. 2004. Nitrogen use efficiency characteristics of commercial potato cultivars. Can. J. Plant Sci. 84: 589-598. One approach for reducing the contribution of potato (Solanum tuberosum L.) production to nitrate contamination of groundwater is to develop cultivars which utilize N more efficiently. In this study, variation in N use efficiency (NUE; dry matter production per unit crop N supply) characteristics of 20 commercial potato cultivars of North American and European origin were evaluated in 2 yr. Cultivars were grown with or without application of 100 kg N ha -1 as ammonium nitrate banded at planting. The recommended within-row spacing was used for each cultivar and no irrigation was applied. Plant dry matter and N accumulation were determined prior to significant leaf senescence. Crop N supply was estimated as fertilizer N applied plus soil inorganic N measured at planting plus apparent net soil N mineralization. Nitrogen use efficiency decreased curvilinearly with increasing crop N supply. Nitrogen use efficiency was lower for early-maturing cultivars compared to mid-season and late-maturing cultivars. A curvilinear relationship was obtained between plant dry matter accumulation and plant N accumulation using data for all cultivars. Deviations from this relationship were interpreted as variation in N utilization efficiency (NUtE; dry matter accumulation per unit N accumulation). Significant differences in NUtE were measured among cultivars of similar maturity. Nitrogen uptake efficiency (NUpE; plant N content per unit crop N supply) and soil nitrate concentration measured at plant harvest were uniformly low for all cultivars when crop N supply was limited, but varied among cultivars when N was more abundant. This suggests that potato cultivars vary more in terms of N uptake capacity (plant N accumulation in the presence of an abundant N supply) than in terms of NUpE. Les variétés ont été cultivées avec ou sans application latérale de 100 kg de N par hectare sous forme de nitrate d'ammonium. Les auteurs ont respecté l'écartement recommandé pour chaque cultivar et n'ont pas irrigué la culture. Ils ont déterminé la quantité de matière sèche dans la plante et l'accumulation de N avant une trop forte sénescence des feuilles. La quantité de N fournie aux plantes a été estimée à partir de l'engrais appliqué et de la concentration de N minéral dans le sol à la plantation, plus la minéral-isation nette apparente de cet élément. L'efficacité de l'assimilation de l'azote diminue de façon curviligne avec la hausse de la quantité de N disponible. Les cultivars hâtifs assimilent moins bien l'azote que les cultivars de mi-saison ou tardifs. Lorsqu'on analyse les données venant des différents cultivars, on remarque une relation curviligne entre la quantité de matière sèche et celle de N accumulées par la plante. Les écarts à cette relation sont attribués à une variation dans l'efficacité de l'assimilation du N (EAsN; accumulation de matière sèche par unité de N accumulée). L'EAsN présente d'importantes variations entre le...

Genomic selection is a promising molecular breeding strategy enhancing genetic gain per unit time. The objectives of our study were to (1) explore the prediction accuracy of genomic selection for plant height and yield per plant in soybean [Glycine max (L.) Merr.], (2) discuss the relationship between prediction accuracy and numbers of markers, and (3) evaluate the effect of marker preselection based on different methods on the prediction accuracy. Our study is based on a population of 235 soybean varieties which were evaluated for plant height and yield per plant at multiple locations and genotyped by 5361 single nucleotide polymorphism markers. We applied ridge regression best linear unbiased prediction coupled with fivefold cross-validations and evaluated three strategies of marker preselection. For plant height, marker density and marker preselection procedure impacted prediction accuracy only marginally. In contrast, for grain yield, prediction accuracy based on markers selected with a haplotype block analyses-based approach increased by approximately 4 % compared with random or equidistant marker sampling. Thus, applying marker preselection based on haplotype blocks is an interesting option for a cost-efficient implementation of genomic selection for grain yield in soybean breeding.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-016-0504-9) contains supplementary material, which is available to authorized users.

No abstract

The first soybean [Glycine max (L.) Merr.] breeding program in China was established in the northeast in 1913. A trend analysis of widely grown cultivars across Chinese soybean breeding history may provide a better perspective on the genetic progress in soybean. The objective of the current study was to assess the genetic change of 15 phenological, yield, and agronomic traits on widely grown cultivars in northeast China. Sixty-four soybean cultivars representing a span of 84 yr of release were included. The field experiments were conducted at three sites in each region during 2009, 2010, and 2011, and the annual genetic changes were obtained by regression analysis. The results showed that the yield gain in widely grown cultivars of different regions ranged from 6 to 16 kg ha −1 yr −1 due to improvements in different yield components in the last nine decades. In addition, modern cultivars demonstrated more upright plant architecture, fewer branches, shorter height, higher lodging resistance, and earlier flowering than obsolete cultivars. However, changes were insignificant in the height of the bottom pod and the node number. The changing rates of yield and phenological traits across these decades were constant, while that of agronomic traits were discontinuous. Days to flowering, branch number, and lodging score were more responsive to environments in new cultivars than in old cultivars. In conclusion, these findings indicate a substantial improvement in the yield, agronomic, and phenological traits resulted from long-term genetic breeding. This study also provides insight into developing new strategies for soybean genetic improvement in China and worldwide. Corresponding authors (hantianfu@ caas.cn; wucunxiang@caas.cn). Abbreviations: 100-SW, 100-seed weight; BLUE, best linear unbiased estimator; BLUP, best linear unbiased predictor; BN, branch number; C, cultivar; CV, coefficient of variability; DTF, days to first flower; DTM, days to maturity; E, environment; HBP, height of the bottom pod; JL, Jilin-Liaoning region; LS, lodging score; MG, maturity group; MSH, midsouth Heilongjiang region; NH, north Heilongjiang region; NN, node number; PH, plant height; PPP, number of pods per plant; R/V, ratio of the reproductive period to the vegetative period; RP, reproductive period; SPP, seeds per plant; SPPOD, seeds per pod; YPP, yield per plant.

Traits related to the number of pods and seeds are important yield factors on soybean. The relationships between phenotype and quantitative trait loci (QTLs) of these traits may reveal the mechanisms underlying productivity. Our study objectives were to analyse phenotypic correlations, detect stable QTLs and identify candidate genes useful for marker‐assisted selection. Phenotypic analyses revealed that NThSP (number of three‐seeded pods) was positively correlated with NPPP (number of pods per plant) and SNPP (number of seeds per plant). Seventy‐five QTLs were identified based on the mean phenotypic data for at least 2 years. We detected two to 15 and one to three significant QTLs identified at the same location, respectively. Six consensus QTLs associated with at least two NPS‐related (number of pods and seeds related) traits were identified. Two of these were verified in another population. The QTLs for NPPP, SNPP and NThSP formed a consensus QTL cluster on GM02. Another 27 QTLs also formed clusters in five regions. Fifteen candidate genes were mined and discussed. The results will provide more information to soybean breeding.