Incidence of Black Point Disease in Agra Region During 2017-2018

INTRODUCTION

In India no major crop has achieved the growth rate comparable to wheat in production with this increase in production and area awareness of diseases and pests has also increased certain disease which was considered unimportant in the past have become disease is ―black point of wheat‖, which is also known as ―smudge‖ in many parts of the world and can be identified as a disease with superficial black to brown lesions on wheat grains (Neergaard 1979). The introduction of Mexican blood in the Indian wheat cultivars has undoubtedly resulted in the development of high yielding wheat varieties but the point (Agarwal and Verma, 1975) The black point disease of wheat was reported for the first time in India by Dasthur in 1932 from the central provinces (Dasthur, 1932). Thus disease has been reported from Canada, the USA, Argentina, Germany, Italy, Morocco, South Africa, India, and java. In India the disease is prevalent in almost all the states where wheat crop is grown Joshi et. al., (1969) reported an outbreak of the disease in an epidemic form in 1967-68 in the northern wheat belt of the country . they stated that due to the prolonged wet weather in Punjab, Haryana, Delhi and Uttar Pradesh in 1967-68 just before harvest, black point disease had a widespread occurrence. Khethrpal et al. , (1980) also observed that high relative humidity with frequent rains was conducive to the incidence of black point disease. In the past 3-4 years, unseasonal rains occur during the harvest period in western UP including Agra. Therefore, it was considered important to assess seed lots of wheat for the occurrence of black point disease, which decreases the quality and germinability of wheat grains.

A total of653 samples of freshly harvested wheat grains were collected from villagers of 5 tehsils viz., Sadar, Etmadpur, Kheragarh, karaoke, and bah of Agra district were collected in sterilized polythene bags in May 2018 these samples were visually observed for black/brown coloration on glass plates and percent incidence of black point disease of wheat was calculated (Table 1). Later,400 grains from each sample showing a discoloration of seeds were surface-sterilized with2% sodium hypochlorite solution for 5 minutes and then washed with sterile water twice and subsequently plated on Petri dishes containing solidified PDA medium@10 grains per plate. The plates were finally incubated in B.O.D. incubator at 28+ 1degree centigrade for 6 days in an alternate cycle of 12 hours fluorescent light and 12 hours darkness following rules of international rules of seed testing Association (Anonymus,1966) after incubation period the plates were studied with the help of stereo binocular and normal compound microscope for the association of molds with the discolored portion of wheat grains. Finally, fungal species were separated, purified, and identified with the help of descriptions given by Barnett

A perusal of Table 1. This indicates that the percent incidence of black point disease of wheat varies from place to place in Agra district. The maximum percent incidence (73.0) of this disease was recorded in samples of Karaoli. The average percent incidence of black point disease in wheat was noted to be 54.6%. the results presented in Table 2 indicate the percent incidence and abundance of fungi found to be associated with a black coloration of wheat grains in the Agra plate technique. This table shows the presence of 11 fungi, of which Alternaria alternate showed maximum percent incidence and percent abundance. On the other hand, the minimum incidence and abundance were shown by Acremonium crits. The next abundant mold was curunlaria lunata followed by Alternaria triticina and Helminthosporium Saturn. Further, Aspergillus flavors and Aochracens revealed an incidence of 32.50 and 32.00% respectively. Other forms showed less than 30% incidence. According to Bolley (1913), species of Alternaria and Helminthosporium are the chief causes of wheat grain discoloration. Galloway However, dastur(1948) isolated cochliobolus tritici, nigrospora sphaerica, sclerotium roofs, Helminthosporium sp, and Rhizoctonia sp. from the black point affected wheat kernels. London and Srivastava were (1953) reported that blackening of wheat grains was due to unusual rains during March and April and the blackening was confined not only to grains but was also present on the glumes. The fungus is mainly responsible for this blackening was Alternaria tenuis (now known as Alternaria alternata). Further, Parashar and prayer (1965) also reported that wheat crops in Punjab were severely damaged by black point caused by Alternaria tenuis (syn. Alternaria alternata) and Helminthosporium sanatorium. However, Hasija (1964) found the presence of auricularia pallascens in black point affected grains of wheat. Thus, these reports support our findings that the black point of wheat is mainly caused by Alternaria alternata, Helminthosporium satire, and auricularia lunata and is favored by high humidity and moderate temperature.

The author is highly thankful to the principal, Agra College, Agra, and Dr. P.B. Jha, Head, Botany Department Agra College for providing lab facilities and encouragement.

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Assistant Professor, Department of Botany, Agra College, Agra