Epidemiological studies on Alternaria blight disease of pigeon pea caused by Alternaria alternata (Fr.) Keissler
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Date
2022
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DRPCAU, PUSA
Abstract
Pigeon pea (Cajanus cajan L. Millsp.) is one of the most important pulse crops grown in India next to Chickpea. Wide range of pests and diseases are known to affect this crop which leads to greater reduction in yield. However, among these Alternaria blight disease is getting major importance and becoming a limiting factor for the pigeon pea cultivation. Keeping this in mind the current study was focused on various aspects such as survey to know the prevalence of Alternaria blight disease in four districts of Bihar, role of weather variables on the progression of Alternaria blight disease in three different dates of sowing and to find out the resistant genotypes among the available pigeon pea genotypes.
Survey conducted in different locations of four districts of Bihar has showed its prevalence and widespread occurrence with frequency of disease varied from 25.22 to 48.05 per cent.
The first symptoms of the disease appeared on the lower leaves as Alternaria spp. is a low sugar fungus. Initially they start as the small, minute brown to black lesions which multiply rapidly and spread to the upper leaves. These lesions coalesce to form a large concentric ring surrounded by a yellow halo. In the later stages these symptoms start appear on all the aerial parts of the plant such as stem and pods, in severe condition blighting of leaf takes place.
The disease incidence was more in case of late sown crop i.e.,15th July 2021 up to 67 per cent when compared to the normal sown crop of disease incidence up to 50.1 per cent. The weather conditions that prevailed in the field had a significant impact on the disease's progression. In case of first date of sowing, maximum periodical rise was noticed in the second and third week of October. The maximum temperature ranges from 27.9oC to 33.1oC, minimum temperature ranges from 24.5oC to 24.7oC with relative humidity (morning) more than 99 per cent, relative humidity (evening) more than 70 per cent, rain fall of greater than 114 mm and 3 rainy days favoured the maximum disease incidence. In case of second and third date viz.30th July 2021, 15th August 2021 the disease progression was more in case of 40th to 42nd meteorological week.
Disease progress was negatively and significantly correlated with the minimum temperature, negatively correlated with maximum temperature and rain fall whereas relative humidity (morning and evening) positively correlated with disease development on pooled basis for three different dates of sowing. The regression equations have been developed with different weather variables interaction on the progress of disease could explained the variation between 64 and 70 per cent.
One hundred and thirty-two genotypes were screened against the Alternaria blight disease under artificial condition in research field using infector row. Only ten genotypes viz. RVSA 14-2, WRGE 138, LRG 224, LRG 275, AKTM 1914, AKTM 1917, WRG 391, WRG 390, PT 11-16 and SKNPCH 1906 were found to be moderately resistant. 64 genotypes were moderately susceptible and remaining 58 genotypes were susceptible to Alternaria blight of pigeon pea. These ten moderately resistant genotypes can be used in breeding programme to develop the resistant varieties or they can be released for general cultivation.