This article is from the March 2009 issue of published by The American Phytopathological Society For more information on this and other topics related to plant pathology, we invite you to visit APSnet at www.apsnet.org Effect of a Chromosome Segment Marked by the Php Gene for Resistance to Phytophthora nicotianae on Reproduction of Tobacco Cyst Nematodes C. S. Johnson, Department of Plant Pathology, Physiology, and Weed Science and Southern Piedmont Agricultural Research and Extension Center, Virginia Polytechnic Institute and State University, Blackstone 23824; E. A. Wernsman, Crop Science Department, North Carolina State University, Raleigh 27695; and J. A. LaMondia, The Connecticut Agricultural Experiment Station, Valley Laboratory, Windsor 06095 cured tobacco cultivars subsequently iden- ABSTRACT tified as G. tabacum subsp. solanacearum- Johnson, C. S., Wernsman, E. A., and LaMondia, J. A. 2009. Effect of a chromosome segment resistant were originally developed for marked by the Php gene for resistance to Phytophthora nicotianae on reproduction of tobacco resistance to other tobacco pathogens, such cyst nematodes. Plant Dis. 93:309-315. as Tobacco mosaic virus (from N. gluti- nosa) and Pseudomonas syringae pv. sy- Host resistance is an important strategy for managing Globodera tabacum subsp. solanacearum ringae (from N. longiflora) (13,14). and G. tabacum subsp. tabacum, important nematode pests of flue-cured tobacco (Nicotiana High levels of resistance to race 0 of tabacum) in Virginia, and cigar wrapper tobacco (N. tabacum) in Connecticut and Massachu- Phytophthora nicotianae (causal agent of setts, respectively. Field research from 1992 to 2005 evaluated reproduction of G. tabacum subsp. solanacearum on genotypes with and without a chromosome segment from N. plum- tobacco black shank) have been incorpo- rated into flue-cured tobacco cultivars baginifolia containing a gene (Php) that conferred resistance to race 0 of Phytophthora nicotia- nae (causal agent of tobacco black shank). Ratios of G. tabacum subsp. solanacearum eggs/500 since the release of flue-cured tobacco cv. 3 cm soil at the end versus the beginning of experiments (Pf/Pi) were significantly lower in culti- Coker 371-Gold (C371G) in 1986. The vars and breeding lines possessing the Php-containing chromosome segment from N. plum- source of this resistance has been identi- baginifolia compared with genotypes without the segment. Numbers of vermiform G. tabacum fied as a gene (Php) located on a chromo- subsp. solanacearum juveniles in roots were similar among genotypes but numbers of swollen somal segment originally transferred inter- and pyriform nematodes were significantly lower for the known G. tabacum subsp. solanacea- specifically from N. plumbaginifolia rum-resistant cv. NC 567 and in genotypes possessing the Php gene compared with genotypes (6,17). Crowder et al. (9) concluded that and cultivars without the gene. In a 2003 greenhouse test, the percentage of plants with visible C371G also possessed an apparent single G. tabacum subsp. tabacum cysts was also significantly lower for parental and progeny geno- dominant gene for resistance to G. ta- types homozygous and heterozygous, respectively, for Php compared with similar lines without bacum subsp. solanacearum. The objective the gene. These results indicate a close linkage or association between a likely single, dominant of the work presented here was to investi- gene (Ph ) for resistance to P. nicotianae and suppressed reproduction by G. tabacum subsp. p gate the possibility of an association be- solanacearum and G. tabacum subsp. tabacum. Further research to accurately elucidate the relationships among these genes could lead to significant improvements in tobacco disease con- tween the chromosomal segment contain- trol. ing the single, dominant gene (Php) for resistance to P. nicotianae and suppressed reproduction of G. tabacum subsp. solana- cearum and G. tabacum subsp. tabacum. The tobacco cyst nematode species Asia; however, few of these reports indi- complex is comprised of three subspecies: cate the subspecies present (16). Yield MATERIALS AND METHODS Globodera tabacum subsp. tabacum losses caused by G. tabacum subsp. ta- General approaches. A field experi- ((Lownsbery & Lownsbery 1954) Behrens bacum can range from 5 to 45% on shade ment to evaluate resistance to G. tabacum 1975), G. tabacum subsp. virginiae tobacco (24). Losses in flue-cured tobacco subsp. solanacearum was conducted each ((Miller & Gray 1968) Behrens 1975), and yield due to G. tabacum subsp. solanacea- year in 1992–94, 1998–99, and 2001–05 in G. tabacum subsp. solanacearum ((Miller rum may average 15%, but complete crop G. tabacum subsp. solanacearum-infested & Gray 1972) Behrens 1975) (16). Al- failures have also occurred (15). Tobacco fields at the Southern Piedmont Agricul- though G. tabacum subsp. virginiae has producers with tobacco cyst nematode- tural Research and Extension Center been reported primarily from horsenettle infested fields routinely apply nematicides (SPAREC) near Blackstone, VA. Unless (Solanum carolinense L.), G. tabacum because the relatively high survival rate of otherwise indicated, all SPAREC experi- subsp. tabacum and G. tabacum subsp. the nematodes requires crop rotation inter- ments were arranged in a randomized solanacearum are important pathogens of vals too long to be economically viable. complete block design with four replica- shade and broadleaf tobacco (Nicotiana Host resistance is an attractive strategy tions, and field plots consisted of single tabacum L.) in Connecticut, and flue-cured for managing G. tabacum subsp. solana- 16.1-m-long rows spaced 1.2 m apart and tobacco in Virginia, respectively. Members cearum and G. tabacum subsp. tabacum containing approximately 24 plants. A of the tobacco cyst nematode complex given the relatively high survival rate of split-plot design was also used in some have been reported from over a dozen the nematodes and the increasing costs and experiments in order to compare yield and tobacco-producing countries in North and restrictions on effective nematicides. Re- quality traits when cultivars were chal- South America, Europe, North Africa, and sistance to G. tabacum subsp. solanacea- lenged by reduced versus large nematode rum has been identified in at least nine populations. Additional trials were con- wild Nicotiana spp., including Nicotiana ducted in 2001 in four commercial flue- Corresponding author: C. S. Johnson glutinosa, N. longiflora, and N. plum- cured tobacco fields in south-central Vir- E-mail: [email protected] baginifolia, and in numerous tobacco ac- ginia. All plots were mechanically trans- cessions and cultivars (1,16). Although planted and fertilized, and other cultural Accepted for publication 29 November 2008. several shade tobacco cultivars have been and pest control practices in all field ex- developed with resistance to G. tabacum periments conformed to recommendations doi:10.1094/ PDIS-93-3-0309 subsp. tabacum derived originally from N. of Virginia Cooperative Extension (26). © 2009 The American Phytopathological Society longiflora (23), all currently available flue- Additional greenhouse experiments were Plant Disease / March 2009 309 conducted in Connecticut in 2002 to consisted of single 16.1-m-long rows, was included only at the Wright farm, and evaluate whether the relationship between spaced 1.2 m apart, and containing ap- GL 973 (Phpphp) was not included at the resistance to G. tabacum subsp. solana- proximately 24 plants for each of nine G. Warren and Wright farms. Flue-cured to- cearum and P. nicotianae also included tabacum subsp. solanacearum-susceptible bacco cv. NC 810 (Phpphp) was included in resistance to G. tabacum subsp. tabacum. flue-cured tobacco cultivars without the the 2001 and 2003 SPAREC tests, but SP Nematode data collection. Initial Php gene (NC 27NF, NC 37NF, K 394, 179 (Phpphp), SP 190 (phpphp), and SP 210 nematode population densities were moni- Reams 134, Reams 158, Coker 319, (phpphp) were included only in the 2001 tored in each plot by collecting soil sam- McNair 944, VA 116, and K 326) and study, while NC291 (Phpphp) and GL 737 ples prior to transplanting, and are reported C371G, now known to be homozygous for (Phpphp) were only present in the 2003 in each table of this article. Final soil sam- the Php gene (PhpPhp) (17). Nematode experiment. Subplots at each farm site ples were collected at the end of the grow- population densities were estimated based consisted of four rows spaced 1.2 m apart. ing season, except in 2002 and 2005, when on soil samples collected before trans- Plot lengths were 86.9 m at the Jennings follow-up samples were collected on 22 planting (4 and 10 May in 1992 and 1993, site and 57.9 to 83.8 m, 53.3 m, and 82.3 August or 28 July, respectively. At least 24 respectively) and after final harvest (30 m at the Parrish, Warren, and Wright 2-cm-diameter by 16-cm-long soil cores September and 18 October in 1992 and farms, respectively. were bulked from each plot to form the 1993, respectively). Plant samples were Field testing of doubled haploid prog- plot sample at each sample date. G. ta- excavated from each plot row 44 days after eny lines against G. tabacum subsp. so- bacum subsp. solanacearum soil popula- transplanting in a 1994 SPAREC field test lanacearum. A 2002 experiment con- tion densities were estimated by extracting to evaluate relative G. tabacum subsp. ducted at SPAREC sought to more closely cysts from 250 cm3 of air-dried soil using a solanacearum parasitism of susceptible examine the influence of the chromosome modified Fenwick can (7), but are reported flue-cured tobacco cv. K 326, known G. segment containing the Php gene on G. in this article on a 500-cm3 basis to be tabacum subsp. solanacearum-resistant cv. tabacum subsp. solanacearum reproduc- consistent with Virginia Cooperative Ex- NC 567, and C371G (apparently G. ta- tion by evaluating G. tabacum subsp. so- tension nematode assay results. Eggs were bacum subsp. solanacearum-resistant, lanacearum parasitism and reproduction released from extracted cysts using a based on 1992 and 1993 results).