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Castor is an industrial oilseed crop with great potential for biorefineries. However, little is known about the variability in the bioactive compounds in castor germplasm. This study evaluated seed weight, oil content, fatty acid profile, tocopherols, and phytosterols in 160 accessions of the USDA-ARS castor germplasm collection. The accessions were grown in Cordoba, Spain, under three different environmental conditions. Environmental and genotype-by-environment interaction effects were predominant for most traits, resulting in moderate to low broad-sense heritabilities, which ranged from 0.12 for total tocopherol content to 0.88 for hundred-seed weight. The genetic variability in the seed quality traits identified in the collection was lower than that reported previously for the germplasm of wild and semi-wild accessions from Spain, which is attributed to the lower genetic diversity in cultivated than in wild forms. The variation in seed quality traits in castor germplasm can be exploited to improve the concentration of bioactive compounds in castor cultivars. [ABSTRACT FROM AUTHOR]

Orobanche cumana is an obligate root parasite of sunflower. It represents a major agricultural problem in many countries of southern and eastern Europe. Information on O. cumana population genetics, structure and dynamics is scarce, particularly due to the lack of suitable molecular markers for such studies. The objective of this study was to identify and characterise simple sequence repeat ( SSR) markers for O. cumana. Four thousand two hundred SSR-containing candidate sequences were obtained from O. cumana using next-generation sequencing, from which 298 SSR primer pairs were designed and 217 of them used for validation. Seventy nine SSR primers produced reproducible, high quality amplicons of the expected size that were polymorphic among 18 O. cumana populations from different geographical locations and hosts (sunflower, wild hosts from the Compositae family). The number of alleles per locus ranged from 2 to 10, with an average polymorphism information content value of 0.37. The O. cumana SSR markers were highly transferable to the closely related species Orobanche cernua. SSR markers showed high resolving power; UPGMA cluster analysis allowed proper classification of Orobanche spp. samples into species ( O. cumana and O. cernua), geographical origin and host. The functional SSR markers reported in this study constitute a valuable tool for genetic analyses in O. cumana and related species and will contribute insights into the biology and genetics of this parasitic weed. [ABSTRACT FROM AUTHOR]

Orobanche cumana is a weed that grows as a root parasite on sunflower. In general, the O. cumana-sunflower parasitic system is regarded to follow the gene-for-gene model, although this has never been demonstrated at the genetic level in O. cumana. The Or5 dominant gene in sunflower confers resistance to O. cumana race E, but not to race F. The objective of this research was to study the inheritance of avirulence/virulence in crosses between plants of O. cumana lines classified as races E and F. Four race E and three race F lines were developed, from which four race E × race F cross-combinations were made, in three cases including reciprocals. In all cases, F1 seeds did not have the ability to parasitise sunflower line P-1380 carrying the Or5 gene, indicating dominance of race E avirulence allele(s). Five F2 populations comprising a total of 387 F2:3 families were evaluated on sunflower line P-1380. In all cases, one-fourth of the F2:3 families did not possess the ability to parasitise P-1380 plants, suggesting that race E avirulence and race F virulence on P-1380 are allelic and controlled by a single locus. This study demonstrated the gene-for-gene interaction in the O. cumana-sunflower parasite system and provided useful information to identify genes involved in O. cumana virulence. The approach followed in this research can contribute to define precisely races of the parasite on the basis of the presence of avirulence genes. [ABSTRACT FROM AUTHOR]

Sunflower broomrape ( Orobanche cumana Wallr.) is a parasitic angiosperm regarded as one of the most serious production constraints in many sunflower-producing countries. Historically, sunflower breeders have been successful in developing cultivars resistant to this parasite, but the introduction of new resistance sources has been frequently followed by the appearance of new pathogenic races overcoming the resistance. The present review sets out to examine the principal achievements in this field that took place during the last decades, focusing on the most recent advances in the research. In recent years, several research groups have made relevant contributions in breeding for the resistance and the development of control strategies. Following the identification and characterization of new virulent races, new sources and mechanisms of resistance have been developed and characterized at the genetic and molecular level. There have been also important contributions to the knowledge of the biology and genetics of the parasite that will contribute to the understanding of the dynamics of broomrape populations and race evolution. Important advances have also been made in the use of imidazolinone (IMI)-resistant hybrids as an alternative method of control. Most of the studies on sunflower breeding for resistance to O. cumana have been concentrated so far on the host plant, but in spite of the recent advances little is known about the important aspects of the parasite side of the equation such as the breeding system and genetics of virulence. An unsolved problem is the existing uncertainty in the designation of races and resistance genes identified in different countries. There is a need for international cooperation in this area using common differentials and molecular tools. Emphasis is given to the need for a multidisciplinary approach ranging from studying the mechanisms underlying resistance in the host plant to the reproductive biology and genetics of traits related to parasitism in O. cumana. The combination of long term strategies involving the complete host-parasite system and the integration of classical and molecular approaches is expected to contribute to the development of more durable sources of resistance and to improve sunflower performance in areas infested by broomrape. [ABSTRACT FROM AUTHOR]

With 2 tables Specific and robust marker resources available for safflower breeding are scarce. The present research was aimed at developing a collection of genomic microsatellite (SSR) markers and to assess their informativeness. A genomic library enriched for AC‐ and AG‐ repeats was constructed from safflower DNA. Around 35% of the 768 clones that were isolated and sequenced contained SSR sequences. From these, 108 unique primer pairs were designed. The majority of the SSRs contained simple di‐nucleotide motifs (77 of 108), most of them being perfect repeats (63 of 77). Reference allele length ranged from 95 to 414 bp, averaging 241.2 bp. The 108 SSRs were amplified in a set of ten safflower lines. From 88 SSR markers that amplified successfully, 64 of them detected polymorphism among the ten safflower lines genotyped. The number of alleles per locus ranged from 2 to 8 (mean value of 3.2), whereas heterozygosity ranged from 0.18 to 0.86 (mean value of 0.52). These genomic SSR markers will contribute to advance in safflower molecular breeding. [ABSTRACT FROM AUTHOR]

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