- Fruits: melons
- Vegetables: cucurbits
- Crop Production: cover crops
- Pest Management: biological control, botanical pesticides, integrated pest management
- Soil Management: soil microbiology
Inhibitory effects of mustard cultivars, Brassica juncea L. ‘Florida ‘Broadleaf’ and Sinapis alba L. ‘Tilney’ on Phytophthora capsici were tested in the laboratory, greenhouse and four field experiments. In the laboratory experiments, inhibitory effects of 0.22 µm-filtered extracts of FBL, Tilney, a 50:50 mixture of FBL+ Tilney, and control (sterile-distilled water) treatments were evaluated on four P. capsici isolates (PC-1, PC-2, PC-3, and PC-4). The FBL extract significantly reduced colony growth of all P. capsici isolates and sporangia production of PC-1 isolate compared to that of Tilney extract and control treatment. None of the mustard extracts significantly inhibited zoospore germination of P. capsici isolates. The FBL extract significantly reduced P. capsici oospore germination compared to that of control treatment. In the greenhouse trial, extracts of FBL, Tilney, a 50:50 mixture of FBL+Tilney and control (sterile-distilled water) treatments were tested on P. capsici crown infection of ‘Eureka’ cucumber, ‘Magic Lantern’ pumpkin, and ‘Dickinson’ pumpkin seedlings. P. capsici infection on ‘Dickinson’ pumpkin was significantly reduced in presence of FBL + Tilney and FBL extracts compared to Tilney extract and control treatment. In the four field trials (2008-spring, 2008-fall, 2009-spring, and 2010-spring), mean glucosinolate content in mustard plants incorporated to 1 sq. m area of the plots was the lowest in 2008-fall and the highest in 2008-spring trials. P. capsici infection of ‘Eureka’ cucumber, ‘Magic Lantern’ pumpkin, and ‘Dickinson’ pumpkin were assessed in the plots incorporated with FBL, Tilney, a 50:50 seed mixture FBL+Tilney, and control (no mustard) treatments. None of the mustard treatments significantly reduced vine- and fruit-infection by P. capsici in the cucurbit crops tested.
Phytophthora capsici has become a serious threat to cucurbit production in the United States (US) and worldwide in recent years (Babadoost and Zitter, 2009; Hausbeck and Lamour, 2004; Islam, et al. 2004). This pathogen can infect cucurbit plants at any growth stage causing up to 100% crop loss (Babadoost and Islam, 2003). P. capsici oospores can survive in the soil for more than three years (Babadoost and Pavon, 2009). The oospore survival in soil and subsequent germination of oospore is the biggest hurdle for management of P. capsici in the soil. There is no cucurbit cultivar available with measurable resistance to P. capsici (Babadoost and Islam, 2003; Gevens et al. 2006). Further, no single method provides adequate protection against this pathogen (Babadoost and Islam, 2003; Hausbeck and Lamour, 2004; Hwang and Kim, 1995). Pathogen exclusion, crop rotation, moisture management, and fungicide application have been used to reduce the severity of P. capsici infection in cucurbits (Hausbeck and Lamour, 2004). However, none of these methods provides complete control of P. capsici infection in the field (Babadoost and Islam, 2003).
Biofumigation using Brassica crops could be used as a viable alternative to manage P. capsici infection of cucurbits. Biofumigation refers to the release of toxic gaseous materials from wounded tissues of Brassicaceae plant family (Kirkegaard et al., 1993). Wounded Brassica tissues release glucosinolates, which undergo hydrolysis in presence of the enzyme myrosinase to form nitriles, isothiocyanates, and thiocyanates (Cole, 1976; Delaquis and Sholberg, 1997; Rosa et al., 1997). The hydrolysis products of glucosinolates from Brassica crops were reported to have fungicidal activities (Brown and Morra, 2005). Brassica juncea and Sinapis. alba suppressed the germination of Pythium deliense Meurs and P. ultimum Trow. var. ultimum in soil samples (Lazzeri and Manici, 2001). B. juncea has been reported to inhibit the hyphal growth of P. ultimum and Rhizoctonia solani (Snapp et al., 2007). Manici et al. (1997) reported that glucosinolates isolated from B. juncea and S. alba when mixed with myrosinase from S. alba, were toxic to fungi including Fusarium culmorum, F. oxysporum and R. solani. Dunne et al. (2003) reported that B. juncea effectively suppressed the growth of Phytophthora cactorum, and Phytophthora cinnamomi. In this study, effectiveness of B. juncea L. ‘Florida Broadleaf’ and S. alba L. ‘Tilney’ were tested on Phytophthora capsici in the laboratory, greenhouse and field experiments.
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Babadoost, M. and S.Z. Islam. 2003. Fungicide seed treatment effects on seedling damping-off of pumpkin caused by Phytophthora capsici. Plant Dis. 87:63-68.
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Babadoost, M. and T.A. Zitter. 2009. Fruit rots of pumpkin: a serious threat to the pumpkin industry. Plant Dis. 93:772-782. doi: 10.1094/PDIS-93-8-0772.
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Delaquis, P.J. and P.L. Sholberg. 1997. Antimicrobial activity of gaseous allyl Isothiocyanate. J. Food Prot. 60:943-947.
Dunne, C.P., B. Dell, and G.E. St. J. Hardy. 2003. The effect of biofumigants on the vegetative growth of five Phytophthora species in vitro. Acta Hort 602: 45-51.
Fan, C.M., G.R. Xiong, P. Qi, G.H. Ji, and Y.Q. He. 2008. Potential biofumigation effects of Brassica oleracea var. caulorapa on growth of fungi. Phytopathology 156:321-325.
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Pavon, C.F., M. Babadoost, and K.N. Lambert. 2008. Quantification of Phytophthora capsici oospores in soil by sieving-centrifugation and real-time polymerase chain reaction. Plant Dis. 92:143-149.
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Project objectives:div style="margin-left:1em;">
This proposal was a two-year project to determine the effectiveness of mustard short-cycle cover crops in managing soil-borne Phytophthora capsici and Fusarium spp in cucurbit fields. The specific objectives are: (i) to compare the effects of the planting seasons of mustard on glucosinolate profile and their release in to the soil; (ii) to determine the specific glucosinolates and their concentration in leaves, root and stem; and (iii) to determine the relationship between allelochemical composition, concentration and pest suppression of the chemicals with fungicidal activities for developing biocontrol integrated pest management (IPM) strategies.