G.Swasti Approach of Disease Prevention:
Swasti has developed a three-pronged approach for prevention of any disease of crops called BIQAVert I.
The program principles are as follows:
Biological program of disease aversion for horticultural crops:
- Block invasion mechanism of pathogen
- Optimize Advantageous microflora
- Vertex inhibitor synthesis within plant defense
The Specific work being done in pomegranate at present is as follows:
1. Creating Entry Barrier for the Pathogen: Xanthomonas, in general, is known to inhibit one plant defense mechanism i.e. callose synthesis. By inhibiting the callose synthesis, Xanthomonas gets free entry into any cell and thereby spreads very rapidly. Dr. K.K. Mondal (Principal Scientist- Plant Pathology- IARI Pusa) and his co-workers have shown that callose synthesis is inhibited specifically by Xanthomonas(XAP) which causes Telya disease in pomegranate.
We have developed a foliar spray that induces callose synthesis. We have shown in pot trials that within 5 days of the spray, a good amount of callose is detected in leaf cells when detected by fluorescence microscopy.
We have shown in pot trails that the treated leaves are resistant to XAP infection. With 3 sprays at 8-day interval, the intensity of the disease could be brought down at least by 70%. Each spray costs approximately INR 3.25 per plant. 3 sprays are proposed within the first month of new leaf emergence after defoliation.
These results are confirmed by data of NRCP on the performance of chitosan derivatives compared with the existing treatments.
Our observation is that an altered active formulation based on the same ingredients works better on mature leaves and fruit skin. Each spray costs about INR 4 per plant and we propose about 6 sprays at 150 days + stage of the crop – depending on need. This formulation was tested in the field.
In the field studies – post hail storm, and end June 2014 – carried out under environment conducive for development of Telya, several farmers have recorded satisfactory results. This means the disease was checked and losses were minimized. Isolated cases of product application and control within the same plot revealed that the progression of the disease was checked only in the treated plot.
2. The killing of Pathogen: Pomegranate leaves contain two classes of biochemical namely Tennis and Flavones, which are capable of killing the pathogenic XAP. Our initial studies have provided us proof of concept that the synthesis of these can be induced. We have used some foliar spay that can increase their activity nominally by 10 folds with the help of 3 such spray applications.
Our preliminary analytical data suggests that the level of these bio-chemicals varies within the plant as per its physiological stage. Thus critical stages within the crop cycle can be ascertained with the help of further fine analysis and appropriate protection developed for these stages. At present we are focusing on the stages of “color change” for the setting and grown fruit as critical stages. We have successfully induced the synthesis of some of this biochemical that reflected in 10 times higher anti-XAP activity. This analysis was done in both pot trails and field evaluation.
At the point of time, we have no separate product for this purpose. The ‘high activity formulation’ mentioned above is intended to have this ‘inducer’ function while we finalize on commercial product formulae at a later stage.
3. Beneficial Microbes: Plant pathogens can live along with the plant (in small numbers) for a very long duration, at times years together, without causing any disease symptom. Alfano and Collmer (1996) presented the following information based on their research findings on Xanthomonas. The data suggests:
a. The pathogen can remain at <100 counts on leaves for ages.
b. When the pathogen count shoots up to about 10,000 and when the plant defense mechanism is activated (humoral response) then the infection does not progress further.
c. It is at 10,000 counts, and when the plant defense is insufficient and also the environment is conducive to the growth of the pathogen, the XAP number may shoot up to tens of crores within 2 to 3 days; and then it causes necrotic lesions – the very first symptom of Telya disease.
At this juncture, on one hand, we are focused on building disease resistance in plants. On another hand we propose to make use of specific beneficial microbes that can keep the number of XAP under control on pomegranate leaves by virtue of competition, elimination, inhibition, antagonism, and physical interaction(s), etc.
We have isolated several microbial strains from wild, untreated, naturally, disease resistant pomegranate plants. We have studied them for their interactions with XAP and leaf. We have identified a few of them, determined the safety for application (short term toxicity, pathogenicity studies).
These beneficial microbes will be an important tool in controlling Telya disease of pomegranate. One such isolate designated as M1C17 was used in pot trails. Small plants were sprayed with the culture – twice at the weekly interval and the culture allowed establishing for 3 weeks. Subsequently, treated and untreated plants were inoculated with XAP. None of the treated plants developed symptoms of Telya disease whereas all the untreated plants had some lesions.
The M1C17 culture was further applied in the field test at 8 locations. Two applications were made at 15-day interval. All the fields had received 2 earlier sprays of ‘defense booster product’. The farmers reported that the progression of Telya was effectively checked as compared with the neighboring farms. The microbial flora of these was determined thrice at about 15 days interval. In the third test (45 days of sprays), in one filed no XAP could be detected on healthy leaves. In two cases, XAP count was observed only up to a few hundred. In the first two tests (day 15 and 30) all fields showed XAP count of as high as 10 lakh (lower by only about 100 folds for the disease-causing potential).
This culture has been identified using 16s rRNA sequencing, and the data has been deposited in the GeneBank (Accession No. KM 538689). Culture is proven to be non-toxic and safe for use.
H. Projections about Possible Control for Bacterial Blight:
We aim at making continuous use of products for building disease resistance, maximizing beneficial microbes, and inducing production of natural antimicrobial biochemical of plants. With this, we project disease incidence potential after 2 years if the reduction in microbial load is respectively at 10, 30 and 70 %. We project the farmers with an initial loss of 100% could expect a yield of 65, 97, and 100% respectively with this method of management of the disease. The analytical steps to be taken and the possible treatment steps are also given along with the disease prediction figures. The treatment steps may have to be altered based on changes in the interactions of the triangle of parameters.