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This brief historical review focuses on durum wheat domestication and breeding in the Mediterranean region. Important milestones in durum wheat breeding programs across the countries of the Mediterranean basin before and after the Green Revolution are discussed. Additionally, the main achievements of the classical breeding methodology are presented using a comparison of old and new cultivars. Furthermore, current breeding goals and challenges are analyzed. An overview of classical breeding methods in combination with current molecular techniques and tools for cultivar development is presented. Important issues of seed quality are outlined, focusing on protein and characteristics that affect human health and are connected with the consumption of wheat end-products.

The study aimed to address the optimal plant population density in maize that maximizes phenotypic expression and differentiation, and lessens environmental effects on genotypic expression in terms of the response to selection. A set of seven short-season hybrids (Rom set) was tested under rainfed conditions (2006, 2007) in Romania, and a set of seven long-season hybrids (Gr set) was tested with irrigation (2007) in Greece. Experimentation was conducted under ultra-low (ULD), low (LD), middle (MD), and high (HD) densities (0.74, 2.51, 4.20, 8.40 plants/m 2 for the Rom set, and 0.74, 3.13, 6.25, 8.33 plants/m 2 for the Gr set). Phenotypic expression and differentiation for grain yield were highest at the ULD. Coefficient of variation (CV) for grain yield, ear length and kernel row number decreased as density decreased. Environmental conditions and hybrid plant-yield potential (i.e., maximum yield per plant) were crucial for the optimal density that achieved the lowest environmental variance. For the Rom set the lowest CV for grain yield was obtained at the LD in the unfavourable season and at the ULD in the favourable season. The less acquired variance was achieved at the ULD for the highest yielding hybrids and at the LD for the lowest yielding hybrids, revealing a negative association between plant-yield potential and optimal density. Concluding, a density proximal to the ULD approximates absence of competition in maize, and optimizes three determinant parameters for successful selection: selection intensity, heritability and phenotypic differentiation.

Plant yield e ciency re ects the single-plant yield at low density that precludes interplant interference for resources. e role of plant yield e ciency in adaptation to water de cit was investigated in maize (Zea mays L.). Also investigated was whether yield of space-planted environments is transferable to densely seeded situations. Further, the correlation and genotype by environment (G × E) interaction of spaced and densely seeded plots were investigated. irty-one lines and 31 crosses among them were tested in three locations under dense stand and the ultra low density of 0.74 plants m -2 as well as in normal and de cit irrigation treatments. e dense stand was 4.44 plants m -2 in the water de cit regime and 6.67 plants m -2 (lines) and 7.84 plants m -2 (hybrids) in the normal water treatment. Hybrids of greater plant yield e ciency were less sensitive to water shortage. Among four hybrids yielding the same at normally irrigated dense stand (11.50 Mg ha -1 ), yield loss due to water shortage was 46% for that of the lowest plant yield e ciency (645 g plant -1 ) and 17% for that of the highest plant yield e ciency (880 g plant -1 ). Correlations between hybrid plant yield e ciency and gas exchange water-use e ciency in dense stand were signi cant. e low density ensured G × E interaction in the quantitative aspect only and thus was of higher heritability, placing emphasis on parental yield per se. Plant yield e ciency is a key element of hybrid ability to withstand water shortage and cope with environmental heterogeneity.Supplemental material available online. I.S. Tokatlidis, C. Tzantarmas, and A. Kargiotidou, Dep. of Agricultural Development, Democritus Univ. of Th race, Orestiada, 68200, Greece; C. Dordas, C. Pankou, F. Gekas, E. Ninou, I. Mylonas, and A. Lithourgidis, School of Agriculture, Aristotle Univ. of Th essaloniki, Th essaloniki, 54124, Greece; F. Papathanasiou, I. Papadopoulos, J.K. Petrevska, and I. Sistanis, Dep. of Agricultural Technology, Technological Educational Institute of Western Macedonia, Florina, 53100, Greece. Received 22 Nov. 2014. Accepted 1 Feb. 2015. *Corresponding author (itokatl@agro.duth.gr; itokatl@hotmail.com).Abbreviations: A, assimilation rate; ASI, anthesis-silking interval; G ´ E, genotype by environment interaction; HI, harvest index; PYE, plant yield effi ciency; T, transpiration; WUE, water-use effi ciency.Ability of a cultivar to tolerate crowding but also perform well at the single-plant level has been asserted to be a determinant element to its crop yield potential (Yan and Wallace, 1995;Fasoula and Tokatlidis, 2012). However, in maize yield more improvement has resulted from improving tolerance to high plant population densities rather than single-plant performance; the per plant yield under minimal competition for light, water, and nutrients remained unchanged (Tollenaar and Lee, 2002;Duvick, 2005). Transition to higher populations in combination with stagnation in yield capacity of individual plants resulted in hybrids characterized as density-dependent (Fas...

Plant yield efficiency (PYE) reflects the ability of the single-plant to respond to additional inputs and is fully expressed at the nil-competition regime (an ultra-low density to preclude inter-plant interference for inputs). The purpose of this study was to determine if PYE could prevent the erratic optimum plant density-yield interaction effect in maize (Zea mays L.). Seven hybrids were evaluated across five environments at four densities, under both the normal-input regime (NIR) and low-input regime (LIR). Plant yield efficiency was measured at the lowest density approaching the nil-competition regime (0.74 plants m -2 ), while crop (per area) yield potential was estimated at the highest density corresponding to the typical farming density in the NIR (8.89 plants m -2 ). In terms of optimum density, the hybrids varied extensively in the NIR (6.64-8.81 plants m -2 ) but performed similarly in the LIR (5.11-5.61 plants m -2 ). The hybrid displaying the highest PYE also had high harvest index (HI) and low anthesis to silking interval (ASI) and was proved the most stable according to various stability statistics including the genotype and genotype by environment (GGE) biplot model. In conclusion, crop yield by density interaction is a matter of hybrid. Hybrids with low PYE have inconsistent optimum density, which is a causal factor of yield loss in rainfed maize. High PYE improves hybrid flexibility and performance at low densities ultimately enhancing crop resilience to extremely fluctuating environments.Abbreviations: AMMI, additive main effect and multiplicative interaction; ASI, anthesis to silking interval; G × E, genotype by environment interaction; GGE, genotype and genotype × environment; HI, harvest index; LIR, low-input regime; NIR, normal-input regime; PYE, plant yield efficiency.