In utero transmission of bovine leukemia virus

In an initial study, 18 calves born to cows persistently infected with bovine leukemia virus (BLV) were tested for infective virus and antibodies at birth, and no infected or seropositive animals were found. Four of these calves were maintained in quarters where infected animals were housed, and 3 of the 4 subsequently became infected. These were probably contact infections acquired during, or at some time after, birth. The remaining 14 calves were kept in isolation pens in a building housing no infected cattle. None of this group was found to be BLV infected during 1 year of observation. In further studies, 15 pregnant cows inoculated with BLV became infected. One abortion, considered to be unrelated to the BLV inoculation, occurred 38 days later. The remaining 14 cows gave birth to 1 dead and 14 live calves. The dead calf and its live twin were seropositive for BLV at birth, indicating that they had been infected in utero. The remaining 13 calves were negative for BLV antibodies at birth and remained so during 1 year of observation.     

Pecan nut germination — A review for the nursery industry

The shell of the pecan nut is freely permeable to water and gases, but retards germination by mechanically restricting growth of the radicle. This mechanical effect, which is pronounced at 20°C, can be overcome by germinating nuts between 30° and 35°C. Cool, moist stratification can substitute for the high-temperature germination-requirement in that following stratification nuts germinate equally well at 20°, 25° and 30°C. During stratification or incubation at high temperature, cytokinin and gibberellin levels increase in the embryo. This increase in endogenous promoter levels is closely correlated with the digestion of food reserves necessary for the resumption of embryo growth.     

The effect of DD and dazomet treatments on nematode populations at various depths in the soil and on the transmission of soil-borne tobacco rattle virus to gladiolus

The relation between log dosage of DD injected at 15 cm depth or of dazomet applied to the soil surface (all in November 1971) and probit mortality ofRotylenchus and trichodorids in the top 20 cm of a field on sandy soil was found to be linear. Dosage increase efficiencies of both chemicals against both nematode species were medium to high. Superficial application of dazomet was very effective against the nematodes that would have survived if only a low dosage of DD had been injected at 15 cm depth. Injection of 40 ml or 80 ml DD per m² at 15 cm depth killed all nematodes between 20 cm and 60 cm deep. Gladiolus planted in the spring of 1972 grew better, flowered earlier and produced more weight of corms on treated than on untreated plots. The poor growth on the untreated plots cannot be ascribed to direct damage by nematodes or to the effect of TRV transmitted to the plants by the viruliferous trichodorids occurring in these plots in high densities. Symptoms of TRV infection in plants grown in 1973 from the corms harvested in the 1972 experimental field showed that only DD treatments had reduced the rate of TRV transmission considerably. However, even the highest dosages of DD had only reduced it from 26% (on untreated plots) to about 8%. Most probably, this residual TRV infection was due to transmission by trichodorids that had survived in soil layers below 60 cm depth. Therefore, soil treatment with nematicides, cannot prevent TRV transmission to gladiolus sufficiently where viruliferous trichodorids occur at great depths, as is the case in many sandy soils having a low water table.