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SUMMARYThe literature suggests that grain number largely determines and as such limits yield in barley. Many of the reported studies were conducted in relatively low-yielding environments and it is unclear if grain number is also a limiting factor in high-yield potential climates. Nor is it known with certainty what physiological or morphological traits must be targeted in order to increase grain number. A detailed programme of assessments was carried out on replicated field plots of a two-row spring barley variety (Hordeum vulgare L. cvar Quench) at three sites (Carlow, Wexford and Cork) in Ireland from 2011 to 2013. Plots were managed for high yield potential as per current best farm practice. Destructive sampling and in-field assessments were carried out at approximately weekly intervals from emergence onwards to gather growth, development and yield component data. Across nine site/seasons, grand means of 8·52 t/ha for yield, 18 419 for grain number/m2 and 46·41 mg for mean grain weight were achieved. Grain number/m2 accounted for most of the variation in yield and ear number/m2 accounted for most of the variation in grain number/m2. Early-season maximum shoot number/m2 had little influence on harvest ear number/m2. The period over which final ear number was determined was more flexible than the literature suggests, where the phases of tiller production and senescence varied considerably. Significant post-anthesis re-tillering occurred following the initial phase of shoot mortality at two out of nine site/seasons, but this appeared to contribute little to yield. Yield was positively associated with the proportion of shoots surviving from an early season maximum to a mid-season minimum (R2 = 0·62). Shoot size and weight at the beginning of stem extension had the largest influence on shoot survival, indicating that crop condition and hence growth and development pre-stem extension may be more important for shoot survival than growth and development during the stem extension period. Achieving high shoot numbers of adequate size and weight at the beginning of stem extension may be an appropriate target for establishing a high-yield potential crop.

SUMMARYBreeding trials for swede (Brassica napus var. napobrassica) in 2000–2010 showed that 0·85 of the incidence of brown heart (BH) in the trials was associated with genotypes that are progeny of Ag31, Or13 and Me77c. In order to investigate this and the effect of treatment with boron (B), established varieties and improved parent lines carrying male sterility (ms), and their F1 hybrids (test hybrids), were grown in a field trial in the UK in 2011 and subjected to four B treatments (0·00, 1·35, 1·80 and 2·70 kg B/ha). The results confirmed that BH incidence and severity was affected by genotype but could be ameliorated by B application. Genotype Ag31 was very susceptible while Or13 and Me77c were of intermediate susceptibility and the hybrids between susceptible parents were also sensitive. Genotypes Gr19 and Ly01 were highly resistant even in the absence of B application. Hybrids between resistant and susceptible lines were highly resistant. The use of ms had no influence on BH. Resistance to BH was a dominant trait: homozygous dominant (BHBH) or heterozygous (BHbh) genotypes confer this trait, while susceptibility is recessive (bhbh). Some quantitative variation existed, suggesting that resistance was not a single gene effect. There was a significant negative correlation (r=−0·632) between root B content and the severity of BH in susceptible genotypes. Severe BH was associated with 12–21·5 μg B/g of root dry weight at zero B applied. Moderate discolouration was associated with 19·5–24·8 μg B/g recorded at moderate B applied and only Ag31 showed BH at 2·70 kg B/ha. Resistant varieties had root contents of 23 μg B/g or more while susceptible varieties required a minimum of 31 μg B/g to offset BH.