Authors: Sunita Dhakar and Anjali Soni
Division of Floriculture and Landscaping
ICAR-Indian Agricultural Research Institute, New Delhi-12
Corresponding author email: sunita.dhakar214@gmail.com
Introduction:
Disease is an abnormal condition in the plant produced by an organism or an environmental factor. More specifically, disease may be defined as ‘the series of invisible and visible responses of plant cells form, function or integrity of plants and may lead to partial impairment or death of plant or its parts’. Disease are produced by a variety of organism from both plant and animal kingdoms, viz., fungi , bacteria, viruses, nematodes and insects.
Losses due to diseases: Diseases reduce total biomass (dry matter) production by the crop in one or more of the following ways:
- Killing of plants (e.g. vascular wilts, various soil borne fungi).
- General stunting caused by metabolic disruption, nutrient drain or root damage (e.g. many viruses).
- Killing of branches (e.g. some fungal diebacks), damage to leaf tissues ( e.g. many rusts, mildews, blights, leaf spots).
( The interaction between host, pathogen and the environment during the development of diseases)
The development of any disease depends on a close interaction among three diverse factors like host, pathogen and environment. The availability of a susceptibility host is a prerequisite for an invasion by an avirulent race of the given pathogen. Similarly, presence of a virulent pathogen is essential for invading a resistant strain of the concerned host.
Stages of disease development:
- Contact: landing of pathogen on host tissue
- Infection: pathogen gains entry in to the host tissue
- Establishment: pathogen proliferates and spreads within host tissue
- Development: spore production/multiplication by pathogen and symptoms developed
Different breeding method used for disease resistance:
- Interspecific and Intergeneric hybridization
- Marker Assisted selection
- Genetic engineering
Interspecific hybridization between Dianthus caryophyllus and Dianthus capitatus, a highly resistant wild species to bacterial wilt caused by Pseudomonas caryophylli, was carried out in order to introduce the resistance into carnation cultivars.
Intergeneric Hybridization:
Intergeneric somatic hybrids between chrysanthemum [Dendranthema × grandiflorum (Ramat.) Kitamura] and wormwood ( Artemisia sieversiana J. F. Ehrh. ex. Willd) were produced by electrofusion of mesophyll protoplasts. The somatic hybrid plants were more resistant to rust than chrysanthemum.
Marker-Assisted Selection:
It is the breeding strategy in which selection for a gene is based on molecular marker closely linked to the gene of interest rather than the gene itself, and the markers are used to monitor the incorporation of the desirable allele from the donor source..
Molecular markers associated with resistance traits in crop plants
| Host species | Disease | Gene | Marker | Reference |
| Rose | Diplocarpon rosae | Rdr1 | RFLP & SCAR | Malek et al., 2000 |
| Rose | Sphaerotheca pannosa | Rpp1 | SCAR | Linde et al., 2004 |
| Carnation | Fusarium oxysporum | _ | RAPD and SCAR | Reuven et al., 2001 |
Genetic Engineering for Disease Resistance:
Genetic engineering alters the genetic make-up of an organism by removing heritable material or that introduce DNA prepared outside the organism either directly into the host or into a cell that is thenfused or hybridized with the host. In case of viral pathogens, several transgenes have been evaluated, viz., virus coat protein genes, DNA copy of viral satellite RNA, defective viral genome, antisense constructs of critical viral genes and ribozymes. In case of bacterial and fungal pathogens, resistance has been sought by expression of the following transgenes: (1) genes encoding insensitive target enzymes, (2) genes specifying toxin inactivation, (3) expression of antibacterial peptides, (4) expression of bacterial lysozymes. In almost all the approaches, transgenic plants showed increase to the concerned diseases.
Genetic engineering of plants for resistance to diseases :
| Disease | Gene | Transformation through | Transgenic plant | Reference |
| Powdery mildew | Ace-AMP1 | Agrobacterium | Rosa hybrida | Li et al., 2003 |
| Gray mouid | Ace-AMP1 | Agrobacterium | Geranium | Bi et al., 1999 |
| Black spot (Diplocarpon rosae) | Chitinase | Agrobacterium | Rose | Marchant et al., 1998 |
| Leaf spot | Chitinase | Agrobacterium | Chrysanthemum | Sen et al., 2013 |
| Poinsettia mosaic virus | hairpin (hp) RNA gene | - | Poinsettia | Clark et al., 2008 |
| Bean yellow mosaic virus | Coat protein | - | Gladiolus | Kamo et al., 2005 |
| CMV | CMV replicase gene | - | Lily | Lipsky et al., 2002 |
Bi, Y.M., B.P.A. Cammue, P.H.Goodwin, S. KrishnaRaj, and P.K. Saxena. (1999). Resistance to Botrytis cinerea in scented geranium transformed with a gene encoding the antimicrobial protein Ace-AMP1. Plant Cell Reports; 18:835-840.
Kamo, K., Jordan, R., Guaragna, M. A., Hsu, H. and Ueng, P. (2010). Resistance to Cucumber mosaic virus in Gladiolus plants transformed with either a defective replicase or coat protein subgroup II gene from Cucumber mosaic virus. Plant Cell Rep; 29: 695–704.
Li, X.Q., Gasic, K., Cammue, B., Broekaert, W. and Korban, S.S. (2003). Transgenic rose lines harboring an antimicrobial protein gene, Ace-AMP1, demonstrate enhanced resistance to powdery mildew ( Sphaerotheca pannosa). Planta; 218 :226-232.
Linde, M., and T. Debener. (2003). Isolation and identification of eight races of powdery mildew of roses (Podosphaera pannosa) (Wallr.: Fr.) de Bary and the genetic analysis of the resistance gene Rpp1. Theoretical and Applied Genetics; 107: 256-262.
Lipsky, A., Cohen, A., Gaba, V., Kamo, K., Gera, A. and Watad, A. (2002). Transformation of Lilium longiflorum plants for cucumber mosaic virus resistance by particle bombardment. Acta Horticulturae; 568: 209-214.
Malek, B. V., Weber, W. E. and Debener, T. (2000). Identification of molecular markers linked to Rdr1, a gene conferring resistance to black spot in roses. Theor Appl Genet 101 :977–983.
Marchant, R., Davey, M.R., Lucas, J.A., Lamb, C.J., Dixon, R.A. and Power, J.B. (1998). Expression of a chitinase transgene in rose (Rosa hybrida L) reduces development of blackspot disease ( Diplocarpon rosae Wolf). Mol Breed; 4 :187-194.
Reuven, M. and Ben-Yephet, Y. (2001). Marker Assisted Selection for Resistance to Fusarium oxysporum in the Greenhouse Carnation. Acta Hort. 552: 151-156.
Sen, S., Kumar, S., Ghani, M. and Thakur, M. (2013). Agrobacterium Mediated Genetic Transformation of Chrysanthemum(Dendranthema grandiflora Tzvelev) with Rice Chitinase Gene for Improve Resistance Against Septoriaobesa. Plant Pathology Journal; 1-10.
About Author / Additional Info:
I am a Research Scholar at IARI New Delhi.