Studies on management of alternaria blight (Alternaria Alternata) of garden pea (Pisum sativum L.)

Introduction

India is primarily an agriculture-based country with rich flora and fauna. The subtropical climatic conditions and geographical location of the country offers an edge for agriculture over other counties. It harbors one of the oldest civilization and cultivation which dates back to 9000 B.C. Cereals and pulses are among the earliest cultivated crops. Pulses are valued both for their nutritional security and soil amelioration effects. They are rich in both protein and essential amino acids, thus making them ideal source of protein for the huge vegetarian population of the country. Their ability to easily fit in crop rotations and to fix atmospheric nitrogen make them a good option for sustainable and profitable crop production strategy. Pigeon pea, chickpea, urad, moong, lentil, pea are among the commonly cultivated pulse crops in India. In the year 2019-2020, total area under pulse production was 28.34 mha and the total pulse production was 23.15 million tonnes which was 3.15 million tonnes less than the targeted production. Rajasthan followed by Maharashtra, Madhya Pradesh and Uttar Pradesh are the major pulse producing states of the country accounting for more than 60 per cent of the total production. Compared to last year i.e., 2018-2019 the total area under pulse production has decreased from 29.16 mha to 28.34 mha in 2019-2020 but the production has increased from 22.08 million tonnes to 23.15 million tonnes. The productivity has significantly increased from 651.2 kg/ha (in 2013) to 817 kg/ha (in 2020) but is still not sufficient to meet the daily per capita minimum requirement of the pulses which is 60g/day. India occupies fourth position in area (10.53%) and 5th position in production (6.96%) of pea (Anonymous, 2014). In India field pea is grown over an area of 11.50 lakh ha with a production of about 10.36 lakh tonnes during XIIth Plan period (2012)(2013)(2014)(2015). In the year 2019-2020 the total area under pea cultivation in India was 568 mha and the total production was 5791 tonnes. Uttar Pradesh is the major field pea growing state. It alone produces about 49 per cent of pea produced in India (Anonymous, 2015-16). Pea is the third most important pulse crop in the world, after dry bean and chickpea and the third most popular rabi pulse of India after chick pea and lentil. Garden Pea (Pisum sativum L.) (2n=14) probably originated in Mediterranean region of Europe and Western Asia (Vavilov, 1926) including North West India, Pakistan and Afghanistan. It belongs to Papilionoidae subfamily of legumes. It is one of the most important winter vegetable crops grown on commercial scale all over the world. The plant is a semierect herbaceous annual but may climb if support is available, have typical tap root system. It may reach a height of 200 cm but normally the height varies from 30-200 cm. It has succulent, slender, upright and hollow stem with pinnately compound leaves with one to three leaflet pair and terminally branched tendrils. Raceme type inflorescence arising from axils of leaves having typical individual papilionaceous flowers are characteristic feature of pea plant. The fruit is straight or curved pod with 4 to 9 seeds. The seed vary in shape. It could be round and smooth or may be angular or wrinkled. The color varies from green yellow to grey and brown. There are two forms of cultivated pea, the field pea (P. arvense L.) and the garden pea (P. sativum L.). It seems probable that garden pea was derived by selection from field pea (Smartt, 1976). Pea is a leguminous crop i.e. it has symbiotic nitrogen fixing bacteria in its root nodules. Symbiotic association of roots of pea plant with Rhizobium leguminosarum fixes nitrogen in the soil and adds to soil fertility, improves productivity of the successive crops without the added expense of supplemental fertilizer. The early maturing pea varieties fits well between crop rotations of rice-wheat and rice-maize. Pea is highly nutritive and very versatile crop grown for fresh green peas, tender green pods, dried seeds, and foliage (Duke, 1981). It contains high percentage of digestible proteins, carbohydrates, fats along with minerals (Ca, P and Mg) and vitamins A, B and C. They are commonly consumed in green fresh form but frozen and canned peas are also becoming very popular because of its all-season availability. Ripe dried seeds are consumed as whole, split or made into flour. The common preparations made from dried peas are dal and chhola. The dried peas are low in anti-nutritional factors and rich in high quality starch, protein and oligosides (Dhall, 2017). The crop is subjected to a number of yields deteorating factors like diseases and environmental stress due to ever changing climate. It reduces both yield and quality. Various diseases that affect the plant can be categorized into fungal, bacterial, viral diseases and nutritional deficiencies and toxicity. There are a lot of major and minor diseases associated with the plant, the most commonly observed disease includes powdery mildew [Erysiphe pisi Syd. (syn. E. polygoni DC)], downy mildew (Pernospora pisi), leaf blight or alternaria blight (Alternaria alternata (Fr.) Keissl.), ascochyta blight or black spot (Ascochyta pisi), rust (Uromyces fabae), wilt of pea (Fusarium oxysporum f. sp. pisi), bacterial blight (Pseudomonas pisi), pea enation mosaic virus (PEMV), pea mosaic virus (PMV) and pea early browning virus (PEBV) (Davis and Shehata 1985;Muehlbauer et. al., 1995;Kraft et. al. 1998) [24, 25, 26] . Alternaria blight of pea is a fungal disease caused by Alternaria alternata (Fr.) Keissl which infects a small number of grain legume species. In U.P. the disease appears in moderate to severe form every year and causes significant yield loss especially during the years when winter rains are frequent. Infection of host plants occur through air and seed borne transmission or planting into infected soil, where rain splash or leaves coming in direct contact with soil leads to infection. Initial symptoms are small lesions on the leaves and seed pods of pea, which grow in size overtime. Under heavy pathogen load the infection and symptoms can spread to the stems and pods where it can have a detrimental effect on seed quantity and quality. (Murray, 2009) [32] . The fungus is hemi-biotrophic and shows high genetic variability. It survives in plant debris and can be effectively transmitted through seeds, and has wide host range as well as has a broad ecological distribution. Eco-friendly and sustainable strategies for management of Alternaria blight has been reported in various other crop such as mustard and pigeon pea. Alternaria blight was considered a minor disease of pea but now a days, there is wide spread occurrence of Alternaria blight of pea in severe conditions in different pea growing areas in U.P. and parts of country.

Materials and method

The effect of five bio-agents and eight chemicals were tested for their efficacy against Alternaria alternata under in vitro condition. Different bio-agents were isolated from soil by serial dilution method. Chemicals were procured from store room, in the Department of Plant Pathology of Agricultural Research Farm field area Dev Bhoomi Uttarakhand University, Dehradun, Uttarakhand T1-Ajwain seed extract @ 5% concentration T2 -Ajwain seed extract @ 10% concentration T3 -Garlic clove extract @ 5% concentration T4 -Garlic clove extract @ 10% concentration T5-Neem leaf extract @ 5% concentration T6-Neem leaf extract @ 10% concentration T7-Tulsi leaf extract @ 5% concentration T8 -Tulsi leaf extract @ 10% concentration T9 -Bael leaf extract @ 5% concentration T10 -Bael leaf extract @ 10% concentration T11-Bhang leaf extract @ 5% concentration T12-Bhang leaf extract @ 10% concentration T13 -Control

The field experiments for integrated disease management were conducted at Agricultural Research Farm field area Dev Bhoomi Uttarakhand University, Dehradun, Uttarakhand during rabi season of 2024-2025 in Randomized Block Design (RBD) with three replications. Plot size was 4.0 x 3.0 m 2 with 30cm inter row spacing. Sowing was done in the month of November and harvested on maturity in the month of March. The recommended seed rate of pea is 80kg/ha. 9.6 kg seed were sown per plot manually in a line at a depth of 8 cm. The row-to-row distance between pea was 30 cm and plant to plant distance was 15cm after placement in furrows seeds were covered with soil. Necessary treatments were done prior to seed sowing. The recommended dose of fertilizer was applied as band placement at the time of sowing. Thinning was done 20 days after sowing to maintain the plant-to-plant distance of 15cm. Treatments were done in order to manage the disease. For evaluating the efficacy of the treatments against the Alternaria alternata untreated plot was taken as check/control plot. The treatment details of the experiments are given in Table 4 6 revealed that all treatments significantly reduced the percent disease incidence, increased the yield and test weight. The lowest percent disease incidence 20.15% was recorded in (T 4 ) Foliar application of Hexaconazole (@ 500 ml/ha after 15 DAS) followed by 23.39% in (T 3 ) Foliar spray of Mancozeb 0.25% + Azoxystrobin 0.1%. The highest percent disease incidence 47.35% was recorded in (T 10 ) Spray of Ajwain seed extract @ 5.0% concentration followed by 33.89% in (T 6 ) Soil application of Trichoderma harzianum [1×10 7 CFU @10 g m -2 )] compared to control (55.76%). The maximum yield was recorded 18.74 q/ha and test weight 177.4 g in (T 4 ) Foliar spray of Hexaconazole @ 500 ml/ha 15 DAS followed by 17.25 q/ha and test weight 175.3 in (T 3 ) Foliar spray of Mancozeb 0.25% + Azoxystrobin @ 0.1% concentration. The minimum yield and test weight 15.02 q ha -1 and 162.3g and was recorded in (T 10 ) Spray of Ajwain seed extract @ 5.0% concentration was recorded in (T 2 ) Soil application of Trichoderma harzianum [1×10 7 CFU @10 g m -2 )] compared to control (12.06 q ha -1 ) and (150.40 g) respectively.

Conclusion

On the basis of all the experiments and analysis of results from this work we came to the followings conclusions In vitro evaluation of biocontrol agents suggested that Chaetomium globosum showed maximum inhibition the mycelial growth of pathogen followed by Pseudomonas fluorescens and Trichoderma harzianum. In vitro evaluation of fungicide suggested Hexaconazole 5% SC and Propiconazole 25% EC exhibited maximum inhibition of Alternaria alternata followed by Carbendazim 12% + Mancozeb 63% also gave promising results. In vitro evaluation of different plant extract suggested Garlic clove extract to exhibit maximum inhibition of Alternaria alternata followed by 10% Bhang leaf extract. For integrated disease management of disease, foliar application Hexaconazole (@ 500 ml/ha after 15 DAS was found most effective to reduce the disease incidence of alternaria blight in pea and increase the yield of pea followed by Foliar spray of Mancozeb 0.25% + Azoxystrobin 0.1%.

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