Downy mildew disease, caused by Peronospora effusa (=P. farinosa f. sp. spinaciae [Pfs]), is the most economically important disease of spinach. Current high-density fresh-market spinach production provides conducive conditions for disease development, and downy mildew frequently forces growers to harvest early owing to disease development, to cull symptomatic leaves prior to harvest, or to abandon the field if the disease is too severe. The use of resistant cultivars to manage downy mildew, particularly on increasing acreages of organic spinach production, applies strong selection pressure on the pathogen, and many new races of Pfs have been identified in recent years in spinach production areas worldwide. To monitor the virulence diversity in the Pfs population, downy mildew samples were collected from spinach production areas and tested for race identification based on the disease reactions of a standard set of international spinach differentials. Two new races (designated races 15 and 16) and eight novel strains were identified between 2013 and 2017. The disease reaction of Pfs 15 was similar to race 4, except race 4 could not overcome the resistance imparted by the RPF9 locus. Several resistance loci (RPF1, 2, 4, and 6) were effective in preventing disease caused by Pfs 15. The race Pfs 16 could overcome several resistance loci (RPF2, 4, 5, 9, and 10) but not others (RPF1, 3, 6, and 7). One novel strain (UA1014) could overcome the resistance of spinach resistant loci RPF1 to RPF7 but only infected the cotyledons and not the true leaves of certain cultivars. A new set of near-isogenic lines has been developed and evaluated for disease reactions to the new races and novel strains as differentials. None of the 360 U.S. Department of Agriculture spinach germplasm accessions tested were resistant to Pfs 16 or UA1014. A survey of isolates over several years highlighted the dynamic nature of the virulence diversity of the Pfs population. Identification of virulence diversity and evaluation of the genetics of resistance to Pfs will continue to allow for a more effective disease management strategy through resistance gene deployment.

The Russian wheat aphid, Diruaphis noxia (Kudjumov) (Hemiptera: Aphididae), is globally one of the most devastating pests of wheat, Tritium aestivum L., and barley, Hordeum vulgare L. Host plant resistance is the foundation of cereal insect pest management programs, and several D. noxia resistance (Dn) genes from wheat have been introduced in commercial cultivars of wheat to manage Russian wheat aphid (RWA). Emergence of D. noxia biotype 2 (RWA2) in Colorado has made all known Dn genes, except the Dn7 gene from rye, Secale cereale L., vulnerable and has warranted exploration for sources of resistance to RWA1 and RWA2. Here, we report antibiosis resistance to RWA1 and RWA2 identified in the wheat breeding line KS94H871. Additional experiments indicated that tolerance and antixenosis are not operating in KS94H871. Segregation studies involving F2-derived F3 families indicated that KS94H871 resistance to RWA1 is controlled by one dominant gene and one recessive gene, whereas resistance to RWA2 is controlled by only one dominant gene. This new genetic resource may serve as a good source of resistance in future breeding programs with proper understanding of the genetics of resistance.

Background Previous reports have shown that soil salinity is a growing threat to cowpea production, and thus the need for breeding salt-tolerant cowpea cultivars. A total of 234 Multi-Parent Advanced Generation Inter-Cross (MAGIC) lines along with their 8 founders were evaluated for salt tolerance under greenhouse conditions. The objectives of this study were to evaluate salt tolerance in a multi-parent advanced generation inter-cross (MAGIC) cowpea population, to identify single nucleotide polymorphism (SNP) markers associated with salt tolerance, and to assess the accuracy of genomic selection (GS) in predicting salt tolerance, and to explore possible epistatic interactions affecting salt tolerance in cowpea. Phenotyping was validated through the use of salt-tolerant and salt-susceptible controls that were previously reported. Genome-wide association study (GWAS) was conducted using a total of 32,047 filtered SNPs. The epistatic interaction analysis was conducted using the PLINK platform. Results Results indicated that: (1) large variation in traits evaluated for salt tolerance was identified among the MAGIC lines, (2) a total of 7, 2, 18, 18, 3, 2, 5, 1, and 23 were associated with number of dead plants, salt injury score, leaf SPAD chlorophyll under salt treatment, relative tolerance index for leaf SPAD chlorophyll, fresh leaf biomass under salt treatment, relative tolerance index for fresh leaf biomass, relative tolerance index for fresh stem biomass, relative tolerance index for the total above-ground fresh biomass, and relative tolerance index for plant height, respectively, with overlapping SNP markers between traits, (3) candidate genes encoding for proteins involved in ion transport such as Na+/Ca2+ K+ independent exchanger and H+/oligopeptide symporter were identified, and (4) epistatic interactions were identified. Conclusions These results will have direct applications in breeding programs aiming at improving salt tolerance in cowpea through marker-assisted selection. To the best of our knowledge, this study was one of the earliest reports using a MAGIC population to investigate the genetic architecture of salt tolerance in cowpea.

No abstract

Peanut (Arachis hypogaea L.) is a highly nutritious food that is an excellent source of protein and is associated with increased coronary health, lower risk of type-2 diabetes, lower risk of breast cancer and a healthy profile of inflammatory biomarkers. The domestic demand for organic peanuts has significantly increased, requiring new breeding efforts to develop peanut varieties adapted to the organic farming system. The use of unmanned aerial system (UAS) has gained scientific attention because of the ability to generate high-throughput phenotypic data. However, it has not been fully investigated for phenotyping agronomic traits of organic peanuts. Peanuts are beneficial for cardio system protection and are widely used. Within the U.S., peanuts are grown in 11 states on roughly 600,000 hectares and averaging 4500 kg/ha. This study's objective was to test the accuracy of UAS data in the phenotyping pod and seed yield of organic peanuts. UAS data was collected from a field plot with 20 Spanish peanut breeding lines on July 07, 2021 and September 27, 2021. The study was a randomized complete block design (RCBD) with 3 blocks. Twenty-five vegetation indices (VIs) were calculated. The analysis of variance showed significant genotypic effects on all 25 vegetation indices for both flights (p < 0.05). The vegetation index Red edge (RE) from the first flight was the most significantly correlated with both pod (r = 0.44) and seed yield (r = 0.64). These results can be used to further advance organic peanut breeding efforts with high-throughput data collection.