Expressing an (E)-ß-farnesene synthase in the chloroplast of tobacco affects the preference of green peach aphid and its parasitoid.

(E)-ß-Farnesene (EßF) synthase catalyses the production of EßF, which for many aphids is the main or only component of the alarm pheromone causing the repellence of aphids and also functions as a kairomone for aphids' natural enemies. Many plants possess EßF synthase genes and can release EßF to repel aphids. In order to effectively recruit the plant-derived EßF synthase genes for aphid control, by using chloroplast transit peptide (CTP) of the small subunit of Rubisco (rbcS) from wheat (Triticum aestivum L.), we targeted AaßFS1, an EßF synthase gene from sweet wormwood (Artemisia annua L.), to the chloroplast of tobacco to generate CTP + AaßFS1 transgenic lines. The CTP + AaßFS1 transgenic tobacco plants could emit EßF at a level up to 19.25 ng/day per g fresh tissues, 4-12 fold higher than the AaßFS1 transgenic lines without chloroplast targeting. Furthermore, aphid/parasitoid behavioral bioassays demonstrated that the CTP + AaßFS1 transgenic tobacco showed enhanced repellence to green peach aphid (Myzus persicae) and attracted response of its parasitoid Diaeretiella rapae, thus affecting aphid infestation at two trophic levels. These data suggest that the chloroplast is an ideal subcellular compartment for metabolic engineering of plant-derived EßF synthase genes to generate a novel type of transgenic plant emitting an alarm pheromone for aphid control.

Studies on wheat mutants induced by nitrogen ion beam implantation.

As a new resource of mutagens,low-energy ion beam implantation is characterized as limited physiological damages,wide mutation spectrum, and high mutation frequency in comparison with the mutations from other inducing methods. We treated a wheat doubled haploid line Yi4212 with this technique by nitrogen ion and established a mutant population with 60 lines in our lab. The mutant lines were systematically investigated about their -developmental periods,agronomical performances, gliadin contents and microsatellite variations in M4 generation. The results revealed that in addition to extensive changes of the developmental, agronomical and economical traits of the mutants,the moblities in acid-PAGE of 7 omega-gliadin subunits were also showed changes as some gliadins lacked and novel gliadins obtained. Deletion, expansion and contraction of SSR amplification products occured frequently in 25 SSR loci in the mutants. Combined with our results and other reports,the application prospects of those wheat mutants and the mutation mechanism by ion beam implantation are discussed.

[Studies of the relationship between the breeding efficiency of anther culture and the use of different hybrid generations as anther-donor plants in wheat].

The wheat haploid plantlets from anther culture were of theoretical and applied interest. Induced haploid spirophytes may play a key role, not only in increasing the efficiency of breeding programs by producing pure lines rapidly, but also in the elucidation of fundamental genetics. However large number of experiments turned out that there are many problems with low rate of green plantlet from anther culture, difficulties of saving plantlets though summer, low rate of double chromosome, extrusive contradiction between technique of wheat anther culture and variety improvement. So wheat anther culture has not played a role in wheat breeding. Studies were carried out on the relationship between the breeding efficiency of anther culture and the use of different hybrid generations as anther-donor plants in wheat. It was shown that previously the low breeding efficiency of anther culture in wheat cross breeding was mainly due to the use of F1 as anther donors. Experimental results demonstrated that the breeding efficiency of anther culture in F1 generation was very low, especially when the doubled haploid population was very small. Based on the experimental results as well as the theoretical analysis this paper proposes that the use of F2 or F3 (especially F3) as anther donors in combination with the conventional selection in the fields will increase the breeding efficiency of anther culture. Under the guidance of this proposal two wheat varieties have been developed within 5-7 years through anther culture.