The aim of the study is to know the diseases symptoms, incidence, and transmission of seed-borne bacteria (Pseudomonas syringae pv. lachrymans, PSL) from the seeds of cucumber (Cucumis sativus L.) that belongs to plant family Cucurbitaceae. The causal agent PSL causes the Angular leaf spot (ALS) disease. A total of 102 seed and, 50 fruit samples were collected by a major and minor survey from various districts of Rajasthan to study the disease incidence. The collected seed samples were categorized in asymptomatic (healthy-looking) and symptomatic (discolored seeds) in dry seed examination using a stereo-binocular microscope. The collected seed samples revealed 20-100% incidence of bacteria on Kings Medium B. On the basis of morphological, physiological, chemical, molecular and pathogenicity test the bacterium find to be Pseudomonas syringae pv. lachrymans. PSL attack caused tiny, round to irregularly shaped, water-soaked lesions with a yellow halo to appear on cotyledonary leaves and other plant components, depending on disease severity. In the pot experiment and field investigation it was found that the bacterial pathogen produced tiny yellow spots covered by halo on leaves which became necrotic at disease severity. As the disease progresses, the whole leaf collapses due to the reduction of photosynthesis capacity and photosynthetic area of the leaf and finally reduces the yield of the crop.