Citrus tristeza virus (CTV) is one of the most devastating disease in areas where sweet orange or grapefruit are budded onto sour orange rootstock. In Texas, the citrus industry is located in the far south of the state in a high pH and calcareous soils region, which makes sour orange the best rootstock option. The Texas industry has been under a threat since the arrival in Florida and Mexico of the most efficient vector of CTV, the Brown Citrus Aphid. In an attempt to find a suitable replacement for sour orange rootstock a field trial was performed to evaluate 10 rootstocks with Rio Red grapefruit scion. Trees on C35 and Carrizo citranges, and Swingle citrumelo became very chlorotic and died. The other rootstocks also showed slight to severe chlorosis but were able to recover. C22 outperformed all rootstocks during the 6 years, producing more than 1.5 times the yield of sour orange, and &2-fold the production of Goutou which was the rootstock with the lowest production. Although significantly lower than C22, the cumulative production of trees on C57 and C146 rootstocks were excellent and their yearly fruit productions were similar to that of C22 in four (

No abstract

Large-scale production of microprotoplasts from `Ruby Red' grapefruit (Citrus paradisi Macf.) and from the Citrus L. sp. relative Swinglea glutinosa (Blanco) Merr., was performed after treatment of suspension cells with APM. An average of 75.2% of the microprotoplasts contained a single chromosome, followed by 17.1% with two, 4.6% with three, and 2.0% with four. Only 1.1% had more than five chromosomes. Maximum chromosome number observed was eight and the average yield was 2 × 106 of total microprotoplasts per gram of suspension cells. Flow cytometry analysis confirmed low DNA content. The polyethylene glycol fusion method was used to fuse microprotoplasts from `Ruby Red' grapefruit with protoplasts of `Succari' sweet orange [Citrus sinensis (L.) Osbeck], and microprotoplasts from S. glutinosa with protoplasts from sour orange (C. aurantium L.). Embryos or suspension cells from the recipient species with a few additional chromosomes were obtained; however, embryogenesis of the fusion products was reduced or inhibited. Chemical name used: amiprophos-methyl (APM).

Oviposition behavior was elicited fromCatolaccus grandis (Burks) (Hymenoptera: Pteromalidae) females, an ectoparasitoid of the boll weevil,Anthonomus grandis Boheman (Coleoptera: Curculionidae), by smears of freshly cut cotton bolls or smears of extracts prepared with boll weevil damaged or undamaged cotton boll tissues. Oviposition behavior was also elicited fromC. grandis females by smears made withn-pentane,n-hexane,n-heptane, and isooctane. This is the first report of oviposition behavior elicited for any parasitoid by these short-chain saturated hydrocarbons (alkanes), introducing a new concept on the chemical mediation of parasitoid behavior during host selection. Oviposition behavior was also elicited fromC. grandis females by volatiles emanating from an artificial diet devoid of insect components that was specifically developed for the in vitro rearing of ectoparasitoids. The possible use of a synergistic combination ofn-hexane and diet to optimize the mechanized production of noncontaminated eggs is also discussed.

Exposure of cold-hardy Rubidoux trifoliate orange [Poncirus trifoliata (L) Raf.] plants to temperatures from 28 degrees C to -5 degrees C enabled us to isolate and characterize a novel citrus low-temperature gene (CLT) with two transcripts, called CLTa and CLTb, from leaves and stems. CLTa was produced when plants were subjected to low temperatures (starting at 10 degrees C), while CLTb was constitutively expressed. Both CLTa and CLTb have the same open reading frame (ORF) of 165 nucleotides and encode a small (54 deduced amino acid) protein. However, CLTa has an additional 98 nucleotides in the 3'-untranslated region (UTR) that are absent in CLTb. Expression analysis using relative quantitative RT-PCR demonstrated that CLTa is expressed exclusively at low temperatures, while CLTb is expressed constitutively (expression verified from 33 degrees C to -5 degrees C). A GenBank database search identified 61 nucleotides inside of the ORF that are highly similar to low-temperature-responsive genes from Arabidopsis thaliana and Solanum tuberosum. The deduced amino acid sequence revealed similarity with low-temperature-responsive proteins from A. thaliana, Oryza sativa, and S. tuberosum of 77%, 81%, and 73.9%, respectively. A genomic clone was isolated, and the genome organization revealed the presence of three exons and two introns, the second of which is in the 3' UTR and participates in alternative 3' splice site selection. One of the 3' splice sites of the second intron was located immediately before the additional 98-bp non-coding fragment of CLTa, and the second at the very end of the 98-bp fragment. Additionally, the presence of the tetranucleotides TCTT and TTCT, which are involved in the regulation of transcript processing in animals and possibly also active in peach, was found in this intron. Competition for splicing sites on the pre-mRNA in the spliceosome, which is induced by low temperature, may be involved in the production of the two transcripts of the CLT gene.