Sterility Mosaic Disease of Pigeonpea

In this article we will discuss about:- 1. Introduction to Sterility Mosaic of Pigeonpea 2. Economic Importance and Nature Loss of Sterility Mosaic of Pigeonpea 3. Symptomatology 4. Biochemical Changes 5. Histopathological Changes 6. Etiology 7. Morphology and Habitat 8. Epidemiology 9. Pigeonpea Sterility Mosaic Virus and Other Pathogens Interaction 10. Management Measures and Others.

Contents:

Introduction to Sterility Mosaic of Pigeonpea
Economic Importance and Nature Loss of Sterility Mosaic of Pigeonpea
Symptomatology of Sterility Mosaic of Pigeonpea
Biochemical Changes of Sterility Mosaic of Pigeonpea
Histopathological Changes of Sterility Mosaic of Pigeonpea
Etiology of Sterility Mosaic of Pigeonpea
Morphology and Habitat of Sterility Mosaic of Pigeonpea
Epidemiology of Sterility Mosaic of Pigeonpea
Pigeonpea Sterility Mosaic Virus and Other Pathogens Interaction
Management Measures of Sterility Mosaic of Pigeonpea
Screening Techniques and Host Plant Resistance of Sterility Mosaic of Pigeonpea
Inheritance and Mechanisms of Sterility Mosaic of Pigeonpea
Conclusion to Sterility Mosaic of Pigeonpea

1. Introduction to Sterility Mosaic of Pigeonpea:

Sterility mosaic (sterility mosaic ), caused by pigeonpea sterility mosaic virus (PPSMV), is most serious disease of pigeonpea because of its wide spread and destructive nature, causes serious loss to pigeonpea production.

Although, sterility mosaic has become a potential threat to the cultivation of pigeonpea in Indian Sub-Continent and causes an estimated annual loss of 300,000 tons of grains (more than US $ 150 million) in India alone and in Nepal more than US $ 143 million, it’s challenging etiology has been found out but control measures are still not well understood except resistant cultivars.

Numerous studies have been attempted to determine the nature of pathogen, symptomatology, epidemiology, disease resistance and control measures since it’s recognition in India in 1931. This review aims to consolidate the existing knowledge about sterility mosaic that may be useful to combat this “green plague” of pigeonpea.

2. Economic Importance and Nature Loss of Sterility Mosaic of Pigeonpea:

Pigeonpea sterility mosaic disease was first reported from Pusa, Bihar and a similar disease was also reported from Bihar in 1931 and Coimbatore in 1938. Earlier disease was confined only to Indian Subcontinent but now it has also been reported from Bangladesh, Nepal and Thailand, Myanmar, Srilanka and China.

Sterility mosaic was more severe in Uttar Pradesh, Bihar, Gujrat, Karnataka, and Tamil Nadu.

According to Kannaiyan (1981) disease was more severe in Bihar (21.4%) followed by Uttar Pradesh (15.4%), Tamil Nadu (12.8%), Gujrat (12.2%), Karnataka (9.8%) and Andhra Pradesh (1.6%), respectively, but now it has become a major constraint in pigeonpea production in South Indian States also. Disease incidence varied in main as well as in ratoon pigeonpea and it appeared in severe out-break in Maharashtra in 1991.

Recently, Singh (1999) reported it’s occurrence from Chhattisgarh. Sterility mosaic causes serious and often total yield loss and a susceptible cultivars infected in early stage (< 45 days) of the crop growth showed complete sterility and yield loss up to 100 per cent but as the plant grew older (> 45 days), their susceptibility to sterility mosaic decreased and such plant showed partial sterility.

Significant reduction, due to sterility mosaic infection, in plant height and number of branches, flowers per plant and pod length and 1000- grains weight has also been reported.

3. Symptomatology of Sterility Mosaic of Pigeonpea:

Sterility mosaic was first described as reduced leaves, a bushy habit and yellowish green leaves accompanied by sterility, pale green color and upright profused vegetative growth. Similar symptoms have been described by other workers.

Nene (1972) reported severe stunting, reduction in leaf size, an increase in number of secondary and tertiary branches arising from the leaf axles and complete or partial sterility of reproductive structures. Initial symptoms of sterility mosaic were vein-clearing in younger leaves in seedlings but primary leaves did not produce any symptoms.

Major three types of symptoms has been described as:

(a) Severe Mosaic on Leaflets:

Severe mosaic on leaflets plants do not produce flowers and pods (complete sterility),

(b) Mild Mosaic:

Mild mosaic plants produce flowers and pods to some extent (partial sterility), and

(c) Ring Spot:

ring spot symptoms are characterized by green island surrounding by a chlorotic halo on leaflets and this symptoms disappear as the plants mature (no sterility).

4. Biochemical Changes of Sterility Mosaic of Pigeonpea:

Biochemical alternation in sterility mosaic diseased plants, studied by several workers, have allocated:

(A) absence of glutamic , alanin, maleic and citric acid and reduced chlorophyll, carotene, xanthophyll, sugar synthesis and it’s translocation, chloroplastic protein, C : N ratio, peroxidase activities, organic and ascorbic acid contents.

(B) increased chlorophyllase, catalase, nitrate reductase and proteolytic enzymes activities and presence of unidentified amino acid and

(C) reduction in total carbohydrate, starch, resin, Ca, K, Na, Mn, photosynthesis rate of hill reaction, reducing sugar contents, RNA and DNA level, total nitrogen and free amino acids in disease plants. Lower in dry weight, chlorophyll and photosynthetic rate and presence of specific peroxidase enzymes and protein in diseased plants has been reported.

5. Histopathological Changes of Sterility Mosaic of Pigeonpea:

In transverse section of diseased mid-vein, fiber was found absent completely or present partially and the phloem cells were hypertrophied with larger cellular spaces.

6. Etiology of Sterility Mosaic of Pigeonpea:

Nature of Causal Pathogen:

Based on the symptoms, Capoor (1950, 1952) thought that it could be caused by a virus and named it pigeonpea sterility mosaic virus (PPSMV). A group of scientist, working at ICRISAT, ruled out the possibilities of fungus, bacterium, nematode or any non-infectious causal agent and they focused their attention on the virus or viroid (or mycoplasma) as the likely pathogen.

They also tried to associate/find out single/ double stranded RNA species or viroid type RNA or mycoplasma/rikettsia like organisms or spiroplasma but all attempts, so for, were abortive.

In a breakthrough in the etiology of sterility mosaic, Singh and Rathi, based on the comparison of Azure A stained healthy and diseased phloem cells of mid-vein, claimed the presence of nuclear inclusions associated with nucleus of phloem cells.

On the basis of megenta color retained by the phloem cells of only diseased mid-vein only and not by healthy, they also concluded the presence of foreign ribo-nucleo-protein in the phloem of diseased mid-vein.

Now it has confirmed that a tenui like virus particle of asymmetric morphology measuring 3-8 nm in diameter with 32 kDa coat protein and 4-5 segmented RNA of size 0.8-3.5 kilo-base is responsible for this sterility mosaic disease. The virus particles are highly flexuous and of branched filamentous.

Transmission:

Transmission of PPSMV has been reported through graft, sap and phytopathogenic nematode, however, phytopathogenic nematode and sap transmission could not be established. It is also not transmitted through seeds and dodder. PPSMV is transmitted through an eriophyid mite (Aceria cajani Channa Basavanna).

7. Morphology and Habitat of Sterility Mosaic of Pigeonpea:

Vector (A. cajani) is worm like eriophyid mite about 200- 250 um in length and have two pairs of legs attached one after another. It belongs to family eriophyidae in order Acarina and have very short life cycle of less than two weeks that comprises eggs, two nymphal stage and adult.

Eggs of A. cajani are about 30 x 40 (am with parallel side and rounded at the ends. A. cajani is light-shy and seen to feed on the lower side of the leaflets, preferably at the terminals of pigeonpea plants and found totally or partially buried in the thick mass of hairs of pigeonpea leaves.

Pathogen-Vector Relationship:

Single mite is sufficient to transmit the PPSMV successfully but 10 viruliferous mites are required for cent per cent infection and nymph and adults both are equally effective in PPSMV transmission. Incubation period may be 18 to 43 days depending upon the number of mites present on the leaves.

Rathi (1983) reported incubation period of 11 to 23 days. The minimum acquisition access period was found to be 30 min. Vector/sterility mosaic pathogen may have more than one biotype/strain at the same location or at geographically separated locations.

8. Epidemiology of Sterility Mosaic of Pigeonpea:

Survival and Spread of PSMV and its Vector:

PPSMV and its vector survive on the pigeonpea, Oxalis corniculata Rathi (1983) and off-season and ratooned pigeonpea. Ghanekar (1992) observed A. cajani and mild mosaic symptoms on Atylosia scarabaeoides but failed to transmit the pathogen to healthy pigeonpea. Later, Reddy, confirmed Cajanus (Atylosia) scarabaeoides as an alternate host of PPSMV and its vector.

Singh and Rathi (1995) observed A.cajani on the Cannabis sativa (Bhang) but it’s role in disease cycle is not confirmed. Vector is carried alive through wind against the wind direction and as for as 2 km in the wind direction from the source of inoculum.

Meteorological Factors and Vector Population:

Seasonal variation in the vector population has been reported by Reddy and Raju (1993). High humidity prevailing after summer rain did not favour mite multiplication but disease was highest up to 95 per cent wherever the crop was irrigated or grown near the other irrigated crops, possibly due to increased population of vector.

Highest summer rainfall (149.1 mm), lowest maximum (37.7°C) and minimum (21.9°C) temperature and highest maximum (69%) and minimum (29.3%) relative humidity were associated climatic factors during summer that favour an outbreak of sterility mosaic in the following crop season at ICRISAT and temperature ranging from 10 to 25°C (minimum) and 25 to 35°C (maximum) was congenial for the build-up of mite population.

Mite population was positively correlated with rainfall and relative humidity and negatively with temperature Reddy and Raju (1993) whereas, Singh and Rathi (1997) reported that mite population was positively correlated with maximum and minimum temperature and negatively correlated with maximum relative humidity.

9. Pigeonpea Sterility Mosaic Virus and Other Pathogens Interaction:

Preceding PPSMV infection of pigeonpea, protected Fusarium udum infection, predispose the plants to powdery mildew infection and, protected from infection of mungbean yellow mosaic virus (MYMV) and vice-versa by 100 per cent in glass-house experiment.

10. Management Measures of Sterility Mosaic of Pigeonpea:

Cultural:

Sterility mosaic may be controlled by removing perennial and volunteer plants of pigeonpea, growing in the vicinity of pigeonpea fields, well in advance of the sowing season.

Ramakrishnan and Kandaswamy 1972 recorded higher disease incidence in the crop sown in February and March than those in other months whereas, Rathi (1977) and Singh and Rathi (1996) found no significant difference in the disease incidence in various dates of sowing.

Sterility mosaic incidence was lower at 50 cm spacing than 150 cm and higher at low plant density. However plant density Ramakrishnan and Kandaswamy (1972), spacing (25 cm, 50 cm and 75 cm), intercropping with sorghum and pearl millets and border and inter-cropping with jwar and sunhemp had no effect on disease incidence.

Chemical:

A large number of granular insecticides viz.; Temik, Thimet and Disyton, as basal and top dressing, were not effective Ramakrishnan and Kandaswamy Q972 but test plants from the seeds treated with Temik 10G exhibited no symptoms after inoculation in glass house.

Nematicides also proved to be ineffective against sterility mosaic while spray of acaricides, viz.; Morocide, Dicofol (Kelthane), Sulphur, Moreston and Golecron, at 10 to 15 interval, reduced the disease incidence up to 50 per cent Ramakrishnan, and Kandaswamy (1972).

Disease incidence was reduced by 43.0 per cent in Demecron (0.05%) and Metasystox (Oxydemeton-methyl) (0.1%) plus Quenching oil (2%) spray, as compared to unsprayed plots.

Seed dressing with Furadan 3G (Carbofuran) (25%) was effective up to 45 days and soil application of Furadan 3G (40 kg/ha) and Temik (15 kg/ha) was effective up to 75 days after sowing and spraying of Tedion, Morestan (Oxythioquinox) and Dicofol (Kelthane) (0.1%) killed the mites 90 per cent.

Three sprays of Metasystox (0.05%), Nuvacran (Monocrotophos) (0.04%) and Karathane (Dinocap) (0.5%), starting from the first symptoms appearance and after 20 days intervals, failed to provide protection under field conditions.

11. Screening Techniques and Host Plant Resistance of Sterility Mosaic of Pigeonpea:

Several screening techniques as “twig tying”, “leaf stapling”, “leaf pinning” spreader row “infector hedge inoculation” and “infector rows” to transfer the viruliferous mites from diseased to healthy plants and petiole grafting to transmit the PPSMV from diseased to healthy plants to screen out the source(s) of resistance to A. cajani and/or PPSMV has been described.

Recently, Kumar prepared anti-PPSMV rabbit polyclonal antibodies for the detection of PPSMV infection. A 9-point disease rating scale for the quantification of disease in the field conditions has been described.

First identification of certain types of pigeonpea resistance to unknown sterility was described in 1931. Alam (1931) claimed that “Sabour 2E” was resistant to sterility mosaic . Excellent work has been done to identify the sources of resistance.

Besides these, few more lines with multiple disease resistance as ICP-7198, 8024, 8860, 8862, 9142, 10960, PR-5149, ICPL-83-227 (wilt and sterility mosaic ), ICPL 11302-11304 (Wilt, sterility mosaic and Phytophthora blight) and ICP-8861, 8862 and 10960 (wilt, sterility mosaic and Alternaria blight) has also been reported.

ICRISAT early maturing lines ICPL-151 is tolerant to sterility mosaic and others as ICPL-146, 269, 366, 8327, DA-12, DA-15, DA-51, MA-17, Sehore-367, DPPA-84-61-3, DP PA -84-8-4, Pant A-104, Bhawanisagar 1 and NPPR 1 all are resistant to sterility mosaic . ICPL-87119, a multiple disease resistant genotype, is being extensively grown by farmers of Andhra Pradesh. Muniyappa and Nangia and Reddy and Nene (1980,1981) reported ring spot symptoms on certain genotype (NPWR 15) and considered it as tolerant reaction because such genotypes showed normal flowering and podding inspite of infection.

Simultaneously, they also observed that these tolerant lines did not permit prolonged multiplication of vector or not preferred by the vector.

Recently, Kulkarni observed that, out of 62 accessions of Cajanus scarabaeoides, 21 accessions (ICP15684, 15688, 15692, 15695, 15697, 15699, 15700,15701, 15702, 15703, 15707,15712, 15725,15726, 15728, 15734, 15736, 15737, 15739, 15740 and 15741) were resistant to both the mild and severe strain of PPSMV.

12. Inheritance and Mechanisms of Resistance of Sterility Mosaic of Pigeonpea:

ICRISAT reported that four allelic genes were involved in the controlling of resistance and susceptibility to sterility mosaic : two allels for immunity, one for tolerance and one for susceptibility. Susceptibility was reported to be dominant to all the resistant genes. Singh found that resistance to sterility mosaic appeared to be govern by four independent non-allelic genes.

Of these four, two dominant and two recessive genes were conferring resistance. Susceptibility to sterility mosaic disease was dominant over resistance and tolerance and that tolerant reaction was dominant over resistance of certain lines.

Two loci and more than two allels at each locus were the suggested explanation resistance F1 and F2 generation in different cross combination. Many of the sources identified as resistance so for do not favour mite multiplication and hence these appear to be resistance to vector.

Line ICP-8136 has been noticed as resistant to PPSMV but not to the vector. Ring spot symptoms in some genotypes, such as ICP-2376, appears to be.’ hypersensitive response of the host to restrict the spread of pathogen, however, these lines favour the mite multiplication at par the susceptible lines Ghanekar, 1992.

Conclusion to Sterility Mosaic of Pigeonpea:

Sterility mosaic has become one of the most devastating disease all over the pigeonpea growing areas of India as well as in few other countries, even though large gaps do exist in our knowledge of disease epidemiology and chemical control measures to combat the disease.

Systematic studies are needed on:

(a) role of Cajanus scarabaeoides, Cannabis sativa, Oxalis corniculata, perennia /long duration pigeonpea in carrying over the pathogen and vector.

(b) precise mechanisms of resistance, such as antibiosis, non-preference and/ or tolerance operative against the mite vector because, till date, with few exceptions, identified resistant source(s) are primarily resistant to vector.

(d) To evolve the high yielding short duration pigeonpea varieties resistant to pigeonpea sterility mosaic virus.

Thus, Plant Pathologists shall be in the position to overcome the losses caused by this nightmare of the pigeonpea.