Effect of potassium-hydrogen interaction in the excretory mechanism of the kidneys on the acid-base and other biochemical values of the blood and urine in calves]

The effect of the competitive relationship between potassium and hydrogen in the excretory mechanism of the kidneys on metabolism was studied in calves. The intraruminal exposure of calves to 5.6 meq potassium chloride (KCl) per kg per day has, in itself, only a slight acidotic effect ascribable to a slight reduction of the excretion of acid by the kidney. The same dose of ammonium chloride (NH4Cl) has a strong acidotic effect combined with a negative influence on weight gain. Both basic types of exposure increase the concentration of inorganic phosphorus and reduce the concentration of chlorine in the blood serum. The addition of 2.8 meq of potassium chloride per kg per day to the basic dose of ammonium chloride increases metabolic acidosis, worsens the health condition (being, at times, hazardeous to life) and leads to weight losses. The same amount of ammonium chloride added to the basic dose of ammonium chloride has a relatively small acidotic action on the blood, evoking only a slight and temporary potassium retention in the serum. The negative action on the weight gains and clinical symptoms are generally weaker than in the other group. The results indicate that the acidotic environment creates in ruminants a very dangerous situation if the organism is excessively exposed to the effect of potassium at the same time.     

Differences in resistance of wild Lactuca species to natural infection of lettuce powdery mildew (Erysiphe cichoracearum)

Summary The natural infection of Erysiphe cichoracearum on 29 accessions of five wild Lactuca species (L. serriola, L. saligna. L. virosa, L. aculeata and L. dentata) and on one hybrid of L. serriola x L. sativa has been investigated for two and three years, respectively. No infection was observed on L. serriola (PI 255665), L. saligna (LSA/92/1 and LSA/92/2), L. virosa (LVIR/26 and LVIR/57/1) and L. dentata (PI 234204). The level of susceptibility of the control cultivars of L. sativa was found to be moderate (Fila) to fairly high (Hilde).     

The Level of Field Resistance to Bremia lactucae in Lettuce (Lactuca sativa) Cultivars Carrying the Resistance Gene Dm11

Forty-one lettuce cultivars (butterhead type), carrying race-specific resistance gene Dm11 in combination with some others, were studied for field resistance to Bremia lactucae. Significant differences in the level of field resistance were revealed. Most of the cultivars under study were highly susceptible under field conditions. There are evident relationships between combinations of race-specific Dm genes and field resistance. The cultivars with gene combinations Dm2, Dm3 and Dm11 are susceptible. A very high level of field resistance was detected in the cultivars with combination of genes Dm5/8, Dm6 and Dm16 (cvs. ‘Celia’, ‘Katanga’ and ‘Musette’). This is in close link with their Lactuca serriola origin and a high level of field resistance in progenitors.     

Evaluation of wild Lactuca species for resistance of natural infection of powdery mildew (Erysiphe cichoracearum)

Summary The 99 accessions of seven wild Lactuca species (L. serriola, L. saligna, L. virosa, L. viminea, L. perennis, L. tenerrima, L. tatarica) and Mycelis muralis (syn. L. muralis) were tested for natural infection of Erysiphe cichoracearum L. serriola accessions were highly susceptible. L. saligna showed highly variable levels of resistance. Other Lactuca species were mostly resistant or only moderately susceptible.     

Variation in chromosome numbers and nuclear DNA contents in genetic resources of Lactuca L. species (Asteraceae)

Fifty accessions of 25 Lactuca species,L. serriola ×L. sativa and Mycelismuralis were analyzed for chromosome number and relative DNA amountvariation. In the majority of Lactuca species studiedchromosome counts, as earlier reported (n = 8, 9, 17), were verified; however,for L. dregeana andL. homblei (probablyL. schweinfurthii orL. longespicata) the chromosome number(n = 9) was determined for the first time. Relative nuclear DNA content,estimated by using flow cytometry (DAPI staining), showed that 2C DNA contentranged from 2.02 pg in L.capensis to 17.96 pg inL. canadensis. Statistical and clusteranalysis of data based on relative nuclear DNA contents correspond fairly wellwith recently accepted taxonomic classification of the genusLactuca. However, the position of certain species as wellas clarification of taxonomic determinations of someLactuca accessions needs further examination.     

Genotypic variation in field resistance of Cucurbita pepo cultivars to powdery mildew (Erysiphe cichoracearum)

Summary Fifty-eight cultivars of Cucurbita pepo (mostly zucchini type) were studied in three-year experiments for field resistance to powdery mildew caused by Erysiphe cichoracearum. No genotypes were found with complete resistance to powdery mildew. There were significant differences in the expression of field resistance characterized by some basic epidemiological parameters (maximum infection degree, area below curve). The highest level of field resistance occurred in 13 cultivars including Acceste F1, Albina, ambassador F1, CU-235, Elite F1, Goldfinger, Parmanta F1, Seneca Hybr. F1.Abbreviations ABC area below curve - ID infection degree - CO Cocozelle - VM Vegetable marrow - ZU Zucchini     

Resistance in Cucurbita pepo and Cucurbita maxima germplasms to cucumber mosaic virus

Summary A total of 384 Cucurbita pepo and Cucurbita maxima accessions were evaluated in growth chambers or glasshouse tests for resistance to cucumber mosaic virus (CMV). Seedlings were mechanically inoculated at the cotyledon stage, and scored for symptoms on cotyledons and true leaves 7 and 18 days after inoculation. Significant variation in resistance was found. A limited number of accessions were free of visual symptoms of infection. One C. pepo accession and thirteen C. maxima accessions showed a high level of resistance. Generally, C. maxima may be considered more resistant to CMV compared to C. pepo. There is no close relationship between origin, fruit morphotypes and CMV resistance in either species. Some accessions (e.g., C. pepo PI 438699; C. maxima PI 176530, PI 265555, PI 368564, PI 500483) could be useful for the future breeding programmes. The C. pepo cvs. Cinderella and Defender F1, previously described as resistant, showed maximum susceptibility to the yellow strain of CMV.Abbreviations CMV cucumber mosaic virus - WMV watermelon mosaic virus - ZYMV zucchini yellow mosaic virus - CYVV clover yellow vein virus - ZYFV zucchini yellow fleck virus