TEMPERATURE AS THE BASIC FACTOR INFLUENCING PHENOLOGICAL STAGES IN ZIZIPHUS JUJUBA MILL

Abstract MISHRA, S., KRŠKA, B.: Temperature as the basic factor infl uencing phenological stages in Ziziphus jujuba Mill. Acta univ. agric. et silvic. Mendel. Brun., 2009, LVII, No. 1, pp. 89-96 The present study to fi nd a suitable base temperature for diff erent phenological stages in Ziziphus jujuba Mill". The data from the automatic meteorological station AMET located inside the orchard were used for the analyses. Since 2006, the automatic station has provided data on the atmosphere condition on a regular quarter-hour basis. The analysis was conducted on the basis of two years observations (2006)(2007). To fi nd out the suitable base temperature for phenology in jujube, we used the sum of active hourly temperatures (hour stages). Evaluations were carried out for each year, 2006 and 2007. In accordance with published data, the base temperatures above 7, 9 and 11 °C were used as threshold values for the phenology of jujube. Statistical evaluations of the data showed diff erences between 2006 and 2007. On the basis of active hourly temperatures (7, 9 and 11 °C), statistically analyzed avera ge 1 day diff erences during 2006 and 2007 were computed from the previous 10 days to fi nd out the diff erences between suitable and recorded dates of the start of each phenological phase, in days. On the basis of these results, 11°C is the most suitable base temperature for jujube. phenology, Ziziphus jujuba Mill., sum of active temperatures, base temperature Phenology is a study of the seasonal timing of events in nature: when fl owers bloom, trees come into leaf, buds break and so on. The precise timing of events in the natural cycle of the seasons o en determines the success or failure of individual plants. Deciduous trees burst bud only when the risk of late frosts is low, but not so long into summer that their annual period of photosynthetic activity is much diminished Fruits have varying amounts of climatic adaptation. Most of them grow only in either the tropical, subtropical, or temperate zones. For example, fruits such as apricot grow the best in the temperate, Mediterranean climate of uniformly cool winters and dry summers. However, jujube is adapted to grow from the equator to the Arctic Circle; it can grow also in temperate climates. The infl uences of temperatures on the phenological phases of jujube in a temperate climate were recorded by eff ect of temperature (Kim, Y. S. and Kim, W. S., 1984). Many phenological models are based on the concept of Degree Day. A degree day is defi ned as the difference between the daily mean temperature and base temperature. The daily mean temperature is generally computed as an average of the daily maximum and minimum temperatures. Over the course of the year, daily heat units are summed. Empirical evidence shows that phenological events are often triggered when a critical sum is exceeded The biological cycle of fruit trees starts with the development of fruiting buds in summer. In response to both, shorter day length and cooler temperatures, these buds enter a period of dormancy. The start of growth of new reproductive structures is observed a er dormancy. Chinese date (Ziziphus jujuba Mill.) is a deciduous tree growing at a moderate climate. Chinese jujube can withstand a wide range of temperatures; virtual ly no temperature seems to be too high in summertime. Winter dormancy allows it to withstan

Selezione con marcatori molecolari per la resistenza a Sharka

La Sharka è una malattia virale molto grave che colpisce le drupacee come l’albicocco ed il cui agente eziologico è il Plum Pox virus (PPV). In albicocco si conosce un QTL maggiore per la resistenza localizzato nella parte alta del cromosoma 1 (regione PPVres). Precedenti studi hanno indicato che le cultivar resistenti al virus e i semenzali resistenti derivati da incrocio possono essere selezionati analizzando una serie di marcatori SSR presenti in questa regione. L’efficienza di questi marcatori per la MAS (molecular assisted selection) è stata verificata in un lavoro recentemente pubblicato sulla rivista Tree Genetics and Genomics (Decroocq et al 2014): l'analisi degli individui di 11 popolazioni segreganti per la resistenza al virus ha dimostrato che la selezione di nuovi genotipi basata solo sui marcatori associati alla regione PPVres non è completamente affidabile. La maggior parte degli individui resistenti al virus della Sharka ha mostrato effettivamente la presenza degli alleli associati alla resistenza mentre la totalità delle piante suscettibili che ne erano privi. Purtroppo però gli alleli associati alla resistenza erano presenti anche in un numero significativo di individui suscettibili . Si è avuto quindi conferma che nel genoma dell'albicocco sono presenti altri fattori o geni in grado di modulare l’azione del gene localizzato nella regione principale. L'identificazione di ulteriori marcatori in queste nuove regioni sarà importante per selezionare in modo inequivocabile le accessioni di albicocco resistenti a PPV. Questo è l'obiettivo del Progetto Europeo MARS (Marker Assisted Resistance to Sharka, https://www6.inra.fr/mars)