<p>Wheat (<italic>Triticum aestivum</italic> L.) is one of the most important staple food crops of India. The leaf blight of wheat caused by <italic>Alternaria triticina</italic> is an important fungal disease in some parts of India and damage up to 30%, may occur when the second and third leaves are severely blighted.</p><p>Healthy and naturally infected seeds of wheat cv. Sonalika were collected separately during 2002–2003. For artificially infected seeds, fresh culture of the fungus was taken and mycelium cum spore suspension was prepared. The seeds were then, heavily coated with this suspension and dried at 15–25°C in laboratory. The healthy, naturally and artificially infected seeds were stored in paper bags till the next sowing season and monthly isolations were made from April to November. These naturally, artificially infected seeds and surface sterilized healthy seeds (served as control) were sown in autoclaved soil in pots (30 cm dia.) during next crop season (2003–2004) in four replications. Five seeds were sown in each pot, in poly house to check the aerial infection.</p><p>Monthly isolations from naturally and artificially infested soil were made using dilution plate method using P.D.A. to know the viability of pathogen. For determining the role of infested soil as primary source of infection, pots (30 cm dia.) were filled with naturally infested field soil, artificially infested autoclaved soil and with autoclaved soil to serve as control. In the another set. diseased leaves, wrapped in tissue paper were buried in the soil in pots at the depth of 10 cm. Isolations from infected sample kept in both conditions were made at monthly intervals to study the viability of the pathogen. In one set of pots heavily infected diseased leaves was thoroughly mixed with autoclaved soil and filled in earthen pots of 30 cm dia. In another set, pots were filled with heavily infested soil taken from the affected field and mixed with diseased leaves and in third set, pots were filled with autoclaved soil which served as control. Five healthy surface seterilized seeds of wheat cv. Sonalika were sown. The presence of pathogenic culture of <italic>A. triticina</italic> from April to November, 2003, indicating that the pathogen remained viable from one season to another in seed, soil and plant debris. Alka and Singh (<xref ref-type="bibr" rid="bib001">2004</xref>) reported survival of <italic>Allernariti tenutissima</italic> causing leaf spot of pigeon pea up to 8 months on diseased leaves. The percentage of infected plants was higher (43.7%) in case of plants raised from artificially infected seeds than that of naturally diseased seeds (23.5%). The plants raised from healthy surface sterilized seeds did not develop any symptom of the disease. This clearly indicated that the diseased seeds served as primary source of inoculum (<xref ref-type="bibr" rid="bib003">Singh <italic>et al.</italic> 2004</xref>), Pandian <italic>et al.</italic> (<xref ref-type="bibr" rid="bib002">2004</xref>) also reported that the population of <italic>Drechslera sorokiniana</italic> estimated in the soil samples, varied from 2.3 to 3.3 cfu in 10<sup>−2</sup> dilution and survived for more than 12 months under natural conditions.</p><p>The plants raised in pots, autoclaved soil with the diseased plant debris, developed typical symptoms of Alternaria leaf blight from first on lower most leaves of the plants. Disease crawled up gradually to upper leaves. Similarly, the disease development also occurred in case of plant raised in pot soil infested with the diseased plant debris. No symptoms could be observed on the plants growing in third set containing autoclaved soil and kept under controlled conditions. These observations are supported by the findings of Alka and Singh (<xref ref-type="bibr" rid="bib001">2004</xref>); Srivastava <italic>et al.</italic> (<xref ref-type="bibr" rid="bib004">2005</xref>). <table-wrap id="tab001"><label>Table 1</label><caption><p>Role of seeds as primary source of inoculum</p></caption><table><thead><tr><th>Treatments</th><th align="center">No. of plants germinated</th><th align="center">No. of plants infected</th><th align="center">% of infected plants</th></tr></thead><tbody><tr><td colspan="4"><hr /></td></tr><tr><td valign="top">Naturally infected seed + Autoclaved soil</td><td align="center" valign="top">17</td><td align="center" valign="top">4</td><td align="center" valign="top">23.5</td></tr><tr><td valign="top">Artificially infested seed + Autoclaved soil</td><td align="center" valign="top">16</td><td align="center" valign="top">7</td><td align="center" valign="top">43.7</td></tr><tr><td valign="top">Surface sterilized healthy seeds + Autoclaved soil (control)</td><td align="center" valign="top">19</td><td align="center" valign="top">Nil</td><td align="center" valign="top">Nil</td></tr></tbody></table></table-wrap><table-wrap id="tab002"><label>Table 2</label><caption><p>Role of infested soil as primary source of inoculum</p></caption><table><thead><tr><th>No. of Treatments plants germinated</th><th align="center">No. of plants infected</th><th align="center">% of infected plants</th></tr></thead><tbody><tr><td colspan="4"><hr /></td></tr><tr><td valign="top">Naturally infested 17 field soil</td><td align="center" valign="top">2</td><td align="center" valign="top">11.7</td></tr><tr><td valign="top">Autoclaved artificially 16 infested soil</td><td align="center" valign="top">3</td><td align="center" valign="top">18.7</td></tr><tr><td valign="top">Autoclaved soil 28</td><td align="center" valign="top">Nil</td><td align="center" valign="top">Nil</td></tr></tbody></table></table-wrap><table-wrap id="tab003"><label>Table 3</label><caption><p>Role of diseased plant debris (leaves) as primary source of inoculum</p></caption><table><thead><tr><th>Treatments</th><th align="center">No. of plants germinated</th><th align="center">No. of plants infected</th><th align="center">% of infected plants</th></tr></thead><tbody><tr><td colspan="4"><hr /></td></tr><tr><td valign="top">Direct seed plant debris + Autoclaved debris</td><td align="center" valign="top">18</td><td align="center" valign="top">4</td><td align="center" valign="top">22.2</td></tr><tr><td valign="top">Diseased plant debris+ infested soil from infested field</td><td align="center" valign="top">17</td><td align="center" valign="top">6</td><td align="center" valign="top">35.2</td></tr><tr><td valign="top">Autoclaved soil without plant debris (control)</td><td align="center" valign="top">18</td><td align="center" valign="top">Nil</td><td align="center" valign="top">Nil</td></tr></tbody></table></table-wrap></p></sec></body><back><ref-list><title>References

APPS

Annals of Plant Protection Sciences

0971-3573

Society of Plant Protection Sciences

apps-14-2-061

SHORT COMMUNICATION

Perpetuation of Alternaria triticina causing leaf blight of wheat

Singh

A.K.

Singh

R.P.

Department of Plant Pathology, N.D. Univ. of Agri. & Tech. Kumarganj, Faizabad 224 229, India.

92006

142482483

<p>Wheat (<italic>Triticum aestivum</italic> L.) is one of the most important staple food crops of India. The leaf blight of wheat caused by <italic>Alternaria triticina</italic> is an important fungal disease in some parts of India and damage up to 30%, may occur when the second and third leaves are severely blighted.</p><p>Healthy and naturally infected seeds of wheat cv. Sonalika were collected separately during 2002–2003. For artificially infected seeds, fresh culture of the fungus was taken and mycelium cum spore suspension was prepared. The seeds were then, heavily coated with this suspension and dried at 15–25°C in laboratory. The healthy, naturally and artificially infected seeds were stored in paper bags till the next sowing season and monthly isolations were made from April to November. These naturally, artificially infected seeds and surface sterilized healthy seeds (served as control) were sown in autoclaved soil in pots (30 cm dia.) during next crop season (2003–2004) in four replications. Five seeds were sown in each pot, in poly house to check the aerial infection.</p><p>Monthly isolations from naturally and artificially infested soil were made using dilution plate method using P.D.A. to know the viability of pathogen. For determining the role of infested soil as primary source of infection, pots (30 cm dia.) were filled with naturally infested field soil, artificially infested autoclaved soil and with autoclaved soil to serve as control. In the another set. diseased leaves, wrapped in tissue paper were buried in the soil in pots at the depth of 10 cm. Isolations from infected sample kept in both conditions were made at monthly intervals to study the viability of the pathogen. In one set of pots heavily infected diseased leaves was thoroughly mixed with autoclaved soil and filled in earthen pots of 30 cm dia. In another set, pots were filled with heavily infested soil taken from the affected field and mixed with diseased leaves and in third set, pots were filled with autoclaved soil which served as control. Five healthy surface seterilized seeds of wheat cv. Sonalika were sown. The presence of pathogenic culture of <italic>A. triticina</italic> from April to November, 2003, indicating that the pathogen remained viable from one season to another in seed, soil and plant debris. Alka and Singh (<xref ref-type="bibr" rid="bib001">2004</xref>) reported survival of <italic>Allernariti tenutissima</italic> causing leaf spot of pigeon pea up to 8 months on diseased leaves. The percentage of infected plants was higher (43.7%) in case of plants raised from artificially infected seeds than that of naturally diseased seeds (23.5%). The plants raised from healthy surface sterilized seeds did not develop any symptom of the disease. This clearly indicated that the diseased seeds served as primary source of inoculum (<xref ref-type="bibr" rid="bib003">Singh <italic>et al.</italic> 2004</xref>), Pandian <italic>et al.</italic> (<xref ref-type="bibr" rid="bib002">2004</xref>) also reported that the population of <italic>Drechslera sorokiniana</italic> estimated in the soil samples, varied from 2.3 to 3.3 cfu in 10<sup>−2</sup> dilution and survived for more than 12 months under natural conditions.</p><p>The plants raised in pots, autoclaved soil with the diseased plant debris, developed typical symptoms of Alternaria leaf blight from first on lower most leaves of the plants. Disease crawled up gradually to upper leaves. Similarly, the disease development also occurred in case of plant raised in pot soil infested with the diseased plant debris. No symptoms could be observed on the plants growing in third set containing autoclaved soil and kept under controlled conditions. These observations are supported by the findings of Alka and Singh (<xref ref-type="bibr" rid="bib001">2004</xref>); Srivastava <italic>et al.</italic> (<xref ref-type="bibr" rid="bib004">2005</xref>). <table-wrap id="tab001"><label>Table 1</label><caption><p>Role of seeds as primary source of inoculum</p></caption><table><thead><tr><th>Treatments</th><th align="center">No. of plants germinated</th><th align="center">No. of plants infected</th><th align="center">% of infected plants</th></tr></thead><tbody><tr><td colspan="4"><hr /></td></tr><tr><td valign="top">Naturally infected seed + Autoclaved soil</td><td align="center" valign="top">17</td><td align="center" valign="top">4</td><td align="center" valign="top">23.5</td></tr><tr><td valign="top">Artificially infested seed + Autoclaved soil</td><td align="center" valign="top">16</td><td align="center" valign="top">7</td><td align="center" valign="top">43.7</td></tr><tr><td valign="top">Surface sterilized healthy seeds + Autoclaved soil (control)</td><td align="center" valign="top">19</td><td align="center" valign="top">Nil</td><td align="center" valign="top">Nil</td></tr></tbody></table></table-wrap><table-wrap id="tab002"><label>Table 2</label><caption><p>Role of infested soil as primary source of inoculum</p></caption><table><thead><tr><th>No. of Treatments plants germinated</th><th align="center">No. of plants infected</th><th align="center">% of infected plants</th></tr></thead><tbody><tr><td colspan="4"><hr /></td></tr><tr><td valign="top">Naturally infested 17 field soil</td><td align="center" valign="top">2</td><td align="center" valign="top">11.7</td></tr><tr><td valign="top">Autoclaved artificially 16 infested soil</td><td align="center" valign="top">3</td><td align="center" valign="top">18.7</td></tr><tr><td valign="top">Autoclaved soil 28</td><td align="center" valign="top">Nil</td><td align="center" valign="top">Nil</td></tr></tbody></table></table-wrap><table-wrap id="tab003"><label>Table 3</label><caption><p>Role of diseased plant debris (leaves) as primary source of inoculum</p></caption><table><thead><tr><th>Treatments</th><th align="center">No. of plants germinated</th><th align="center">No. of plants infected</th><th align="center">% of infected plants</th></tr></thead><tbody><tr><td colspan="4"><hr /></td></tr><tr><td valign="top">Direct seed plant debris + Autoclaved debris</td><td align="center" valign="top">18</td><td align="center" valign="top">4</td><td align="center" valign="top">22.2</td></tr><tr><td valign="top">Diseased plant debris+ infested soil from infested field</td><td align="center" valign="top">17</td><td align="center" valign="top">6</td><td align="center" valign="top">35.2</td></tr><tr><td valign="top">Autoclaved soil without plant debris (control)</td><td align="center" valign="top">18</td><td align="center" valign="top">Nil</td><td align="center" valign="top">Nil</td></tr></tbody></table></table-wrap></p></sec></body><back><ref-list><title>References

Alka

Singh

S.P.

(2004). Survival of Alternaria tenutissima causing leaf spot of pigeon pea in diseased plant debris. Ann. Pl. Protec. Sci., 12: 231–232.Pandian

C.S.

Singh

D.V.

Srivastava

K.D.

(2004). Survival ability of Drechsfera sorokiniana in soil, stubbles and weeds. Ann. Pl. Protec. Sci., 12: 328–331.Singh

B.K.

Singh

Narain

Udit

(2004). Role of diseased plant debris and seed in the perpetuation of Myrothecium roridum leaf spot of pigeon pea. Ann. Pl. Protec. Sci.12: 96–98.Srivastava

K.C.

Ghosh

Mishra

(2005). Survival of Alternaria alternata in plant debris under different temperatures and soil depths. Ann. Pl. Protec. Sci., 13: 213–269.