Wild oat continues to reduce spring wheat yields and profits despite the wide spread use of herbicides. Further reductions in the occurrence of wild oat could be achieved with the development of competitive cropping systems. Field studies were conducted to investigate the effects of wheat seed size and seeding rate on wild oat demographic processes under a range of wild oat densities. Spring wheat competitiveness increased as seed size and seeding rate increased, significantly reducing wild oat biomass and seed production. Averaged across all other factors, spring wheat plants derived from large seed reduced wild oat panicle numbers 15% and biomass and seed production 25% compared with small seed. Increasing spring wheat seeding rate from 175 to 280 plants m−2 reduced the number of panicles 10% and wild oat biomass and seed production 20%. The combined effect of large seed plus increased seeding rate reduced wild oat biomass and seed production 45%. Results demonstrate that the use of large seed size and increased seeding rates can improve wheat competitiveness and provide an effective means to reduce wild oat biomass and seed production.

Introduction. Mango productivityis low in seasonally wet-dry tropical areas where breeding programsrequire information on factors affecting productivity of mango cultivars.Specifically, our study tested a novel hypothesis that, among Australian-and Florida-bred cultivars, the greater growth of vegetatively vigorouscultivars would contribute to lower levels of fruit production in comparisonwith less vegetatively vigorous cultivars, in a wet-dry tropical environment. Materials and methods. A field experiment was conductedon trees of the cultivars ‘Kensington Pride’ and ‘Strawberry’, both polyembryoniccultivars, and ‘Haden’, ‘Irwin’ and ‘Tommy Atkins’, all monoembryoniccultivars. Results. Shoot growth was recorded overtwo years; in both years the polyembryonic cultivars produced morenew shoot length than the monoembryonic cultivars; ‘Irwin’ was theleast vigorous cultivar in both years. Across cultivars, there wasa negative relationship between normalised (by flowering intensity andcanopy area) fruit number or yield and vegetative vigour as representedby new shoot length. Conclusion. The results supportedthe hypothesis that the greater shoot growth of vegetatively vigorouscultivars contributed to lower levels of fruit production in comparisonwith less vegetatively vigorous cultivars in a tropical environment.This is the first study which demonstrates that the extent of seasonalshoot growth had a fruit production cost for mango.

Introduction. Probably because pomegranate trees are established in orchards as own-rooted plants, there are no studies regarding scion-rootstock combination effects on growth, tree size, yield and fruit quality of this fruit tree. Thus, the main aims of our experiment were to study the effects of some pomegranate rootstocks on growth and yield characteristics of Iranian commercial cultivars used as scions. Materials and methods. Our research was carried out between the 1999 and 2007 growing seasons at a collection of 760 pomegranate cultivars in the Yazd Province of Iran. Rootstocks were provided via clonal propagation using stem cuttings similar in height, diameter and age (2 years old) from ‘Golnar Farsi’, ‘Torsh Ma’ moly Zabol’, ‘Yek Killoy Hoshak Saravan’, ‘Poost Syah’, ‘Khafri Poost Sefid Jahrom’, ‘Zagh’, ‘Shavar’ and ‘Malas Esfahani’. Budding materials were provided from fruit-bearing trees in good vigor, using buds on current season growth of the ‘Zagh’, ‘Shavar’ and ‘Malas Esfahani’ pomegranate cultivars. Effects of the scion-rootstock combinations were investigated on tree size, vigor and yield of pomegranate. Results. The data indicated that grafting led to higher yield than the own-rooted plants, but grafted trees showed lower vigor and tree size compared with ungrafted trees. Application of ‘Torsh Ma’ moly Zabol’ as a rootstock led to the lowest tree size and height, and the lowest rate of sunburn scald disorder. The highest yield and the lowest sucker production were obtained in plants grafted on ‘Golnar Farsi’ rootstock. Conclusion. Our results suggest that application of ‘Torsh Ma’ moly Zabol’ as a rootstock can be useful to establish a high-density plantation.