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|Authors:||Mangav, Kakasaheb Krishnappa|
|Title:||SCREENING OF CITRUS ROOTSTOCKS FOR DROUGHT TOLERANCE|
|Publisher:||MAHATMA PHULE KRISHI VIDYRPEETH RAHURI, 413 722 DlST- AHMEDNAGAR. Maharashtra State (India)|
|Abstract:||The investigation on "Screening of citrus rootstocks for drought tolerance" was conducted in pot culture under glasshouse conditions in the Department of Horticulture, Mahatrna Phule Krishi Vidyapeeth, Rahuri (M.S.). For this purpose, morphological, physiological and bio-chemical criteria were studied.The experiment was laid out in a completely randomized design (C.R.D.). Eight rootstock species viz. Sour orange,Jamberi Kodur, Rough lemon Chethali, Rangpur lime, Marmalade orange, Cleopatra mandarin (Morocco) , Carizzo citrange and Billikichilli were replicated six times. For this, six-months-old,healthy seedlings, grown in polybags were subjected to moisture stress. The leaf rolling and unrolling were takenas the symptoms of water stress and relief from water stress,respectively. Among the rphological arameters, minimum decrease in number of secondary, tertiary roots and leaf angle were found to be the useful criteria for screening citrus speciesfor their drought tolerance. The seedlings of Cleopatra mandarin (Morocco) and Carizzo citrange registered significantly less reduction in secondary and tertiary roots due to waterstress than those of Rough lemon Chethali and Sour orange. The seedlings of Carizzo citrange and Cleopatra mandarin(Morocco) registered significantly less increase in leaf anglethan those of Sour orange. Rough lemon Chethali and Billikichilli due to water stress condition and had revived their leafangles but ever reached their original position.Under physiological parameters, the seedlings ofCleopatra mandarin (Morocco) followed by Carizzo citrange registered significantly less number of stomata per mm2 and the stomatal pores were found to be completely closeddue to water stress. After relief from water stress, these seedlings had reopened their stomata rapidly than those of Billikichilli. The seedlings of Carizzo citrange, JamberiKodur and Cleopatra mandarin (Morocco) registered significantly lower rates of transpiration, those of Cleopatra mandarin(Morocco) followed by Rangpur lime and Carizzo citrange had significantly less per cent reduction in RWC and those of Cleopatra mandarin (Morocco)» Carizzo citrange and Marmaladeorange registered significantly more increase in the root : shoot ratio both on fresh and dry weight basis, while thoseof Carizzo citrange followed by Cleopatra mandarin (Morocco) registered sinificantly less decrease in leaf thickness due to water stress. The seedlings of Rough lemon Chethaliand our orange registered ignificantly more rates of transpiration, more per cent reduction in RWC, less increase in the root :shoot ratio and more decrease in leaf thickness at stress.After relief from water stress, all rootstock species resumed their turgidity (RWC). Similar trend was observed in root :shoot ratio. However, all the rootstock species had recoveredalmost equally well in respect of leaf thickness on re-watering. In respect of the bio-chemical parameters, the seedlings of Cleopatra mndarin (Morocco) followed by Jamberi Kodur and Carizzo citrange registered maximum increasein proline content at stress, while those of Carizzo citrange and Cleopatra mandarin (Morocco) had accumulated significantlymore amounts of ABA than those of Billikichilli, Sour orangeand Rough lemon Chethali and just a reverse trend was observed On recovery of ABA after stress, while all the rootstockspecies had recovered almost equally well in respect of proline content. The seedlings of Carizzo citrange followed by Cleopatra mandarin (Morocco) registered significantly less decrease in total protein content at stress than thoseT- 35JV < ^ r ^of Rough lemon Chethali and Ma malade orange.On re watering, all he species had ered equally well. The decreasesin chlorophyll 'a1 , 'b' and total chlorophyll content inthe leaves were significantly less in Cleopatra mandarin(Morocco) , Carizzo citrange and Rangpur lime, while seedlingsof Rough lemon Chethali, Sour orange registered significantly more decreases in chlorophyll contents and all the rootstockspecies had recovered equally well on rewatering. TheC.S.I, values ranged from 9.33 to 21.42 units. The seedlingsof Rangpur lime followed by Cleopatra mandarin (Morocco)and Carizzo citrange registered significantly low C.S.I, valuesthan those of Billikichilli, Sour orange and Rough lemonChethali. The seedlings of Cleopatra mandarin (Morocco)followed by Carizzo citrange registered significantly moreincrease in epidermal wax content, while Rough lemon Chethali,Marmalade orange and Sour orange registered less increasein this parameter due to water stress. On rewatering, allthe species were found to have recovered almost equallywell. Considering the above mentioned morphological,physiological and bio-chemical parameters, the rootstockspecies viz. Cleopatra mandarin (Morocco) and Carizzo citrangeare the most drought tolerant. It is therefore, suggestedto use Cleopatra mandarin (Morocco) or Carizzo citrangeas rootstocks for raising commerical citrus orchards in thearid regions prone -to drought.|
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