Zea mays L. (cv Dea) plants grown to the stage of stalk elongation, were allowed to assimilate 13C02 and 15N-nitrates from 45 to 53 days after sowing. Isotopic abundances in labeled nutrients were slightly enriched compared to natural abundances. The new C in plant was acropetally distributed and the new N was preferentially accumulated in the sheath and stalk in the medium region. C input was 25-fold higher than N input. The new C in total plant C was 20%, whereas it was 10% for N. The stalk acted as a major sink because it accumulated, respectively, 27.5 and 47.5% of the C and N inputs. The new C in soluble carbohydrates was 76% in growing organs (upper stalk) and only 39% in source leaves, whereas it was 43% and 13% in starch, respectively. New N in nitrates+amino-acids spanned in the range from 20% (leaf) to 50% (stalk). New C and N in soluble proteins were, respectively, 13.4 and 3.8% in leaves, 8.8 and 9.6% in stalk, and 8.7 and 14.3% in roots. In the middle stalk and leaves, the proteins and carbohydrates represent an equivalent C and N source for remobilization.Plant growth and seed production of grain crops are the result of the photosynthetic ability of source leaves and the integrated processes of allocation, accumulation and utilization of assimilated carbon at the whole plant level (14). Efficient translocation of photoassimilates to sink organs is one of the key factors in increasing production (14, 27). C and N metabolism are closely linked, so both should be considered when attempting to determine factors that limit efficient translocation. Recently, attention has been paid to relationships between C and N metabolism in the productivity of maize (1,26,28). However, only a few data are available on 13C and '5N redistribution in the Graminae (18), and little information is available for maize (8). Our interest was focused on C and N allocation in the stalk. This organ acts first as a sink during elongation and then as a source when ears develop (1, 23). We used here a CO2 assimilation system designed for long-time incorporation of C at a constant '3C

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Changes in plant, ear, and grain traits after three cycles of S1 recurrent selection for resistance to Diplodia stalk rot (SR) and mechanical stalk breakage (MS) were evaluated in the BSI maize (Zea mays L.) synthetic. The cycle populations (BS1 and C1 C3 for BSISR and BSIMS for stalk‐rot and stalk‐strength selection, respectively), populations crossed to a single‐cross tester, and crosses between populations of each procedure of selection were evaluated in replicated experiments in 1980 and 1981. The two procedures of selection gave contrasting responses in plant traits. The BSIMS populations showed increased plant height, internode number and length, and delayed anthesis, whereas the BSISR populations showed a trend toward earlier anthesis, with reduced plant height and internode length. Most of the changes for plant traits occurred during the initial cycle of selection when there was no control on flowering date of selected Sl lines. Grain yield was reduced from 7.08 t ha−l in BSI to 4.95 and 5.42 t ha−1 in BSIMSC3 and BSISRC3, respectively. Although the population crosses also showed significant yield reductions, they yielded higher than either parent. No significant yield change was observed in testcross performance. All yield components except kernel weight also were reduced by both selection procedures. Ear diameter and length, however, had the highest correlations with yield and contributed most to yield reductions observed in the improved populations for stalk quality. Thus, mild selection should be practiced for yield and other agronomic traits of importance when undertaking a population improvement program for stalk quality.

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Although maize (Zea mays L.) is a major forage crop, little attention has been given to possible alteration of forage quality associated with breeding for increased resistance to stalk lodging. This study was designed to evaluate changes in stalk composition and digestibility resulting from three cycles of recurrent selection each for improved stalk strength (BSlMS) and stalk‐rot [Diplodia maydis (Berk.) Sacc.] resistance (BSlSR). The second elongated internmode plus half of each adjacent internode from plants of the original population (BSlCO) and from C1 to C3 for the BSlMS and BSlSR populations were sampled approximately 35 days after midsilking for chemical and in vitro digestible dry matter (IVDDM) evaluation. Major composition changes from the BSlCO to BSlMSC3 and BSlSRC3 populations, respectively, were: concentration of cell wall constituents, 616 to 520 and 542 g kg−1; concentration of acid detergent fiber, 422 to 353 and 373 g kg−1; concentration of lignin, 57 to 42 and 47 g kg−1; concentration of total nonstructural carbohydrates (TNC), 184 to 258 and 244 g kg−1; and concentration of IVDDM, 514 to 621 and 594 g kg−1. Both selection regimes increased TNC concentration, which diluted stalk fiber concentration and resulted in a net increase in IVDDM. Recurrent selection for traits associated with improved stalk lodging resistance did not have negative effects on the forage quality of maize stalks in late reproductive stages.

In Northwestern Europe, Germany, France, the Netherlands, the UK and Belgium constitute the biggest five potato producers, with total potato crop production around 60% of EU-28 production before Brexit. Soil and climate conditions are highly favourable for potato growth in this region. Production is under driving forces of (i) the potato processing industry, particularly in Belgium; (ii) the innovation for fresh potato in the UK, France and Germany; (iii) the leadership of Germany and the Netherlands for starch potato; and (iv) the dominance of the Netherlands for seed production. Based on an industrial agri-food production system, the region has the highest potato yield levels worldwide and developed relevant trade networks for export of seed, fresh and processed potato products in and outside Europe. Conventional and intensive potato production is widespread over the region, whilst organic production started to develop in Germany and France. Whether the coming decades will be as successful as the last ones for sustainable potato production will depend on how the sector and stakeholders of the whole potato value-chain will overcome new issues and challenges. These are mainly soil quality and health conservation, consequences of climate change, increasing bans on the use of plant protection products, tightening environmental standards, food waste reduction and increasing trade tensions hampering the flow of potatoes around the world. After a detailed description of the potato production in the region, this paper contains a SWOT analysis aiming to identify potential solutions to overcome environmental, technical, economic, political and societal issues in the region for sustainable potato production in the coming years and decades.

Recurrent selection, based on S1 lines in replicated experiments, was used in separate trials for three cycles to improve the maize (Zea mays L.) synthetic BS1 for resistance to artificial stalk rot (Diplodia maydis) and resistance to mechanical stalk breakage. The cycle populations (BS1 and C1 to C3 for BS1SR and BS1MS for stalk‐rot and stalk‐strength selection, respectively), populations crossed to a low‐stalk‐quality single cross, and crosses of populations between each procedure of selection were evaluated for stalk and rind strength, Diplodia stalk rot, field stalk rot, and field stalk and root lodging. Random S1 lines from BS1 and C3 populations of BS1SR and BS1MS were evaluated for Diplodia stalk rot and stalk and rind strength. Highly significant improvements were observed for all stalk‐quality traits. Changes from the CO to BS1MSC3 and BSISRC3, respectively, were as follows: stalk strength, 34.8 to 56.5 and 46.7 kg; Diplodia stalk‐rot rating, 3.5 to 1.8 and 1.7; rind strength, 3.4 to 4.2 and 4.3 kg; field stalk‐rotted plants, 25 to 5 and 8%; and field stalk‐lodged plants, 13 to 6 and 3%. Improvements in population crosses, population testcrosses, and random S1 lines closely paralleled the improvements in the populations per se, indicating that stalk quality is controlled primarily by additive type gene action. Highly significant correlations were observed among all stalk‐quality traits. Recurrent selection for rind strength and stalk‐rot resistance, simultaneously, may be the most desirable method of improving populations for development of inbred lines with superior field stalk quality.