Previous PageTable Of ContentsNext Page

Influence of Seed Origin on Scale Insect (Maconellicoccus hirsutus) Damage and Severity in Teak Provenance Trial

T.N. Neelannavar1 and Manjunath R. Chavan1,2

1Forest College & Research Institute, Mettupalayam–641 301 Tamil Nadu, India
2
Presently Indian Forest Service Officer Trainee, Indira Gandhi National Forest Academy Dehradun, India.

Abstract

Scale insect damage was observed in an international teak provenance trial conducted at Forest College & Research Institute, Mettupalayam (Tamil Nadu, India) located at 11 19' N and 7656' E involving 29 half-sib families with three replications (9 plants in each). The study revealed that there was a profound influence of original locations of seed sources on the per cent damage incidence, number of scales per plant, damage severity index, seedling vigour and per cent seedling mortality. The clustering of seed sources for these traits resulted in five clusters with maximum of 15 seed sources in cluster-1 and 8 in cluster-5 leaving the rest three clusters with 2 seed sources each. Seed sources in cluster-5 were found to be most tolerant to scale insect damage with mean cluster value of 19.443 % while cluster-2was found to be most susceptible with mean cluster value of 35.182 %. The clusters 5 & 2 were found to be most divergent (4.588) and clusters 4 & 2 were nearest ones (2.292) with respect to inter cluster diversity. Cluster-5 contained maximum diversity (4.732) within cluster. A strong and significant association was observed for per cent damage incidence with Number of scales per plant (0.406), damage severity (0.395) and teak seedling mortality (0.411). Also a significant correlation was recorded between per cent seedling mortality and scale insect damage severity index (0.434). Number of individuals per plant showed maximum (0.597) positive association with scale insect damage severity index. The study signifies the importance of seed origin in selection and breeding for insect tolerance/resistance in important tree species.

Key Words

teak, scale insect, genetic divergence, resistance, provenance.

Introduction

Teak (Tectona grandis ) is commercially one of the most valuable timber species of the world, especially in India and other Southeast Asian countries. This tree grows naturally between 100 to 230N latitudes. About 288 species of insects have been so far reported to feed and cause major or minor damage to teak (Meshram et al., 1994), Regupathy et al. (1995) reported 41 species of insects that cause moderate to severe damage to teak throughout its life cycle and cottony cushion scale, Maconellicoccus hirsutus (Hemiptera: Pseudococcidae) is one of them. Both nymphs and adult scales are reported to cause serious damage to seedlings and saplings of teak in nurseries as well as in the field.

The cottony cushion insects are one of the most common species of insects damaging seedlings of most of the species in the nursery. It has been reported that the continued feeding habits of phytophagous insects of tree species invariably lead to the genetic adaptation and pest epidemics when environmental factors favour. Such pests become specialised to a level that they become unable to develop normally even on different clone or closest relative of the host species (Brues, 1924; Brown, 1964).

Methods

A study was undertaken on a three-year-old teak provenance (seed source) trial involving 29 half-sib families from within India and abroad. The trial was laid-out in a randomised block design (RBD) with 10 replications of nine plants each with 3 x 3 spacing. Seed sources planted were :- Lao PDR (S1), Bangladesh (S2), Uttar Pradesh (S3), Uttaranchal (S4), Madhya Pradesh (S5), Assam (S6), Meghalaya (S7), Tripura (S8), Orissa (S9), Maharashtra (S10, S11, S12, S13, S14 and S15), Karnataka (S16), Tamil Nadu ( S17, S18, S19, S20 and S21), Kerala ( S22, S23, S24, S25, S26, S27, S28 and S29).

The observations on the scale insect incidence were made on three replications selected systematically. The percentage of scale insect incidence was assessed by counting the number of individual plants infested by the scale insects in each replication. Similarly, the per cent mortality of seedlings in each replication was assessed by counting the number of blank spaces. The damage severity was worked out by visual scoring using a 0 to 5 grade scale (Grade-0: unaffected plant; Grade-1: slight discolouration of leaves; Grade-2: severe discolouration and curling of leaves; Grade-3: partial defoliation and deformation of shoot; Grade-4: complete defoliation and severe deformation of shoot; Grade-5: drying and death of plant), as suggested by Mahal (1991) with suitable modifications. The scale insect damage severity index was worked out using the formula of Hooda, et al. (1992), given below;.

Where, G1 to G5 were grades of injury and Pa to Pe were number of plants in each grade in each replication. An empirical assessment of the vigour of teak seedlings and scoring of seedling mortality was also done. The data thus collected were subjected to standard statistical analysis.

Results and Discussion

The general observations made in the plantation, upon statistical analysis revealed that the traits observed viz., scale insect damage incidence (%), number of individuals per plant, scale insect damage severity index, vigour of seedlings and mortality of seedlings (%), showed significant differences among seed sources indicating thereby existence of considerable amount of genetic variability in Tectona grandis for these parameters. Application of Mahalanobis D2 statistics for the analysis of diversity among 29 seed sources resulted in identifying five clusters (Table 1). Cluster 1 included the maximum number of 15 seed sources followed by cluster-5 with 8 seed sources. Cluster 2, 3 and 4 included two sources each. The larger group size of cluster 1 may be due to greater homogeneity among them. Though entries from different geographic locations were combined together into clusters, there is a positive linear relation between latitudes and scale insect incidence. Therefore, the pattern of divergence may be slightly dependent on the geographical nearness. Genetic distance and make-up can be attributed to this as observed by Bagchi (2000).

Table 1. Clustering of 29 teak seed sources (3-year old seedlings) evaluated for scale insect incidence and biometric parameters (At critical value=50).

Cluster No

Seed Sources

Cluster 1

S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15

Cluster 2

S22 S25

Cluster 3

S24 S28

Cluster 4

S20 S29

Cluster 5

S16S17 S18 S19 S21 S23 S26S27

The range of values for intra and inter cluster distances was between 0.962 to 4.732 and 2.292 to 4.588 respectively (Table 2). Maximum distance was observed between clusters 2 and 5, while clusters 2 and 4 were found to be closest among all the five clusters. The examinations of the intra cluster distances revealed that the cluster-5 has maximum and cluster-2 has the least diversity within cluster.

Table 2. Inter and intra cluster distances for 29 seed sources of teak (3-year old) evaluated for scale insect resistance

Cluster

1

2

3

4

5

1

2.740

2.695

3.252

2.534

4.151

2

 

0.962

2.647

2.292

4.588

3

   

1.179

2.694

4.025

4

     

1.503

4.179

5

       

4.732

Underlined diagonal values indicate intra-cluster distances

Arunachalam et al., (1980) emphasised the importance of using genetically divergent parents in hybridisation programmes to gain highly heterotic effects. The clustering of genotypes on the basis of their genetic proximity will help include large number of individuals and/or seed sources in the breeding programme. The cluster means presented in the Table 3 depict that cluster 5 recorded minimum (19.443%) scale insect damage incidence, while cluster-2 (35.182%) recorded maximum. Similar trends were observed in case of damage severity index. Cluster- 5 recorded minimum (0.643) and cluster-2 recorded maximum (1.417). Cluster- 4 showed minimum (1.148) and cluster - 2 showed maximum (2.472) values for number of scale insects per plant. Cluster-3 recorded maximum (1.853) and cluster-2 recorded minimum mean values (1.385) for seedling vigour. Minimum cluster mean values for seedling mortality was observed for cluster-4 (7.703%) while cluster-5 recorded a mean value of 7.722 %. It may be inferred that cluster 4 and 5 were found to be superior for most of the parameters in contrast to cluster-2.

Table 3. Contribution of different parameters to the diversity among seed sources of teak seedlings evaluated for scale insect resistance.

Sl. No.

Character

No. of first rank

Percentage Contribution

1

Scale insect damage incidence (%)

47

11.57

2

Number of individuals/plant

32

7.88

3

Scale insect damage severity index

16

3.94

4

Vigour of seedlings (empirical scaling)

36

8.87

5

Mortality of seedlings (%)

275

67.74

Total

406

100.00

The analysis of biometric characters of both seedlings and scale insect for possible association revealed a highly significant association among characters (Table 4).The number of scales per plant had significant positive association with damage severity index (0.597) and damage incidence (0.406). Seedling vigour showed non-significant association with all the parameters, this trait had a very small non-significant negative correlation with scale insect damage incidence (-0.04). Seedling mortality showed statistically significant positive correlation with scale insect incidence (0.411) and damage severity index (0.434). The most genuine reason for the variation among and within the seed sources is the perceivable latitudinal effect rather than the longitudinal effect. Since the climate changes over changing latitudes most rapidly when compared to change in climate with longitudes (theoretically no change should occur). Therefore, seed sources in the present study showed perceivable association with changing latitudes of their origin with their insect tolerance/resistance parameters. However, genotypes/clusters (groups) of genotypes with better and stable tolerance/resistance have to be identified and verified. Further, the groups/genotypes with better correlation with timber quality, growth and yield attributes have to be identified for the better use of the insect resistance/tolerance in tree crops.

Table 4. Simple Correlation Coefficient matrix for 29 seed sources of teak (3-year old) evaluated for scale insect damage incidence

   

SI No.

Sl. No.

Character

1

2

3

4

5

1

Scale insect damage incidence (%)

1.000

0.406*

0.395*

-0.041

0.411*

2

Number of individuals/plant

 

1.000

0.597**

0.180

0.115

3

Scale insect damage severity index

   

1.000

0.059

0.434*

4

Vigour of seedlings (scaling)

     

1.000

0.164

5

Mortality of seedlings (%)

       

1.000

Association significant at 5% (*) and 1% (**) level of significance

References

Arunachalam, V., Bandopadhayay, A., Nigam, S. N. and Gibson, S. N. 1980. Some basic results of applied value in groundnut breeding. Paper presented in National Seminar on the Application of Genetics to Improvement of groundnut. July 16-17, 1980. Tamil Nadu Agri Univ Coimbatore. pp225.

Bagchi, S. K. 2000. Divergence in Tectona grandis. Ann. For., 8(1): 25-27.

Brown, W.J. 1964. Sibling species of leaf beetles. Cana. Ent., 96:104

Brues, C.T. 1924. The specificity of food plants in the evolution of phytophagous insects. Amer. Nat., 58:127-144.

Goulden, C.H. 1952. Methods of Statistical analysis, John Wiley and Sons, Inc., New York.

Hooda, V. S., B. S. Dhamkhara and Ram Singh, 1992. Evaluation of wild taxa of okra against leafhopper Amarasca biguttula biguttula (Ishida). Test. Agrochem. Cultivars (Annu. Appl. Biol., 120-supplment), 13: 108 - 109.

Mahal, M. S., H. Lal and R. Singh, 1991. Standardisation of techniques for screening okra germplasm for resistance against cotton jassid, Amrasca biguttula biguttula (Ishida) I. Development and survival of nymphs. J. Insect Sci., 4(2): 135-137.

Mathur, R.N. 1960. Pests of teak and their contrl. Ind. For. Rec., 10: 43-65.

Meshram, P.B., K.C. Joshi and A.K. Sarkar, 1994. Relative resistance of certain clones of Tectona grandis to teak leaf skeletoniser, Eutectona machaeralis WLK (Lepidoptera: Pyralidae). The Ind. For., 120(1):58-61.

Panse, V. G. and Sukhatme, P. V. 1967. Statistical methods for agricultural workers. Indian council of Agricultural Research, New Delhi: pp380.

Rao, C. R. 1952. Advanced statistical methods in Biometrical Research. John Wiley and Sons, Inc. New York.

Regupathy, A., Chandrasekaran, T. Manoharan and S. Kuttalam, 1995. Guide to forest entomology. Sooriya Desktop Publ. Coimbatore. 76-89.

Previous PageTop Of PageNext Page