Genetic Transformation Studies on Avocado Cultivar “Hass” (Persea americana)

The use of traditional breeding for improvement of avocado cultivars is time consuming, hence other methods such as genetic transformation by Agrobacterium is indispensable to adopt. The strain GV3850/pBI121gave best transformation outcome compared to five other binary vectors (AGL1/pCGP904;AGL1/pBI121;GV3850/pCGP904;LBA4404/pCG-P904 and LBA4404/pBI121) under different pH and acetosyringone concentrations. The optimal condition for reliable transformation was by using 200 μM acetosyringone and a pH of 5.2. Transformed embryonic shoots co-cultivated with GV3850/pBI121 were tested using the histochemical x-gluc assay. Further analysis was conducted by polymerase chain reaction using specific primers for the reporter gene (GUS).

Repellent effect of guava leaf volatiles on settlement of adults of citrus psylla, Diaphorina citri Kuwayama, on citrus

The Asiatic citrus psyllid （Diaphorina cirri Kuwayama [Hemiptera： Sternorrhyncha： Psyllidae] is a vector ofhuanglongbing （citrus greening）, a devastating disease of citrus caused by phloem-limited bacteria. Growing guava （Psidium guajava） as an intercrop appears to be a successful means of reducing psyllid numbers within citrus orchards; however, the mechanism by which such a reduction is achieved is unknown. To determine the repellent effect of guava leaf and factors attributed to this activity, responses of adult psyllids to guava leaf and its odor were evaluated in cage tests and Y-tube olfactometer test. The results showed that guava leaf possessed a repellent effect against the adult citrus psyllids. Fewer psyllids were found on citrus leaves in the presence of guava foliage than in its absence. Young and old guava leaf showed equal repellent activity. By covering the guava shoots with net cloth, it was revealed that the repellent effect of guava leaf against adult psyllids on citrus was attributed to the volatile compounds, rather than physical factors. The olfactometer response of adult psyllids to guava leaf odor was dosage-dependent. Between guava odor and control, only 35.00%, 25.00% and 16.25% of the psyllids moved toward guava odor when presented with 5.0, 10.0 and 15.0 g of guava shoots, respectively. The olfactometer experiments also showed that both male and female psyllids responded similarly to the guava leaf odor.

Primary parasitoids of red scale （Aonidiella aurantii） in Australia and a review of their introductions from Asia

We used morphological and molecular differences to confirm the identities of red scale （Aonidiella aurantii） and yellow scale （A. citrina）, and their primary parasitoids, in Australia. An extension to the distribution of yellow scale was confirmed. Six primary parasitoids of red scale were identified： Aphytis chrysomphali, A. lingnanensis, A. melinus, Comperiella bifasciata, Encarsia citrina, and E. perniciosi. With the exception of A. lingnanensis, these parasitoids, and a species of Aphelinus, were detected in association with red scale during studies in citrus orchards in coastal New South Wales between 2009 and 2012. Two races ofA. melinus were recorded： one from the Indian Subcontinent, the other previously only recorded in China. The studies, and reviews of historical records, led us to conclude that 4 parasitoids, A. lingnanensis, C. bifasciata, and both species of Encarsia, were present in Australia before successful or unsuccessful formal introductions between 1902 and 1970. The A. melinus race previously recorded in China may also have been present before the Indian Subcontinent race was formally introduced in 1961. We suggest the possibility that the natural distribution of some of the parasitoids may include East and Southeast Asia, and parts of Australasia. We found no reports of native armored scales being recorded on species and hybrids of Citrus introduced to Australia, and no reports of introduced armored scales being recorded on native Rutaceae, including 6 species of Citrus. However, we subsequently recorded yellow scale on Geijera parviflora, a native rutaceous tree.

Genetic variation amongst biotypes of Dactylopius tomentosus

The tomentose cochineal scale insect, Dactylopius tomentosus （Lamarck） （Hemiptera： Dactylopiidae）, is an important biological control agent against invasive species of Cylindropuntia （Caryophyllales： Cactaceae）. Recent studies have demonstrated that this scale is composed of host-affiliated biotypes with differential host specificity and fitness on particular host species. We investigated genetic variation and phylogenetic rela-tionships among D. tomentosus biotypes and provenances to examine the possibility that genetic diversity may be related to their host-use pattern, and whether their phylogenetic relationships would give insights into taxonomic relatedness of their host plants. Nucleotide sequence comparison was accomplished using sequences of the mitochondrial cytochrome c oxidase I （COI） gene. Sequences of individuals from the same host plant within a region were identical and characterized by a unique haplotype. Individuals belonging to the same biotype but from different regions had similar haplotypes. However, haplotypes were not shared between different biotypes. Phylogenetic analysis grouped the monophyletic D. tomentosus into 3 well-resolved clades of biotypes. The phylogenetic relationships and clustering of biotypes corresponded with known taxonomic relatedness of their hosts. Two biotypes, Fulgida and Mamillata, tested positive for Wolbachia （α-Proteobacteria）, a common endosymbiont of insects. The Wolbachia sequences were serendipitously detected by using insect-specific COI DNA barcoding primers and are most similar to Wolbachia Supergroup F strains. This study is the first molecular characterization of cochineal biotypes that, together with Wolbachia sequences, contribute to the better identification of the biotypes of cochineal insects and to the biological control of cacti using host-specific biotypes of the scale.

Proto Kranz-like leaf traits and cellular ionic regulation are associated with salinity tolerance in a halophytic wild rice

Species of wild rice(Oryza spp.)possess a wide range of stress tolerance traits that can be potentially utilized in breeding climate-resilient cultivated rice cultivars(Oryza sativa)thereby aiding global food security.In this study,we conducted a greenhouse trial to evaluate the salinity tolerance of six wild rice species,one cultivated rice cultivar(IR64)and one landrace(Pokkali)using a range of electrophysiological,imaging,and whole-plant physiological techniques.Three wild species(O.latifolia,O.officinalis and O.coarctata)were found to possess superior salinity stress tolerance.The underlying mechanisms,however,were strikingly different.Na+accumulation in leaves of O.latifolia,O.officinalis and O.coarctata were significantly higher than the tolerant landrace,Pokkali.Na+accumulation in mesophyll cells was only observed in O.coarctata,suggesting that O.officinalis and O.latifolia avoid Na+accumulation in mesophyll by allocating Na+to other parts of the leaf.The finding also suggests that O.coarctata might be able to employ Na+as osmolyte without affecting its growth.Further study of Na+allocation in leaves will be helpful to understand the mechanisms of Na+accumulation in these species.In addition,O.coarctata showed Proto Kranz-like leaf anatomy(enlarged bundle sheath cells and lower numbers of mesophyll cells),and higher expression of C4-related genes(e.g.,NADPME,PPDK)and was a clear outlier with respect to salinity tolerance among the studied wild and cultivated Oryza species.The unique phylogenetic relationship of O.coarctata with C4 grasses suggests the potential of this species for breeding rice with high photosynthetic rate under salinity stress in the future.