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Capsicum frutescens belong to the family of Solanaceae. The Begomovirus, Tymovirus, Potyvirus, Chilli veinal mottle virus, Zucchini yellow mosaic virus and Cucumber mosaic virus cause infection in chilli species. The large numbers of plant viruses reported thus far have been shown to be transmissible by insects such as aphids, grasshoppers, mites, mealy bugs, plant bugs, and white flies. Aphid gossypii, A. craccivora, and Myzus persicae and Bemisia tabaci transmitted the yellow mosaic virus.

 

Fig1. (A). Myzus persica feeding time on Capsicum frutescens (B). Aphis craccivora

Aphids and whiteflies transmitted the virus isolates that cause mosaic and leaf curl diseases in chilli cultivars (Khan et al., 2006). Although Aphis gossypii (Glov.) transmitted ChiVMV to its natural host chilli pepper. The plants caused systemic vein mottling symptoms, which were confirmed by DAS-ELISA (Shah et al., 2008). Cucumber mosaic virus (CMV) and Chilli veinal mottle virus (ChiVMV) are major destructive viruses spread by aphids that affect chilli crops (Naresh et.,al 2016 and Myti et.,al 2014). Papaya ring spot virus affected the behaviour and biology of its vector, the melon aphid (Aphis gossypii Glover), as well as the non-vector, silver leaf whitefly (Bemisia tabaci Gennadius) (Gadhave et.,al 2019). The genetic diversity of mosaic and chlorosis-inducing Cucumber mosaic virus (CMV) strains infecting chilli. It was discovered to contain a cryptic mutation of Threonine amino acid, which is conserved for aphid transmission (Vinodhini et.,al 2022).

Materials and Methods

During the month of June to November a field study was undertaken in the village of Badripur area of Dehradun district, Uttarakhand. The infection was found in Adhoyiwala, Badripur, and Prem nagar area, Dehradun. Back inoculation on healthy chilli seedlings was used to determine whether the plant species was a latent host of the viruses in plants where no symptoms emerged. The majority of plant viruses transmitted by the three aphid species, Aphis craccivora koch, Aphis gossypii golvz, Myzus persica, and Bemisia tabaci (white flies), which are common on chilli plants in Doon velly, Uttarakhand, were tested for their ability to spread chilli mosaic virus isolates within that study.

Fig2.(A) Aphids collection on Capsicum frutescens

(B). Aphid transmission on four-leaf seedlings

Vector virus association of mild and severe isolates with Aphis craccivora

Aphis craccivora is a common species found in Dehradun's solanaceae crops. During preliminary transmission testing, this aphid was determined to be the most efficient vector of chilli mosaic virus isolates, both mild and severe. A.craccivora association with these two isolates was determined by changing pre-acquisition fasting periods, acquisition feeding time, number of aphids, minimum infection feeding required time, post-acquisition fasting periods, and virus persistence in the vector.

Materials and methodology are briefly described after the Discussion and Result.

Discussion and Result

The presence of A. gossypii within five minutes of feeding on a diseased plant massively increased the extent of transmission (Swenson et al.,1952). However M. persicae and A. gossypii transmitted pepper vein banding virus at 90 and 100%, respectively. M. persicae, A. gossypii, and A. craccivora transmitted pepper veinal mottle potyvirus, resulting in 90, 100, and 30% infection, respectively (Gowda et al., 1989). Overall, the appropriate integrated pest management strategies for A. gossypii and CVMV in small farm agro-ecosystems in the tropics (Hussein et.,al 1993).Whereas After a minute of acquisition, the virus from the chilli pepper leaf was transferred by the peach potato aphid, Myzus persicae, to immature chilli pepper plants (Chiemsombat et al., 1998).

Barrier cropping will be interconnected with other disease management strategies, and its use as a strategy for managing aphid-transmitted virus diseases will be improved (Hooks & Fereres, 2006). In different circumstances the DAG motif, which is common in aphid-transmitted potyviruses, was found in all isolates like pepper vein banding virus (PVBV), chilli vein-banding mottle virus (CVbMV) and Chiengmai isolate (Tsai et al., 2008).

The aphids were fasted for three hours pre-acquisition. Fasted aphids were given a two-minute acquisition feeding time on infected chilli plants. As test plants, young vigorously growing chilli seedlings were used (Table -1).

Chilli mosaic virus mild and severe isolates were transmitted by aphids.

Table 1

Aphids	Number of aphids in per chilli plants	Mild				Severe
		Ist trial	2ed trial	Transmission percentage (%)		Ist trial	2ed trial	Transmission percentage (%)
Bemisia tabaci	10	5	6	55		4	6	50
Aphis craccivora	10	7	7	70		7	8	75
Aphis gossypii	10	5	4	45		6	6	60
Myzus persica	10	7	6		65	5	7	60

← Number of Aphids →

Table 1 indicates that all aphid species can efficiently transfer both isolates from infected to healthy plants. Within 8-12 days, symptoms occurred on the infected seedlings. Aphis craccivora was found to be the most effective vector, causing 75% ChiMV severe and 70% ChiMV mild infection. 60% A.gossypii and 60% Myzus persicas.

Effect of pre-acquisition fasting and acquisition eating timings on mild and severe isolate transmission:

According to experiment during the virus's assimilation, it comes into contact with some chemical that partially or completely damages its infectivity. It is assumed that this chemical is either not generated at all or is produced at a significantly reduced rate in fasting insects. During the present study, when an aphid is given a short feeding 1-2 minutes after hunger, the amount of inactivater is insufficient to inactivate the virus taken in, resulting in greater infection. However, with a 5 minute increase in acquisition feeding time, the benefit of fasting begins to fade and the quantity of inactivater increases, resulting in reduced infection. When aphids are not starving, the quantity of inactivater already present in the insect reaches a peak, inactivating a high proportion of the virus ingested during the acquisition feeding phase, resulting in decreased infections. Table-2 shows the results.

Table 2

Isolates	Pre–acquisition fasting time (hrs)	Acquisition Feeding time min						Total
		0.5	1.0	2.0	3.0	4.0	5.0
Mild isolates	0.0	-	1	2	3	2	3	11
Severe isolates	0.0	1	1	2	3	3	2	12
Mild isolates	1.0	1	2	3	4	2	2	14
Severe isolates	1.0	2	3	4	5	4	3	22
Mild isolates	2.0	2	4	3	6	5	4	24
Severe isolates	2.0	3	5	5	7	5	4	29
Mild isolates	3.0	3	5	6	5	4	3	26
Severe isolates	3.0	4	6	7	7	4	4	32
Mild isolates	4.0	4	5	2	3	5	3	22
Severe isolates	4.0	3	7	5	4	3	2	24
Mild isolates	5.0	0	0	1	3	2	1	07
Severe isolates	5.0	0	1	2	3	2	1	09
Mild isolates	Total	10	17	17	24	20	16
Severe isolates		12	22	23	26	18	16

Transmission of CMV mild and CMV severe isolates by A.craccivora with varying pre-acquisition fasting and acquisition eating times:

The effect of the number of aphids on the transmission of mild and severe isolates: Some viruses were only transmitted when a high number of vectors were used. This has frequently resulted in the conclusion that insects can inject virus with sub-minimal infective concentrations into plants. These have a cumulative impact, and none of them could have caused infection on its own. After getting enough of these dosages, a plant will become infected. Table 11 shows the results of an experiment conducted in two trials to determine the impact of the number of aphids on the transmission of the present virus isolate. According to the data in table 11 and figure -1, even a single aphid can spread the virus, however the percentage of transmission is relatively low. However, for optimal transmission of both strains, a group of 5 or 10 aphids per plant is recommended. When 15 and 20 aphids per plant were sampled, the percentage transmission declined steadily.

Table 3

Isolates	Number of Aphids per plant	No of trials		Out of 20 treated total number plant infected	Transmission percentage      (%)
		Trial I	Trial II
Mild isolates	01	2	2	4	20
Severe isolates	01	2	3	5	25
Mild isolates	05	3	2	5	25
Severe isolates	05	4	3	7	35
Mild isolates	10	5	6	11	55
Severe isolates	10	7	7	14	70
Mild isolates	15	6	6	12	60
Severe isolates	15	7	6	13	65
Mild isolates	20	4	4	8	40
Severe isolates	20	3	5	8	40

Minimum infection feeding time necessary for mild and severe isolate transmission:

An experiment was conducted to determine the minimum infection feeding time needed for transmission of isolates of chilli mosaic virus, and the findings are provided in table-3.

Based on the findings in Table 3 it is concluded that viruliferous aphids may spread mild and severe isolates to healthy plants in as little as two minutes of infection feeding time. In both cases, however, optimum infection is reached in 30 to 60 minutes after infection feeding.

Table 4

Isolates	Aphids infection feeding time	No of trials		Out of 20 treated total number plant infected	Transmission percentage     (%)
		Trial I	Trial II
Mild isolates	02	1	1	2	10
Severe isolates	02	1	2	3	15
Mild isolates	05	2	2	4	20
Severe isolates	05	3	3	6	30
Mild isolates	15	5	4	9	45
Severe isolates	15	4	5	9	45
Mild isolates	20	6	7	13	65
Severe isolates	20	6	6	12	60
Mild isolates	30	7	8	15	75
Severe isolates	30	8	6	14	70
Mild isolates	60	7	7	14	70
Severe isolates	60	6	8	15	75
Mild isolates	120	6	8	14	70
Severe isolates	120	6	9	15	75

ChiMV mild and ChiMV severe isolate minimum feeding time for aphids transmission:

Mild and severe isolates transmission of post-acquisition fasting effect:

Fig.3 Post-acquisition fasting periods

 An experiment was conducted to determine the effect of aphid starvation after acquisition feeding, and the findings are presented in table 4.

Table 4 demonstrate that percentage transmission lowered transmission, but only when the aphids fasted following acquisition feeding. Fasting for 30 minutes reduced transmission slightly, but the reduction became more significant as post-acquisition fasting duration increased to 4 hours in mild isolates and 6 hours in severe isolates, after which no infection occurred.

Table 5

Isolates	Post–acquisition fasting time	Number of plants infected out of 10 treated		Total plants infected out of 20 treated	Transmission percentage     (%)
		Trial  I	Trial II
Mild isolates	0.0	7	8	15	75
Severe isolates	0.0	8	8	16	80
Mild isolates	0.5	7	6	13	65
Severe isolates	0.5	6	7	13	65
Mild isolates	1.0	5	6	11	55
Severe isolates	1.0	6	6	12	60
Mild isolates	2.0	4	4	8	40
Severe isolates	2.0	3	3	6	30
Mild isolates	3.0	3	3	6	30
Severe isolates	3.0	2	3	5	25
Mild isolates	4.0	1	1	2	10
Severe isolates	4.0	2	2	4	20
Mild isolates	5.0	1	-	1	5
Severe isolates	5.0	1	1	2	10
Mild isolates	6.0	-	-	-	-
Severe isolates	6.0	1	-	1	5
Mild isolates	7.0	-	-	-	-
Severe isolates	7.0	-	-	-	-
Mild isolates	8.0	-	-	-	-
Severe isolates	8.0	-	-	-	-

Mild and severe isolates persist in the vector:
An experiment was carried out to find out how many plants a single viruliferous aphid may infect when fed on a series of plants. Table 5 displays the acquired data.
According to the results, seven of the ten aphids infected mild isolates only on the first plant and three on the second plant. None of the aphids were capable of producing more than one infection. In the event of severs, segregate all 10 aphids to feed initially. The remaining plants were unaffected. This demonstrates that a single viruliferous aphid is incapable of causing more than one infection and loses its infectivity after that.
Table 6

ChiMV Isolates	Number of aphids	Plants in series
		1	2	3	4
Mild	1	+	_	_	_
Severe	1	+	_	_	_
Mild	2	-	+	_	_
Severe	2	+	_	_	_
Mild	3	+	_	_	_
Severe	3	+	_	_	_
Mild	4	-	_	_	_
Severe	4	+	_	_	_
Mild	5	+	_	_	_
Severe	5	+	_	_	_
Mild	6	-	+	_	_
Severe	6	+	_	_	_
Mild	7	+	_	_	_
Severe	7	+	+	_	_
Mild	8	+	_	_	_
Severe	8	+	_	_	_
Mild	9	+	_	_	_
Severe	9	+	_	_	_
Mild	10	+	_	_	_
Severe	10	+	_	_	_

 (+) Mild and severe infection (-) No infection on mild and severe isolates 

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