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Crown gall disease (Agrobacterium tumefaciens), crown/root rot disease (Phytophthora spp.), root lesion disease (Pratylenchus vulnus) and tree vigor are key traits affecting the productivity and quality of walnuts in California. Unchallenged hybrid rootstocks were analyzed by RNA-seq to examine pre-formed factors affecting these traits. Enrichment analysis of the differentially expressed genes revealed that the increased expression of cell wall biogenesis-related genes plays a key role in susceptibility to A. tumefaciens, susceptibility to Phytophthora spp. and increased vigor. Analysis of the predicted subcellular loci of the encoded proteins revealed that many gene products associated with vigor and susceptibility were targeted to the plasma membrane and extracellular space, connecting these traits to sustaining barrier function. We observed that RNA processing and splicing, along with predicted nuclear targeting, were associated with resistance to A. tumefaciens, resistance to Phytophthora spp. and low vigor. Four genes within the J. microcarpa QTL region for resistance to A. tumefaciens and Phytophthora spp. were represented among our transcripts, with two of the genes being differentially expressed in association with resistance to A. tumefaciens and decreased vigor. No differential expression related to Phytophthora spp. or P. vulnus resistance was observed in this region. Additionally, the J. microcarpa haplotype expressed more transcripts associated with resistance to A. tumefaciens, Phytophthora spp. and low vigor, but not P. vulnus, than the J. regia haplotype. We also report unique and shared hormone and defense responses associated with each trait. This research suggests a link between cell wall biogenesis, vigor and critical root diseases of walnut.

English walnuts are the walnut species of choice for nut production. In the United States, edible English walnuts are almost exclusively produced in California, using soil and water resources on more than 370,000 acres. Scion cultivars of English walnuts are grafted onto rootstocks. Traditional rootstocks are seedling populations of so-called Paradox hybrids generated from crosses of black walnut with English walnut. These rootstocks are susceptible to soil-borne diseases, including crown gall, Phytophthora root and crown rot, and plant-parasitic nematodes. Strategies to respond to these diseases include the use of newly developed clonal walnut rootstocks with genetic resistance. In a survey conducted during 2020 through 2021, walnut growers revealed their willingness to pay higher prices for clonal walnut rootstocks with some disease resistance. The survey showed that they were most concerned with crown gall and nematodes, and were willing to pay significant price premiums for rootstocks that are resistant to these pathogens.

Soil-borne plant pathogens represent a serious threat that undermines commercial walnut (Juglans regia) production worldwide. Crown gall, caused by Agrobacterium tumefaciens, and Phytophthora root and crown rots, caused by various Phytophthora spp., are among the most devastating walnut soil-borne diseases. A recognized strategy to combat soil-borne diseases is adoption of resistant rootstocks. Here, resistance to A. tumefaciens, P. cinnamomi, and P. pini is mapped in the genome of Juglans microcarpa, a North American wild relative of cultivated walnut. Half-sib J. microcarpa mother trees DJUG 31.01 and DJUG 31.09 were crossed with J. regia cv. Serr, producing 353 and 400 hybrids, respectively. Clonally propagated hybrids were genotyped by sequencing to construct genetic maps for the two populations and challenged with the three pathogens. Resistance to each of the three pathogens was mapped as a major QTL on the long arm of J. microcarpa chromosome 4D and was associated with the same haplotype, designated as haplotype b, raising the possibility that the two mother trees were heterozygous for a single Mendelian gene conferring resistance to all three pathogens. The deployment of this haplotype in rootstock breeding will facilitate breeding of a walnut rootstock resistant to both crown gall and Phytophthora root and crown rots.

In April-August 2018, samples of galled roots with rhizosphere soil were collected from almond orchards in Atwater, Merced County and Bakersfield, Kern County, California. Almond trees (Prunus dulcis) grafted on ‘Hansen 536’ and ‘Brights Hybrid®5’ (peach-almond hybrid) rootstocks showed strong symptoms of growth decline. Extracted root-knot nematodes were identified by both morphological and molecular methods as M. floridensis. Meloidogyne floridensis was initially found in Florida, USA, and has not been reported from any other states and countries. This is a first report of M. floridensis in California and outside of Florida.

The immune system is tightly controlled by regulatory processes that allow for the elimination of invading pathogens, while limiting immunopathological damage to the host. In the present study, we found that conditional deletion of the cell surface receptor Toso on B cells unexpectedly resulted in impaired proinflammatory T cell responses, which led to impaired immune protection in an acute viral infection model and was associated with reduced immunopathological tissue damage in a chronic inflammatory context. Toso exhibited its B cell-inherent immunoregulatory function by negatively controlling the pool of IL-10--competent B1 and B2 B cells, which were characterized by a high degree of self-reactivity and were shown to mediate immunosuppressive activity on inflammatory T cell responses in vivo. Our results indicate that Toso is involved in the differentiation/maintenance of regulatory B cells by fine-tuning B cell receptor activation thresholds. Furthermore, we showed that during influenza A-induced pulmonary inflammation, the application of Toso-specific antibodies selectively induced IL-10--competent B cells at the site of inflammation and resulted in decreased proinflammatory cytokine production by lung T cells. These findings suggest that Toso may serve as a novel therapeutic target to dampen pathogenic T cell responses via the modulation of IL-10--competent regulatory B cells., Introduction A key feature of the immune system is the maintenance of a delicate balance between protecting against infectious agents and minimizing immune-mediated tissue damage. To achieve this critical equilibrium, [...]

Soybean cultivars of maturity groups II to IV were tested in the greenhouse for resistance to Meloidogyne incognita (Kofoid and White) Chitwood. Selected cultivars were tested in a field of sandy loam soil naturally infested with M. incognita and Heterodera glycines Ichinohe (2004) or in a silt loam soil artificially infested with M. incognita (2005). In 2004, H444NRR was resistant to M. incognita, but not to H. glycines; LS943207 and LNX97164-35-5 were resistant to both nematodes; Gateway 427, H444NRR, LNX9716435-5, and SB4399CT were moderately resistant to M. incognita in greenhouse tests; HF96652-15 was resistant to M. incognita but highly susceptible to H. glycines. In 2005, LS94-3207, H444NRR, LNX97164-35-5, and Manokin were resistant to M. incognita. In microplots with two sandy loam soils, HF9665-2-15 exhibited tolerance to increasing inoculum levels of M. incognita. High-yielding soybean cultivars in maturity groups II to IV with resistance and tolerance to M. incognita were identified. Under field conditions, resistance to the more widespread nematode H. glycines, combined with resistance to M. incognita, is highly desirable to reduce the risk of yield reduction and to improve cropping sequences that include soybean.

Rotylenchulus reniformis Linford & Oliveira is increasing in incidence in cotton-growing areas throughout the southern USA east of New Mexico. Cotton (Gossypium hirsutum L.) cultivars resistant to R. reniformis are currently unavailable. Management depends on a crop sequence with nonhosts of the nematode. In South Texas, the sequence of cotton with grain sorghum [Sorghum bicolor (L.) Moench] or corn (Zea mays L.) has become a standard practice. To improve farm efficiency, the implementation of rotation crops that are economically superior to grain sorghum is desirable. Eighteen cultivars of soybean [Glycine max (L.) Merr.] were tested in nonfumigated and in fumigated sandy loam soil infested with R. reniformis to evaluate nematode resistance of soybean under field conditions. Shank application of 1,3-dichloropropene at a 38-cm depth reduced R. reniformis population densities at the 15- to 60-cm depth compared with preseason counts. The effect of each soybean cultivar on the growth and yield of a subsequent cotton crop was compared with the impact of grain sorghum and fallow. High-yielding cultivars of soybean (HY574, Padre, DP7375RR, and NK83-30) with reniform nematode-suppressing potential were identified among cultivars within maturity groups 5, 6, 7, and 8. In contrast, cotton yields following the susceptible cultivars Santa Rosa-R, Vernal, and DP6880RR were on average 25% lower than those following grain sorghum. The enrichment of cotton sequences with reniform nematode-resistant soybean cultivars is viable when the proper cultivars are chosen, whereas the use of reniform nematode-susceptible soybean cultivars is discouraged. The effective use of R. reniformis-resistant soybean cultivars to manage R. reniformis in cotton will depend on a number of additional economic parameters not studied in these experiments., INTEGRATED MANAGEMENT uses all cultural tools and control measures that keep soil-borne diseases and plant-parasitic nematodes under economic threshold levels. Strategies can include the use of host plant resistance, crop [...]