Genetics and mapping of the \u3ci\u3eR\u3c/i\u3e11 gene conferring resistance to recently emerged rust races, tightly linked to male fertility restoration, in sunflower (\u3ci\u3eHelianthus annuus\u3c/i\u3e L.)

Sunflower oil is one of the major sources of edible oil. As the second largest hybrid crop in the world, hybrid sunflowers are developed by using the PET1 cytoplasmic male sterility system that contributes to a 20 % yield advantage over the open-pollinated varieties. However, sunflower production in North America has recently been threatened by the evolution of new virulent pathotypes of sunflower rust caused by the fungus Puccinia helianthi Schwein. Rf ANN-1742, an ‘HA 89’ backcross restorer line derived from wild annual sunflower (Helianthus annuus L.), was identified as resistant to the newly emerged rust races. The aim of this study was to elucidate the inheritance of rust resistance and male fertility restoration and identify the chromosome location of the underlying genes in Rf ANN-1742. Chi-squared analysis of the segregation of rust response and male fertility in F2 and F3 populations revealed that both traits are controlled by single dominant genes, and that the rust resistance gene is closely linked to the restorer gene in the coupling phase. The two genes were designated as R11 and Rf5, respectively. A set of 723 mapped SSR markers of sunflower was used to screen the polymorphism between HA 89 and the resistant plant. Bulked segregant analysis subsequently located R11 on linkage group (LG) 13 of sunflower. Based on the SSR analyses of 192 F2 individuals, R11 and Rf5 both mapped to the lower end of LG13 at a genetic distance of 1.6 cM, and shared a common marker, ORS728, which was mapped 1.3 cM proximal to Rf5 and 0.3 cM distal to R11 (Rf5/ORS728/ R11). Two additional SSRs were linked to Rf5 and R11: ORS995 was 4.5 cM distal to Rf5 and ORS45 was 1.0 cM proximal to R11. The advantage of such an introduced alien segment harboring two genes is its large phenotypic effect and simple inheritance, thereby facilitating their rapid deployment in sunflower breeding programs. Suppressed recombination was observed in LGs 2, 9, and 11 as it was evident that no recombination occurred in the introgressed regions of LGs 2, 9, and 11 detected by 5, 9, and 22 SSR markers, respectively. R11 is genetically independent from the rust R-genes R1, R2, and R5, but may be closely linked to the rust R-gene Radv derived from wild Helianthus argophyllus, forming a large rust R-gene cluster of Radv/ R11 /R4 in the lower end of LG13. The relationship of Rf5 with Rf1 is discussed based on the marker association analysis

Molecular mapping of the rust resistance gene R4 to a large NBS-LRR cluster on linkage group 13 of sunflower

Rust is a serious fungal disease in the sunflower growing areas worldwide with increasing importance in North America in recent years. Several genes conferring resistance to rust have been identified in sunflower, but few of them have been genetically mapped and linked to molecular markers. The rust resistance gene R4 in the germplasm line HA-R3 was derived from an Argentinean open-pollinated variety and is still one of most effective genes. The objectives of this study were to determine the chromosome location of the R4 gene and the allelic relationship of R4 with the Radv rust resistance gene. A total of 63 DNA markers previously mapped to linkage group (LG) 13 were used to screen for polymorphisms between two parental lines HA 89 and HA-R3. A genetic map of LG 13 was constructed with 21 markers, resulting in a total map length of 93.8 cM and an average distance of 4.5 cM between markers. Two markers, ZVG61 and ORS581, flanked the R4 gene at 2.1 and 0.8 cM, respectively, and were located on the lower end of LG 13 within a large NBS-LRR cluster identified previously. The PCR pattern generated by primer pair ZVG61 was unique in the HA-R3 line, compared to lines HA-R1, HA- R4, and HA-R5, which carry other R4 alleles. A SCAR marker linked to the rust resistance gene Radv mapped to LG 13 at 13.9 cM from the R4 locus, indicating that Radv is not an allele of the R4 locus. The markers tightly linked to the R4 gene will facilitate gene pyramiding for rust resistance breeding of sunflower

Comparison of Greenhouse-Based Inoculation Methods to Study Aggressiveness of Diaporthe helianthi Isolates Causing Phomopsis Stem Canker of Sunflower (Helianthus annuus)

Phomopsis stem canker is an economically important disease of sunflower (Helianthus annuus), and Diaporthe helianthi is one of the primary causal agents of the disease in the United States. The objective of this study was to evaluate inoculation methods of D. helianthi isolates on sunflower in the greenhouse. Four isolates of D. helianthi were selected to test the effectiveness of four inoculation methods using mycelial plugs as the inoculum, including stem wound, wound inoculation, petiole wound, and straw test. Infection was established by the D. helianthi isolates at 14 days after inoculation for all inoculation methods used. However, recovery of the pathogen from the inoculated plants differed significantly (P \u3c 0.0001) among inoculation methods. Given higher mean recovery of D. helianthi isolates from the inoculated plants and the size of the lesions caused by the pathogen, the stem-wound inoculation method was found to be the most user friendly of the four inoculation methods

First Report of Stem Disease of Soybean (Glycine max) Caused by Diaporthe gulyae in North Dakota

The planted soybean (Glycine max L.) acreage in North Dakota increased approximately six-fold in the last two decades to over 6 million acres in 2016. In September 2012, soybean plants exhibiting reddish-brown stem cankers (∼60 mm length) were observed in a production field in Grand Forks county (49°11′N; 98°09′W). Incidence of infected stems was estimated in excess of 95% in parts of the field. Ten plants exhibiting symptoms were randomly sampled and brought to the Department of Plant Pathology at NDSU to identify the causal pathogen

Handbook of Florists\u27 Crops Diseases

Febina M. Mathew (with T.J. Gulya, R. Harveson, S. Markell, and C. Block ) is a contributing author, Diseases of the Sunflower. From the publishers website: Chapters outline up-to-date strategies regarding breeding, chemical and biological control, cultural and environmental manipulation, diagnosis, nutrition, and sanitation and how these approaches directly influence ornamental plant health. This book is a presentation of the latest techniques for disease management by a global team of experts. The book addresses the major diseases of economically important ornamentals with the goal of capturing the latest disease management strategies along with diagnostic photographs. Florists’ crops production has evolved considerably through new technological advances in irrigation, environmental control, along with the appearance of new centers of large scale production of plant material. These changes have necessitated the development of newer and innovative ways of suppressing pathogenic fungi, bacteria, viruses, and nematodes.https://openprairie.sdstate.edu/plant_book/1004/thumbnail.jp

First Report of Phomopsis Stem Canker of Sunflower (Helianthus annuus) Caused by Diaporthe gulyae in Canada

During September 2012, Phomopsis stem canker was observed on sunflowers (Helianthus annuus L.) in a production field during seed filling with an average incidence of 15% in Morden, Manitoba (approximately 49°11′N and 98°09′W)

First Report of Diaporthe stewartii Causing Phomopsis Stem Canker of Sunflower (Helianthus annuus) in Minnesota

Phomopsis stem canker is one of the most economically important sunflower diseases in the northern Great Plains (Mathew et al. 2015). In October 2015, lesions consistent with Phomopsis stem canker were observed on sunflower (Helianthus annuus L.) in a commercial field in Polk County, MN (47°46′12″ N, 96°24′00″ W). Five plants displaying elongated, brown stem lesions were obtained. Stems were cut into small pieces (10 mm), surface-sterilized, and plated onto potato dextrose agar (PDA). The plates were incubated for 10 days at 22°C under 12 h of alternating light/dark conditions. Two isolates of brown colonies were hyphal-tipped and transferred to fresh PDA plates