INVESTIGATION ON BUD FAILURE DISEASE OF ALMOND (Prunus dulcis (Mill.) D.A. Webb.)
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Date
2024-04-24
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UHF Nauni
Abstract
Surveys of 40 almond orchards of Shimla, Kullu, Lahaul & Spiti and Kinnaur districts of
Himachal Pradesh conducted during 2021, 2022 and 2023 revealed the incidence of Prunus necrotic
ring spot virus (PNRSV) ranging from 0 to 100 percent. The predominant symptoms observed
included chlorotic spot, shot holes, necrotic rings and mid vein distortion. Almond orchard in the
Experimental Farm of the Department of Fruit Science, Dr YS Parmar University of Horticulture and
Forestry, Nauni, Solan was selected for serological indexing through DAS-ELISA which resulted in
the detection of PNRSV in all trees marked on the basis of visual symptoms. Association of PNRSV
with viral symptoms in almond was further confirmed by RT-PCR assays. Phylogenetic analysis
revealed that PNRSV isolate from Lippa (OQ784876) had maximum homology with that of the
isolate from Canada (JQ005050); Nirath isolate (OQ734566) with isolate from Germany (QP357944);
Duttnagar isolate (OQ434579) with isolate from Italy (AJ133213); Bagara isolate (OQ434576) with
Italian isolate ( AJ133204) and almond isolate from Nauni (OQ434580) with two isolates from China
(MH730938, MF198443). Among all plant parts used throughout the year for DAS-ELISA based
detection of PNRSV, leaves of the almond collected from symptomatic plants had the maximum
concentration of PNRSV and petals had a high concentration of virus can be used in the month of
march for detecting PNRSV. Plants germinated from seeds of infected almond trees with PNRSV
yielded positive results in DAS-ELISA assays. Serological host range of PNRSV has also been
established in peach, nectarine, plum, cherry and almond. Nectarine has been serologically established
to be a new host of PNRSV in our conditions and this finding is of vital importance as nectarine has a
great potential of becoming a highly remunerative crop due to its attractive colour and fuzzless skin.
None of the 12 almond varieties indexed serologically were found to be free from PNRSV infection
with California Paper Shell recording the maximum virus concentration and Sharbo selection had the
minimum virus concentration. Visual and serological indexing in all orchards surveyed in the Districts
of Shimla and Kullu revealed the association of PNRSV with almond trees whereas almond orchards
at Triloknath, Geu and Hurling in Lahaul & Spiti district and Pooh in District Kinnaur were found to
be free from PNRSV infection. During the course of studies, a new phytoplasma disease of almond
was detected which is a new report from India.