Quantification of Infection by Alternaria cassiae Using Leaf Immuno-Autoradiography and Radioimmunosorbent Assays

The severity of fungal infection is usually estimated visually as a rating of injury. A more quantitative method was needed to ascertain the effect of additives used to enhance the virulence of mycoherbicidal preparations. A sensitive and accurate serological method is presented for quantitative measurement of Alternaria cassiae infection of Cassia obtusifolia. An antiserum was prepared against a homogenate of mycelium of A. cassiae. A fast and simple procedure of leaf immuno-autoradiography was developed for the visualization of A. cassiae mycelium on inoculated leaves. A radioimmunosorbent assay (RISA) was developed for quantification of the extent of fungal infection. As little as 1. 6 ng/ ml dry weight equivalent of mycelium could be detected by RISA. There was a linear relationship between the logarithm of the RISA values and the logarithm of fungus concentration up to 300 ng/ml. Reduced sensitivity of the assay was pronounced in extracts containing 400 μ g/ml or more fresh weight of leaves. There was 30–40 % cross-reactivity of the antiserum with two other species of Alternaria, as well as with Monilinia fructicola, and almost no reactivity was found with three other fungi tested.     

Ecomigration and Violent Conflict: Case Studies and Public Policy Implications

In 2005, a hurricane named Katrina hit the states of Louisiana and Mississippi in the US, destroying properties and flooding areas. Many people left the region and still have not returned. While some of these people may eventually return, some may not, becoming “migrants.” Assuming this phenomenon will occur, is it unique? What is the role of the environment in migration? Can there be violent conflict between such migrants and residents in areas absorbing migrants? We evaluate these questions in the cases of Hurricane Katrina, the US Dust Bowl in the 1930s, and Bangladesh since the 1950s, demonstrating that environmental change can trigger large out-migration, which can cause violent conflict in areas receiving migrants. These findings have important policy implications. Climate change is expected to degrade the environment considerably in this century. Minimizing climate change-induced migration and violent conflict in receiving areas requires an engineered economic slowdown in the developed countries, and population stabilization and economic growth in the developing countries financed by the developed countries.     

Selective adherence of neurons and glial cells from dissociated cerebral and spinal cord microcarrier cultures.

In stationary cultures of dissociated brain and spinal cord grown on microcarriers (MCs), the neuronal and ependymal cells attached to the MCs forming floating aggregates in which they grow in a three-dimensional pattern. The glial and meningeal elements on the contrary, tend to dissociate from the aggregates and adhere to the plastic dish where they divide to form a monolayer. This different behavior of CNS components is not observed in rotating cultures in which all CNS cells remain attached to the MCs and develop into mature floating structures. This cell separation in stationary MC-cultures which is documented here by SEM and immunocytochemistry, may be useful for analysis and evaluation of the metabolic biochemical events of each of the cellular components derived from the same culture.     

Comparative Behavioural Studies of Larval and Adult Stages of the Phytoseiids (Acari: Mesostigmata) Typhlodromus Athiasae and Neoseiulus Californicus

We compared the behaviours of the indigenous Typhlodromus athiasae Porath and Swirski and the exotic Neoseiulus californicus (McGregor) (= Amblyseius chilenensis Dosse) relative to their persistence in apple orchards in Israel. We studied (1) larval feeding, walking, intraspecific interactions (cannibalism, touch-avoidance responses and/or touching with palps and tarsi) and tendency to aggregate (when resting), (2) predation and cannibalism on phytoseiid eggs by young females and (3) the effects of starvation for 10 days on young females relative to ambulation speed, longevity, fecundity, progeny survival and sex ratio. Larvae of T. athiasae were almost inert, did not feed and hardly walked or interacted whereas larvae of N. californicus fed, walked and interacted, mainly by touching with palps and tarsi. No cannibalism in the larval stage was observed for either species. The presence of prey increased the larval walking and intraspecific interactions of N. californicus but not of T. athiasae. Egg predation by adult females of both species was substantially higher than cannibalism, implying that both are capable of distinguishing their eggs from those of other species. Soaking eggs for 30 min in deionized water increased cannibalism in both species. During the 10 days of starvation, the ambulation speed of adult female N. californicus ranged from 1.8 to 10.1 times that of T. athiasae. The 50% lethal time value (LT₅₀) of T. athiasae (6.0 days) was significantly lower than that of N. californicus (10.4 days). None of the starved T. athiasae recuperated following the reintroduction of prey, whereas 75% of N. californicus did and oviposited after 2 days. These traits should enable N. californicus to persist when prey is scarce; however the selective predation of N. californicus eggs by T. athiasae could prevent establishment of N. californicus. The degree of specialization of these two predators is discussed.     

Petunia flower longevity: the role of sensitivity to ethylene

Two petunia ( Petunia hybrida L.) lines, differing in their flower longevity, were studied, Similar tendencies were found in the changes of corolla fresh weight, electrolyte leakage and membrane microviscosity over the life spans of the two lines. Ethylene production by flowers of the two lines showed a similar pattern, peaking at 3 nl flower⁻¹ h⁻¹. However, in flowers of the short-lived line, ethylene production peaked at 6 days of age, but in the long-lived line, the peak appeared at 10 days of age. A large difference was found in the responsiveness of the flower to ethylene, Flowers of the short-lived line responded to a similar ethylene by immediate wilting, while those of the long-lived line responded to a similar ethylene treatment only after two days. Differences in sensitivity to ethylene were also, observed when the flowers were treated continuosly with (aminooxy)acetic acid, which blocks ethylene synthesis. Flowers of both lines responded to ethylene treatment by increased ethylene production to a similar rate. Differential sensitivity to ethylene, independent of ethylene production, seemingly governs flower longevity in the two petunia lines studied.