Stagonospora atriplicis. [Descriptions of Fungi and Bacteria].

A description is provided for Stagonospora atriplicis, a potential biological control agent of Atriplex and Chenopodium weeds. Information is included on the disease caused by the organism, its transmission, geographical distribution (Kenya, South Africa, Zimbabwe, Canada, USA, Colombia, Cyprus, Georgia, Kyrgyzstan, Russia, Australia, New Zealand, Austria, Belgium, Bulgaria, Czech Republic, Estonia, France, Germany, UK, Hungary, Italy, Latvia, Romania, Sweden, Ukraine and Hawaii) and hosts (Allenrolfea occidentalis, Atriplex spp., Chenopodium spp. and Syzygium guineense).

Alleviation of salinity and dark-enforced dormancy in Allenrolfea occidentalis seeds under various thermoperiods

The effect of germination-regulating chemicals on the alleviation of salinity-enforced germination inhibition of Allenrolfea occidentalis (S.Wats.) Kuntze at various thermoperiods in complete darkness was investigated. There was poor germination at cool temperatures and germination-regulating chemicals were ineffective in alleviating this effect. Germination in the dark increased progressively with increase in temperature and maximum germination was obtained at 25–35˚C thermoperiod. Ethephon and fusicoccin (FC) substantially reverted dark-induced inhibition at moderate thermoperiods. All other germination-regulating chemicals were more effective at moderate temperature, while germination was not specifically different from control at higher temperature. Salinity-enforced germination inhibition was partially alleviated by all growth regulators at the higher temperature regime (25–35˚C). Best reversal was obtained with the application of ethephon and FC. Our results suggest that temperature is the most critical factor influencing the germination of Allenrolfea seeds. Allenrolfea occidentalis seeds germinated better at higher than at lower temperatures in the dark and all of the growth-promoting compounds showed their maximum reversal effect at higher temperatures.

Effect of salinity, light, and temperature on germination in Allenrolfea occidentalis

Allenrolfea occidentalis (S. Wats.) Kuntze, a halophytic perennial shrub in the family Chenopodiaceae, is widely distributed in inland salt marshes and salt playas of western North America. Experiments were conducted to determine the effects of NaCl, light, and temperature on seed germination and their recovery of germination from saline conditions after being transferred to distilled water. Seeds of A. occidentalis were germinated at various temperatures (5:15, 10:20, 10:30, 15:25, 20:30, and 25:35°C (night:day)) and salinities (0, 200, 400, 600, 800, and 1000 mM NaCl) in a 12 h light : 12 h dark photoperiod and in 24 h darkness. Increases in NaCl concentration progressively inhibited seed germination, and this inhibition was greater in the dark than in light. No seeds germinated at concentrations higher than 800 mM NaCl. Cooler temperatures significantly inhibited germination in all treatments, while regimes of high night (25°C) and high day (35°C) temperatures showed higher germination. Rate of germination decreased with an increase in salinity. Germination rate was higher at 25:35°C and lower at 5:15°C. Seeds were transferred from salt solutions to distilled water after 20 days, and those from high salinities recovered quickly at all temperature regimes. Recovery germination percentages at higher salinities varied from 51 to 100% at various temperatures, but recovery of germination of seeds from salt stress was significantly affected by temperature regime.Key words: Allenrolfea occidentalis, halophyte, light, recovery of seed germination, salt playas, thermoperiod, Utah.