This trade-off was described by Comstock and Moll (1963), who noted that partitioning of a target popula-In a small target region, it may be possible to exploit local adaptation of environments into several more homogeneous tion to increase gains from selection. However, in a large region subdivisions could increase within-subdivision genetic more extensive testing is usually possible, resulting in more precise estimation of genotype means. A correlated response model was variance, but recognized that increased testing effort adapted to determine if division of a large target region is likely to would be required if a single large breeding program increase gains. Genotypic value in a large region and constituent were to be replaced by several smaller ones. The effect subregions are considered correlated traits. Correlated response in a of subdivision depends not only on the magnitude of subregion to indirect selection across the undivided region, relative genotype ϫ subregion (GS) interaction but also on the to direct response to selection within the subregion, is expressed as precision with which means are estimated within the a function of heritability in the undivided region (H) and in the newly created subregions, relative to the precision of subregion (H i ), and of the genotypic correlation between region and their whole-region estimates. Curnow (1988) noted that subregion means (r G ). r G depends on the magnitude of the genotype ϫ when GS interaction is relatively small and error varisubregion interaction ( 2 GS ) relative to the genotypic variance ( 2 G ).ances are relatively large, greater gains within a subre-2 GS is the portion of the genotype ϫ location interaction ( 2 GL ) caused by local adaptation, rather than by random site-to-site variability in gion may be achieved by selecting on the basis of mean genotype means. Subdivision can increase heritability through the yield across the undivided region than within a single

. 2000. Herbicidal weed control and crop-year NPK fertilization improves lowbush blueberry (Vaccinium angustifolium Ait.) production. Can. J. Plant Sci. 80: [351][352][353][354][355][356][357][358][359][360][361]. Past research has shown that fertilizer applied in the vegetative year can increase yield, but not always. Fertilizer applied in the crop year without weed control also has been shown to increase yield. The present study, conducted on a natural lowbush blueberry stand for 8 yr, compared the effects of factorial combinations of two rates each of N (0, 60), P (0, 26), and K (0, 50 kg ha -1 ) applied either in the vegetative or crop year, with or without weed control. Greatest production was obtained with weed control, which increased ripe fruit yield by 247% over that from plots without weed control. Nitrogen alone or P and K with N also increased yield, but only when applied in the crop year to weed-controlled plots. Phosphorous or K alone was of little benefit. Nitrogen increased ripe fruit yield from 3910 (unfertilized plots with weed control) to 4440 kg ha -1 and in combination with P and K to 5520 kg ha -1 . Yield increases from weed control and N were due to increased berry weight and hastened maturity, but weed control also increased total berry number. The increase by P and K was due to an increase in total and ripe berry numbers. Nitrogen applied in the vegetative year, although producing more flower buds m -2 than when applied in the crop year, gave lower yields. Fruit abortion, due to insufficient nutrients in the crop year, particularly N, is suspected to be the reason for the reduced yield. La recherche a montré que la fumure du bleuet nain dans l'année de croissance végétative peut à l'occasion accroître le rendement. La fumure dans l'année de frutification, sans maîtrise des mauvaises herbes, a également démontré des effets positifs sur le rendement. Dans nos travaux, réalisés pendant 8 ans sur un peuplement naturel de bleuets nains, nous avons comparé les effets de combinaisons factorielles de deux doses chacun des trois éléments N (0 et 60), P (0 et 26) et K (0 et 50 kg ha -1 ), apportés soit dans l'année végéta-tive soit dans l'année de production, avec ou sans désherbage chimique. C'est le désherbage chimique qui a donnait lieu à la production la plus forte, accroissant le rendement en fruits mûrs de 247 % par rapport aux parcelles non désherbées. L'azote, seul ou avec P et K, causait également des hausses de rendement, mais seulement lorsqu'il était utilisé l'année de récolte dans les parcelles désherbées. Employés seuls, le phosphore ou le potassium n'apportaient que peu d'avantages. La fumure N faisait monter le rendement en fruits mûrs de 3910 (parcelles non fertilisées avec désherbage) à 4440 kg ha -1 et, complétée par P et K, à 5520 kg ha -1 . Les augmentations de rendement résultant du désherbage et de la fumure N étaient dues à l'accroissement du poids du fruit et à l'accélération de la maturité, le désherbage produisant en plus une augmentation du nombre total de fruits. Les g...

Cultures of two cranberry (Vaccinium macrocarpon Ait.) cultivars,`Ben Lear' and`Pilgrim', and three cranberry clones from natural stands in Newfoundland were established in a nutrient medium containing N 6 [2-isopentenyl]adenine (2iP) from nodal and/or shoot-tip explants obtained under aseptic conditions. The cultivars differed in shoot regeneration in terms of shoot number per explant with various concentrations of 2iP over two culture periods. Best total shoot production was obtained when nodal segments were cultured in the medium supplemented with 2.5±5.0 mg 2iP l 21 (12.3±24.6 mM). With higher 2iP levels, shoots did not expand and had a high mortality rate. Nodal explants of the three clones cultured in the same nutrient medium supplemented with 2.5 mg 2iP l 21 (12.3 mM) produced three to five healthy axillary shoots per explant. In another experiment, nodal explants were more productive than shoot tips. In all experiments with subculture, there was an increase in shoot multiplication rate for all genotypes. Shoots were rooted in vitro in the same media used for shoot proliferation, but without any growth regulators. After their transfer to potting medium, almost all of the rooted plants survived. Cranberry genotypes can be efficiently propagated and maintained through nodal culture in a nutrient medium without auxin that contains 2.5±5 mg 2iP l 21 (12±25 mM).

. 1999. Fall cutting management affects yield and persistence of alfalfa in Atlantic Canada. Can. J. Plant Sci. 79: 57-63. The existing recommendation to avoid harvesting alfalfa during a critical fall rest period, based on calendar dates, is under review in Canada and adjacent areas of the United States. The effect on yield and persistence of four fall cutting management treatments (based on cumulative growing degree-days between harvests) was investigated for two cultivars of alfalfa (Medicago sativa L. 'Apica' and 'Oneida VR') at five sites in Atlantic Canada. The average seasonal DM yield for the five sites in the first production year was 1.6 to 2.3 t ha -1 greater with an additional harvest as compared with the two-harvest system (Truro, Nappan, Fredericton, and Charlottetown) and the one-harvest system in St. John's. Seasonal DM yield benefits were reduced over time; by the third production year, there was no increase in seasonal DM yield with an additional harvest. The seasonal DM yield increased with increasing the interval between the final harvest and the previous one. Taking an additional harvest resulted in higher winter plant mortality between the first and second production years in Truro and Nappan, and the third and fourth production years in St. John's. At the other two sites (Charlottetown and Fredericton), and for the first three production years in St. John's, winter plant mortality was unchanged with an additional harvest but regrowth potential in the following year was reduced. At the two sites that experienced a severe winter (Nappan and Truro), the cultivar Oneida VR was more adversely affected by the additional harvest than Apica. Our results indicate that in Atlantic Canada, taking an additional harvest increases the risk of winterkill. If an additional harvest is to be taken, increasing the interval between the final harvest and the previous one to at least 500 growing degree-days will decrease the risk of winterkill and might have a positive effect on next year's regrowth.

A B S T R A C TConcentrations of the major jlavonoids and phenolic acids in the peel und cortex of fiuit of eight commercial apple cultivars were determined by H P L C . The multivariate statistical technique of correspondence analysis was applied to the polyphenol profiles to describe distinctive groups of cultivars and of polyphenois, and their joint correspondences.Cultural and growing conditions had u limited eflect on the polyphenol profiles of the cortex and peel. Chlorogenic acid was the principal polyphenol in the cortex with the lowest levels being in Red Delicious and the highest in Jerseymac, which were compensated by changes in phlorizin. Cortland had low levels of' chlorogenic acid and Gravenstein had high levels, but these were oflset by the levels of catechins.The quercetin, rhamnoside, was the principal phenolic compound for the peel data with low levels in Red Delicious, Cortland, Spartan and Jerseymac and high levels in Golden Delicious, Gravenstein and Northern Spy. Levels of chlorogenic acid, offset by levels of phlorizin and catechins, distinguished between Red Delicious and Cortland. Rutin was important in distinguishing between Jerseymac and Spartan.