The relative susceptibility of grapevine rootstocks to black foot disease is dependent on inoculum pressure

Black foot disease of grapevines is a major economic issue for the viticulture industry worldwide. The disease is mainly associated with a complex of pathogen species within the genera Dactylonectria and Ilyonectria. The susceptibility of six grapevine rootstock cultivars to black foot disease under field conditions was assessed. Callused rootstocks of 101-14, 5C, 420A, Riparia Gloire, Schwarzmann and 3309C were planted into soil containing low natural pathogen populations or inoculated with isolates representing the species diversity in New Zealand. Disease incidence, disease severity and dry weight accumulation were assessed after 8 months of growth. Root and shoot dry weights were not significantly affected by inoculation treatment, but differed among rootstock cultivars, with cultivar 420A having the lowest root and shoot dry weight, cultivar 3309C having the largest shoot dry weight and cultivar 5C the largest root dry weight. The relative susceptibility of rootstocks differed significantly depending on whether they were grown under low natural inoculum pressure or a higher pressure in artificially inoculated soil. Schwarzmann and Riparia Gloire rootstock cultivars were the least susceptible under natural low inoculum pressure, but were the most susceptible in inoculated soil. In contrast, 5C was one of the most susceptible under low inoculum levels but was the least susceptible under high pathogen pressure. The result of the study indicate that black foot pathogen inoculum levels in soil affect the relative susceptibility of grapevine rootstocks to infection, and may have implications for the selection of rootstocks for planting.

High regional and intra-generic variation in susceptibility to mass bleaching in Indo-Pacific coral species

AimMass bleaching is a major threat to reef-building corals and the ecosystems they underpin. Here, we identified regional variation in the nature of this threat in terms of the bleaching-susceptibility of individual coral species on some Indian Ocean and Pacific Ocean reefs.Location22 sites in the central Great Barrier Reef, Australia (GBR) and 30 sites in the central Maldives Archipelago (MA).Time period2002 for the GBR and 2016 for the MA.Major taxa studiedCorals (Order Scleractinia).MethodsFollowing marine heat-wave conditions, timed in-situ surveys were used to record bleaching responses (tissue colour) of large samples of individual coral colonies. Responses of 106 shared species were analysed for sites with similar levels of temperature stress, depth of occurrence and mortality. In each region, phylogenetic mixed models were used to partition the effects on responses of species of deep-time phylogeny, contemporary history and local-scale, among-site variability.ResultsRelative susceptibility to bleaching varied widely between regions: only 27 of the 106 shared species were in the same quartile for relative susceptibility in both regions. Few species were highly susceptible in both regions. Closely related species varied widely in their individual susceptibilities. Phylogenetic effects were moderate in both regions, but contemporary phenotypic effects indicative of recent evolution and acclimatization were greater in the MA, consistent with a stronger history of recent bleaching.Main conclusionsThe high regional and intra-generic variation in coral bleaching-susceptibility described here suggests there may be important differences in the extent to which these Indian and Pacific Ocean coral populations are exhibiting responses to deep-time evolutionary changes on the one hand, versus recent adaptation, on the other. There is a concerning scarcity of this type of data, by which coral species most at risk from bleaching in particular regions may be more accurately identified.

Estimating COVID-19 pandemic severity in Indian context

The case fatality rate (CFR) represents one of the most vital factors in demonstrating the severity of novel infectious disease, COVID-19. Various estimates of COVID-19 fatalities (based on the publicly and published information and data in Indian context of COVID-19): confirmed CFR, asymptomatic CFR, symptomatic CFR, and hospitalized CFR were 2.32% (2.05-2.59), 0.14% (0.12-0.16), 0.32% (0.27-0.36), 1.86% (1.64-2.07) respectively. The relative susceptibility of developing symptoms (RSODS) and relative susceptibility of developing infection (RSODI) of COVID-19 were ~33 times higher among people aged <45 years. The RSODS estimates were 1.97 (0.47-3.47), 0.62 (0.15-1.09), 0.29 (0.07-0.52), 0.06 (0.02-0.10) respectively, for patients <45 years, 45-60, 60-75, >75 years. Similar trend, for RSODI were found, with relatively higher value, compared to RSODS, which decreased with the increase of age. The 14-day lag estimate of CFR were 18.07 (15.67-20.47), and outcome (deaths plus recoveries)-based estimate of CFR were 16.57 (14.65-18.49). The growth rate, serial interval, reproduction number and average time from onset of COVID-19 infection to death were 6.12% (5.30%-6.99%), 11.4 days (9.91-12.85), 1.03 (1.01-1.05), and 11.85 days (10.55-13.15), respectively. Among 1,673,688 samples tested, 62,939 (3.76%) were positive for COVID-19 accounting 1,228 tests per million population of India, as of May 10, 2020. The average daily recovery was 19.45% (14.75- 24.15) and average cumulative recovery was 12.68% (10.70- 14.66) among COVID-19 patients. As per our belief and knowledge, this is the first study of its kind in reporting COVID-19 severity in Indian context during pandemic.

Screening of Coriander Genotypes for their Relative Susceptibility against Aphids under Field Conditions

The field experiments were conducted during Rabi 2013-14 and 2014-15 to screen out twelve varieties/entries of coriander (Coriandrum sativum L.) for their relative susceptibility against aphids. None of the varieties/entries escaped the infestation of aphids. The build-up of aphid infestation started from second half of December and reached to its maximum in the first to third week of February in both years and then gradually declined. On the basis of grade index of mean aphid population, coriander varieties RCr- 684 (25.45 aphids/plant), RCr-446 (26.45 aphids/plant), ACr-1 (26.60 aphids/plant), RCr- 436 (41.75 aphids/plant), Gujarat Coriander-2 (42.45 aphids/plant), Pant Haritma (43.50 aphids/plant) and Gujarat Coriander-1 (43.70 aphids/plant) were categorized as least susceptible, Rajendra Swati and RCr-41 were moderately susceptible, whereas, Swati (CS-6), Sadhna (CS-4) and Sindhu (CS-2), 73.88, 70.60 and 69.50 aphids/plant, respectively were categorized as highly susceptible varieties of coriander against aphids under field conditions. Coriander variety RCr-684 received maximum yield (16.82 and 16.63 q/ha) for both the years followed by ACr-1 and RCr-446.