Atypical correlation of otolith strontium : calcium and barium : calcium across a marine–freshwater life history transition of a diadromous fish

Variation in strontium (Sr) and barium (Ba) within otoliths is invaluable to studies of fish diadromy. Typically, otolith Sr : Ca is positively related to salinity, and the ratios of Ba and Sr to calcium (Ca) vary in opposite directions in relation to salinity. In this study of jungle perch, Kuhlia rupestris, otolith Sr : Ca and Ba : Ca, however, showed the same rapid increase as late-larval stages transitioned directly from a marine to freshwater environment. This transition was indicated by a microstructural check mark on otoliths at 35–45 days age. As expected ambient Sr was lower in the fresh than the marine water, however, low Ca levels (0.4 mg L–1) of the freshwater resulted in the Sr : Ca being substantially higher than the marine water. Importantly, the otolith Sr : Ba ratio showed the expected pattern of a decrease from the marine to freshwater stage, illustrating that Sr : Ba provided a more reliable inference of diadromous behaviour based on prior expectations of their relationship to salinity, than did Sr : Ca. The results demonstrate that Ca variation in freshwaters can potentially be an important influence on otolith element : Ca ratios and that inferences of marine–freshwater habitat use from otolith Sr : Ca alone can be problematic without an understanding of water chemistry.

Efficacy of acibenzolar-S-methyl (Bion®) treatment of Australian commercial passionfruit, Passiflora edulis f. sp. flavicarpa, on resistance to Passionfruit woodiness virus (PWV) and activities of chitinase & β-1,3-glucanase

This greenhouse study investigated the efficacy of acibenzolar-S-methyl (Bion®) treatment of lower leaves of passionfruit, (Passiflora edulis f. sp. flavicarpa), on Passionfruit woodiness disease and activities of two pathogenesis-related proteins, chitinase and β-1,3-glucanase after inoculation with passionfruit woodiness virus (PWV). All Bion® concentrations reduced disease symptoms, but the concentration of 0.025 g active ingredient (a.i.)/l was the most effective, reducing disease severity in systemic leaves by 23, 29 and 30 compared with water-treated controls at 30, 40 and 50 days post inoculation (dpi) with PWV, respectively. Correspondingly, relative virus concentration as determined by DAS-ELISA in the upper, untreated leaves (new growth) above the site of inoculation at 50 dpi was reduced by 17 and 22 in plants treated with 0.025 and 0.05 g a.i./l, respectively. Bion® treatment and subsequent inoculation with PWV increased chitinase and β-1,3-glucanase activities in the new leaves above the site of inoculation at 30 dpi with PWV. It was concluded that optimal protective Bion® treatment concentrations were 0.025 and 0.05 g a.i./l.

Impact of 1-methylcyclopropene treatment on the sensory quality of 'Bartlett' pear fruit

The ethylene biosynthesis inhibitor, 1-methylcyclopropene (1-MCP), has been commercially used to extend the storage life of European pear fruit and to allow shipment to distant markets. However, the influence of 1-MCP on the ability of fruit to ripen to an acceptable sensory quality has not been investigated in 'Bartlett' pear, one of the most aromatic of pear fruit. In the current study, early-, mid- and late-season 'Bartlett' pear fruit were treated with 0.6μLL-1 1-MCP at 0°C for 24h, 100μLL-1 ethylene at 20°C for 24h, or untreated before immediate transfer to 20°C for ripening until eating soft (13N firmness). Fruit from each treatment were subjected to objective and sensory quality evaluation once ripe. Sensory quality showed differences related to harvest maturity; the importance of harvest maturity depended on the treatment. Treatment with 1-MCP effectively slowed fruit ripening and therefore extended postharvest life, but also resulted in fully ripened pears with more desirable sensory traits, as compared with ethylene-treated and untreated pears. The enhanced sensory quality was related to higher sweetness, juiciness and pear aroma and reduced fermented aroma, gritty texture and tart taste. In addition, the sensory profiles of 1-MCP-treated pears were more stable among fruit from the three harvest dates than the ethylene-treated pears, which exhibited very different sensory profiles between early- and late-season fruits. © 2015 Elsevier B.V.

Low-dose methyl bromide fumigation as a quarantine disinfestation treatment for nectarines against Queensland fruit fly (Diptera:Tephritidae)

White nectarines (Prunus persica var. nucipersica) were fumigated with methyl bromide (MB) at a nominal treatment dose of 18 g m-3 at 18°C for 5 h and 30 min as a quarantine disinfestation treatment against Bactrocera tryoni, the Queensland fruit fly. Three large scale trials were conducted against each of the four immature lifestages, eggs and first, second and third instars. There were no survivors from the estimated 43,614 eggs, 41,873 first instars, 41,345 second instars and 33,549 third instars treated, thereby resulting in an efficacy of GROTERDAN99.99% mortality at the 95% confidence level for each lifestage. Of the 12 trials reported herein, the highest concentration of MB, sampled from the chamber headspace analysed by gas chromatography, was 18.7 g m-3. The maximum chamber temperature from 5 min readings was 19.7°C and the maximum fruit core temperature was 19.5°C. The treatment time for all trials was exactly 5.5 h. Thus the recommended treatment dose to disinfest nectarines from B. tryoni is 19.0 g m-3 MB at 20.0°C for 5.5 h. Fruit quality trials were conducted on white nectarines at three combinations of treatment parameters: 15 g m-3 MB at 19°C for 5.25 h; 18 g m-3 MB at 19°C for 5.5 h and 21 g m-3 MB at 19°C for 5.5 h. The fruit were stored at 0, 4 and 8 days at 4°C and 8 days at 4°C followed by 4 d at 22°C. They were then were assessed for skin colour, flesh colour, skin defects, flesh defects, fruit weight loss, flesh firmness, total soluble solids, titratable acidity and rots. There was no significant difference between untreated control and MB treated fruits in any of the parameters measured. Thus the treatments did not have adverse effects on fruit quality.