Cytogenetic studies in trifolium spp. related to berseem

Summary In order to clarify the interspecific relationships between T. carmeli Boiss., T. echinatum M.B. and T. latinum Seb., numerous F₁, F₂ and BC₁ hybrids of these species were raised, and their growth, pollen fertility, cytology and seedset were determined. T. carmeli was found to differ from both T. echinatum and T. latinum by at least three translocations, and their hybrids were semisterile as to pollen and seedset. T. latinum was more or less interfertile with T. echinatum and hybrids had normal meiosis, except for T. echinatum NYT 1401, whose hybrids with T. latinum were semisterile and evinced major chromosomal changes. Some implications of sterility and chromosomal heterogeneity are discussed. Backcrosses of T. echinatum × T. latinum F₁s to either parent resulted in partial breakdown of the self-incompatibility system found in both parental species and their F₁ hybrids.Contribution from the Volcani Center, Agricultural Research Organization, Bet Dagan, Israel, 1972 Series, No. 2207-E. The work reported here was financed by Grant FG-IS-222 from the U.S. Department of Agriculture under P.L.480.     

Studies in clover soil sickness

Summary The clover soil sickness phenomenon (CSS) was studied over a five-year period in plots of different berseem (Trifolium alexandrinum L.) history and used (a) to quantify the decrease in yields and its components with increase in previous clover cropping, (b) to assess the role of nutritional imbalance as a cause of CSS. The detrimental effect of CSS on growth of berseem was never found to operate before the first harvest. Less and mainly smaller branches developed on CSS conditions toward the second harvest, followed by plant death and poor branching, with a corresponding increase in the amount of weeds. When CSS conditions were more severe, the stand of berseem degenerated completely after fourth or even the third harvest. Berseem from plots previously cropped to berseem had a much lower phosphorus level in leaves than under non CSS conditions; the addition of copper, cobalt and/or molybdenum did not cure the CSS. Alternating berseem with Persian clover was found impracticable, since growing Persian clover also resulted in CSS symptoms, in both berseem and Persian clover. Nematodes may be a cause of CSS in Persian clover, but not in berseem. Contribution from The Volcani Institute of Agricultural Research, Bet Dagan, Israel. 1971 Series, No.1882-E. This work was financed by Grant FG-IS-222 from the U.S. Department of Agriculture, under P.L. 480.     

Studies in clover soil sickness

Summary The nature of clover soil sickness (CSS) was studied in pot experiments using soils on which berseem had been grown for three, two, one and no years. Both the distribution of CSS with soil depth, and the effect of soil sterilization by dry heat and methyl bromide on the manifestation of CSS in berseem and Persian clover, were studied.CSS factors disappeared in berseem following heat sterilization and in both Persian clover and berseem following methyl bromide treatment.The CSS phenomenon was found in berseem grown on soil from the 0–20-cm and 60–80-cm soil layers of three-year berseem plots. The effect of upper layer-CSS was discernible only after the first harvest, while that of the deep layer one affected growth drastically immediately after germination. Other possible CSS factors are suggested.5012 plant and soilContribution from The Volcani Institute of Agricultural Research, Bet Dagan, Israel, 1971 Series, No. 1884-E. This work was financed by Grant F. G.-IS-222 from the U.S. Dept. Agriculture, under P.L. 480.     

Cytogenetic studies in Trifolium sp. related to berseem

Summary In a cytogenetic study of five annual Trifolium spp. the genetical relationships between (1) T. scutatum Boiss. and (2) T. plebeium Boiss., and between them and (3) T. carmeli Boiss., (4) T. echinatum M. B. and (5) T. latinum Seb., were studied in intra- and interspecific F₁ and F₂ hybrids. Germination, seedlings development, pollen fertility and chromosome configurations during meiosis and seedset were recorded. All the T. scutatum x T. plebeium F₁ were green, but the hybrids between either T. plebeium or T. scutatum and T. carmeli, T. echinatum or T. latinum were mainly albinos. Those that were green had a very high rate of mortality and the survivors produced many albino seedlings. Pollen fertility was about 60% in scutatum x plebeium F₁s, and one of their eight bivalents was heteromorphic. Hybrids between either of these and T. carmeli, T. echinatum or T. latinum had 30–50% stainable pollen and had several multivalents, suggesting the existence of a system of chromosomal translocations in these species. Seed set was roughly correlated with pollen stainability. The nature of the isolation mechanisms operating between these species is discussed.Contribution from the Volcani Center, Agricultural Research Organization, Bet Dagan, Israel. 1973 Series, No. 186-E. The work reported here was financed by Grant FG-IS-222 from the U.S. Department of Agriculture under P. L. 480.     

Congenital hypoaldosteronism. Thirteen year follow-up in identical twins.

Identical male twins suffering from congenital hypoaldosteronism due to a rare adrenal enzyme deficiency between corticosterone and aldosterone were followed-upfrom birth till their present age of 13 years. The symptoms of salt loss disappeared and normal growth rate resumed following treatment with DOCA and salt supplementation. Discontinuation of mineralocorticoid administration at the age of 7 years resulted during a 5-year period in a marked decline in their growth rate. Labororatory data revealed a persistent, albeit less pronounced, metabolic impairment. Mineralocorticoid administration was resumed and the twins entered normal puberty and increased their growth rate, emphasizing their need for continued mineralocorticoid administration to maintain adequate growth rate and development.     

Digestion of free-living nematodes fed to fish

Free-living nematodes— Panagrellus sp., Turbatrix aceti, Caenorhabditis elegans and C. briggsae—were each fed to the fish Danio sp. and the process of their digestion, in the fish alimentary canal, was studied by light and electron microscope.
Almost no identifiable nematodes were found in the fish gut when the digestion period was 3 h or more, except for buccal capsules of the four studied species, males' spicules of Panagrellus sp. and Turbatrix aceti and egg-capsules of the Caenorhabditis species. These structures could serve as indicators that the nematodes had been preyed on and digested by the fish.
Differences in the mode of digestion were noticed between the various species of nematodes studied, after a period of 0·5–1 h, in the fish gut. In Panagrellus sp. and T. aceti disintegration of the soft inner tissues occurred mostly at the anterior or posterior ends of the nematode's body, while in Caenorhabditis the majority of digested nematodes were affected at both ends or evenly along the entire body. Digestion seemed to be initiated mostly at the nematodes' body apertures: mouth, anus or cloaca, and vulva which could be due to a more vulnerable cuticle around those areas. Disintegration proceeded from the soft inner parts to the more resistant cuticle that was finally disintegrated. Of the three layers of cuticle the most resistant were the external cortex and the basal layers.