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Sunflower (HelianthusL.) production ranked third in global oilseed production in 2021. Downy mildew (DM), caused by the oomycete pathogen Plasmopara halstedii(Farl.) Berl. et de Toni, is a major constraint for worldwide sunflower production, causing significant yield losses in susceptible hybrids. The search for new sources of resistance to DM is the primary objective of all sunflower breeding programs. Germplasms HA‐DM15 (Reg. no. GP‐385, PI 702359) and HA‐DM16 (Reg. no. GP‐386, PI 702360) were developed by introgressing two new DM resistance genes, Pl37and Pl38, from the wild sunflower species H. annuusand H. praecoxinto oilseed sunflower, respectively. The BC1F3‐derived HA‐DM15 harboring the Pl37gene was selected from the cross of HA 89//NMS HA 89/wild H. annuusPI 435417. The germplasm line HA‐DM16 carrying the Pl38gene is an improved oilseed derivative of Rf PRA‐417 with DM resistance originally derived from the wild H. praecoxPRA‐417 from the cross of cytoplasmic male sterile (CMS) HA89*2/wild H. praecoxPRA‐417. HA‐DM15/Pl37and HA‐DM16/Pl38are immue to the most predominant and virulent DM races idenfied in North America and Europe. Pl37and Pl38have been genetically mapped to sunflower chromosomes 4 and 2, respectively, with single nucleotide polymorphism markers linked to the both genes facilitating their transfer to elite sunflower lines by marker‐assisted selection, providing new and diverse sources for sunflower DM‐resistance breeding. Resistance to downy mildew in HA‐DM15 and HA‐DM16 was introgressed from two wild sunflower species.HA‐DM15 and HA‐DM16 harbor the new downy mildew resistance genes Pl37and Pl38, respectively.HA‐DM15 and HA‐DM16 are immune to the most predominant and virulent P. halstediiraces found in the United States and Europe.

Rust and downy mildew (DM) are detrimental diseases in global sunflower (Helianthus annuusL.) production. Disease often results in yield loss and reduced seed quality. Host resistance to DM and rust is mediated by single dominant genes in sunflower. To better utilize genetic resistance, gene pyramiding is a common practice in crop breeding to extend the durability and longevity of resistance. Two confection sunflower germplasm lines, HA‐R20 (Reg. no. GP‐387, PI 702361) and HA‐R21 (Reg. no. GP‐388, PI 702362), were developed using the pedigree breeding method and DNA marker‐assisted selection and released by the USDA‐ARS Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station in September 2022. HA‐R20 is an F3‐derived F4confection restorer selection from the cross of HA‐DM2 and HA‐R8, carrying rust resistance genes R12and R15and DM resistance gene PlArg. HA‐R21 is an F3‐derived F4confection maintainer selection from the cross of HA‐DM3 and HA‐R8, carrying rust resistance genes R13aand R15and DM resistance gene Pl17. Disease reaction and marker testing for DM and rust confirmed that both germplasms harbor DM and rust Rgenes in the homozygous condition and are resistant to all DM and rust races identified in North America to date. These multiple disease‐resistant lines will provide the sunflower industry with durable disease‐resistant sources for the continued improvement of the crop. Two confection sunflower germplasms, HA‐R20 and HA‐R21, were developed by marker‐assisted selection.HA‐R20 (R12/R15/PlArg) and HA‐R21 (R13a/R15/Pl17) harbor two rust and one downy mildew Rgenes each.Both lines have durable resistance to all rust and downy mildew races identified to date.

Downy mildew (DM), caused by the obligate pathogen Plasmopara halstedii(Farl.) Berl. & de Toni, is a worldwide yield‐limiting disease of sunflower (Helianthus annuusL.). To obtain durable DM resistance in sunflower hybrids, there is a need to stack new resistance genes into the best available germplasm. The DM resistance genes Pl8, Pl17, and Pl18were recently fine mapped to sunflower chromosomes 13, 4, and 2, respectively. The current study pyramided these genes into a single genotype by marker‐assisted selection. Three oilseed sunflower germplasms, HA‐DM9 (Reg. no. GP‐381, PI 700009), HA‐DM10 (Reg. no. GP‐379, PI 700004), and HA‐DM11 (Reg. no. GP‐380, PI 700005), are dual DM‐resistant germplasm lines developed and have been released by the USDA‐ARS, Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station in 2021. The three lines, HA‐DM9 (Pl8Pl8/Pl17Pl17), HA‐DM10 (Pl8Pl8/Pl18Pl18), and HA‐DM11 (Pl17Pl17/Pl18Pl18), each stacked two different DM genes, providing broad resistance to all P. halstediiraces identified in North America and Europe so far, and can be used in sunflower breeding programs to enhance DM resistance. Three oilseed sunflower germplasms with dual resistance to downy mildew were developed using marker‐assisted selection.HA‐DM9, HA‐DM10, and HA‐DM11 each pyramided two different downy mildew R genes.All germplasms exhibit resistance to all known downy mildew races identified in North America and Europe.

Downy mildew (DM) is a primary biotic threat to sunflower (Helianthus annuusL.) production worldwide, negatively impacting yield. Germplasms HA‐DM5 (Reg. no. GP‐367, PI 687025) and HA‐DM6 (Reg. no. GP‐368, PI 691507) were developed and released through the collaboration of the USDA‐ARS and the North Dakota State University as new sources of resistance to downy mildew for confection sunflower. The backcross breeding method and DNA marker‐assisted selection were used to develop HA‐DM5 and HA‐DM6. HA‐DM5 is a BC2F3‐derived BC2F4maintainer selection from the cross of CONFSCLB1*2//CMS CONFSCLB1/ PI 435414 with the DM resistance transferred from a wild H. annuusPI 435414. Phenotypic/molecular characterizations confirmed the presence of the DM resistance gene Pl19located on sunflower chromosome 4 derived from PI 435414 in HA‐DM5. HA‐DM6 is a composite of seed from individual BC2F4plants from the cross of CONFSCLB1*2//CMS CONFSCLB1/ PI 494576. The DM resistance in HA‐DM6 is controlled by a single dominant gene Pl35located on chromosome 1 derived from wild H. argophyllusPI 494576. Both HA‐DM5 and HA‐DM6 confer resistance to several modern P. halstediiraces currently identified in the United States and Europe. They provide new genetic diversity in addition to the few currently used DM‐resistant inbred lines in confection sunflower ensuring protection from yield loss.

Sclerotinia basal stalk rot (BSR) and downy mildew (DM) are agronomically important diseases of sunflower (Helianthus annuusL.) worldwide. Three sunflower germplasm lines, HA‐BSR6 (Reg. no. GP‐353, PI 685019), HA‐BSR7 (Reg. no. GP‐354, PI 685020), and HA‐BSR8 (Reg. no. GP‐355, PI 685021), were developed with dual resistance to both BSR and DM. Their resistance to BSR was transferred from the wild annual sunflower H. praecoxsubsp. runyoniiEngelmann & A. Gray (Heiser) (PI 468853), and DM resistance was introgressed from inbred line HA 458 possessing the Pl17gene. The germplasms were tested for BSR resistance in inoculated field trials in multiple locations over 4 yr. All three germplasm lines showed significantly higher BSR resistance (p< 0.05) than the recurrent parent and the checks across environments, with a 4‐yr mean disease incidence (DI) ranging from 1.2 to 4.8%, while ‘Cargill 270’ (susceptible hybrid check) and HA 89 (recurrent parent) had DI of 36.1 and 31.0%, respectively, and HA 441 (resistant inbred check) and ‘Croplan 305’ (resistant hybrid check) had DI of 19.5 and 11.6%, respectively. Whole genome scan using genotyping‐by‐sequencing revealed the presence of H. praecoxsubsp. runyoniichromosome segments in HA‐BSR6, HA‐BSR7, and HA‐BSR8, which are potentially associated with BSR resistance. Phenotypic evaluation identified DM resistance in all three germplasm lines, with flanking DNA markers confirming the presence of the Pl17gene in the lines. These germplasm lines can be used in sunflower breeding programs for pyramiding both BSR and DM resistance genes.

Downy mildew (DM) and rust are two destructive diseases in sunflower (Helianthus annuusL.) production worldwide that limit yield and reduce seed quality. Combining different disease resistance (R) genes in a single genotype of sunflower can increase the field performance due to host resistance. The confection sunflower germplasm lines HA‐DM2 (Reg. No. GP‐350, PI 687022), HA‐DM3 (Reg. No. GP‐351, PI 687023), and HA‐DM4 (Reg. No. GP‐352, PI 687024), developed using backcrossing, pedigree breeding, and DNA marker‐assisted selection, were released by the USDA‐ARS Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station in June 2017. HA‐DM2 harbors the DM Rgene, PlArg, and rust Rgene, R12, both transferred from an oilseed sunflower line RHA 464. HA‐DM3 harbors the DM Rgene, Pl17, and rust Rgene, R13a, transferred from an oilseed line HA 458 and confection line HA‐R6, respectively. HA‐DM4 harbors the DM Rgene, Pl18, and rust Rgene, R13a, transferred from an oilseed line HA‐DM1 and confection line HA‐R6, respectively. Phenotypic and marker testing for DM and rust confirmed that the BC4F4–derived HA‐DM2, HA‐DM3, and HA‐DM4 germplasm each harbors DM and rust Rgenes in the homozygous condition and are resistant to all DM and rust races identified in North America to date. These disease‐resistant lines are a valuable contribution for breeding‐enhanced DM and rust resistance in confection sunflower in North America and globally.

Sclerotinia basal stalk rot (BSR) and downy mildew (DM) are two fungal diseases that are major yield limiting factors in global sunflower (Helianthus annuusL.) production. Four oilseed sunflower germplasm lines, HA‐BSR2 (Reg. No. GP‐346, PI 685015), HA‐BSR3 (Reg. No. GP‐347, PI 685016), HA‐BSR4 (Reg. No. GP‐348, PI 685017), and HA‐BSR5 (Reg. No. GP‐349, PI 685018), were developed to provide diversity for resistance to BSR and DM. The BSR resistance in HA‐BSR2 was derived from the wild annual H. petiolarisPI 435843, while BSR resistance in HA‐BSR3 to HA‐BSR5 was derived from wild annual H. argophyllusPI 494573. The four lines were tested for resistance to BSR in inoculated field nurseries from 2012 to 2015 and consistently showed high levels of BSR resistance across environments. A 4‐yr mean BSR disease incidence for HA‐BSR2, HA‐BSR3, HA‐BSR4 and HA‐BSR5 was 4.4, 3.0, 0.8, and 1.9%, respectively, compared with an average disease incidence of 36.1% for ‘Cargill 270’ (susceptible hybrid check), 31.0% for HA 89 (recurrent parent), 19.5% for HA 441 (resistant check), and 11.6% for ‘Croplan 305’ (resistant hybrid check). Genetic analysis detected the presence of wild sunflower species chromosome segments in all four germplasm lines, which are presumably associated with BSR resistance. HA‐BSR2, HA‐BSR3, and HA‐BSR4 are also resistant to DM, derived from the parental line HA 458. HA‐BSR2, HA‐BSR3, and HA‐BSR4 represent the first sunflower germplasm to combine resistance against both Sclerotinia BSR and DM.

Basal stalk rot (BSR) is a devastating disease that causes a significant damage to sunflower (Helianthus annuusL.) production worldwide by reducing seed yield and quality. The objective of this research was to develop highly BSR tolerant sunflower germplasm by incorporating genetic factors from various partially tolerant breeding lines. HA‐BSR1 (Reg. No. GP‐336, PI 678571) sunflower germplasm is an F7–derived oilseed maintainer developed from the cross HA 441/RHA 439, selected for tolerance to Sclerotinia BSR. HA‐BSR1 showed significantly higher tolerance to BSR disease than both of the parents and the checks when evaluated across seven environments in North Dakota and Minnesota from 2012 to 2015. A 4‐yr mean disease incidence of HA‐BSR1 was 1.6% compared with the parents HA 441 (20.0%) and RHA 439 (12.6%), the susceptible hybrid check ‘Cargill 270’ (32.8%), and the resistant hybrid check ‘Croplan 305’ (10.4%). Molecular genetic analysis of HA‐BSR1 indicated the presence of six alleles associated with quantitative trait loci (QTL) conferring resistance against BSR, three alleles derived from each parents. The release of HA‐BSR1 along with the information of single nucleotide polymorphism markers linked to QTL will be useful in marker‐assisted selection breeding to pyramid BSR resistance with other desirable agronomic traits in elite sunflower lines.

HA‐DM1 (Reg. No. GP‐335, PI 674793) sunflower (Helianthus annuusL.) germplasm was developed and released cooperatively by the USDA‐ARS, Sunflower and Plant Biology Research Unit and the North Dakota Agricultural Experiment Station in 2015. HA‐DM1 is a BC2F4–derived oilseed maintainer line from the cross HA 89*2/NMS HA 89/Helianthus argophyllusPI 494573, selected for resistance to downy mildew (DM) [caused by Plasmopara halstedii(Farl.) Berl. et de Toni], a destructive disease in sunflower. The DM resistance in HA‐DM1 originated from wild H. argophyllusaccession PI 494573 and is conditioned by a single dominant gene designated Pl18. Pl18has been mapped to linkage group 2 of the sunflower genome and is independent of all known identified DM resistance genes in sunflower. HA‐DM1 has resistance to all P. halstediiraces identified in the United States to date, providing a potential new source for resistance to emerging virulent races of P. halstediiin sunflower in North America and around the world.

Two confection sunflower (Helianthus annuusL.) germplasms, HA‐R12 (Reg. No. GP‐333, PI 673104) and HA‐R13 (Reg. No. GP‐334, PI 673105), were developed by the USDA‐ARS, Sunflower and Plant Biology Research Unit, Fargo, ND, in collaboration with the North Dakota Agricultural Experiment Station, and released in July 2014. Sunflower rust (caused by Puccinia helianthiSchwein.) is a major yield‐ and quality‐limiting factor for sunflower production worldwide. Because of the evolution of new rust pathotypes, it is important to combine multiple resistance genes into one sunflower genotype to overcome the newly emerging virulent races. HA‐R12 and HA‐R13 were developed by the pedigree method and DNA marker‐assisted selection. HA‐R12 harbors the rust resistance (R) genes, R2from MC29 (AUS) and R13afrom HA‐R6. HA‐R13 contains R5from HA‐R2 and R13afrom HA‐R6. Marker testing and rust resistance evaluation confirmed that HA‐R12 and HA‐R13 each separately harbors two rust resistance genes in the homozygous condition, with both lines showing high levels of resistance to rust races 336 and 777, a predominant race and one of the most virulent races currently identified in the United States, respectively. HA‐R12 and HA‐R13 will provide urgently needed rust resistance genes that can be incorporated into commercial confection hybrids, providing broad‐spectrum rust resistance.

AbstractWild Helianthusspecies possess valuable resistance genes for sunflower broomrape (Orobanche cumanaWallr.), especially the 39 largely underutilized perennial species. Resistance to race F has been transferred into a cultivated background via bridging of interspecific amphiploids. More recently, a single dominant gene resistant to race G was identified in annual H. debilisssp. tardiflorusand transferred into cultivated HA 89. Interspecific crosses between wild annual Helianthusspecies and cultivated lines are relatively easy compared to those involving wild perennial species, which were made easier only after the development of embryo rescue techniques. Interspecific amphiploids resulting from colchicine treatment of F1hybrids provide bridging materials for transferring genes without relying on embryo rescue. Among the diploid, tetraploid, and hexaploid perennial species, the speed of gene utilization follows the ploidy level of diploids, tetraploids, and hexaploids due to the time-consuming backcrosses required to eliminate the extra chromosomes in the latter two groups. In the development of pre-breeding materials, the retention rate of genetic material of the wild species is another concern with each additional backcross. For crosses involving tetraploid and hexaploid wild perennials, the use of 2n=51 chromosome F1or BC1F1generation, as pollen source, could accelerate chromosome reduction to 2n=34 in BC1F1or BC2F1, resulting in useful materials with fewer backcrosses for trait selection.

Two confection sunflower (Helianthus annuusL.) germplasm lines, HA‐R10 (Reg. No. GP‐327, PI 670043) and HA‐R11 (Reg. No. GP‐328, PI 670044), developed by the USDA–ARS Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station were released in December 2013. Both lines have resistance to sunflower rust (caused by Puccinia helianthiSchwein.), which is an emerging production issue for confection sunflower in North America due to the spread of new rust races and the lack of resistance sources. HA‐R10 is a BC3F3–derived BC3F4maintainer line of confection sunflower selected from the cross CONFSCLB1*4/HA‐R2, and HA‐R11 is a BC4F3–derived BC4F4restorer line of confection sunflower selected from the cross CONFSCLR5*5/HA‐R3. The rust resistance genes R5in HA‐R10 and R4in HA‐R11 were introduced from oilseed lines HA‐R2 and HA‐R3, respectively, with the two confection sunflower genetic stocks CONFSCLB1 and CONFSCLR5 as the recurrent parents. Greenhouse testing of rust resistance and DNA marker‐assisted selection were used during development and progeny testing of the germplasm lines. HA‐R10 and HA‐R11 are morphologically similar to the recurrent parents but possess the rust resistance gene(s) transferred from oilseed sunflower. These sources will afford confection sunflower breeders an opportunity to incorporate rust resistance genes into their parental lines, thus facilitating the development of disease‐resistant hybrids.

The sunflower (Helianthus annuusL.) germplasm HA‐R9 (Reg. No. GP‐326, PI 667595) was developed by the USDA‐ARS, Sunflower and Plant Biology Research Unit in collaboration with the Agricultural Experiment Station of North Dakota State University and released in January 2013. Sunflower rust (caused by Puccinia helianthiSchwein.) is a worldwide disease of sunflower that is an increasing threat to North American production due to newly emerged virulent races. HA‐R9 was selected from an oilseed male fertility restorer line, Rf ANN‐1742 (PI 596476), which was released by the USDA‐ARS and the Agricultural Experiment Station of North Dakota State University in 1997. The rust resistance in HA‐R9 originated from wild H. annuusPI 613748. Rust evaluation was conducted at the seedling stage under greenhouse conditions. HA‐R9 has resistance to all rust races tested so far, including the most predominant and the most virulent races currently identified in the United States. The rust resistance in HA‐R9 is conditioned by a single dominant gene R11which has been mapped to linkage group 13 of sunflower and is closely linked to the Rf5male fertility restorer gene present in HA‐R9 in the coupling phase. Germplasm HA‐R9 will fill an urgent need for resistance to new virulent rust races and diversify the pool of fertility restoration genes in sunflower.

Pericarp resistance to mechanical puncture using a penetrometer was determined for achenes of 72 sunflower (Helianthus annuusL.) genotypes grown in a greenhouse and sampled at 1, 5, 10, 15, and 20 days after fertilization. This study was undertaken to determine resistance of developing sunflower achenes to mechanical puncture and to relate this to possible genetic resistance to the sunflower moth, Homoeosoma electellum(Hulst). Pericarp resistance to puncture was found to be directly correlated with presence of phytomelanin. Significant genotypic differences in resistance to puncture were found among restorer (RHA) and maintainer (HA) lines. Achenes of the restorer lines RHA 272 and RHA 274 were most resistant to pericarp puncture. Of the maintainer lines, achenes of HA 65, HA 246, and HA 250 showed greatest resistance to pericarp puncture. Prediction equations indicated a positive linear relationship between resistance to puncture of the pericarp and age of the respective achene.

To determine the potential of genetically different lines and cultivars of guar [Cyamposis tetragonoloba(L.) Taub.], breeders must observe many different characteristics in their breeding and selection programs. Factor analysis is a type of multivariate analysis that can be used to reduce a large number of correlated variables to a smaller number of main factors, thus helping to elucidate the number and nature of causative influences and aiding in the selection of better genotypes. The objective of this study was to use factor analysis to determine the dependence relationship between 10 components of yield and morphological characteristics of 12 field‐grown guar genotypes from three locations. Principal factor analysis was used for factor extraction and varimax rotation was used to uniquely define factors. Four factors adequately accounted for most of the intercorrelations. Grams of seed/plant, number of pods/plant, number of seeds/plant, and number of racemes/plant constituted the productivity per plant factor (Factor 1). Factor 2 was considered a branchingproductivity factor consisting of number of primary branches and number of pods/raceme. Factor 3, a growth factor, consisted of plant height and number of nodes/plant. Factor 4 was considered a yield per unit area factor, and consisted of variables concerned with number of seeds/pod and wt/100 seeds. Factor analysis reduced a large number of correlated variables to a small number of main factors and also clarified the relationship between correlated characters in the dependence structure. This study indicated that selection of variables concerned with productivity per plant (Factor 1), and yield per unit of area (Factor 4) should enable breeders to better realize the desired gains in seed yield of guar.

American sunflower breeders have not actively selected for the phytomelanin layer in breeding programs. Phytomelanin in the pericarp of sunflower (Helianthus annuusL.) achenes can be an effective mechanism for reducing yield losses due to achene injury by larvae of the sunflower moth, Homoeosoma electellum(Hulst). The objectives of the present study were to screen achenes of publicly released parental breeding lines and wild species (Helianthusspp.) for presence of phytomelanin in the pericarps and to evaluate and compare a rapid, inexpensive mechanical (scraping) test to a more time consuming, expensive chemical (potassium dichromate‐sulfuric acid) test, which served as the standard in this study. One hundred one parental breeding lines and 50 species of wild sunflower were grown during 1980–1982 at Bushland, TX. Five 20‐achene subsamples were examined from each line or wild species. Phytomelanin was present in 90% of the cms HA and HA lines, 37% of the RHA lines, and 100% of the wild species as determined by the chemical test. The mechanical (scrape) test agreed with the chemical test 92% of the cms HA and HA and 100% of the RHA and wild species cases when phytomelanin was present. There was not a significant difference between the two techniques for detecting the presence or absence of the phytomelanin layer in cms HA and HA lines as determined by Chi‐square analyses.

Sunflower species (Helianthus) were evaluated for resistance to a stem weevil, Cylindrocopturus adspersus (LeConte). In greenhouse tests, foliar feeding by C. adspersus adults was significantly less in 11 of 18 annual and in 13 of 34 perennial species tested than in commercial hybrid ‘894’. The number of C. adspersus larvae recovered was significantly lower in eight annual and all perennial species than in hybrid 894. Significantly fewer larvae of C. adspersus occurred in 27 perennial species of Helianthus in the field during 3 consecutive years (1981–1983) than occurred in nearby wild H. annuus L. or hybrid 894. However, the number of C. adspersus larvae found in F1 progeny of interspecific crosses between the wild species and cultivated hybrid parental lines in the field was equivalent to the number of larvae found in the cultivated parents.

Larvae of Stibadium spumosum Grote inhabit the inflorescence of common annual sunflower, Helianthus annuus L., in southern latitudes of the United States. A single larva of S. spumosum may consume up to 50% of achenes in an H. annuus receptacle. A minor part of the S. spumosum population appears to be bivoltine in the southern Plains. However, univoltinism is the rule, with an obligatory pupal diapause lasting from 6 to 13 months in varying laboratory conditions. At Bushland, Tex., pupal development required an average of 133 days in ambient soil conditions. Parasitization of second instars by six species of Hymenoptera ranged up to 50%. Small larvae also were preyed on by larvae of Phyllobaenus pubescens (LeConte) at Bushland, Tex.