Alterations of Endogenous Cytokinins in Transgenic Plants Using a Chimeric Isopentenyl Transferase Gene

Cytokinins, a class of phytohormones, appear to play an important role in the processes of plant development. We genetically engineered the Agrobacterium tumefaciens isopentenyl transferase gene, placing it under control of a heat-inducible promoter (maize hsp70). The chimeric hsp70 isopentenyl transferase gene was transferred to tobacco and Arabidopsis plants. Heat induction of transgenic plants caused the isopentenyl transferase mRNA to accumulate and increased the level of zeatin 52-fold, zeatin riboside 23-fold, and zeatin riboside 5[prime]-monophosphate twofold. At the control temperature zeatin riboside and zeatin riboside 5[prime]-monophosphate in transgenic plants accumulated to levels 3 and 7 times, respectively, over levels in wild-type plants. This uninduced cytokinin increase affected various aspects of development. In tobacco, these effects included release of axillary buds, reduced stem and leaf area, and an underdeveloped root system. In Arabidopsis, reduction of root growth was also found. However, neither tobacco nor Arabidopsis transgenic plants showed any differences relative to wild-type plants in time of flowering. Unexpectedly, heat induction of cytokinins in transgenic plants produced no changes beyond those seen in the uninduced state. The lack of effect from heat-induced increases could be a result of the transient increases in cytokinin levels, direct or indirect induction of negating factor(s), or lack of a corresponding level of competent cellular factors. Overall, the effects of the increased levels of endogenous cytokinins in non-heat-shocked transgenic plants seemed to be confined to aspects of growth rather than differentiation. Since no alterations in the programmed differentiation pattern were found with increased cytokinin levels, this process may be controlled by components other than absolute cytokinin levels.     

Agistemus exsertus Gonzalez (Acari: Stigmaeidae) as a predator of two scale insects of the family Diaspididae (Homoptera: Diaspididae)

Abstract

The predacious mite Agistemus exsertus Gonzalez completed its life-span when fed on eggs and crawlers of the Florida red scale Chrysomphalus ficus Ashmead and the white date scale Parlatoria blanchardi (Targioni). The development was faster when individuals were maintained on eggs and crawlers of C. ficus, compared with both stages of P. blanchardi. The average number of eggs/female/day was 2.5 and 1.1 on eggs and crawlers of C. ficus, respectively. Eggs and crawlers of P. blanchardi were an unsuitable food for egg laying for A. exsertus. Life table parameters showed that A. exsertus preferred eggs of C. ficus to the crawlers as prey. The population of the predator feeding on eggs and crawlers of Florida red scale multiplied 45 and 7 times in a generation time of 23 and 20.5 days, respectively. Under these conditions, the intrinsic rate of increase (r _m) was (0.17 and 0.098) individuals/female/day on eggs and crawlers of C. ficus, while the finite rate of increase (λ) was (1.18 and 1.11) on both stages of C. ficus.     

Biological aspects and life tables of the predacious mites,Typhlodromips swirskii (Athias-Henriot) and Euseius scutalis (Athias-Henriot) feeding on two scale insect species and plant pollen

Biological aspects and life table parameters of the predacious mites, Typhlodromips swirskii (Athias-Henriot) and Euseius scutalis (Athias-Henriot) (Acari: Phytoseiidae) consuming eggs of the Maskell scale insect, Insulaspis pallidula (Green) and the red date scale insect, Phoenicococcus marlatti Cockerell (Homoptera: Diaspididae, Phoenicococcidae) as well as pollen grains of date palm, Phoenyx dactylifera L. were determined under laboratory conditions. The life cycle and pre-oviposition period of T. swirskii were the shortest, while the oviposition period and female longevity were the longest as well as the egg production was the highest when fed on pollen compared with eggs of I. pallidula and P. marlatti. On the other hand, the life cycle, pre-oviposition and oviposition periods as well as the female longevity of E. scutalis were the best when devoured P. marlatti followed by pollen and I. pallidula. However, the total and daily fecundity of E. scutalis were the highest after consuming pollen compared with eggs of P. marlatti and I. pallidula. The sex ratio of females to total in the progeny of T. swirskii and E. scutalis was the highest when consumed I. pallidula followed by pollen and P. marlatti. Life table parameters were the most favourable for T. swirskii and E. scutalis feeding on date palm pollen compared with eggs of I. pallidula and P. marlatti.     

The life – history of the peach silver mite,Aculus fockeui (Acari: Eriophyidae) in Egypt

The peach silver mite Aculus fockeui (Nalepa and Trouessart) successfully developed from egg to adult stage when reared on a nectarine or peach leaflet attached with soft lateral divided branch dipped in test tube at different constant temperatures and 70% r.h. The effect of temperature on the development, reproduction and population growth was investigated. Below 20°C all activity ceased and by 33°C the adult began to slow down and cease all activity. At least of 34% of the generation time was spent in the egg stage at 29°C. Adult longevity decreased with increasing temperature. Fecundity was highest at 29°C with 43.16 eggs per female. Life table parameters showed that the population of A. fockeui on nectarine leaves multiplied 30.04 times in a generation time of 18.49 days at 29°C, while the population on peach leaves increased 13.87 times in a generation time of 19.18 days under the same conditions.