Asian soybean rust (ASR), caused by Phakopsora pachyrhizi Syd., is a widespread disease of soybean [Glycine max (L.) Merr.] with the potential to cause serious economic losses. The objective of this study was to genetically map red‐brown lesion type resistance from the cultivar Hyuuga. A population of 117 recombinant inbred lines (RILs) from the cross of Dillon (tan lesion) × Hyuuga (red‐brown [RB] lesion) was rated for ASR lesion type in the field and inoculated with P. pachyrhizi in the greenhouse. The RB resistance gene mapped between Satt460 and Satt307 on linkage group (LG)‐C2. When field severity and lesion density in the greenhouse were mapped, the Rpp?(Hyuuga) locus explained 22 and 15% of the variation, respectively (P < 0.0001). The RB lesion type was associated with lower severity, fewer lesions, and reduced sporulation when compared to the tan lesion type. A population from the cross of Benning × Hyuuga was screened with simple sequence repeat (SSR) markers in the region on LG‐C2 flanked by Satt134 and Satt460. Genotype at these markers was used to predict lesion type when the plants were exposed to P. pachyrhizi All the lines selected for the Hyuuga markers in this interval had the RB lesion type and they averaged approximately 50% fewer lesions compared to lines with tan lesions. Sporulation was only detected in 6% of the RB lines compared with 100% of the tan lines. Marker‐assisted selection can be used to develop soybean cultivars with the Rpp?(Hyuuga) gene for resistance to ASR.

Frogeye leaf spot (FLS), caused by Cercospora sojina K. Hara, is a common disease of soybean [Glycine max (L.) Merr.] in most soybean‐growing countries of the world. Significant yield losses of soybean (10–60%) have been attributed to FLS under hot and humid growing conditions. The FLS in the southern United States has been kept under control by planting resistant cultivars. Cercospora sojina is a dynamic pathogen with extensive virulence or race diversity. The current number of C. sojina isolates at the University of Georgia collection is 93. Assigning race designations to this large number of isolates has been difficult because of the lack of a well‐defined set of differentials. To facilitate future studies of the genetics of soybean resistance to FLS and the identification and comparison of existing and future races of C. sojina, we have reassessed both the soybean differentials and the C. sojina races. Based on the reactions of 93 isolates of C. sojina on 38 putative soybean differentials, we propose a core set of 12 differentials and 11 races that represent the major diversity among the 93 C. sojina isolates. The definition of these 12 differentials and 11 races should provide the foundation for the identification and comparison of additional soybean resistance genes and new races of C. sojina

Soybean [Glycine max (L.) Merr.] resistance to soybean rust (SBR) caused by Phakopsora pachyrhizi could reduce reliance on fungicides to manage this disease. The objective of this study was to identify soybean germplasm with resistance to field populations of P. pachyrhizi in the United States. Field evaluations of 576 accessions from the USDA Soybean Germplasm Collection for resistance to SBR were conducted at seven locations in the southern United States between 2006 and 2008. Accessions from maturity groups (MG) 000 to X and North American susceptible check cultivars from each MG except X were rated for disease severity in all year–location environments, and for disease incidence, fungal sporulation, lesion type, and/or uredinia density in certain environments. While none of the accessions was immune in all environments, 64 were resistant in two or more locations each year that they were tested. Some accessions appeared to be more resistant in certain environments than in others. Of the original four Rpp genes described in the literature, Rpp1 provided the highest level of resistance, and among the accessions with uncharacterized Rpp genes, PI 567104B had the highest overall resistance across environments. The plant introductions confirmed to be resistant in these evaluations should be useful sources of genes for resistance to North American populations of P. pachyrhizi

Feeding injury caused by nymphs, males and females of the azalea lace bug, Steplwnitis pyrioides (Scott), reduced rates of photosynthesis and transpiration in 'Delaware Valley White' azalea, RllOdodendron mucronatulIl leaves. Females caused substantially more leaf feeding injury than males or nymphs. S. pyrioides was observed to insert stylets through stomata on the lower leaf surface and to feed almost entirely on upper palisade parenchyma tissue by piercing and removing cell contents. Lace bug feeding increased leaf stomatal resis tance which indicated that gas exchange was restricted by stomatal closure. Feeding injury also reduced leaf chlorophyll content and photosynthetic capacity of remaining chlorophyll, but did not consistently affect chlorophyll a:b or specific leaf weight. Net leaf photosynthesis was negatively correlated with stomatal resistance and positively correlated with both chloro phyll content per unit leaf area and photosynthetic rate of remaining chlorophyll. These results indicated that S. pyrioides reduced leaf photosynthesis in azalea by damaging palisade paren chyma which restricted gas exchange through stomata and reduced leaf chlorophyll content and photosynthetic capacity of remaining chlorophyll.

1990). Greater than 60% yield loss due to FLS has been reported in the tropical environment of Nigeria Frogeye leaf spot (FLS) (caused by Cercospora sojina Hara) is a (Dashiell and Akem, 1991). foliar disease of soybean [Glycine max (L.) Merr.] that causes significant yield loss in southeastern USA. The Rcs 3 gene in soybean has At least five races of the fungus have been reported been reported to condition resistance to all known races of C. sojina. in the USA (Phillips and Boerma, 1981). Twenty-two Molecular mapping of the Rcs3 gene will be helpful in breeding races of C. sojina were identified in Brazil (Yorinori, soybean for resistance to FLS. The objective of this study was to map 1992). In a recent study designed to further elucidate the Rcs 3 gene with DNA markers. The parents, 123 F 2 plants, and the extent of pathogen variability and to define a set of the F 2:3 families from the cross of 'Blackhawk' (susceptible) ϫ 'Davis' differential cultivars to aid in race identification of C. (resistant and original source of the Rcs3 gene) were scored for FLS sojina, D.V. Phillips identified over 40 races of the funreaction in the greenhouse after inoculation with race 5 of C. sojina. gus on a set of 38 differential cultivars (unpublished In addition, 'Wright' and the Wright 6 -Rcs 3 (near isoline of Wright) data, 1998). Three single genes conditioning resistance were also scored for FLS by the same protocol. A resistant and a to C. sojina are currently recognized by the Soybean susceptible DNA bulk were created by pooling the DNA of 15 resistant and 15 susceptible F 2 plants, respectively, from the Blackhawk ϫ