Activity, isoenzymes and purity of mushroom tyrosinase in commercial preparations

Several lots of commercial tyrosinase preparations were examined with regard to their enzyme activity, isoenzyme composition and purity. Enzyme activity toward catechol, -dopa and tyrosine showed significant variations from lot to lot and activation by SDS. Distribution of isoenzyme forms also varied from lot to lot. Comparisons of electrophoretic and isoelectric focusing protein profiles showed considerable differences and distributions of the proteins in each sample. Tyrosinase appeared to be a minor component in each preparation when compared to a partially purified enzyme. Investigators using commercial tyrosinase should exercise caution in interpreting data due to the presence of different isoenzyme forms, their distribution in various lots, and the presence of numerous other proteins.     

Length-weight relationships of three Clupeiformes species from the Southeast coast of India,Bay of Bengal,Eastern Indian Ocean

This study deals with the length-weight relationships (LWRs) of three commercially important marine fishes belonging to the family Clupeidae from the major landing centers in Tuticorin, Mandapam, Thondi, Nagapattinam and Chennai in southeast coast of India. Monthly sampling were done at the respected landing centers from June, 2018 to April, 2019 from the commercial trawlers (with cod-end mesh size of 25–35 mm) and gill netters (with different mesh size vary from 20 to 170 mm). The estimated ‘b’ values ranged from 3.1215 (Sardinella albella) to 3.1819 (Amblygaster clupeoides) and ‘a’ values varied from 0.0059 (A. clupeoides) to 0.0074 (S. albella). The study also provides a new maximum total length (TL_max) for two species A. clupeoides and Sardinella fimbriata.     

Genetic characterisation of traditional chestnut varieties in Italy using microsatellites (simple sequence repeats) markers

European chestnut (Castanea sativa) is an important multipurpose tree that has been cultivated for wood and fruit in the Mediterranean basin since ancient times. Cultivation of traditional chestnut varieties has a long tradition in Italy, where cultivars have been selected over centuries as a function of the best nut traits. In this study, 94 grafted chestnuts corresponding to 26 representative cultivars from Italy were evaluated by seven simple sequence repeat (SSR) markers to establish whether they corresponded to varieties in the narrow sense. The results allowed 20 genotypes to be identified that corresponded to the same number of clones. In total, 52 alleles were identified, eight of which were exclusive. Cases of homonymies and synonymies were detected. Moreover, our results highlighted a considerable genetic uniformity among ‘Marrone-type’ cultivars and, on the contrary, a high genetic diversity among the evaluated cultivars demonstrating that this is a valuable germplasm and an important genetic resource to be preserved.     

Comparison of the effects of different virus infections on performance of three Majorcan grapevine cultivars in field conditions

The effects of viruses on grape production and must quality are not fully understood. In this study, the evaluation of the impact of different virus infections on performance of the main autochthonous grapevine varieties of Mallorca (Callet, Manto Negro and Moll) was pursued. Therefore, a large number of vines were observed in field conditions over 4 years and tested by enzyme-linked immunosorbent assay for viruses listed by the international certification programmes. In each variety, some specific virus infections resulted to be more effective than the others in inducing losses in production. In Callet, yield (Y) reduction was over 20% in plants infected by Grapevine fanleaf virus (GFLV). In Moll, plants subject to more than one infection showed over 40% Y decrease. In Manto Negro, the most surprising results were obtained, because plants showed almost 40% Y reduction because of Grapevine leafroll-associated virus-1 (GLRaV-1) infection. In addition, virus infections were linked to some must quality parameter increase in Manto Negro and Moll, but in the majority of cases it was an indirect effect, because the decrease in production parameters played a predominant role by producing an important concentration effect. However, in Manto Negro, anthocyanin content decrease was directly related to GFLV infection.     

Performance of the tobacco aphid Myzus persicae (Hemiptera: Aphididae) on Oriental and Virginia tobacco varieties

Abstract 1 The life parameters of one red and one green clone of Myzus persicae reared on 11 Oriental tobacco type varieties (KP7, K63, KZ10/z, MA13/b, BX2/a, N34/4, KP14/a, Kolindros, S79, TA21 and BX81) and on five Virginia ones (VE9, VE3, SPG28‐VE2, Kleio‐KN1 and Niki‐NK3) at 20 °C and LD 16 : 8 h were examined. 2 In general, the clones, performed better on Oriental than on Virginia type varieties. The varieties TA21 and Kolindros could be considered as the most resistant among the Oriental ones. Aphids on Virginia varieties showed longer developmental time (9.1–9.6 days), a lower intrinsic rate of increase (0.2347–0.2647) and higher nymphal mortality (27.9–52.5%) than on Oriental varieties. The corresponding values in the latter were 7.3–9.0 days, 0.2784–0.3302 and 10.0–47.9%. 3 The leaves of Virginia type varieties (188–471 hairs/cm²) and one Oriental (K63) 273 hairs/cm² were more hairy than the other Oriental type varieties (61–150 hairs/cm²). The Virginia type varieties showed also a lower level of reducing sugars (3.5–7.2%) than the Oriental ones (7.0–9.8%). Trichome density and level of reducing sugars were significantly negatively correlated with developmental time and intrinsic rate of increase. 4 An interclonal variation in performance, possibly related to the colour of aphids, was observed. The red clone performed better than the green one. The same trend was observed when the results of the previous clones on the variety KP14/a were analysed with the data obtained on the same variety from two other clones (one red and one green).