Field and greenhouse evaluation of the components of partial resistance to early leafspot in peanut

Summary Ten peanut (Arachis hypogaea L.) genotypes were evaluated fro components of partial resistance to Cercospora arachidicola Hori in the field and in two detached leaf tests in the greenhouse. The relationships among the resistance components in the two environments were examined by computing rank correlations among the components measured in the greenhouse and among those measured in the field. A comparison of field and greenhouse testing for partial resistance was made by determining the correlations between components measured in the two testing methods. The genotypes were significantly different for all the components of resistant measured in the field and for most of the components measured in the greenhouse. In the field study necrotic area/10 cm² leaf area was moderately correlated (r=0.58) with lesion number/10 cm² leaf area and highly correlated (r=0.71–0.76) with total lesion number, predicted number of days after planting (X) to reach a standard lesion count, and defoliation. In the greenhouse only the correlation between necrotic area (mm²)/10 cm² leaf area and sporulation/leaf was highly significant (r=0.71–0.83) in both greenhouse tests. Necrotic area (mm²)/10 cm² leaf area measured in the field was significantly correlated with that measured in the greenhouse (r=0.66). Sporulation/leaf measured in the greennhouse was significantly correlated (r=0.66) with lesion increase in the field (measured as predicted X). It should thus be possible to evaluate and select for components of partial resistance in the greenhouse to develop resistant lines for the field.     

Evaluating drought resistance in germplasm of meadow fescue

Summary The drought resistance of 25 accessions of meadow fescue (Festuca pratensis Huds.) from seven countries was investigated in four experiments: two in the glasshouse using pot-grown plants from which water was withheld for various periods, and two in controlled environments under osmotic stress.There were significant differences between populations (broad-sense heritabilities or repeatabilities) in all four experiments. In the glasshouse there was a large residual effect of yield potential on production during and after slight-to-moderate drought, and different susceptibilities appeared only after very severe drought. The most consistently high-yielding accessions were from the Bergamo alps in Italy. Recovery after drought was strongly correlated with tiller survival. Continued production under moderate drought was considered important in wetter climates, whereas survival and recovery under severe drought was often associated with low production or flowering in the seeding year, and more typical of summer-drought climates.Leaf growth rates of plants subjected to zero or moderate osmotic stress were correlated with yields of irrigated or moderately-stressed plants in the glasshouse, although there was no differential susceptibility to mild stress. Under severe osmotic stress there were very large differences in survival between populations, but there was no relationship with survival under glasshouse conditions.The inconsistency of population rankings across experiments shows that no one technique gives a full evaluation of drought resistance, and emphasizes the complex nature of the phenomenon. It was possible, however, to identify (a) regions meriting further collections, and (b) ecotypes that had desirable responses in all experiments and could contribute to variety improvement.     

Book reviews and notices

Book reviews and notices     

Effects of disease control by fungicides on greenhouse gas emissions by UK arable crop production

BACKGROUND: The UK government has published plans to reduce UK agriculture's greenhouse gas (GHG) emissions. At the same time, the goal of global food security requires an increase in arable crop yields. Foliar disease control measures such as fungicides have an important role in meeting both objectives. RESULTS: It is estimated that UK winter barley production is associated with GHG emissions of 2770 kg CO₂ eq. ha^?1 of crop and 355 kg CO₂ eq. t^?1 of grain. Foliar disease control by fungicides is associated with decreases in GHG emissions of 42–60 kg CO₂ eq. t^?1 in UK winter barley and 29–39 kg CO₂ eq. t^?1 in UK spring barley. The sensitivity of these results to the impact of disease control on yield and to variant GHG emissions assumptions is presented. Fungicide treatment of the major UK arable crops is estimated to have directly decreased UK GHG emissions by over 1.5 Mt CO₂ eq. in 2009. CONCLUSION: Crop disease control measures such as fungicide treatment reduce the GHG emissions associated with producing a tonne of grain. As national demand for food increases, greater yields as a result of disease control also decrease the need to convert land from non‐arable to arable use, which further mitigates GHG emissions. Copyright © 2011 Society of Chemical Industry     

The distribution of peach scab lesions on the surface of diseased peaches

The aim of the study was to quantify peach scab (Fusicladosporium carpophilum) lesion distribution relative to the point of maximum lesion number on the fruit surface, the relationship between lesion count and distance from the point of maximum lesion density, and establish whether the distribution of lesions was consistent with a splash dispersed pathogen, and to assess the effect of lesion number on fruit size. Fruit of four cultivars, Jerseyqueen, Jefferson, BY07-6428r and Dixiland were collected and the fruit (assumed spherical) sliced taking three horizontal planes across the axis from the point of maximum disease, such that each horizontal zone (Z1-Z4) had the same vertical height, and thus equal surface areas. Lesion counts were analysed using general linear modeling with a Poisson distribution and a log-link function. Zones on the fruit had different numbers of lesions (P < 0.0001), with most lesions found on Z1. Cvs differed in the number of lesions per fruit (P = 0.0042–<0.0001). An analysis of covariance showed that although fruit size varied among most cvs (P = 0.1614–<0.0001), the number of lesions on a fruit did not affect fruit size (P = 0.5654). Measurements of the point of maximum disease relative to the peduncle-flower scar axis of the fruit suggest that fruit are not always held upright when infection occurs, such that up to 40% of fruit showed maximum infection at an angle >90° to the peduncle. This pattern of disease is consistent with observations of the splash-borne nature of conidia, with the most exposed, easily wetted, uppermost portion of fruit developing most disease.     

Patterns of solanidine glycoalkaloid variation in four gene pools of the cultivated potato

Patterns of variation for the solanidine-based glycoalkaloids have been determined for tuber material of genebank accessions of landraces of the cultivated potato and three closely-related wild species. Total levels were low in the cultivated taxa investigated,S. phureja, S. stenotomum, and the tetraploidS. tuberosum in its two formsS. tuberosum ssp.tuberosum andS. tuberosum ssp.andigena. The only solanidine-based glycolkaloids found in the tubers investigated in this study were-solanine and-chaconine, with one additional related compound, dehydrocommersonine, found in tubers of an accession ofS. canasense. The ratio of chaconine : solanine differed markedly from a mean of 0.98 inS. phureja to 2.28 in ChileanS. tuberosum ssp.tuberosum. The chaconine : solanine ratio was relatively constant within these two taxa, reflecting their relatively narrow genetic bases, but was much more variable within the taxa regarded as ancestral,S. stenotomum andS. tuberosum ssp.andigena. The wild speciesS. sparsipilum has been implicated in the origin of the tetraploid potato,S. tuberosum, but there was no support for this from the patterns of variation in chaconine : solanine ratio. The cline of chaconine : solanine ratios in cultivated potatoes along the spine of S. America does not appear to relate to the influence of local wild species through introgression, but may instead reflect differing selective pressures acting in different parts of the native range of the cultivated potato.     

Variation in progenies of an Arachis hypogaea x diploid wild species hybrid

Summary Derivatives of a cross between cultivated peanuts, Arachis hypogaea L. (2n=40), and the wild species collection GKP 10017 (2n=20) were compared morphologically, for leafspot resistance and for yield. The objective of the study was to determine the effects of wild species germplasm on the A. hypogaea genome. The sterile F₁ hybrid which resulted from crossing the two species was treated with colchicine to restore fertility at the 6x ploidy level. The resulting hexaploid was cytologically unstable and progeny lost chromosomes until stability was regained at the 2n=40 chromosome level. Forty-seven characters were used to analyze the variation among plants in the tetraploid interspecific hybrid population. The plants were compared to four cultivated lines plus GKP 10017. Many hybrids were intermediate to the two parents in morphology. Individual traits such as growth habit, pod and seed size, elongation of the constricted area between pods, nodulation and leaflet size were altered by the presence of GKP 10017 germplasm in many of the hybrid plants. Cercospora arachidicola Hori and Cercosporidium personatum (Berk. & Curt.) Deighton resistances were evaluated for all plants. Several hybrids had few lesions due to either leafspot pathogen. In addition, 24 largeseeded interspecific hybrid selections were compared to the cultivated variety NC 5 for yield. Five selections were superior to both parents at p=0.01. Morphology, disease resistance and yields appeared to be greatly influenced by the wild species GKP 10017 germplasm in plants of the interspecific hybrid population. The potentials of using wild species for improvement of the cultivated peanut are discussed.Paper number 5948 of the journal series of the North Carolina Agricultural Research Service, Raleigh, NC 27650. The investigation was supported in part by ICRISAT and SEA-CR grant no. 701-15-51.     

Prediction of Serum IgG1 Concentration in Holstein Calves Using Serum Gamma Glutamyltransferase Activity

We examined the relationship between serum gamma glutamyltransferase (GGT) activity and serum gamma immunoglobulin G (IgG1) concentration in Holstein calves. Blood samples were collected from calves aged 1 to 3 days. A follow-up sample was obtained from each calf 2, 7, or 15 days after the initial sampling. Serum GGT activity and lgG1 concentration were measured. Regression models were used to predict lgG1 concentration as a function of age and serum GGT activity measured 2, 7, or 15 days later.
Serum GGT activity and calf age at the time of the second sample were directly related to serum IgG1 concentration in the initial sample in calves aged 3 to 17 days ( r = .54) and in calves aged 3 to 10 days ( r = .63). Models were used to estimate the serum GGT activity equivalent to a serum IgG1 concentration of 1,000 mg/dL. One-day-old calves should have serum GGT activities > 200 IU/L. Four-day-old calves should have serum GGT activities > 100 IU/L. One-week-old calves should have serum GGT activities > 75 IU/L. Calves with serum GGT activities < 50 IU/L should be classified as having failure of passive transfer.