White blister of mustard

Pathogen: Albugo candida

1. COLLEGE OF AGRICULTURAL TECHNOLOGY (Affiliated to Tamil Nadu Agricultural University, Coimbatore-3) Kullapuram (Po), ViaVaigai Dam, Theni-625 562 WHITE BLISTER OF MUSTARD STUDENT COURSE TEACHER Miss. SANKARESHWARI S Dr . PARTHASARATHY S ID NO : 2015021115 Asst. Prof., ( Plant Pathology )

2. HOST RANGE Disease affects large number of crucifers of economic importance like Mustard, Rape, Radish, Cabbage, Cauliflower and turnip. In India the disease is reported on Mustard, Rape, Eruca sativa , Turnip, Cauliflower and Cleome viscosa . The disease in association with downy mildew disease of crucifers caused by Peronospora parasitica cause severe damage to the crop.

3. ECONOMICAL LOSSES In India, it causes a yield loss of 24-54.5% due to both phases (leaf and staghead ) of white rust. The yield loss is due to the malformation of floral parts and as a result seeds are not formed.

4. DISTRIBUTION MAP Occurs in all parts of the world where cruciferous crops are grown. https://www.cabi.org/isc/datasheet/4051 ©http://www.cabi.org

5. CAUSAL ORGANISM Albugo candida (Pers. ex J.F. Gmel .)Kuntze.,1891. (or) Cystopus candidus (Pers. ex J.F. Gmel .) Lév ., 18 47.

6. PATHOGEN Asexual Stage Mycelium: Endophytic , non septate , branched, hyaline and having knob shaped haustoria . Conidiophores: Short, hyaline, clavate , thick walled, basally branched, club shaped and gives rise to simple chains of conidia. Conidiosporangia : Produced in the basipetal succcession and are attached by a gelatinous pads called disjunctor which releases zoospores.

7. Asexual structure of Albugo candida © cdn.biologydiscussion

8. PATHOGEN Sexual Stage Antheridium : Elongated and club shaped, multinucleate (6-12 nuclei), Paragynous  i.e., laterally attached to the oogonium . Oogonium : Spherical and multinucleate containing as many as 65 to 115 nuclei. Oospore : Uninucleate and on maturity secretes two to three layered walls- outer thick wall called Exospore and inner thin wall called Endospore .

9. Antheridium and Oogonium Oospore © cdn.biologydiscussion ©istudy.pk/ albugo

10. SYSTEMIC POSITION Domain: Eukaryota      Kingdom: Chromista          Phylum: Oomycota              Class: Oomycetes                    Order: Peronosporales                        Family: Albuginaceae                            Genus: Albugo                               Species: A. candida

11. Symptoms The disease affects all the aerial parts of the plant, but the roots are not attacked. Symptoms may appear as a result of two types of infection: Local and Systemic. Local infection: Isolated spots or pustules appear on leaves or stems or inflorescence. The pustules are of variable size, measuring 1 -2 mm in diameter and are raised shiny white areas.

12. Pustules occurring on leaves are usually confined to the lower surface only. Usually, the pustules appear in circular or concentric arrangement with one or two central areas. https://www.apsnet.org

13. Systemic infections: Abnormal growth, distortion and sterility of flowers or inflorescences due to Hypertrophy and Hyperplasia. These abnormalities are known as stagheads and consist mostly of thick-walled oospores. The peduncle and pedicel may become enormously thickened upto 12-15 times, the normal diameter. The petal may turn green sepal like and stamens and carpels are also converted to swollen leaf like structures.

14. The ovules are usually atrophied as also the pollen grains resulting in total sterility. The stem and the axis of the inflorescence may get twisted appearing in a zigzag sequence. Stag head deformation with white pustules on inflorescence of mustard

15. © biologydiscussion

16. LIFE CYCLE http://cdn.biologydiscussion.com

17. FAVOURABLE CONDITIONS Heavy dew or fog favours zoospore activity. Formation of stagheads is favoured when there is little sunlight (2-6 hours per day) and extended rainfall (up to 161 mm) during the flowering period. Optimum temperature between 10 and 20˚C for sporangia and zoospore germination.

18. MODE OF SPREAD Primary infection: Oospore contaminated seeds and zoospore infected flower buds. Secondary infection: Conidiosporangia produced during the early phase of the growing season. Zoosporangia are blown away by wind or any other agency such as rain.

19. Management Physical methods Ploughing or disking diseased plants and plant parts results in rapid decomposition of infected tissues and reduce the future infection. Crop rotation with noncruciferous host plants is also effective. Weed control and other sanitary methods are necessary too.

20. Resistance Resistance has been successfully deployed with mustard and rutabaga, however, with Asian vegetables such as Chinese mustard, Chinese cabbage, pak choi , and diakon resistant varieties have not yet been identified.

21. Chemical methods The acylalanine fungicide metalaxyl ( Ridomil ) is effective. Applications should be made to the soil and subsequently applied to the foliage. In temperate environments a soil applications and minimum of 1-2 foliar applications during the crop cycle is suggested.