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An important step towards reducing the vulnerability of wheat in Africa and Asia to the Ug99 race of the stem rust pathogen is the substitution of current susceptible varieties with superior resistant varieties. In the 2008-2009 cropping season both seed multiplication and dissemination of Ug99 resistant varieties were initiated in Afghanistan, Bangladesh, Egypt, Ethiopia, Iran, India, Nepal and Pakistan. Ug99 resistant varieties must occupy about 5% of the area sown to wheat in each country to ensure sufficient seed to displace current popular varieties. Because of the underdeveloped seed industry and small farm sizes in most of these countries, various strategies are being applied for rapid multiplication and dissemination of resistant varieties. Approaches being used include pre-release seed multiplication while candidate resistant lines are being tested in national evaluation trials and farmer participatory selection. Resistant varieties are already released in Afghanistan, Bangladesh, Egypt and Pakistan and more varieties are expected to be released in 2010 in these and other countries. Our results show that some new Ug99 resistant lines have yield superiority over dominant local varieties. Activities and progress in seed multiplication using existing and new Ug99 resistant varieties are discussed.

The number of productive tillers is an important yield component in wheat and is affected by water stress and genetic factors. A greenhouse experiment was conducted during spring 1992 at ICARDA, Tel Hadya, Syria, with eight genotypes representing two Triticum species (Triticum turgidum L. ssp. durum and Triticum aestivum L. ssp. aestivum) under four soil‐moisture regimes (95 %, 75 %, 55 %, and 35 % field capacity) to study the effect of water deficit on tiller development and tiller contribution to grain yield. In the highest watering regime appearance of Tiller 1 was delayed in both species. Also Tiller 2 was suppressed in this treatment in durum, while its appearance was delayed in aestivum. In the driest treatment, a majority of the tillers were suppressed and the ones which emerged were delayed. In durum, the heat units required to produce successive leaves on the tillers were higher than that for the main stem and increased with increasing water stress, causing high rate of tiller abortion. In aestivum, each tiller, once produced, developed leaves at the same rate as on the main stem. Phyllochron of tillers as well as main stem was not affected by water stress in aestivum. In aestivum, contribution by tillers to yield was higher than that of durum in all treatments. Results indicate that early appearance of tillers and faster rate of leaf appearance under water stress result in higher tiller survival and greater tiller contribution to final yield. Hence, tiller dynamics under water stress can be used as a selection criterion for breeding for drought tolerance.

Hexaploid wheat has the largest cultivated area among crop plants due to its adaptability to different agroclimatic regions. A large part of this adaptability depends upon the variation in vernalisation and photoperiod requirements. A better understanding of the genetic control of flowering in wheat, as expressed by vernalisation requirements and photoperiod response, will guide breeders in targeting crosses of different types and will also improve our understanding of regional adaptation requirements. Characterisation of large numbers of breeding lines for photoperiod and vernalisation response in wheat is needed to assign the lines to geographic areas of most probable adaptation. Simple screening methods to quantify the effects of these two factors and their interaction are needed to assist breeding progress. Twenty wheat lines were evaluated for response to photoperiod and vernalisation under two controlled environments and under high ambient air temperatures in field conditions. Vernalised and non vernalised seedlings were transplanted into pots and placed in three photoperiod (8, 12 and 16 h light) cabinets, in the greenhouse or in growth chambers. Days to anthesis decreased with increasing length of photoperiod. Vernalised plants flowered earlier than non vernalised plants. There was a significant correlation between days to anthesis in the greenhouse and the growth chamber (r = 0.88, P <0.001). Length of basal vegetative period, effects of vernalisation, and photoperiod from the two screening techniques were positively correlated with each other. Growth habit score, vernalisation requirement and heading date in the field were highly correlated with the main effect of vernalisation in the two controlled environments. The results indicated that selection for vernalisation response in a large number of genotypes can be achieved under high ambient air temperatures in the field. The selected material can subsequently be screened for photoperiod response under greenhouse conditions. Using these techniques, 49 local and improved cultivars from the Mediterranean region in west Asia and north Africa (WANA), showing differences in response to photoperiod, vernalisation, and earliness independent of vernalisation and photoperiod, affecting time to anthesis, were identified. Most old local cultivars were sensitive to both photoperiod and vernalisation. All the improved genotypes were insensitive to photoperiod. Responses to vernalisation were generally small under short photoperiods, but were more pronounced in long photoperiod, particularly in winter and facultative types from northern latitudes. These results should help to explain the adaptability of cultivars based on photoperiod and vernalisation requirements and their interaction.

Characterization of large numbers of breeding lines for vernalization and photoperiod response in wheat is needed to enhance adaptation. A total of 20 wheat lines were evaluated for response to vernalization and photoperiod under two controlled environments and high ambient air temperatures under field conditions. Vernalized and non-vernalized seedlings were transplanted into pots and placed in three photoperiod (8, 12 and 16 h of light) cabinets, in the greenhouse or in growth chambers. Days to anthesis decreased with increasing photoperiod. Vernalized plants fiowered earher than non-vernalized. There was a significant correlation between days to anthesis in the greenhouse and the growth chamber (r = 0.88, P < 0.001). Basal vegetative period, effect of vernalization and photoperiod from the two screening techniques were positively correlated with each other. Growth habit, vernaUzation requirement and heading date in the field were highly correlated with the main effect of vernalization in the two controlled environments. The results indicate that selection for vernalization response in a large number of genotypes can be achieved under high ambient air temperatures in the field and the selected material can subsequently be screened for photoperiod response under greenhouse conditions.Key words: Triticum aestivum -daylength sensitivity sic earUness -growth habit intrinBecause of its wide adaptability to different agrocUmatic regions (Flood and Halloran 1984), hexaploid wheat {Triticum aestivum L. em TheU.) has the largest cultivation area among crop plants. A large part of this adaptability depends upon the variation in vernalization and photoperiod requirements. A better understanding of the genetic control of fiowering in wheat as expressed by vernalization requirements and photoperiod response will guide breeders in targeting crosses of differing maturity types and will also improve our understanding of regional adaptation requirements.Vernalization and photoperiod responses interact in wheat in such a way that vernaUzation reduces the need for subsequent long days (Fvans et al. 1975). Prolonged vernaUzation does not however overcome the long-day requirement in photoperiodsensitive wheats, and in the vernalization-sensitive genotypes, long-day treatment does not overcome the vernalization requirement (Flood and Halloran 1984). Large differences between varieties in sensitivity to these two factors have been reported. Sensitivity to these factors may be linked to the pattern of daylength and temperature in the regions of the origin or adaptation of varieties. The lack of simple screening methods to quantify the effect of these two factors Umits the extent of adaptation of wheat to broad target environments. Therefore, a reUable method of simultaneously classifying vernalization requirement and photoperiod response is required. The aim of this study was to examine two techniques for screening wheat genotypes for their response to photoperiod and vernaUzation and to compare them with field screening. Materials an...