MOLECULAR DETECTION AND NON CHEMICAL MANAGEMENT OF PAPAYA RINGSPOT VIRUS IN PAPAYA (Carica papaya L.)
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Date
2019-02-05
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UNIVERSITY OF AGRICULTURAL SCIENCES, GKVK BENGALURU
Abstract
Papaya ringspot virus became a major constraint for papaya cultivation
worldwide. The highest PRSV incidence (90%) was recorded in Bengaluru rural and
Mandya district and lowest (35%) in Hassan district during 2015-16 in surveyed districts
of southern Karnataka. Development of mutants through various mutagens like, UVradiation,
sodium salts (0.1M sodium acetate and 0.4M sodium nitrate), sodium azide
(0.1 and 0.2%) and ethyl methane sulphonate (500 and 1000 ppm) showed mild mosaic,
mosaic and chlorosis at 15 days after treatment (DAT) but became severe at 30 DAT. In
DAS-ELISA, PRSV showed strong reaction with PRSV specific antibody indicating no
mild strain development. RT-PCR detection showed decreased PRSV concentration
(4.179) in papaya plants treated with combination of fresh milk (5%) and sea plant
extract Kappaphycus alverezii-1(0.4%) compared to control (11986714). PRSV
inoculated plants sprayed with K. alverezii-1 showed high chlorophyll content, stomatal
conductance, photosynthesis, total sugars, total phenols total proteins and lower
transpiration rate. Among the major nutrients, nitrogen found significantly decreased with
increased phosphorus and potassium in addition to micronutrients viz., magnesium, iron,
boron, zinc and manganese compared to PRSV infected plants. Growing two rows of
African tall maize 40 days before planting as live barrier around papaya field + silver
reflective mulch row cover + soil & foliar application of micronutrients at 15th day after
transplanting (DAT) + neem leaf extract (5ml.L-1) at 30th DAT + neem oil (5ml.L-1) at
45th DAT + K. alvarezii-1(4ml.L-1) at 60th DAT + K. alvarezii-2 (6ml.L-1) at 75th DAT
and synthetic nucleoside (0.25mg.L-1) at 90th DAT (T10) and repeated the same
treatments in similar sequence till 9th month was found significantly efficient in reducing
PRSV infection (86.76 per cent disease control) with an average plant height (4.40 ft)
and yield (48.52 kg/ plant) with B.C ratio of 1:51.