Relative susceptibilities of eleven potato cultivars and breeders' clones toGlobodera pallida pathotype Pa 3, with a discussion of the interpretation of data from pot experiments
Curves according to the equationPf=M′ (1-e−aPi/M′) fitted well to the relations according to Seinhorst's (1993) modelPf=yeyhM(1-e−aPi/M) between initial egg densities of potato cyst nematodes (Globodera rostochiensis, G. pallida)Pi up to 5Th (Th=the tolerance limit of haulm weight) andPf at the end of the growing season (a=maximum rate of reproduction,M, M′=different theoretical maximum egg densities). Variation of estimates ofM′, due to variation of the parameters of the submodelsye andyh for the effect of weight reduction of haulms (and, therefore, of roots) on cyst production and damage to root tissue on egg production, respectively, was small enough to be ignored relative to experimental error. Therefore, ratios of values ofM′, determined in simultaneous pot experiments with different potato cultivars, are reliable measures of the relative host status of these cultivars at initial egg densitiesPi of these nematodes up to about 5Th. Variation between potato cultivars of growth reduction and damage to root tissue by the nematodes reduces the reliability of ratios of rates of relative susceptibility of these cultivars.The ratios between the maximum rates of reproduction ofG. pallida, pathotype Pa 3, on 8 out of 9 cultivars and one breeder's clone of potatoes and this rate on the susceptible cvs Bintje and Irene (relative susceptibilitiesrsa) could be considered to be equal to the ratios of maximum population densitiesM′ on these cultivars (relative susceptibilitiesrsM′) (relative susceptibilities independent of initial egg density). The latter ratios were 0.59 times the first (relative susceptibilities negatively correlated with initial egg density) in one cultivar and one breeder's clone. Relative susceptibilitiesrsa andrsM′ of the tested cultivars and breeders clones suggest the existence of continuous ranges of both relative susceptibilities between 0.50 and 0.15 with, in a great majority of cases,rsa=rsM′.
Tuber and root resistance of potato genotypes against Meloidogyne chitwoodi in the presence of Avena strigosa, related to tuber quality
Relative tuber infestation and quality of two Meloidogyne chitwoodi resistant potato genotypes, AR04-4096 and 2011M1, were compared in glasshouse experiments at initial population density (Pi) = 16 second-stage juveniles (g dry soil)−1 in the presence and absence of the bristle oat, Avena strigosa. When A. strigosa was added, Pfroot+soil (Pf= final population) on both AR04-4096 and 2011M1 increased 130×, Pftuber increased 1.9 and 3.7×, respectively, while Pftuber × fresh root weight (FRW)−1 was the same. Nematode hatch from peel of AR04-4096, without A. strigosa, was delayed by 3 weeks but relative hatching rate was increased. Although the RStuber (RS = Relative Susceptibility) of both AR04-4096 and 2011M1 were lower than 1%, in the presence of A. strigosa tuber quality of 2011M1 dropped below the marketable level, while that of AR04-4096 was hardly affected. We conclude that: i) Pftuber is influenced by root mass; ii) root quality influences nematode hatch; iii) tuber quality is not an estimator for tuber resistance, and the reverse; iv) root resistance is equal to tuber resistance.
Diagnostic and therapeutic studies on chronic diarrhea in dairy animals
The study was conducted to determine the etiology of chronic diarrhea in dairy animals. Seven causes of chronic diarrhea were established in dairy cattle and buffaloes. Balantidiasis in 37.6 per cent, dietary diarrhea in 9.9 per cent, chronic salmonellosis in 6.9 per cent cases of chronic diarrhea, secondary copper deficiency and amphistomiasis in 6.9 per cent, clinical Johne‘s disease in 3.9 per cent and chronic peritonitis in 2.97 per cent of dairy animals, manifest chronic diarrhea. The precise diagnosis could not be established in 24.50 per cent of animals. Lymphosarcoma was confirmed in one of the dairy cattle. Body condition score was associated to the etiology of chronic diarrhea. B. coli infected cattle and buffalo revealed cysts in 32.3 per cent cases while 5 per cent positive cases revealed both cysts and trophozoites. Mean cyst count was 2.73±0.91 hpf in diarrheic animals compared to 0.11±0.447 hpf in healthy animals. Clinical Johne‘s disease was confirmed in four animals. Hematological changes revealed anemia and neutrophilia with morphological changes suggestive of regenerative to degenerative left shift. High plasma phosphorus, hypoproteinaemia and hypoalbuminaemia was seen in clinical Johne‘s disease. Salmonella isolates showed higher in-vitro sensitivity to enrofloxacin (87%), ciprofloxacin (87%), gentamicin (75%), and tetracycline (66.7 %) and were resistant to ampicillin and amoxicillin. Mean cyst count reduction from 2.41±1.16 to 0.11±.33 was observed in oral metronidazole treated group where as reduction of mean cyst count from 2.73±0.918 to 0.18±0.44 in intravenous metronidazole treated group. Recovery rate with oral and intravenous metronidazole was 42.1 and 63.1 per cent respectively. Recovery results in significant decrease in eiosionphil count and increase in total plasma protein in both oral and intravenous treatment groups. Complete recovery response approaches 60 per cent in balantidiasis affected adult dairy animals. Balantidiasis was the major cause of chronic diarrhea and intravenous administration of metronidazole was more effective than oral metronidazole.