No abstract

ABSTRACTin order to investigate the effects of soluble chitosan on plantlets growth in vitro and increase of minituber yield in potato micropropagation, plantlets of agria cultivar were treated in vitro with soluble chitosan at different concentrations including 0, 5, 15, 50, 150, 500, 750 and 1000 mg/l added to the MS tissue culture medium. Plantlets were subsequently transferred to the greenhouse and minituber yield parameters were evaluated. at the concentrations of 750 and 1000 mg/l of chitosan the culture medium failed to solidify. application of 500 mg/l of soluble chitosan increased the shoot fresh weight, but its lower concentrations did not significantly affect this trait (P < 0.05). The 5 and 15 mg/l of soluble chitosan led to a significant increase in root fresh and dry weight of in vitro plantlets, whereas, higher concentrations, especially 500 mg/l, significantly decreased root fresh weight of in vitro plantlets. application of 500 mg/l chitosan in vitro resulted in improved acclimatization of plantlets in the greenhouse as expressed by significant (P < 0.05) increase in minituber number and yield, compared to the control. The tested lower concentrations had no effect on yield parameters. The present results indicate that soluble chitosan can be successfully incorporated into potato seed production from in vitro plantlets.

The experiment was aimed to study the effect of colchicine concentrations (0.025, 0.05, 0.1 and 0.2%) and treatment times (8, 24 and 48 h) on polyploidy induction and morphological characteristics in Petroselinum crispum. Polyploidy induction was carried out in two independent experiments; seed treatment under in vivo, and node treatment under in vitro condition. Polyploids were confirmed by chromosome counts, density and size of stomata and other morphological characters. The survival rate for nodes and seeds decreased significantly with increasing concentration of colchicine and its treatment duration. Moreover, the induction of polyploidy was better in the node explants compared with the seeds. The maximum amount of tetraploidization of plants from the seeds was achieved at 0.05% colchicine after 24 and 48 h incubation. The most induction of the tetraploid plants was observed 24 h after treatment with 0.05% and 0.1% colchicine under in vivo and in vitro conditions, respectively. Furthermore, morphological measurements revealed that the size of the stomata and leaves in tetraploid plants was larger than those in diploid plants. However, the density of stomata was decreased in tetraploid plants as compared to the diploids.

In order to determine proper selection criteria for tuber yield in potato clones obtained from true potato seed (TPS) and to evaluate relationships between tuber yield and its components, an investigation was conducted using the five check cultivars Agria, Marfona, Draga, Agata, and Arinda, and 120 potato clones obtained from TPS. The study was conducted in an augmented randomized complete block design with three replications. Yield and its components were recorded. Correlation coefficient analysis showed that tuber yield had significant positive associations with number of tubers per plant, average weight per tuber (tuber size), plant height, diameter of main stem, and number of main and secondary stems per plant, whereas its correlation with tuber dry-matter concentration was significantly negative. Number of tubers per plant, tuber size, and plant height had significant standardized partial regression coefficients with very small tolerance and large variance inflation factor (VIF) values. These were considered as the first-order variables in sequential path analysis.

Trichogramma brassicae (Bezdenko) is the most important species of Trichogramma parasitoids in Iran. The cotton bollworm, Helicoverpa armigera (Hubner) is a polyphagous insect pest that attacks many crops including cotton, maize, soybean, tomato, etc. The bollworm egg is a suitable target for many Trichogramma species. Factitious hosts such as eggs of the flour moth, Anagasta kuehniella (Zeller) and cereal moth, Sitotroga cerealella (Hubner) are used for mass rearing purposes. But a problem that arises sometimes in laboratory cultures is the development of a tendency toward laboratory hosts following a few generations rearing with them. This may tend to a low efficiency on target pest in field conditions. In this study the possibility of declining efficiency of the parasitoid on target pest by developing such a preference to alternative hosts in previous generations were investigated when the flour moth or cereal moth uses as laboratory host. Two generations of T. brassicae were reared on each of the mentioned hosts and then transferred to H. armigera eggs for two further generations. The intrinsic rate of natural increase as well as other life table parameters were used for monitoring fitness of the parasitoid at successive generations. Even generations were included to determine if previously rearing host affected parasitoid performance. Results revealed that host shift from cereal moth to bollworm caused a sudden fall in population growth parameters (both intrinsic rate of natural increase and net replacement rate). Further rearing on bollworm eggs led to a relapse in both parameters. No similar effect was observed in cultures initiated with the flour moth. As a whole, cereal moth was a more suitable host than flour moth.