Enhanced resistance to two stem borers in an aromatic rice containing a synthetic cryIA(b) gene

Rice cultivars of isozyme group V include high-quality, aromatic rices that are difficult to improve by traditional methods because of the loss of quality characters upon sexual hybridization. Their low-tillering plant type predisposes them to economic loss from attack by stem borers, a group of insects to which they are susceptible. We report here the enhancement of stem borer resistance in cv. Tarom Molaii through transformation by microprojectile bombardment. Embryogenic calli derived from mature seeds were bombarded with gold particles coated with plasmid pCIB4421, carrying a synthetic truncated toxin gene based on the cryIA(b) gene from Bacillus thuringiensis, and plasmid pHygII, carrying the hygromycin phosphotransferase (hpt) selectable marker gene. Inclusion of 50 mg/l hygromycin B in culture media from bombardment through to rooting of plantlets eliminated escapes. The procedure generated three independent hpt transformants of which two also contained the cryIA(b) gene. One such line (No. 827) produced truncated (67 kDa) CryIA(b) protein equivalent to about 0.1% of total soluble protein. The cryIA(b) gene was controlled by the promoter of the maize C₄ PEP carboxylase gene and was expressed in leaf blades but was not expressed to a detectable level in dehulled mature grain. Line 827 contained about 3 copies of the cryIA(b) gene which segregated as a single dominant Mendelian locus in the second (T₁) and third (T₂) generations and co-segregated with enhanced resistance to first-instar larvae of striped stem borer (Chilo suppressalis) and yellow stem borer (Scirpophaga incertulas). T₂ line 827-6 homozygous for the cryIA(b) gene showed no dead hearts or whiteheads after infestation with stem borers, whereas T₂ line 827-25 lacking the gene averaged 7 dead hearts per plant and 2.25 whiteheads per plant. These results establish that transformation of high-quality rices of group V is a feasible alternative to sexual hybridization.     

Simultaneous Application of Rhizobium Strain and Melatonin Improves the Photosynthetic Capacity and Induces Antioxidant Defense System in Common Bean (Phaseolus vulgaris L.) Under Salinity Stress

Melatonin (N-acetyl-5-methoxytryptamine) as a natural biostimulating substance provides a number of benefits in stimulating plant growth in stress situations due to its natural antioxidant capacity. Rhizobia also play crucial roles in supporting plant growth under environmental stress conditions. The overall goal of this research is to study the possible positive effects of melatonin and rhizobacterium in enhancing the growth and salinity tolerance of common bean. To accomplish this objective, we conducted in vitro experiment to select the optimal melatonin concentration and treatment time of seed priming for the best germination. Also, a greenhouse experiment was performed to investigate the effect of melatonin pre-treatment applied before rhizobial inoculation to improve the fitness of common bean under salinity stress. The experiment was conducted using a completely randomized factorial design with six replications and three treatments: priming treatments (melatonin priming (PM100), hydro priming (PH) and dry (PD)), salinity (0, 4, 8, 10 and 16 dS m^?1) and Rhizobium strain (inoculated (RS?+) and uninoculated (RS?)). Our results showed that melatonin priming promoted bacterial colony size in Petri-dishes. The interactive effects of melatonin and RS?+?was found to alleviate reactive oxygen species (ROS) burst, and hence protect common bean chlorophylls a, b and carotenoid and photosynthetic activity and decrease malondialdehyde content through activation of antioxidant enzymes (superoxide dismutase, peroxidase, catalase and ascorbate peroxidase), facilitation of soluble protein synthesis, maintenance of Na⁺ and K⁺ homeostasis, and finally increase shoot dry weight (33.2, 39.5 and 31.5%) and seed yield (78.6, 91 and 54.2%) compared to the combination of PD and RS- treatments under 0, 4 and 8 dS m^?1 salinity levels, respectively. Thus, our findings suggest that seed priming with melatonin, especially 100 µM melatonin is an effective strategy that can be used to enhance salt tolerance in common bean.

     

Heritability of tolerance to the Cry1Ab toxin of Bacillus thuringiensis in Chilo suppressalis (Lepidoptera: Crambidae)

Heritability of Chilo suppressalis (Walker) tolerance to the Cry1Ab toxin of Bacillus thuringiensis Berliner was estimated using a half-sibling design. Artificial diet with and without Cry1Ab was infested with progenies of 20 males, each mated with 2 females, and mortality was scored 5 d after infestation. The progeny of each female was reared and scored separately. Mean mortality of the 20 families on the Cry1Ab diet was 46.5%. The effects of both male parent and of female parent within male parent were significant. Heritability was estimated to be 0.52, suggesting that a high proportion of phenotypic variation was because of genetic differences. Mortality on the Cry1Ab diet was not correlated with mortality on control diet, indicating that differences among families in tolerance to Cry1Ab were not attributable to differences in general fitness. Our results indicate that "high dose" Bt rice plants may be particularly important for Cry1Ab resistance management in C. suppressalis populations.     

Effect of plant age, larval age, and fertilizer treatment on resistance of a cry1Ab-transformed aromatic rice to lepidopterous stem borers and foliage feeders

The resistance of vegetative, booting, and flowering stage plants of a variety of an aromatic rice, Oryza sativa L., transformed with a Bacillus thuringiensis Berliner cry1Ab gene under control of the maize phosphoenolpyruvate carboxylase (PEPC) promoter was evaluated against four lepidopterous rice pests--the stem borers Chilo suppressalis (Walker) (Lepidoptera: Crambidae) and Scirpophaga incertulas (Walker) (Lepidoptera: Pyralidae), and the foliage feeders Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) and Naranga aenescens Moore (Lepidoptera: Noctuidae). Plants of the cry1Ab-transformed line (no. 827) were more resistant to young larvae of S. incertulas, C. suppressalis, and C. medinalis than control plants at the vegetative stage but not at the flowering stage. Survival of 10-d-old stem borer larvae did not differ on cry1Ab plants and control plants at either the vegetative or flowering stage, but the development of 10-d-old C. suppressalis larvae was retarded on the vegetative stage cry1Ab plants. Immunological analysis also showed an apparent decline in Cry1Ab titer in leaf blades and leaf sheaths at the reproductive stage. In experiments comparing three fertilizer treatments (NPK, PK, and none), there was a significant interaction between fertilizer treatment and variety on larval survival only in whole-plant assays at booting stage with C. suppressalis. On cry1Ab plants, larval survival did not differ significantly among the three fertilizer levels, whereas on control plants survival was highest with the NPK treatment. cry1Ab plants tested at the sixth and seventh generations after transformation were more resistant than control plants to N. aenescens and C. suppressalis, respectively, suggesting that gene silencing will not occur in line 827. The results of the experiments are discussed in terms of resistance management for B. thuringiensis toxins in rice.     

On Black Feminist Thought: thinking oppression and resistance through intersectional paradigm

Located in African American women's everyday and historical experiences of oppression and resistance, black feminist epistemology and critical social theory, Patricia Hill Collins raises the intellectual level in all these arenas. Developed through a dynamic interaction with black women's everyday struggles, black feminist thought is important not only for its contribution to critical social theories and methodologies, but also for providing important knowledge for the use of social justice movements. It uses intersectional analysis to shed light on the relationships between the structural, symbolic and everyday aspects of domination and individual and collective struggles in various domains of social life. Collins offers an interpretive framework for understanding the experiences of African American women. However, the significance of black feminist thought reaches far beyond US and black American communities. This article is a reading of Collins’s concept of intersectionality, the relationship between oppression and resistance, and the politics of empowerment.     

Cataclysta lemnata Linnaeus, 1758 (Lepidoptera: Crambidae) expanded its host range feeding on invasive aquatic ferns,species of Azolla Lamarck, 1783 (Hydropteridales: Azollaceae): fitness factors and costs

Cataclysta lemnata Linnaeus, 1758 is a semi-aquatic moth that feeds on Lemnaceae and few of other aquatic plants. In recent years, this moth has been seen feeding on Azolla Lamarck, 1783 Lamarck, J.B. (1783), Encyclopedie methodique: botanique, 1, Paris: Panckouche. 752 pp. [Google Scholar] in Iran in high numbers. The effect of the host plant on preference and performance of the moth was assessed under laboratory conditions. Despite the high survival rate of the young larvae, due to high mortality of the late instars and pupa on Lemna Linnaeus, 1753, the total survival rate on Azolla was higher. Feeding on Azolla increased the development time by almost a week and reduced fertility to half. However, by consuming more food, regulating the egg laying dynamic, and increasing emergence period, the moth retrieved most of the losses and adapted to feed on Azolla. A week before pupation, feeding activity increased between 2 and 8 times in all treatments and on Azolla, the larvae growth rate was slightly higher.