Papers by Chandrasekar Kousik
Compendium of Plant Genomes
Hortscience, Dec 1, 2017
A greenhouse trial was used to evaluate 159 accessions of bottle gourd [Lagenaria siceraria (Mol.... more A greenhouse trial was used to evaluate 159 accessions of bottle gourd [Lagenaria siceraria (Mol.) Standl.] obtained from the U.S. National Plant Germplasm for tolerance to clomazone herbicide. Most accessions tested were moderately or severely injured by clomazone at 3.0 mg • kg L1 incorporated into greenhouse potting medium; however, several exhibited lower injury. Seeds were produced from tolerant and susceptible plants for use in a greenhouse concentration-response experiment. About three to four times higher clomazone concentrations were required to cause moderate injury to tolerant bottle genotypes in comparison with susceptible genotypes. The differences in tolerance among genotypes were observed with injury ratings, chlorophyll measurements, and shoot weights. Clomazone may be used safely on tolerant bottle gourd genotypes, but the herbicide may not be safe for susceptible genotypes. Also, tolerant genotypes such as Grif 11942 may be desirable for use as rootstocks in grafted watermelon production.
Phytopathology, Feb 15, 2009
Phytophthora capsici Leonian is a destructive oomycete plant pathogen that causes diseases in a w... more Phytophthora capsici Leonian is a destructive oomycete plant pathogen that causes diseases in a wide range of crops worldwide. Benzothiostrobin is a broad-spectrum strobilurin fungicide that may control pepper Phytophthora blight. In the current study, the sensitivities of 90 P. capsici isolates collected from different regions in southern China to benzothiostrobin were measured. The curative and protective effects of benzothiostrobin against pepper Phytophthora blight were also determined. The formation of sporangia was inhibited by lower concentrations of benzothiostrobin, approximately 1 μg mL −1 on V8 media, than was necessary to inhibit zoospore discharge. The frequency distribution curve for the benzothiostrobin sensitivity was unimodal with mean EC 50 values of 1.84 ± 0.24, 0.60 ± 0.10 and 4.44 ± 0.27 for inhibiting mycelial growth, sporangia formation and zoospore discharge, respectively. The P. capsici isolates used in this study exhibited decreased sensitivity to several commonly used effective fungicides, including mefenoxam, cyazofamid, fluazinam and propamocarb. Furthermore, benzothiostrobin had no cross-resistance with azoxystrobin, pyraclostrobin or famoxadone. The disease severity of pepper Phytophthora blight on pepper leaves and plants was dramatically reduced by benzothiostrobin application of 150 μg mL −1. Benzothiostrobin provided both curative and protective properties against pepper Phytophthora blight on detached pepper leaves and potted pepper plants, with greater protective activity than curative activity. These results suggested that benzothiostrobin may be used for the management of P. capsici.
Plant Disease, Aug 1, 2013
In an effort to develop bottle gourd (Lagenaria siceraria) as a widely adapted rootstock for wate... more In an effort to develop bottle gourd (Lagenaria siceraria) as a widely adapted rootstock for watermelon grafting, we sought to identify lines with broad resistance to several cucurbit viruses that are economically important in the United States. Preliminary analysis under greenhouse conditions indicated that the currently available commercial watermelon rootstocks were either highly susceptible or somewhat tolerant to one or more viruses. However, in greenhouse screening, several breeding lines of bottle gourd displayed broad-spectrum resistance to four viruses tested, including Zucchini yellow mosaic virus, Watermelon mosaic virus (WMV), Papaya ringspot virus watermelon strain (PRSV-W), and Squash vein yellowing virus. Resistance to PRSV-W and WMV was confirmed through field trials in two consecutive years at two different locations in South Carolina. Two breeding lines (USVL#1-8 and USVL#5-5) with broad-spectrum virus resistance could be useful materials for watermelon rootstock development.
Phytopathology, 1996
... Auteur(s) / Author(s). KOUSIK CS (1) ; SANDERS DC ; RITCHIE DF (1) ; Affiliation(s) du ou des... more ... Auteur(s) / Author(s). KOUSIK CS (1) ; SANDERS DC ; RITCHIE DF (1) ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). (1) Department of Plant Pathology, Box 7616, North Carolina State University, Raleigh 27695, ETATS-UNIS Résumé / Abstract. ...
Phytopathology, Mar 1, 2002
The pepper genotype, ECW-12346, was developed with bacterial spot resistance derived from Pep13, ... more The pepper genotype, ECW-12346, was developed with bacterial spot resistance derived from Pep13, PI 271322, and ECW123 (Early Calwonder containing Bs1, Bs2, and Bs3 genes). For genetic analysis of this resistance, ECW12346, ECW123, F 1 , F 2 , and backcrosses were inoculated with a pepper race 6 (P6) strain. Two recessive genes were identified that determined resistance. The genes are designated bs5 and bs6 for the resistance derived from PI 271322 and Pep13, respectively. In greenhouse and field studies, ECW12346 was highly resistant, whereas ECW123 had significant defoliation. In growth-room studies, electrolyte leakage and population dynamics were determined. Following infiltration of both genotypes with 10 8 CFU/ml of a P6 strain, there was no rapid increase in electrolyte leakage within 72 h, whereas a rapid increase in electrolyte leakage occurred within 24 h when a similar concentration of a P3 strain (containing the avrBs2 gene) was infiltrated into the intercellular spaces of the leaf. When 10 5 CFU/ml of a P6 strain was infiltrated into leaves, complete tissue collapse was evident in ECW123 10 days later as determined by visual assessment and electrolyte leakage data, but no confluent necrosis was detected in ECW12346. Internal populations were at least two logarithmic units higher in ECW123 than in ECW12346. Therefore, ECW12346 inhibits population build-up without inducing the typical hypersensitive reaction characterized by an increase in electrolyte leakage.
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Plant Health Progress, 2020
Watermelon is an important cucurbit crop grown in 44 states in the United States of America (USA)... more Watermelon is an important cucurbit crop grown in 44 states in the United States of America (USA). South Carolina (SC) had the seventh largest watermelon production area in USA with 4,500 acres in 2018 valued at approximately $17 million. In June 2019, four watermelon plants displaying symptoms of virus infection including stunting, leaf crumpling, interveinal chlorosis, and necrosis of leaf margins were observed in a research trial in Charleston, SC. Whiteflies were observed on the abaxial surface of the leaves. One plant was tested for the presence of whitefly-transmitted cucurbit leaf crumple virus (CuLCrV), cucurbit yellow stunting disorder virus (CYSDV), and squash vein yellowing virus and aphid-transmitted papaya ringspot virus by RT-PCR. Amplicons of the expected size were only observed for CuLCrV (∼1 kb) and CYSDV (∼0.7 kb). Because CYSDV was not previously reported from SC, we continued to monitor the field for virus symptoms during the summer season. By mid-August 2019, 15 additional plants (1.9% incidence) were observed with similar symptoms of virus infection. Two virus identification methods (CP and Hsp70h) confirmed that CYSDV was indeed present in watermelon samples in SC. The geographic range of CYSDV and other whitefly-transmitted viruses continues to expand into and within major cucurbit-producing regions with each production season, especially in the southeastern USA. This is the first report of CYSDV infecting watermelon or any other plant in SC. These three whitefly-transmitted viruses now need to be considered in management plans by SC growers. Knowledge of the presence of CYSDV, an additional virus, infecting cucurbits, in SC is also important from a regulatory perspective.
Phytopathology, Nov 1, 1999
Kousik, C. S., and Ritchie, D. F. 1999. Development of bacterial spot on near-isogenic lines of b... more Kousik, C. S., and Ritchie, D. F. 1999. Development of bacterial spot on near-isogenic lines of bell pepper carrying gene pyramids composed of defeated major resistance genes. Phytopathology 89:1066-1072. Disease severity caused by races 1 through 6 of Xanthomonas campestris pv. vesicatoria on eight near-isogenic lines (isolines) of Early Calwonder (ECW) with three major resistance genes (Bs1, Bs2, and Bs3) in different combinations was evaluated in the greenhouse and field. Strains representing races 1, 3, 4, and 6 caused similar high levels of disease severity, followed by races 2 and 5 on susceptible ECW. Race 3 caused severe disease on all isolines lacking resistance gene Bs2. Race 4, which defeats Bs1 and Bs2, caused less disease on isoline ECW-12R (carries Bs1 + Bs2), than on isolines ECW, ECW-10R (carries Bs1), and ECW-20R (carries Bs2). Similar results were obtained with race 4 strains in field studies conducted during 1997 and 1998. In greenhouse studies, race 6, which defeats all three major genes, caused less disease on isoline ECW-13R (carries Bs1 + Bs3) and ECW-123R (carries Bs1 + Bs2 + Bs3) than on isolines ECW, ECW-10R, ECW-20R, and ECW-30R (carries Bs3), but not on ECW-23R (carries Bs2 + Bs3). In greenhouse studies with commercial hybrids, strains of races 4 and 6 caused less disease on Boynton Bell (carries Bs1 + Bs2) than on Camelot (carries no known resistance genes), King Arthur (carries Bs1), and X3R Camelot (carries Bs2). Race 6 caused less disease on hybrid R6015 (carries Bs1 + Bs2 + Bs3) and Sentinel (carries Bs1 + Bs3) than on Camelot. Residual effects were not as evident in field studies with race 6 strains. Defeated major resistance genes deployed in specific gene combinations (i.e., gene pyramids) were associated with less area under the disease progress curve than when genes were deployed individually in isolines of ECW or commercial hybrids. Successful management of bacterial spot of pepper is achieved incrementally by integrating multiple tactics. Although there is evidence of residual effects from defeated genes, these effects alone likely will not provide acceptable bacterial spot control in commercial production fields. However, when combined with sanitation practices and a judicious spray program, pyramids of defeated resistance genes may aid in reducing the risk of major losses due to bacterial spot.
Plant Disease, Feb 1, 2001
The use of trade names in this publication does not imply endorsement by the North Carolina Agric... more The use of trade names in this publication does not imply endorsement by the North Carolina Agricultural Research Service of the products named nor criticism of similar ones not mentioned.
Horttechnology, Oct 1, 1994
The impact of a single hail storm injury in combination with bacterial spot caused by Xanthomonas... more The impact of a single hail storm injury in combination with bacterial spot caused by Xanthomonas campestris pv. vesicatoria was assessed on three commercial pepper (Capsicum annuum) cultivars-King Arthur, Jupiter, and Rebell. In addition, the effectiveness of copper plus maneb sprays on hail-damaged plants to suppress bacterial spot was evaluated. A hail storm of ≈5-min duration severely damaged and defoliated the pepper plants. Severe bacterial spot was ob-Recently, wind and wind-gener
Plant Health Progress, 2021
Phytophthora capsici is an oomycete pathogen causing economically important diseases in a wide ra... more Phytophthora capsici is an oomycete pathogen causing economically important diseases in a wide range of hosts worldwide including cucurbitaceous, solanaceous, and fabaceous crops. All plant parts, crown and roots, or only the fruit may be affected depending on the host, and symptoms can range from wilting to rot and plant death. Considered a hemibiotroph, P. capsici can be cultured in artificial media and maintained in long-term storage. In this diagnostic guide, we describe methods to identify P. capsici infection based on disease symptoms and pathogen signs. We also outline methods for molecular identification, pathogen isolation, storage of single-sporangium cultures, and pathogenicity testing.
Plant Pathology, Jun 1, 1995
Isolates representing 11 anastomosis groups (AGs) of Rhizoctonia solani from various geographic l... more Isolates representing 11 anastomosis groups (AGs) of Rhizoctonia solani from various geographic locations and host plants were tested for virulence on soybean leaves at 15, 20, 25, 30, and 35°C, and on soybean seedlings at 20, 25, and 30°C. Numbers of infection cushions formed on soybean leaves were determined using light microscopy. Isolates of AG-1 IA, AG-1 IB and AG-5 were more virulent on soybean leaves at 20, 25, and 30°C than isolates of AG-1 IC and AG-4. Maximum numbers of infection cushions were formed on soybean leaves by AG-1 (IA, IB, and IC), AG-4, and AG-5 at 25 and 30°C. The other AGs tested did not form infection cushions on soybean leaves although some caused minimal disease severity. Isolates of AG-1 IA formed significantly more infection cushions and caused greater disease severity than AG-1 IB and other isolates at 35°C. Maximum seedling infection, based on per cent area of hypocotyl region covered by lesions occurred at 25 C for AG-1 (IA, IB, and IC) and AG-4. Isolates of AG-5 caused greater seedling infection at 20°C than at 25 and 30°C. The other AGs tested caused only minimal damage to the seedlings. Isolates of AG-4 and AG-5 are not known to cause Rhizoctonia foliar blights of soybean in Louisiana, but their potential to be destructive foliar pathogens is confirmed.
Plant Pathology, Apr 1, 1994
Infection cushions were formed by isolates of Rhizoctonia solani, anastomosis group 1 IA (AG-I I ... more Infection cushions were formed by isolates of Rhizoctonia solani, anastomosis group 1 IA (AG-I I A, aerial blight) and AG-1 IB (web blight) on leaves ofall 10 soybean cullivars tested. Isolates of AG-1 IA and IB did not form infection cushions on soybean leaf surface replicas of either resistant or susceptible cultivars. More infection cushions were formed by isolates of AG-1 IA and IB on collodion membranes placed over leaves of susceptible cultivars compared with resistant cultivars. Isolates of AG-1 IC. AG-4 and AG-5, also formed infection cushions on soybean leaves. However, the isolates of other anastomosis groups did not form infection cushions on soybean leaves. Differential induction of infection cushion formation by the leaves of various plant species was observed, AG-1 IA formed infection cushions on more graminaceous hosts than AG-1 IB, Our results suggest that a chemical stimulus is needed for infection cushion formation. Glucose and 3-O-methylglucose repressed disease severity caused by AG-1 IA and IB isolates to the same extent. Disease severity and the number of infection c^shions formed on leaves of ten soybean cultivars were correlated. Fewer infection cushions were formed on resistant cultivars than on susceptible cultivars. * Based on observations of soybean leaves inoculated with isolate of Rhizocionia solani AG-1 IB (BHIB), ** Diseased samples were obtained at random from soybean plots at Ben Hur Reseiirch Farm. Baton Rouge, Louisiana ' Mean numbers of infection cushions formed per soybean leaflet, '' Correlation coeflicicnta, based on individual observations of disease seventy and infection cushion counts per soybean leuflet. t orrelations were highly significant (/»<O-OI), ' Not tested
Plant Disease, 1998
The effect of major resistance genes (Bs1, Bs2, and Bs3) or gene combinations for resistance to b... more The effect of major resistance genes (Bs1, Bs2, and Bs3) or gene combinations for resistance to bacterial spot of bell peppers (Xanthomonas campestris pv. vesicatoria) in 15 commercial cultivars on disease reduction and yield were studied during 1995 and 1996. Reaction of cultivars to specific races (races 1, 2, or 3) of the pathogen corresponded with seed company claims for resistance against these races. Races 1 to 4 were used as initial inoculum in 1995, and races 1 to 6 in 1996 field experiments. Cultivars with no known resistance genes to bacterial spot (e.g., Camelot, Jupiter, and Valiant), a single resistance gene (X3R Camelot, King Arthur), or a combination of Bs1 and Bs3 genes (Guardian, Sentinel, and Admiral) were severely diseased. Yields were reduced in all inoculated cultivars compared to non-inoculated cultivars used as controls. Although races 4 and 6 caused significant disease in cultivars with only Bs1 (King Arthur) or Bs2 (X3R Camelot) genes, cultivars with a combi...
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Papers by Chandrasekar Kousik