Jatti Khatti Research Articles

Oxidative stress dynamics revealed the role of H2O2 in citrus rootstocks sensitivity to Phytophthoranicotianae

Phytophthora nicotianae is a devastating pathogen in citrus and tolerant rootstocks are required for its management. Seven Jatti Khatti (JK, a rough lemon strain; susceptible) × Poncirus trifoliata (PT; tolerant) hybrids were screened against P. nicotianae. In feeder root rot based evaluation, three hybrids were found moderately tolerant (MT) while four were moderately susceptible (MS). The H2O2 in plant pathogen interactions contributes in resistance/susceptibility to the biotrophic/necrotrophic pathogens. To comprehend its role in citrus against Phytophthora (a hemi-biotrophic pathogen), H2O2, lipid peroxidation, and peroxidase (POD) activity were determined in Phytophthora inoculated and non-inoculated roots of JK, PT, three MT and one MS hybrids at 10, 20 and 30 days post inoculation (dpi). The tolerant parent, PT and MT hybrids exhibited lower or stable H2O2 content in Phytophthora inoculated plants at 20 or 30-dpi. Their POD activity increased at 10-dpi, depicting its role in H2O2 homoeostasis. At 30-dpi, JK and MS hybrid showed significantly higher H2O2 content (4.10 and 3.62 μmol g−1 FW), compared to 1.88 μmol g−1 FW in PT. The lipid peroxidation content significantly increased in JK or MS hybrid at 20 or 30-dpi. The susceptible or MS individuals displayed significantly higher (18–25 % higher) electrolyte leakage than their control. A strong positive association (r = 0.89) was found between electrolytes leakage and H2O2 accumulation at 30-dpi. The POD activity and H2O2 at 10-dpi showed strong negative correlation (r = −0.86). Results infer that high H2O2 causes cellular death and contributes to Phytophthora susceptibility in citrus. It can serve as a biomarker for predicting relative sensitivity to Phytophthora.

Morpho-physiological characterization of second generation colchiploids in sweet orange (<i>Citrus sinensis </i>(L.) Osbeck) cv. Mosambi

Induction of tetraploidy in citrus is commonly meant for the development of triploid seedless cultivars as well as resistance against abiotic and biotic stresses. Three-year-old, 20 second-generation colchicine treated (0.05, 0.10, 0.15 and 0.20%) plants (colchiploids), established from the putative tetraploid branches of the first generation colchiploids of sweet orange (Citrus sinensis (L.) Osbeck) cv. Mosambi vegetatively propagated on Jatti khatti rootstock, along with their wild (parent) type, were characterized based on morphological and physiological traits. Plant height and canopy volume were reduced, but stem girth, nodes per shoot and bark: wood increased in the majority of the second-generation colchiploids related to the wild type. Colchiploids also possessed improved flower characteristics in terms of length and width. The stomatal dimensions increased, but stomatal concentration reduced in all the colchiploids. Colchicine treatment also caused significant variations in leaf gas exchange parameters, including photosynthetic rate, intercellular CO2 concentration, leaf net transpiration rates, stomatal conductance, and intrinsic water use efficiency in colchiploids affecting their photosynthetic activities. The solid tetraploids identified on the basis of morpho-physiological characterization can be used in future breeding programmes for the development of triploid seedless citrus cultivars or can be used for the mitigation of biotic and abiotic stresses.

Morpho-physiological characterization of second generation colchiploids in sweet orange (<i>Citrus sinensis </i>(L.) Osbeck) cv. Mosambi

Induction of tetraploidy in citrus is commonly meant for the development of triploid seedless cultivars as well as resistance against abiotic and biotic stresses. Three-year-old, 20 second-generation colchicine treated (0.05, 0.10, 0.15 and 0.20%) plants (colchiploids), established from the putative tetraploid branches of the first generation colchiploids of sweet orange (Citrus sinensis (L.) Osbeck) cv. Mosambi vegetatively propagated on Jatti khatti rootstock, along with their wild (parent) type, were characterized based on morphological and physiological traits. Plant height and canopy volume were reduced, but stem girth, nodes per shoot and bark: wood increased in the majority of the second-generation colchiploids related to the wild type. Colchiploids also possessed improved flower characteristics in terms of length and width. The stomatal dimensions increased, but stomatal concentration reduced in all the colchiploids. Colchicine treatment also caused significant variations in leaf gas exchange parameters, including photosynthetic rate, intercellular CO2 concentration, leaf net transpiration rates, stomatal conductance, and intrinsic water use efficiency in colchiploids affecting their photosynthetic activities. The solid tetraploids identified on the basis of morpho-physiological characterization can be used in future breeding programmes for the development of triploid seedless citrus cultivars or can be used for the mitigation of biotic and abiotic stresses.

Rootstock mediated alteration in morphology and photosystem in sweet orange (Citrus sinensis) scion cv. Pusa Sharad under NaCl stress

There is a dearth of rootstock studies on how salinity stress imparts tolerance to the scion cultivar in citrus [Citrus sinensis (L.) Osbeck]. The impact of sodium chloride on sweet orange cv. Pusa Sharad (PS) grafted on 11 different rootstocks i.e. Jatti khatti (JK), X–639 (X9), CRH–12 (C12), NRCC–1 (N1), NRCC–2 (N2), NRCC–3 (N3), NRCC–4 (N4), NRCC–5 (N5), Troyer citrange (TC), CRH–47 (C47) and Cleopatra mandarin (CM) was evaluated at the nursery unit of ICAR-Indian Agricultural Research Institute, New Delhi, during 2019–22. Irrigation water containing 30 and 60 mM of sodium chloride (NaCl) was applied to scion/rootstock combinations in comparison to control (without NaCl) till the onset of salt injury symptoms i.e. 42 days. Under salinity stress, the PS scion grafted onto CM, X9, C47, N1, and N3 rootstocks exhibited minimum reduction in the scion height, leaf area ratio, root to shoot ratio, total chlorophyll content, total carotenoid content, transpiration rate, photosynthesis rate, internal CO2 concentration and stomatal conductance as compared to PS scions grafted onto JK, C12, N2, N4, N5, and TC rootstocks under 60 mM NaCl stress. Results showed that specific rootstock can enhance salt-tolerance potential by increasing pigment content and strengthening the photosystem. PS scions grafted onto CM, C47, X9, N1, and N3 demonstrated greater NaCl tolerance compared to those grafted onto JK, C12, N2, N4, N5, and TC and hence recommended for areas having salinity level up to 60 mM.

Long-term performance of grapefruit cultivars on different rootstocks

The present study was conducted to standardize the rootstock(s) for grapefruit cvs. Marsh Seedless andRedblush, suitable to grow commercially in northern India, budded on eight rootstocks. The sour orange andRLC-4 proved to be the vigorous rootstocks for Marsh Seedless (220.32 m3) and Redblush (175.65 m3) cultivars,respectively. The trees of Marsh Seedless were dwarf (51.23 – 52.27m3) on Attani-1 and Attani-2 rootstocks,while statistically similar growth of Redblush (46.52 m3) was observed on Jatti khatti rootstock. Jatti khatti andBillikhichli proved to be the good nutrient accumulators (P, K, and Mg) for Redblush; and Jatti Khati and RLC-4for Marsh Seedless (N, P, and Zn). Billikhichli and sour orange proved to be the sodium excluder rootstocks forboth varieties. RLC-4 and Rough lemon proved to be the most productive rootstocks for Redblush and MarshSeedless, respectively. It was followed by Troyer citrange for both the cultivars. These rootstocks also yieldedthe juiciest fruits in their respective cultivars. Attani-1 and Troyer citrange produced fruits with low acid contentin the tested cultivars of grapefruit.

Response of citrus (Citrus sps.) rootstock hybrids to PEG induced drought under hydroponic system

Present study was carried out at the glasshouse facility of the ICAR-Indian Agricultural Research Institute, New Delhi during 2020–21 using a simple hydroponic platform to assess the polyethylene glycol (PEG) induced drought impact on shoot-root morphology and physio-biochemical traits of 4 newly developed citrus (Citrus sps.) rootstock hybrids. Hybrid CRH 21-13/14 displayed superior shoot morphological performance in drought, articulated in terms of increment in plant height (4.5%), leaf numbers (9.5%), and dry weight of shoot (7.0%) with the lowest leaf wilting index (LWI). A contrasting pattern was noticed in CRH 23-5/15, CRH 23-9/17 akin to sensitive check Jatti khatti. Hybrid CRH 21-13/14 exhibited extensively, ramified and improved root system, and was able to sustain root growth under drought. It also showed an increment in root tips (116.1%) and forks (12.6%) during drought, whereas the rest hybrids along with sensitive check (Jatti khatti) exhibited a declining trend. The strong positive association of most root traits with relative water content (RWC) and membrane stability index (MSI) underscored the contribution of root traits towards drought avoidance by optimizing water resources. Although all tested hybrids declined total chlorophyll, chlorophyll a/b ratio and CSI (chlorophyll stability index) to varying degrees during drought, CRH 21- 13/14 exhibited minimum decline. Study postulate superior drought tolerance of CRH 21-13/14 conferred by the drought avoidance mechanism and moderate performance of CRH 21-14/14 (Pummelo × Troyer) as against CRH 23-5/15 and CRH 23-9/17 (Pummelo × Morton hybrids).

Variability in 'Rough Lemon' × 'Sour Orange' Hybrids for Foliar Traits and their In vitro Screening against Phytophthora nicotianae

Phytophthora nicotianae, a deadly fungus, causes huge damage to citrus. Developing tolerant rootstocks is an eco-friendly solution to manage it. In this study, we characterized 21 'Jatti khatti' (a strain of 'Rough lemon') × 'Sour orange' hybrids for four leaf traits and determined their tolerance against using leaf inoculation method. For leaf traits, the hybrids displayed a higher magnitude Phytophthora nicotianae in vitro of variation than the parents. The hybrids represented five different leaf lamina shapes, six leaf apex types, three leaf margins and three petiole wing shapes. The appearance of novel leaf variability pointed to the possibility of recombination in parental gametes. In leaf inoculation based screening, the susceptibility to infection was related to the size of lesions on leaf discs. The parents 'Jatti khatti' and 'Sour orange' Phytophthora recorded significantly different sized lesions of 2.6 and 1.3 cm, respectively. The hybrid 83-3 produced significantly smaller lesion size (1.0 cm) while six other hybrids recorded lesions of size similar to 'Sour orange'. Hence, these seven hybrids can be considered tolerant to Phytophthora and can be further tested for other biotic and abiotic stresses to ultimately find a rootstock that possess most of the desirable features of the two parents.

Effect of ionizing radiation on morphological characters and leaf nutrient content of sweet orange cv. Mosambi

In the present study, sweet orange cv. Mosambi mutants were developed through treating bud stick with different doses of gamma irradiation (10, 15, 20, 25, 30 and 35 Gray) and budded in situ on Jatti Khatti rootstock. Two years after the establishment of plants, the impact of ionizing radiations on the mutated population was studied for the alterations in growth and plant nutrient status, showing differential stimulatory and inhibitory dose dependent responses. Mutants developed with lower doses of gamma irradiation stimulated plant height in the mutants GS-3 (39.30 per cent) and GS-8 (40.80 per cent) developed from 15 and 20 Gy, respectively. Contrary to the stimulatory effects, higher irradiation doses inhibited plant height and other growth parameters in the mutants GS-16, GS-30, GS-32 and GS-34 developed from 35 Gy. The macro-nutrient concentrations were higher at lower doses of 10 and 15 Gy in the mutants GS-2, GS-3 and GS-8, while the micro-nutrient contents in the leaf tissue were higher in the mutants GS-21 and GS 14 developed from intermediate doses of 20 and 25 Gy. Although lower accumulation of macro-nutrients was observed at higher dosimetery, however, reverse trend was noticed with respect to the micro-nutrients, being minimum at the lowest dosimetery i.e., 10 Gy.

Record of pestiferous land snail, <i>Macrochlamys indica</i> Godwin-Austen 1883 (Gastropoda: Ariophantidae), on citrus and guava plants in Punjab, India

Occurrence of land snail, Macrochlamys indica Godwin-Austen, 1883 (Gastropoda: Ariophantidae) in citrus (Kinnow mandarin and its rootstock Jatti khatti) and guava nursery of Punjab, India is reported. This species has been observed as an important mollusc pest of citrus and guava nursery plants in Punjab. Snails avoid hot, dry weather and are active during night when temperature is less. They feed on succulent, tender leaves and create irregular holes with smooth edges on leaves by scraping with their rasp-like tongues. Their peak activity period in Punjab is rainy season. This is the first report of occurrence of this snail in nursery of fruit crops from Punjab, particularly citrus and guava plants. Further studies are required to know its behaviour and economic loss on agricultural crops so as to develop a suitable management strategy.

Effect of colchicine on plant growth and leaf nutrient acquisition of sweet orange (Citrus sinensis (L.) Osbeck) cv. Mosambi

The present study was conducted on sweet orange cv. Mosambi mutants, developed by treating with different doses of colchicine (0.05%, 0.10%, 0.15% and 0.20%) and raised on Jatti Khatti rootstock. Two years after the field establishment of plants, the developed mutants were examined in terms of alterations in growth parameters and leaf nutrient acquisition. Colchicine had both inhibitory and stimulatory effects on the mutants developed at different doses. Reductions in stem girth and TCSA were recorded at 0.05% and 0.20% of colchicine treatment. Mutants developed at 0.10% and 0.15% colchicine concentration, had stimulatory effect on plant growth parameters. Higher nutrient acquisition was noticed in the leaves of mutants developed at 0.10%-0.15% doses, while lower macronutrient acquisition was recorded at 0.05% and 0.20% doses. Variation induced in the mutants by colchicine indicated that both lower and higher doses of mutagenic treatments may give rise to the mutants of economic importance and indicating its potential use as a mutagen.

Citrus rootstock genotypes response to drought: Alternation in morphology, physiology and leaf mineral content

The potted seedlings (18 months old) of seven citrus genotypes were imposed to drought-rewater cycles for every 24 days to study the alterations in morpho-physiological traits and leaf mineral nutrients. The continued growth under drought was observed in Soh sarkar (11.88% more), RLC-7 (10.25% more) and Karna Khatta (10.74% more) as of normal conditions. Moreover, after re-watering, RLC-7 enhanced the plant height to the great extent (17%) as compared to drought. RLC-7, RLC-5 and Soh sarkar maintained a leaf area ratio even under drought condition, while it was inhibited in Jatti khatti and Karna khatta significantly under drought as compared to well-watered conditions. Moreover, reduction in the root volume in most of the rootstocks except RLC-5 and Soh sarkar was noticed. Most of the rootstocks were able to maintain intrinsic water use efficiency after rewatering except RLC-6. Chlorophyll ‘b’ enhanced under drought in RLC-5, RLC-6 and RLC-7, while it was inhibited in Soh sarkar at the end of the drought. Concomitantly, Soh sarkar and RLC-5 exhibited a noticeable alternation of mineral nutrients, having sharp increase of K (RLC-5), but P, Fe and Zn were relatively stable throughout the experiment as compared to start of drought and after rewater stage. From the study, it could conclude that Soh sarkar and RLC-5 (Citris jambhiri) can escape moderate drought. Further, it can also be argued that differential mechanism works for drought tolerance in RLC-5 and Soh sarkar genotypes.

Tree morphology, yield and fruit quality of grapefruit cultivars on different rootstocks in Inceptisol

Influence of seven rootstocks on tree morphology, fruit quality and leaf physiology of ‘Marsh Seedless’ and ‘Redblush’ grapefruits was evaluated under subtropical north India. Rootstock effect on shoot relative elongation rate was found to be negligible. Both the cultivars showed higher fruiting density on rough lemon and Troyer citrange. ‘Marsh Seedless’ fruits did not differ much among rootstocks owing to sphericity. However, most spherical ‘Redblush’ fruits were recorded on Jatti Khatti (98.31%). Sour orange and Billikichlli induced very firm fruits in both the cultivars. ‘Marsh Seedless’ fruits on sour orange and Billikichlli developed maximum colour, whereas more bright and coloured ‘Redblush’ fruits were noticed on rough lemon, sour orange and Billikichlli. Moreover, while sour orange imparted the highest total phenol content (TPC) (490.23 mg Catechol/l juice) in ‘Marsh Seedless’ fruits, Billikichlli induced the highest (480.24 mg Catechol/l juice) in ‘Redblush’ fruits. ‘Marsh Seedless’ fruits with the highest naringin content (238.27 μg/ml) were recorded on Troyer citrange and those of ‘Redblush’ (122.17 μg/ml) on rough lemon. Billikichlli for ‘Marsh Seedless’ and Jatti Khatti for ‘Redblush’ were found desirable under moisture stress condition due to their lowest LWL (30.55 and 34.21%, respectively). Furthermore, highest leaf stomatal density in both ‘Marsh Seedless’ (0.48/mm2) and ‘Redblush’ (0.40/mm2) were reported on rough lemon.

Rootstock evaluation for sweet orange cv. Early Gold in arid irrigated region of Punjab

The performance of sweet orange cv. Early Gold on different rootstocks was evaluated at Regional Research Station Abohar, Punjab during 2013–16. The plants budded on different rootstocks were supplied by Punjab Agri Export Corp. Ltd., imported from USA. The data was analyzed in a randomized block design, replicated fourtimes. Fruit yield was significantly higher and comparable in trees raised on Carrizo citrange (39.1 kg/tree) and Jatti khatti rootstock (37.7 kg/tree) than other rootstocks. Fruits on Carrizo rootstock registered maximum juicecontent (48.47%), which was statistically same as observed on Jatti khatti and Volkamer lemon. Total soluble solids were also highest on Carrizo. Fruit quality index (TSS: acid ratio) was comparable in Volkamer lemon, Jatti khatti and Carrizo citrange rootstocks. The trees raised on commercial Jatti khatti rootstock were quite younger but resulted comparable yield and fruit quality to that of Carrizo. Hence, Jatti khatti seem to be the most suitable rootstock for raising ‘Early Gold’ sweet orange in arid irrigated regions of Punjab.

Root morphology and the effect of rootstocks on leaf nutrient acquisition of Kinnow mandarin (Citrus nobilis Loureiro × Citrus reticulata Blanco)

ABSTRACTThe study aimed to understand the root morphological character of 1 year old seedling rootstock of citrus genotypes viz., rough lemon, Karna Khatta, Carrizo citrange, Rangpur lime, Troyer citrange, Jatti Khatti and sour orange as well as to investigate the effect of these rootstocks on the leaf mineral composition of Kinnow. Root morphological traits showed significant genotypic variation. Rough lemon seedlings had a higher root length, projected area, surface area, volume and the number of forks. Sour orange was moderate rootstock of the 7 genotypes for most of the root morphological characters, while citrange rootstocks expressed poor root morphology. The rootstocks also imparted significant influence on the leaf mineral composition. Leaf K, Ca and Mg content was recorded maximum in plants grown on rough lemon seedling, while N, P, Fe, Zn, Mn and Cu concentration was higher on sour orange rootstock. Kinnow trees on Rangpur lime rootstock accumulated more Na in their leaf tissue, where as Troyer citrange restricted the accumulation of Na. Considering the root morphological characters and nutrient accumulation pattern, rough lemon and sour orange for areas free from tristeza virus could be suggested as alternative rootstocks for the studied Kinnow mandarin under similar ecological conditions.

Rootstock induced changes in tree physiology and antioxidant enzymes activity in lemon cv. Kagzi Kalan

Lemon cultivar Kagzi Kalan was evaluated on eight rootstocks under Delhi conditions during 2013–14. Rootstocks significantly affected all the physiological and biochemical parameters. Higher transpiration rate (E) and stomatal conductance (gs) were observed in lemon trees budded on sour orange, Jatti khatti (C jambhiri), Troyer citrange (C. sinensis X Poncirus trifoliata) and rough lemon (C. jambhiri) rootstocks. The higher values of photosynthetic rate (A) were observed in trees on sour orange and Troyer citrange rootstocks compared to other rootstocks. Lemon trees budded on Billikhichlli (C. reshni) and Attani-2 (C. rugulosa) had the highest intrinsic water use efficiency (WUEi), while it was lower in trees budded on Jatti khatti and rough lemon rootstocks. Higher relative water control (RWC) was recorded in trees on Troyer citrange and sour orange rootstocks, while highest excised leaf water loss (ELWL) was observed on sour orange followed by trees on rough lemon and Troyer citrange rootstocks. Trees on Billikhichlli rootstock had the highest superoxide dismutase (SOD) activity. However, the highest catalase (CAT) activity was found in the leaves of Kagzi Kalan on Jatti khatti. Leaves of Kagzi Kalan had the highest glutathione reductase (GR) activities on Karna khatta rootstock. The lowest values E, gs, ELWL, and activities of SOD, CAT and GR were observed in the leaves of Kagzi Kalan lemon on Attani-2 rootstock.

Effect of different rootstocks on growth, leaf sclerophylly and chlorophyll fractions of Kinnow mandarin

A study was undertaken to evaluate growth performance, leaf sclerophylly and chlorophyll content ofKinnow mandarin budded on different rootstocks. In the pre-bearing stage, the magnitude of vegetative growthrevealed stimulated increase during April-September compared to September-December. The vegetative growth ofKinnow on Jatti khatti was better in terms of per cent increase in plant height, plant spread and canopy volume. Reduced vegetative growth was observed in Kinnow trees on Troyer citrange rootstock. Maximum incrementin scion (88.37%) and root diameter (83.64%) was recorded on Jatti khatti between April-September. Congenialrelationship was observed between scion and rootstock and had mean values for this relationship close to 1.0. Leaf sclerophylly studies exhibited higher leaf area (166.24 cm2), fresh mass (4.36 g) and dry matter (1.85 g) on Jatti khatti with higher density of foliar tissue (433.70 g−1 kg) on Karna khatta. Minimum leaf area (85.07 cm2), fresh mass (2.50 g) and dry matter (0.92 g) was recorded on rough lemon, but leaves were significantlymore succulent. Chlorophyll fractions, viz., Chlorophyll ‘a’ (1.60 mg g−1 FW), total chlorophyll (1.87 mg g−1 FW)and chlorophyll a: b (6.20) were significantly higher in leaf of Kinnow on rough lemon and minimum on Carrizo citrange rootstock.

Effect of rootstocks on tree growth, yield, quality and leaf mineral composition of lemon (Citrus limon (L.) Burm.)

The present study aimed to evaluate the horticultural performance of lemon cv ‘Kagzi Kalan’ on eight rootstocks under typical subtropical conditions for maximizing the production and fruit quality. The experiment was conducted on five years old Kagzi Kalan lemon plants budded on eight rootstocks. The variables collected over two successive years included vegetative growth, fruiting density, fruit quality, and leaf nutrient concentrations. Results revealed a significant effect of rootstocks on all the variables studied. Tree height and canopy volume were found higher on rough lemon and RLC-4 rootstocks, while trunk cross sectional area was higher on Billikichlli and RLC-4 rootstocks than other rootstocks. RLC-4 and Attani-2 rootstocks had higher fruiting density, while it was lowest on Troyer citrange. RLC-4 produced heaviest fruits, while trees on rough lemon and RLC-4 had significantly higher juice recovery. RLC-4 and Karna Khatta improved TSS and acid contents in the fruit juice. RLC-4 and Troyer citrange proved their superiority in terms of higher ascorbic acid content. Foliar N concentration in scion cultivars was found higher on RLC-4, rough lemon and Attani-2 rootstocks, while the foliar K content was higher on RLC-4 and rough lemon. Jatti Khatti was more efficient in accumulating Mg in leaf tissues, whereas Troyer citrange restricted accumulation of Na in leaf tissues. Sour orange was more capable of accumulating Cu and Zn in leaf tissues, while other rootstocks had similar uptake of Cu. Karna Khatta, rough lemon and RLC-4 absorbed more Fe, while the foliar Mn content was highest on rough lemon rootstock. Troyer citrange appeared poor performer in terms of fruiting density and nutrient concentration. A positive significant correlation was found between leaf Ca concentration and canopy volume. Hence, considering growth performance, fruit quality and nutrient concentration, RLC-4, rough lemon and Karna Khatta rootstock could be suggested for lemon under alike ecological conditions.

Physiological and biochemical changes in pre-bearing mutants of Kinnow mandarin (C. nobilis Lour × C. deliciosa Tenora)

Impact of gamma (γ) irradiation and ethyl methanesulfonate (EMS) on leaf physio-biochemical parameters were studied in pre-bearing induced mutants of Kinnow mandarin budded on uniform Jatti Khatti rootstock. The mutants were developed by treating Kinnow bud sticks with different doses (5, 10, 15 and 20Gy) of gamma rays and EMS (0.05, 0.1, 0.2 and 0.5%). The Survival rate (%) of the mutants were recorded minimum at 20Gy (60%) and 0.5% EMS concentration (70.0%). The surviving mutants 24-month-old for each mutagenic dose were assessed for different parameters. Mutagenic treatments significantly reduced the leaf area in the surviving mutants at 20Gy and 0.5% EMS treatments. The mutants at these doses, however maintained high relative water content (RWC) with lower leaf membrane injury. Maximum chlorophyll breakdown in the mutants were observed due to 20 and 15Gy doses. The induced biochemical changes revealed enhanced proline accumulation in the leaves at 0.2% EMS followed by 0.5% EMS treatment, while elevated phenol contents were recorded in the mutants at 20Gy followed by 15Gy and 0.5% EMS doses. Mutagenic treatments at 20 and 15Gy upregulated superoxide dismutase, catalase and peroxidase enzyme activities. The study highlights that both physical and chemical mutagens at higher doses have the potential to generate much needed variation in ‘Kinnow’ mandarin with respect to physio-biochemical traits including antioxidant enzyme and should thus help in evolving desired mutants for economic traits including seedlessness and subsequent use in future breeding programmes.

Effect of polyamines on physio-chemical and biochemical parameters of citrus rootstocks under NaCl stress

The present study was carried out to understand the role of polyamines on physiological and biochemical changes in citrus rootstocks grown under NaCl stress. Citrus is highly salt sensitive crop and salinity is a major constraint hindering its successful production. In general, soil salinisation with NaCl resulted in lowered photosynthetic activity, growth as well as RWC but increased MII. However, application of polyamines in different concentrations reduced the negative effects of NaCl stress and improved the overall growth of the plants. In this experiment, citrus rootstocks, viz., Jatti khatti, Rangpur lime, Attani-1 and Soh-sarkar were used. The maximum superoxidase dismutase (39.44 units 10 min−1 mg−1 of protein) and catalase (5.96 μmoles H2O2 reduced mg−1 protein−1) activities were also noted in spermidine (0.75 mM) treated Rangpur lime rootstock under salt stress. The concentration of sodium and chloride in leaf tissue increased with NaCl treatment and maximum Na+ (2.21%) and Cl-(3.18%) concentrations were observed in Soh sarkar rootstock. Putrescine (0.75 mM) in citrus rootstock Jatti khatti and Soh sarkar and spermidine (0.75 mM) in Rangpur lime and Attani-1 showed better effects in reducing the negative effects of NaCl stress. It was observed that polyamines could improve the salinity tolerance of citrus rootstocks by regulating absorption and accumulation of ions and improving antioxidant enzyme activities.

Physiology of grapefruit (Citrus paradisi Macf.) cultivars as affected by rootstock

Summary‘Marsh Seedless’ and ‘Redblush’ cultivars of grapefruit (Citrus paradisi Macf.) were budded on nine different rootstocks under the typical sub-tropical growing conditions of North India. Significant variations in tree physiology were observed due to rootstock effects. Trees of both scions had the highest photosynthetic rate (A) and stomatal conductance (gs) on ‘Rough Lemon’ rootstock. Rates of transpiration (E) in ‘Marsh Seedless’ were higher on ‘Sour Orange’, ‘Rough Lemon’, ‘KarnaKhatta’,‘Billikhichli’,‘RLC-4’, ‘Troyer Citrange’, ‘Jatti Khatti’, or ‘Attani-2’ rootstocks than on ‘Attani-1’. In ‘Redblush’, values of E were significantly higher on ‘Troyer Citrange’, ‘Attani-2’, ‘Jatti Khatti’, ‘Billikhichli’,‘Sour Orange’, and ‘Karna Khatta’ than on ‘Attani-1’ or ‘RLC-4’. In ‘Marsh Seedless’, higher relative water content (RWC) values and lower excised leaf water loss (ELWL) values were observed on the rootstocks ‘Billikhichli’ and ‘RLC-4’, but the RWC was highest in ‘Redblush’ on ‘Rough Lemon’ rootstock, and the lowest ELWL value was recorded on ‘Troyer Citrange’. ‘Redblush’ had the highest superoxide dismutase (SOD), peroxidase (POD), and glutathione reductase (GR) activities on ‘Attani-2’ rootstock, whereas catalase (CAT) was most active in the leaves of ‘Redblush’ trees budded on ‘RLC-4’. The highest activities of CAT and GR in ‘Marsh Seedless’ were on ‘Billikhichli, whereas SOD and POD activities were highest in the leaves of ‘Marsh Seedless’ on ‘Rough Lemon’ and on ‘Attani-2’ rootstocks, respectively. ‘Marsh Seedless’ on ‘Troyer’ or ‘Karna Khatta’, and ‘Redblush’ on ‘Billikhichli’ or ‘Rough Lemon’, had the highest total soluble protein concentrations in their leaves. Overall, differential responses to rootstock were observed in both grapefruit scion cultivars. ‘Rough Lemon’ was the best rootstock to induce high metabolic activity in both scion cultivars under normal growing conditions. However, high RWC values and antioxidant enzyme activities in ‘Marsh Seedless’ on ‘Billikhichli’ and in ‘Redblush’ on ‘Troyer Citrange’, ‘Attani-2’, or ‘RLC-4’, indicated their utility as rootstocks under stressful growing conditions.