The tropical legume sunn hemp (Crotalaria juncea L.) cultivar AU Golden' has the potential to provide substantial nitrogen (N) to subsequent crops to reduce recommended application rates of synthetic N fertilizers. A mineralization field trial was conducted to measure mass decomposition and N and carbon (C) amounts remaining from sunn hemp residue following three planting dates (May, June, and July) during the 2013 growing season at the Tennessee Valley (TVS) and Coastal Plain (WGS) locations of AL. Residue from June and July plantings contained 50.0% and 61.1% N at WGS and 41.5% and 66.5% N at TVS by the end of their respective incubation periods compared to residue from the May planting, which contained 21.1% N at WGS and 47.8% at TVS. In order to create a more synchronous relationship between AU Golden' residue N mineralization and crop demand, termination must be delayed until approximate planting of the following crop.

Genetic diversity is an important breeder’s tool for selection and improvement in crop cultivar development. Any successful breeding program depends on selecting superior quality parents. Lack of genetic diversity limits the potential of the breeder in selecting elite parents. Genetic uniformity predisposes cultivars to many pests and diseases and can make the adapted germplasm pool genetically vulnerable as it is evident from the past hence, there is a need for expanding and improving the genetic base of upland cotton. Our study was designed to study the effect of exotic germplasm introgression on agronomic and fiber quality traits of the adapted cotton gene pool. We developed eight populations derived from crossing two exotic parents (TX 245 and TX 1419) with four adapted cultivars (FM 966, PM 1218, Deltapearl and SG 747). In each population we developed five combinations with 0, 25, 50, 75 and 100 percent exotic germplasm. We tested the experimental material using RCBD with two years, two locations, five blocks and two replications. Across populations, no significant difference was observed for days to first flowering, lodging percent and bolls per plant, whereas seeds per boll, seed cotton yield and lint yield had no significant difference up to 25 percent but upon further introgression significant decline was observed. However, lint mass per seed and lint percent declined significantly with increase in exotic germplasm introgression. Fiber properties declined significantly with increase in exotic introgression except for fiber elongation and short fiber content. Fiber elongation improved significantly with increase in exotic percentage.

Rotylenchulus reniformis (reniform nematode) can be a yield-limiting factor for upland cotton. Resistance to this nematode was discovered in a wild cotton relative, transferred to an upland background and released as the germplasm LONREN. The LONREN source of resistance to reniform nematode in upland cotton was evaluated for reaction to increasing levels of inoculum on root and shoot growth and nematode reproduction compared to susceptible genotypes. Genotypes tested were LONREN-1 and LONREN-2 (resistant); Fibermax 966 and Deltapine 555BR (susceptible); and one susceptible and one resistant F 2: 4 line from the cross LONREN-1 x Fibermax 966. Inoculum levels of 0, 500, 1000, 5000, 10,000, or 50,000 juveniles and vermiform of R. reniformis were used. Plant height and vigor ratings were collected weekly. Root and shoot fresh and dry mass, and nematode numbers were collected 60 days after inoculation. Based on inoculation rate, a reproduction factor (Rf) was calculated as the ratio Pf/Pi, where Pf = final nematode population and Pi = initial inoculum level. Root dry mass of genotypes with the LONREN resistance source was reduced at high inoculation density compared to low inoculum levels. An opposite trend was observed for root dry mass of reniform nematode susceptible genotypes, where root dry mass increased at higher inoculum levels. Shoot dry mass for all genotypes was largely unaffected except at the highest inoculum level. Shoot to root dry mass ratios for the LONREN resistance source genotypes were found to trend higher with increased inoculum levels, whereas the same ratios decreased in case of the susceptible genotypes. Examination of the roots of LONREN resistant source genotypes showed signs of necrosis. We conclude that the LONREN resistance source exhibits a type of hypersensitive response to reniform nematode. This reaction, while inhibiting reniform nematode reproduction, appears to be a factor in seedling stunting at higher nematode density levels.

ABSTRACTSoybean [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

In the last 8 yr, Cotton (Gossypium hirsutum L.) growers in North Carolina have experienced variations in the year-to-year lint yield averages that range from a 56% increase to a 49% decrease. This variability results in wild fluctuations in income and a desire for more stable yields. Genetic structure may contribute to stability. This study was conducted to determine the impact of heterozygosity and heterogeneity on lint yield stability. Lint yield was observed in 18 environments over 3 yr among four population types that included homozygous lines grown in pure stands, homozygous lines grown in blended stands, hybrids grown in pure stands, and hybrids grown in blended stands. Comparisons were made using trait means, standard deviations, and the coefficients of variation (CVs) calculated over environments. There was no significant difference between lines grown in pure stands and blended lines with respect to yield or stability. Hybrids had a lower CV (were more stable) than homozygous lines. This stability was attributed to the hybrids and blends of hybrids out-yielding the homozygous lines and blends of homozygous lines in the low-yielding environments, but having similar yields in the high-yielding environments. These results do not support growing blends to increase stability or yield; however, growing hybrid cultivars could result in increased yields while reducing variability compared with current production practices.

Historically,re-selection,pedigree,and mass selection breeding methods have been used to develop open-pollinated cultivars of Upland cotton(Gossypium hirsutum L.). Due to the predominance

Historically, reselection, pedigree, and mass‐selection breeding methods have been used to develop open‐pollinated cultivars of upland cotton (Gossypium hirsutum L.). As a result, modern cotton cultivars should have accumulated additive genetic effects with time, while also possessing fewer nonadditive gene effects than obsolete cultivars. A topcross test was conducted to compare the heterotic effects of obsolete and modern cultivars for yield, yield components, and fiber quality. Significant differences were detected between heterosis values for the modern and obsolete cultivar groups for seed cotton yield, lint yield, lint percentage, and boll weight. No significant heterotic effects were detected for fiber quality. The obsolete group of cultivars showed average lint yield heterosis values of 34% compared with 23% for the modern cultivars. Both cultivar groups displayed significant, but similar heterosis values for the number of bolls per square meter (17 and 15%, respectively). The major yield component associated with lint yield heterosis for both groups was bolls per square meter, although boll weight heterosis also contributed to lint yield heterosis for the obsolete cultivars. Although modern cultivars produced considerable heterotic effects for yield, this study demonstrates that obsolete cultivars may provide an additional source of nonadditive genetic effects that can be exploited in a hybrid production system.

The National Plant Germplasm System (NPGS) is a cooperative effort among State, Federal and Private organizations aimed at preserving one of agriculture’s greatest assets: plant genetic diversity. The NPGS serves the scientific community by collecting, storing, and distributing germplasm as well as maintaining a searchable database of trait descriptors. Serving the NPGS, a Crop Germplasm Committee (CGC) is elected for each crop and is comprised of a group of scientists concerned with development, maintenance, characterization, and utilization of germplasm collections. Each CGC serves in an advisory role and provides a status report every seven years to determine scientific efforts, adequacy of germplasm base representation, and progress in breeding through utilization of germplasm. In addition, each committee can call attention to areas of concerns regarding facilities and staffing associated with the maintenance, collection, and taxonomic activities for a specific crop within the system. The following report was developed by the CGC for cotton and provides a record of collections, activities, concerns, crop vulnerabilities, and recommendations associated with the cotton collection for the period 1997–2005. Information provided within this document is a much expanded and detailed description of a report provided to the NPGS and includes the most exhaustive citation of germplasm depositions and research activity descriptions available anywhere in the USA for this time period. This documentation will be a valuable resource to breeders, geneticists, and taxonomists with an interest in this important food and fiber crop.

In double‐cropped soybean [Glycine max (L.) Merr.] planting is delayed, with a corresponding decrease in yield associated with photoperiod‐induced early flowering and reduced accumulation of dry matter during the vegetative growth period. Application of nitrogen (N) has been shown to improve yield of late‐planted soybean. We conducted a field study to determine the optimum economic rate of N that would stimulate early dry matter accumulation, and thus yield, in late‐planted soybean. The effects of three planting dates (mid‐June, late‐June, and mid‐July), two MG VIII cultivars (Kuell and Prichard), and five N rates (0, 25, 50, 75, and 100 kg ha−1) were studied for 2 yr at three Alabama locations (Fairhope, Shorter, and Crossville). Nitrogen application of 60 to 70 kg ha−1 maximized yield and R1 dry matter accumulation. However, N reduced nodule number and mass, but had no effect on R1 plant height, mature plant height, or seed quality, protein and oil content. Yield was reduced linearly by later planting, but there was no interaction between N rate and planting date for yield. Kuell was taller at maturity and had more R1 dry matter than Prichard, but Kuell yielded more than Prichard in only one environment and there was no cultivar × N rate interaction for yield. At current prices for N and soybean, we concluded that N can be a viable input for double‐cropped soybean at an optimal economic rate of 59 kg ha−1.

Velvetbean (Mucuna sp., n=11), a self-pollinated species, is an important legume used in tropical agricultural systems in rotation with other crops for nematode management and/or soil improvement. A genetic map of velvetbean was constructed in order to identify potential molecular markers linked to important morphological and agronomic traits that would be particularly useful for developing and improving the species. Traits such as seed coat color, pod color, and pod pubescence were among the main parameters observed in a process of genetic diversity estimation. Two slightly divergent velvetbean accessions, PI364362 and 'Edgar Farm White', a land race from Alabama, were used to make an intraspecific F-1 hybrid. Amplified fragment length polymorphism analysis (AFLP) detected an average of six polymorphic fragments per primer pair between the two parents. As expected for dominant markers, the sum of all AFLP bands from both parents was generally observed to be present in the AFLP profiles of the F-1 progeny, indicating full penetrance and the dominant nature of AFLP markers. An F-2 population was generated by self-pollinating a single F-1 plant. Using 37 AFLP primer pairs, we detected 233 polymorphic markers of which 164 (70.4%) segregated in 3:1 Mendelian ratios, while the remaining 69 (29.6%) both segregated and were scorable. The genetic linkage map constructed from this population comprised 166 markers, including two morphological traits (pod color and pod pubescence). Twenty linkage groups were found with an average distance between markers of 34.4 cM, covering a total of 687.9 cM. The linkage groups contained from 2 to 12 loci each and the distance between two consecutive loci ranged from 0 to 21.8 cM. The newly designated morphological traits pod color (pdc) and pod pubescence (pdp) co-segregated with each other at a distance of 4.2 cM. Two DNA markers designated ACGCAG2 and ACTCTG1 were located in the same group as pdc and pdp. The AFLP linkage map provides opportunities for use in marker-assisted selection and in the detection of loci controlling morphologically important traits.

Foot and mouth disease (FMD) is endemic in African buffalo (Syncerus caffer) in the Kruger National Park (KNP) and surrounding game parks in South Africa. The last outbreak of the disease in domestic stock outside the FMD control zone occurred in 1957. Due to the success in containing the disease, the country was accorded zone freedom from FMD without vaccination by the Office International des Epizooties (OIE: World organisation for animal health) in 1995. This status was lost in September 2000 when the first-ever recorded case of serotype 0 in South Africa was diagnosed in a piggery in KwaZulu-Natal after the illegal feeding of untreated swill. In November 2000, an outbreak of FMD caused by serotype South African Territories (SAT) 1 was diagnosed in a feedlot within the free zone of Mpumalanga Province. The SAT 1 outbreak was traced to cattle in the FMD control zone south of the KNP after the game-proof fence surrounding the KNP was severely damaged by floods. This enabled buffalo to come into direct contact with cattle outside the KNP. A further outbreak caused by SAT 2 was diagnosed within the FMD control zone in February 2001, also as a result of buffalo having escaped from the KNP. All these outbreaks were successfully contained, with the re-instatement of zone freedom from FMD without vaccination by the DIE in May 2002. These outbreaks made it necessary to re-examine the methods of control and containment of FMD that have been practised for many years and which are in line with accepted international practices. The authors describe the rationale for the different control strategies that were followed,the need for a multidisciplinary approach to disease control, the interface between control and technological and diagnostic support and the lessons learned. Some suggestions for future control strategies are also offered.

Amplified fragment length polymorphism (AFLP) and microsatellite (simple sequence repeat, SSR) techniques were used to map the Rcs(Peking) gene, which is resistant to most isolates of Cercospora sojina in the soya bran cultivar 'Peking'. The mapping was conducted using a defined F-2 population derived from the cross of 'Peking' (resistant) x 'Lee' (susceptible). Of 64 EcoRI and MseI primer combinations, 30 produced polymorphisms between the two parents. The F-2 population, consisting of 116 individuals, was screened with the 30 AFLP primer pairs and three mapped SSR markers to detect markers possibly linked to Rcs(Peking). One AFLP marker amplified by primer pair E-AAC/M-CTA and one SSR marker Satt244 were identified to be linked to Rcs(Peking). The gene was located within a 2.1-cM interval between markers AACCTA178 and Satt244, 1.1 cM from Satt244 and 1.0 cM from AACCTA178. Since the SSR markers Satt244 and Satt431 have been mapped to molecular linkage group (LC) J of soya bean, the Rcs(Peking) resistance gene was putatively located on the LG J. This will provide soya bean breeders an opportunity to use these markers For marker-assisted selection for frogeye leaf spot resistance in soya bean.

Frogeye leaf spot (FLS) (caused by Cercospora sojina Hara) is an important foliar disease in many soybean [Glycine max (L.) Merr.] production areas of the world. It can cause severe yield losses, but can be completely managed with genetic resistance. Three dominant genes for resistance have been reported. However, the fungus is known to be genetically variable, and in the past, new races have developed that were capable of infecting previously resistant genotypes. Finding additional sources of resistance may reduce the impact of new virulent races. The objective of this study was to evaluate all available soybean plant introductions in maturity groups VI and VII for resistance to FLS. Plants were inoculated with C‐32, an isolate of C. sojina, in the greenhouse. Genotypes were rated on a scale of 0 to 6 on the basis of percent leaf area infected with lesions. Six hundred sixty (39.3%) of the accessions received a rating of 3 or lower, and were identified as resistant. Twelve accessions remained completely disease free after repeated inoculation, thus were considered highly resistant or immune. There appears to be adequate resistance to FLS within the germplasm collection, and many of these may have unique resistance genes.

Velvetbean (Mucuna sp.) is a self-pollinated crop classified within the Leguminosae. Using AFLP markers, gene diversity and phenetic relationships were estimated in a collection of 40 velvetbean accessions from cultivated species and different eco-geographic regions. Eleven selective primer combinations generated a total of 508 amplification products. The average number of scorable fragments was 23 per primer combination. A total of 251 polymorphic markers was detected. The polymorphisms obtained ranged from 36% to 61% with an average of 49%. The final phenetic trees were constructed using Nei and Li’s coefficient of similarity with UPGMA. Other clustering algorithms were examined and all had high co-phenetic correlations, indicating the goodness of fit for the resulting phylogenetic trees. The phenetic tree as well as principal component analysis (PCA) separated the 40 velvetbean accessions into two main clusters. Bootstrap and Jackknife analyses were completed and their values indicated strong to moderate support for the two main clusters. This grouping confirmed the existing phenological difference with regard to maturity. The high values of the similarity coefficients observed (0.87 to 0.97) imply that the accessions used in this study are similar. The level of genetic variability detected within the velvetbean accessions with AFLP analysis suggests that it is a reliable, efficient, and effective marker technology for determining genetic relationships in velvetbean.

The effects of elevated compared to current atmospheric CO2 concentration (720 and 365 L L –1 , respectively) on antioxidative enzymatic activities of two soybean (Glycine max (L.) Merr.) genotypes (R and S) grown in open-top field chambers were investigated. Enzymatic activities of leaves collected 40, 47, 54 and 61 d after planting were measured. Elevated CO2 significantly decreased activities of superoxide dismutase (SOD, EC 1.15.1.1), peroxidase (POD, EC 1.11.1.7), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APOD, EC 1.11.1.7), gluta-thione peroxidase (GPOD, EC 1.11.1.9) and glutathione reductase (GR, EC 1.6.4.2) in both genotypes. The activi-ties of dehydroascorbate reductase (DAR, EC 1.8.5.1) and monodehydroascorbate reductase (MDAR, EC 1.1.5.4.) increased in genotype S, but decreased in genotype R under elevated CO2. Elevated CO2 decreased rubisco activity and rubisco, chlorophyll, carotenoids and total soluble protein contents in both genotypes. Results indicate that constitutive antioxidative enzymatic activities may decrease in a high-CO2 world. Significant CO2 ¥ genotype interactions, however, suggest that there may be key genotypic differences in response patterns, potentially conferring differential resistance to biotic and abiotic stress.

Frogeye leaf spot (FLS) of soybean [Glycine max (L.) Men.] is caused by the fungus Cercospora sojina Hara. The fungus is ubiquitous, but only problematic in hot humid soybean‐producing regions such as Brazil, China, Nigeria, and the southern USA. Significant yield losses (10–50%) are commonly associated with FLS epidemics. The quantification of unique alleles for resistance within the southern germplasm pool is an essential step toward developing a more usable set of differential genotypes and thereby clarifying the race situation within the C. sojina‐soybean interaction. Our objective was to determine the inheritance of resistance to FLS in PI54610 and Peking and their allelic relationship to Res,. ‘Lee’ soybean was used as a susceptible parent for crosses and control in all experiments. Parents and F2 seedlings were inoculated with a C. sojina spore suspension in the greenhouse or field and then rated for disease development 14 to 21 d later. On the basis of segregation ratios (3:1 resistant/susceptible in Peking × Lee and PI54610 × Lee, and 15:1 in ‘Davis’ × Peking and PI54610 × Peking), we found resistance in Peking was determined by a single dominant gene nonallelic to Rcs3. We also found, based on nonsegregation of resistance within the Davis × PI54610 population, that PI54610 has the same gene as in Davis (Rcs3). Resistance in Peking should be considered unique for the purpose of race differentiation and as a commercial source of resistance to FLS should Rcs3 fail.

Frogeye leaf spot (FLS) caused by Cercospora sojina Hara is a disease of soybean (Glycine max (L.) Merr.) that causes significant seed yield losses in warm, humid environments of southeastern United States. The Rcs 3 gene in soybean has been reported to condition resistance to all known races of C. sojina. The objectives of this study were to determine the effectiveness of Rcs 3 in limiting seed yield loss due to FLS and to compare the seed yield of the resistant and susceptible near-isolines (NILs) in the absence of significant FLS disease. Four pairs of NILs—Colquitt/Colquitt-Rcs 3 , Gordon/Gordon-Rcs 3 , Thomas/Thomas-Rcs 3 , and Wright/Wright-Rcs 3 —were evaluated in 23 field experiments in Alabama, Florida, Georgia, Louisiana, Mississippi, and South Carolina during 1992 to 1994. The amount of damage to susceptible soybean caused by FLS was dependent on the specific environment. All four of the Rcs 3 NILs were resistant to the prevalent races of FLS in all environments. In the absence of significant FLS disease, each of the Rcs 3 NILs was at least equal to the respective susceptible line in its seed yield. In the presence of FLS infestation, the susceptible lines suffered significant seed yield loss (up to 31%) compared to their Rcs 3 NILs. The effect of FLS on seed yield was dependent on cumulative disease severity over the growing season. Thus, the area under disease progress curve was more useful than percent of leaf area infected at the end of the growing season (R7 stage of development) in explaining the seed yield loss due to FLS.