VX211, a vigorous new walnut hybrid clone with nematode tolerance and a useful resistance mechanism

VX211 is a highly vigorous Paradox hybrid clone that outgrew other walnut seedlings in the presence of nematodes. A four-year macroplot trial involving Paradox VX211 and a standard Paradox selection, AX1, demonstrated that the damage threshold level of Pratylenchus vulnus on commercially available walnut rootstocks is < 1 nematode/250 cm³ of soil. Using 1 as the initial population level (Pi) within an inoculation zone of 80 L of soil, the P. vulnus population level increased 2,500-fold in the first year of growth. Three years after inoculation soil population levels of P. vulnus on VX211 were significantly reduced compared to that of the moderately vigorous AX1. Growth of VX211 was 35% greater than that of AX1 regardless of the Pi. Examination of stained roots revealed that feeding and reproduction by P. vulnus on VX211 was primarily ectoparasitic. This is the first report on a new walnut rootstock that can be readily cloned, has high vigor, exhibits tolerance to low population levels of P. vulnus, reduces nematode feeding and reproduction within the root terminus, and is currently available to California growers.

Splenic tuberculosis presenting as pyrexia of unknown origin

We report a case of a previously healthy 38-year old lady who presented with prolonged fever and hepatosplenomegaly. Intensive investigations were performed for pyrexia of unknown origin which revealed negative. CT scan of the abdomen showed multiple hypodense lesions which did not respond to broad-spectrum antibiotics. Percutaneous biopsy of the splenic lesion revealed granuloma formation and Langhan's giant cells suggestive of TB. She responded well with anti- TB medication but required extended treatment duration of 24 months due to persistence of the splenic lesion on repeated CT scans. This case illustrates a very rare clinical entity of isolated splenic TB with a therapeutic dilemma following incomplete resolution, despite prolonged treatment.

Reproductive Variability of Field Populations of Meloidogyne spp. on Grape Rootstocks

Variability in penetration, development, and reproduction of two resistance-breaking field pathotypes (pt.) of Meloidogyne arenaria, M. incognita, and a population of mixed Meloidogyne spp. virulent to grape hosts were compared on two resistant Vitis rootstocks 'Freedom' and 'Harmony' in separate tests. 'Cabernet Sauvignon' was included as a susceptible host to all four nematode populations. Secondstage juveniles (J2) of the mixed population failed to penetrate Freedom roots. By contrast, 6% of J2 in the M. incognita population penetrated Freedom roots but did not develop beyond the swollen J2 stage. The two resistance-breaking populations of M. arenaria differed in their virulence except on susceptible roots of Cabernet Sauvignon. More J2 of M. arenaria pt. Freedom penetrated Freedom roots and reached adult stage than did M. arenaria pt. Harmony. Later life stages of M. arenaria pt. Freedom occurred earlier and in greater numbers in Harmony roots than did M. arenaria pt. Harmony. Reproduction of M. arenaria pt. Freedom was greater in Freedom and Harmony roots than M. arenaria pt. Harmony. Thus, one population of M. arenaria is highly virulent and the other is moderately virulent.

Influence of four nematodes on root and shoot growth parameters in grape

Two grape cultivars, susceptible French Colombard and tolerant Rubired, and four nematodes, Meloidogyne incognita, Pratylenchus vulnus, Tylenchulus semipenetrans, and Xiphinema index, were used to quantify the equilibrium between root (R) and shoot (S) growth. Root and shoot growth of French Colombard was retarded by M. incognita, P. vulnus, and X. index but not by T. semipenetrans. Although the root growth of Rubired was limited by all the nematodes, the shoot growth was limited only by X. index. The R:S ratios of Rubired were higher than those of French Colombard. The reduced R:S ratios of Rubired were primarily an expression of reduction in root systems without an equal reduction in shoot growth, whereas in French Colombard the reduced R:S ratios were due to a reduction in both shoot growth and root growth and to a greater reduction in root growth than shoot growth. All nematodes reproduced equally well on both cultivars. Both foliage and root growth of French Colombard were significantly reduced by M. incognita and P. vulnus. Nematodes reduced the shoot length by reducing the internode length. Accumulative R:S ratios in inoculated plants were significantly smaller than those in controls in all nematode treatments but not at individual harvest dates. Bud break was delayed by X. index and was initiated earlier by P. vulnus and M. incognita. All buds in nematode treatments were less vigorous than in controls.