Multivariate analysis of superficial scald susceptibility on Granny Smith apples dipped with different postharvest treatments

Multivariate methods were used to present the results of different postharvest treatments applied to control superficial scald disorder in Granny Smith apples. In a two-season study, the treatments applied by dips were diphenylamine (DPA), Semperfresh (a sucrose ester coating) formulated alone or with either ascorbyl palmitate or n-propyl gallate, and CaCl(2). DPA correlated negatively with scald, whereas the rest of the treatments showed no clear relationship with the disorder. By means of partial least squares, the incidence of superficial scald after cold storage was shown to correlate with quality parameters (firmness and acidity), measured at the end of storage. In contrast, ethylene production did not appear as a relevant factor in the incidence of scald.     

A survey of Lolium rigidum populations in citrus orchards: Factors explaining infestation levels

The presence of herbicide‐resistant Lolium rigidum in Mediterranean (Spanish) citrus orchards was reported in 2005 and it poses a serious threat to crop management. The main objective of this research was to investigate which components could be responsible for the persistence of annual ryegrass populations in Mediterranean mandarin and orange orchards. This is the first study regarding L. rigidum populations in Mediterranean citrus orchards. Surveys were conducted in 55 commercial citrus orchards in eastern Spain in 2013 by interviewing technicians who were working in cooperatives about crop management. The level of infestation by L. rigidum and the presence of harvester ants (Messor barbarus) then were estimated in the same orchards. The variables were subjected to a two‐dimensional analysis and both univariate and multivariate logistic regression models were fitted for each of the three L. rigidum density levels that had been established. The multivariate models showed the significant factors that were associated with various L. rigidum densities: (i) at a low density, the herbicides that were applied, the number of applications in 2013 and the type of irrigation (flood or drip); (ii) at a medium density, the presence of harvester ants; and (iii) at a high density, the herbicides that were applied in 2013. The results indicated that drip irrigation and one application of glyphosate mixed with other herbicides (or herbicides other than glyphosate) were associated with a lower L. rigidum density. The alternative management options that are presented here should help farmers to reduce weed problems in Mediterranean citrus orchards. Future research is required to better understand the presence of herbicide‐resistant populations, as well as the possible beneficial presence of granivorous ant species.     

Describing Polygonum aviculare emergence in different tillage systems

Effects of four tillage systems (direct drill, subsoiler, chisel plough and mouldboard plough) on the dynamics of Polygonum aviculare populations were studied over three growing seasons. Cumulative emergence on a weekly basis was determined. Cumulative emergence from two years of chisel ploughing was used to develop an emergence model for P. aviculare based on hydrothermal time. Results showed that direct drilling, which had the highest seed yields of winter cereal crops every season, was the unique soil management system that lowered P. aviculare populations because of effective weed emergence reduction. The model accurately described seedling emergence in different tillage systems, although it failed in direct drilling, probably due to very low numbers of emerged seedlings. To better control this weed, direct drilling may be the best tillage option, but if this cannot be implemented, the hydrothermal time model is a practical tool that can describe the relative proportions of emergence and assist in the timing for management operations of P. aviculare in different tillage systems.     

INTERRELATION BETWEEN FRUIT MINERAL CONTENT AND PRE-HARVEST CALCIUM TREATMENTS ON ‘GOLDEN SMOOTHEE’ APPLE QUALITY

The effects of different pre-harvest calcium treatments and their interrelation with other nutrients in apples (Malus domestica Borkh, ‘Golden Smoothee’) on quality attributes at harvest and after cold storage and on relation between calcium (Ca) and other nutrients were investigated. Calcium sprays were applied during three-seasons beginning 60 days after full bloom (DAFB), with 6 or 12 applications in the second part of the growing season. It was confirmed that calcium treatments generally resulted in increased flesh firmness at harvest but not sufficient to maintain during storage. Treatments reduced bitter pit and lenticel blotch pit after cold storage, but these disorders were not totally eliminated. The treatments did not influence evolution of titratable acidity and soluble solids. Total fruit calcium increased with number of applications, but this increase was not proportional with number of applications. The beneficial effect of calcium treatments was reflected in the nitrogen/Calcium (N/Ca), potassium/calcium (K/Ca), and (K+Mg)/Ca ratios.     

Demography of Lolium rigidum in winter barley crops: analysis of recruitment,survival and reproduction

Demographic studies were conducted with Lolium rigidum Gaud. growing in winter barley crops at five sites in central and eastern Spain, over a period of 2 or 3 years. Although threefold differences (34–97%) in annual recruitment were recorded in the various experiments, most of the values were close to the overall average (67%). Seedling emergence took place in a very short period of time after sowing, with 90% emergence generally being reached after a thermal time of 242 d°C (provided soil moisture was adequate at sowing). Seedling survival was very high (78–95%) in most experiments, with no clear relationship between this parameter and any of the environmental variables studied. Survival curves were relatively linear, with plant mortality increasing gradually throughout the life cycle of the plant. There were 34‐fold differences (from 7 to 237 seeds per plant) in the fecundities recorded in the various experiments. Variation in fecundity resulted partly from differences in crop and weed densities and total precipitation received during the growth cycle. The annual rate of population growth was estimated based on the above‐mentioned parameters. The potential for population growth was high (average λ=6.21), but large differences were obtained for the different sites and years.     

Reviewing research priorities in weed ecology,evolution and management: a horizon scan

Weedy plants pose a major threat to food security, biodiversity, ecosystem services and consequently to human health and wellbeing. However, many currently used weed management approaches are increasingly unsustainable. To address this knowledge and practice gap, in June 2014, 35 weed and invasion ecologists, weed scientists, evolutionary biologists and social scientists convened a workshop to explore current and future perspectives and approaches in weed ecology and management. A horizon scanning exercise ranked a list of 124 pre‐submitted questions to identify a priority list of 30 questions. These questions are discussed under seven themed headings that represent areas for renewed and emerging focus for the disciplines of weed research and practice. The themed areas considered the need for transdisciplinarity, increased adoption of integrated weed management and agroecological approaches, better understanding of weed evolution, climate change, weed invasiveness and finally, disciplinary challenges for weed science. Almost all the challenges identified rested on the need for continued efforts to diversify and integrate agroecological, socio‐economic and technological approaches in weed management. These challenges are not newly conceived, though their continued prominence as research priorities highlights an ongoing intransigence that must be addressed through a more system‐oriented and transdisciplinary research agenda that seeks an embedded integration of public and private research approaches. This horizon scanning exercise thus set out the building blocks needed for future weed management research and practice; however, the challenge ahead is to identify effective ways in which sufficient research and implementation efforts can be directed towards these needs.     

Macronutrient accumulation dynamics in apple fruits

In this study, we assessed the macronutrient levels of apple fruits cv. “Golden Smoothee” by monitoring their fruit absorption rates (mg fruit^?1 day^?1) and accumulation patterns (mg fruit^?1) throughout fruit development. Nutrient accumulation was a continuous process throughout the growing season, with patterns of absorption rates varying according to the nutrients concerned. Calcium was chiefly absorbed by the fruit during the first developmental stage, while the greatest absorption rates of other macronutrients occurred later in fruit development (from the end of shoot growth until harvest). From these patterns, it would be desirable to reduce the supply natural calcium (Ca) antagonists, such as potassium (K), ammonium (NH⁴⁺), and magnesium (Mg), during the first part of fruit development in order to achieve a good Ca balance with other nutrients and, consequently, an optimum fruit quality. Knowing these nutrient absorption and accumulation patterns is essential for planning optimum nutrient supply and improving their influence on fruit quality.     

A qualitative quick-test for detection of herbicide resistance to tribenuron-methyl in Papaver rhoeas

A qualitative seed-based method useful for the detection of resistance to the herbicide tribenuron-methyl in Papaver rhoeas L. is described. Seeds were germinated on 35 mL of a 1.3% agar medium containing 2 g KNO₃ L^–1 in 8.5 cm Petri dishes in a growth chamber under 20 μmol s^–1 m^–2 of fluorescent light. When 0.24 μM tribenuron-methyl or more was added, growth in susceptible plants stopped after the cotyledon stage and they turned chlorotic. The resistant plants continued developing new leaves. The same effect was achieved when 0.2 g gibberellin (GA₃) L^–1 and 7.68 μM tribenuron-methyl or 0.5 g GA₃ L^–1 and 61.44 μM tribenuron-methyl were added. Germination percentage rose with gibberellin in the presence or absence of the herbicide. Plants developed rapidly, with only about 14 d needed to finish the test but sometimes root growth was reduced because of the addition of gibberellin. In the absence of gibberellin but in the presence of the herbicide, plants grew more slowly and developed smaller leaves with a 17-d evaluation period requirement. The test was validated with pot experiments in a greenhouse and also with field trials. The best combination was found to be 0.2 g GA₃ L^–1 and 7.68 μM tribenuron-methyl, assuring homogenous germination and testing of dormant seeds but avoiding root inhibition associated with too much gibberellin.