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.

Landraces are a valuable source of genetic variability for breeders to develop high-yielding lentil varieties. Apart from productivity, simultaneous breeding for lentil seed nutritional quality is of paramount importance for wider lentil consumption. This work examined the indirect effect of single plant selection for high yield on important seed quality traits within three Greek lentil landraces ("Elassona" (EL), "Lefkada" (L), and "Evros" (EV)). The breeding methodology applied was proved to help either maintain or improve such characteristics in the high-yielding second-cycle lines (SLs) selected. Compared to the parental landrace "Elassona", the high-yielding lines showed increased crude fiber by 30-110%; the line 2-SL-EL-6 had higher starch content by 3.9% and reduced cooking time by 6.67 min, while the 2-SL-EL-10 line had higher crude fiber by 73%. In the case of "Lefkada", the high-yielding lines selected maintained the protein content present in the parental landrace, apart from the 2-SL-L-1 where a decrease by 5% was recorded; however, most of them showed increased crude fiber (5.59-7.52%) in comparison with the parental landrace (4.65%). Finally, in relation to the "Evros" parental landrace, the 2-SL-EV-3 and 2-SL-EV-4 showed higher crude fiber and reduced cooking time. This study provides evidence that proper management of genetic variability could improve productivity without compromising or sometimes improving some seed quality traits.

SummaryPlants of early potato cultivars were sampled at successive harvests during tuber development and individual tubers were analysed for ct-solanine and (x-chaconine using high-performance liquid chromatography. Mean tuber total glycoalkaloid concentration (ct-solanine plus ~t-chaconine) per plant decreased with time and statistically significant differences between cultivars were observed in the patterns of decline during tuber growth. The mean tuber ratio of t~-chaconine to tx-solanine increased during tuber development and was also affected by genotype. Total glycoalkaloid concentration for individual tubers of marketable sizes (up to 50 g fresh weight) exceeded the safety limit of 20 mg per 100 g fresh weight for cultivars Home Guard and British Queen but not for Rocket. These differences were attributable to differences in both rates and patterns of glycoalkaloid accumulation during tuber development, although in all cultivars results were consistent with glycoalkaloid accumulation occurring in the expanding peripheral cell layers of tubers for a considerable period after tuber initiation.

The effects of low temperature and of combined stresses, cool temperature and waterlogging and also warm temperature and drought, on potato tuber glycoalkaloid levels were investigated, with emphasis on comparison of tubers of similar size. The early maturing cultivars Home Guard, Rocket and British Queen were grown under favourable controlled environment conditions (18/14°C day/night temperature, 14 h photoperiod) until the imposition of treatments after the start of tuber initiation. Transfer to low temperature (12/9°C) did not increase total glycoalkaloid concentration in any of the three cultivars. However, waterlogging at 12/9°C increased total glycoalkaloid concentration during the later stages of development of British Queen. Drought stress at 24/18°C also increased total glycoalkaloid concentration in British Queen, although the response varied between individual tubers of similar size. Total glycoalkaloid concentrations in tubers of Rocket were not affected by the combined stress treatments, and any effects on Home Guard were very much less than on British Queen.