,说明内蒙古乌拉特前旗列当生理小种级别高于新疆阿勒泰地区列当生理小种。另外,油葵品种对列当的抗性较食葵高。     

Evaluation of Differential Lines and a Collection of Sunflower Parental Lines for Resistance to Broomrape (Orobanche cernua) in Spain

Broomrape (Orobanche cernua Loelf.) is a sunflower parasite which has become a potential threat to this crop in Spam with an increasing incidence in recent last years. In order to investigate the racial situation of the parasite in Spam and to evaluate the resistance of differentials and inbred lines currently used in breeding programmes, two experiments were carried out. In the first, two sets of European sunflower differentials were inoculated with three broomrape populations from different geographical origin. The second experiment studied the reaction to the parasite of 38 inbred lines in comparison with resistant and susceptible checks. Reactions of differential lines resistant to known European broomrape races ranged from complete immunity of lines P-1380-2A and ‘Jdanovski 8281’ to complete susceptibility of ‘Record’ and the universal suscepts. These results confirmed the existence of several physiological races of broomrape in Spain and a different racial composition from that of Eastern Europe. Results from the second experiment showed good resistance of half the restorer lines tested and 36 % of the maintainers and cms lines. This material together with the resistant differential lines constitutes good starting material to be used in developing cultivars resistant to broomrape populations in Spain.     

Screening for resistance in wild Lycopersicon species to Fusarium oxysporum f.sp. lycopersici race 1 and race 2

Wild Lycopersicon accessions were screened for resistance to the Fusarium wilt disease caused by Fusarium oxysporum f.sp. lycopersici (Fol) race 1 and race 2. In total, four isolates of each race were used. Among 17 accessions of six Lycopersicon species tested, a wide genetic variation for wilt resistance was observed. Most accessions were highly susceptible, some showed intermediate resistance, but one accession of L. cheesmanii (G1.1615 = PI 266375) and two accessions of L. chilense (G1.1556 and G1.1558) were highly resistant to Fol races 1 and 2. The resistance in the latter three accessions equalled or was higher than the resistance determined by the known I-genes, that have been widely used in breeding programmes. These newly found resistant accessions provide breeders with more opportunities for Fusarium disease resistance and may contribute to our understanding of Fusarium disease resistance gene organisation and evolution.     

Resistance to broomrape in wild lentils (Lens spp.)

Orobanche crenata , Orobanche aegyptiaca and Orobanche foetida constitute serious threats to grain legumes in the Mediterranean Basin. Lentil can be severely infected by O. crenata . It can also be damaged although with less virulence by O. aegyptiaca , and can only be slightly infected by O. foetida . Resistance breeding is hampered by scarcity of proper sources of resistance in cultivated lentil and of a reliable and practical screening procedure. A germplasm collection of 23 wild Lens spp. accessions was screened for resistance to O. crenata under field conditions. A wide range of responses was observed, from complete resistance to susceptibility. The higher levels of resistance were observed in accessions of Lens ervoides , Lens odemensis and Lens orientalis . Resistance of selected accessions proved to be mainly because of early hampered tubercle formation, with no observed necrosis of established tubercles. No differences were observed in levels of induction of broomrape germination, but necrosis of broomrape radicles was significant in some cases, particularly in the L. odemensis–O. foetida interaction. Escape because of the reduced root biomass diminishing the chance of contact between host and parasite was also observed in L. odemensis .     

Variation of resistance to broomrape (Orobanche ramosa) in tomatoes

Summary Twenty five tomato cultivars and one accession of wild tomato were evaluated for their resistance to branched broomrape (Orobanche ramosa) infestation. Tomato cultivars were found different in their resistance to Orobanche based on different growth parameters. Total Orobanche number, haustoria development and number of emerged Orobanche shoots were all different between tomato cultivars. Differences in the growth and fruit yield among tomato cultivars were also found in response to Orobanche infestation. Ranking tomato cultivars for Orobanche resistance indicates the existence of different resistance mechanisms in these cultivars. Relatively high to moderate levels of resistance were obtained in Tiny Tim, Acora, Castler, Pomodora, Orient, Red Alert and the accession LA 1478 of L. pimpinellifolium. The cultivar Tiny Tim showed the highest level of resistance for all measured parameters and in all experiments.     

Genetic control of in vitro-organogenesis in recombinant inbred lines of sunflower (Helianthus annuus L.)

Ninety-three recombinant inbred lines (F₈) of sunflower developed by the single-seed descent method from the cross ‘PAC-2 × RHA-266’ were used to screen their regenerability by organogenesis. The experiment was designed in randomized complete blocks with three replications. Each replication consisted of 10 Petri dishes with four explants. Cotyledons were excised from 2-day-old seedlings. Each cotyledon was divided into two pieces (four explants), which were incubated in solid regeneration medium consisting of full-strength Murashige and Skoog medium modified by adding hormones. A high genotypic variability for organogenesis parameters between genotypes was observed in this study. The difference between all recombinant F₈ lines and their parents was not significant, showing that the 93 inbred lines used in this experiment are representative of the total possible recombinant lines from the cross ‘PAC-2 × RHA-266′. These F₈ lines were not consciously selected for any trait; therefore, they represent a random set of lines segregating for the organogenesis parameters, as well as for other traits which could be important for breeding.     

Fertility restoration of new CMS sources in sunflower (Helianthus annum L.)

The development of commercial sunflower hybrids based on new CMS sources is of special interest for reducing the potential risk of vulnerability to pathogens and for increasing genetic diversity. From 263 test crosses involving nine new CMS sources, i.e. ANL1, ANL2, MAX1, PEF1, PET2, ANN1, ANN2, ANNS and ANN4, five lines were selected as potential restorers for PEF1, PET2 and ANN4. In test crosses between all nine CMS sources and these five restorer lines evaluated in 2 years, seven fully restored hybrids could be identified. These hybrids, based on ANL1, ANL2, MAX1, PEF1, PET2, and ANN4, showed good agronomic performance for plant height, days to flowering, maturity and oil content. Segregation analyses of the F2 populations indicate that a single dominant restorer gene was sufficient to restore pollen production of hybrids based on ANL2, PEF1 and PET2. For restoration of ANN4, two dominant complementary genes are required. In restoration of fertility in the crosses of ANL1 and MAX1 investigated, two dominant genes are involved each of which on its own allows the production of fertile plants.     

Vertical resistance to late blight in wild potato species from Argentina

The possible presence of vertical resistance to late blight conferred by R genes in Argentine wild Solanum species, which presumably have not evolved under the pressure of the fungus, was investigated. Solanum microdontum, S. commersonii and S. chacoense clones were tested in the greenhouse and with detached leaves in the laboratory after inoculation with a complex race and a non-virulent race of Phytophthora infestans. Two progeny tests were carried out to assess the performance of contrasting parents in regards to their resistance. A varying frequency of incompatible clones was detected among the species, with S. microdontum having the higher proportion of clones yielding incompatible reactions both in the laboratory and in the greenhouse. S. chacoense and S. commersonii showed a small but still considerable frequency of incompatible clones. The progeny tests confirmed the presence of R genes in a S. commersonii cross and their absence in a S. chacoense cross. The unexpected presence of R genes, its evolutionary significance and the consequences on the use of these species in breeding is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic variability in plants regenerated from in vitro culture of sunflower (Helianthus annum L.)

In vitro regenerated sunflower (Helianthus annuus L.) plants (R₁) were self-fertilized and the R₂ generation was evaluated for qualitative traits. A broad range of phenotypic variation was observed and mutation frequencies were calculated. Some in vitro induced variant phenotypes were similar to known spontaneous or induced mutations in sunflower, while others were new. Chlorophyll and carotenoid deficiencies, chimaerical variegation, fasciated stem and capitulum, abnormal shoot development, and other morphological variations, were noted. Substitution of anthers with petaloid structures in a disk-floret mutant indicates a possible homeotic mutation induced by in vitro tissue culture.     

Morphological and cytological study in a new type of cytoplasmic male-sterile line CMS-GIG2 in sunflower (Helianthus annuus)

Cytoplasmic male sterility (CMS) is essential for sunflower hybrid production. CMS-GIG2, a new sunflower CMS type, was further confirmed by crossing with the maintainer and restorer lines for the CMS-PET1, both of which maintain the male sterility of CMS-GIG2. Meiotic division in CMS-GIG2 was observed with 4'6-diamidino-2-phenylindole dihydrochloride staining, indicating that microspore formation was disrupted before the meiotic cytokinesis was completed. Light microscopy observation showed that both middle layer and tapetal cells expand radially rather than degrade over time, followed by failure to form tetrads and normal microspores. This morphological defect leading to male sterility in CMS-GIG2 differs from that observed in the PET1 CMS type. CMS-GIG2 will certainly provide additional genetic diversity for sunflower hybrid breeding programmes.