A.K. Dubey

Paclobutrazol minimises the effects of salt stress in mango (Mangifera indica L.)

Summary We investigated the effects of paclobutrazol (PBZ) on 1-year-old plants of ‘Olour’ mango subjected to NaCl stress under polythene tunnel conditions. Plants were treated with two levels of salt [0.0 g NaCl kg−1 soil (control) or 1 g NaCl kg−1 soil] and three concentrations of paclobutrazol [PBZ; 0.0 mg l−1 (control), 750 mg l−1 or 1,500 mg l−1] after 30 d of establishment. Mortality in saline-treated mango plants was reduced significantly (LSD = 8.55; P ≤ 0.05) following the application of PBZ. NaCl-stress reduced the survival of plants without PBZ treatment by 89%, but only by 28.4% for 1,500 mg l−1 PBZ-treated plants. PBZ-treated plants also showed less defoliation, and fewer leaves per plant exhibited salt stress symptoms. It was also evident that treatment with PBZ increased the relative water and chlorophyll contents of mango seedlings, and reduced membrane injury, under salt stress. Furthermore, saline treatment without PBZ increased the Na+ and Cl− ion contents of leaves and roots; however, application of PBZ consistently and significantly lowered these ion contents (P ≤ 0.05). The Na+ content of leaves on saline-treated plants was reduced by 1.96- to 2.12-fold, whereas Cl− ion contents were reduced by 22 – 39% by PBZ treatment compared to salt-treated seedlings without PBZ. Our results suggest a role for PBZ in promoting the avoidance of salt stress in mango by increasing the levels of photosynthetic pigments, water content, K+ uptake and accumulation, and by reducing defoliation, the membrane injury index, and the uptake and accumulation of harmful Na+ and Cl− ions. These findings may be used to improve the yields and quality of mango trees grown in salt-affected areas.

Biochemical and salt ion uptake responses of seven mango (Mangifera indica L.) rootstocks to NaCl stress

Summary Uniform-sized, 6-month-old seedlings of seven mango (Mangifera indica L.) rootstocks (‘Moovandan’, ‘Bappakai’, ‘Nekkare’, ‘Kurukkan’, ‘Olour’, ‘Terpentine’, and ‘Chandrakaran’) were irrigated with tap water containing 0, 50, 100, or 150 mM NaCl at 4 d intervals for 40 d. NaCl stress increased the activities of peroxidase (POX), catalase (CAT), and superoxide dismutase (SOD), and the concentrations of malondialdehyde (MDA), proline, and trehalose. The highest anti-oxidant enzyme activities were observed in the rootstocks ‘Olour’, ‘Bappakai’ and ‘Terpentine’ at the highest level of salinity (150 mM NaCl). Leaf proline concentrations increased most in ‘Olour’, ‘Kurukkan’, and ‘Terpentine’ with increasing levels of salinity. The concentration of Na+ ions in leaf tissues increased to a maximum (123.5%) of the respective (0 mM NaCl) control in ‘Chandrakaran’, while ‘Bappakai’ had the highest Na+ ion concentration in root tissues at the highest level of salinity (77.3%) compared to the respective control. Compared to the respective controls, the maximum increase (109.1%) in leaf Cl– ion concentration was recorded in ‘Moovandan’, while ‘Chandrakaran’ had the highest concentration of Cl– ions (139.3%) in its root tissues when irrigated with water containing 150 mM NaCl. Our results suggest that the salt-tolerant behaviour of the mango rootstocks ‘Olour’ and ‘Terpentine’ may be due to their ability to inhibit the uptake of Cl– and Na+ ions, combined with higher accumulations of proline.These two rootstocks may therefore be used to improve the yield and quality of commercial mango cultivars grown in salt-affected areas.

EFFECT OF PACLOBUTRAZOL AND PUTRESCINE ON ANTIOXIDANT ENZYMES ACTIVITY AND NUTRIENTS CONTENT IN SALT TOLERANT CITRUS ROOTSTOCK SOUR ORANGE UNDER SODIUM CHLORIDE STRESS

The effects of paclobutrazol (PBZ) and putrescine (Put) on antioxidant enzymes activity, proline contents and nutrients uptake were studied on salt tolerant citrus rootstock sour orange. Six-month-old nucellar seedlings grown in pots and subjected to three levels of PBZ and two levels each of salinity and Put for 90 days. Seedlings treated with PBZ or Put alone or in combination had higher anti-oxidant enzymes activities, accumulation of proline and nutrients contents like potassium (K+) and calcium (Ca2+) under both saline and non-saline conditions. Further, application of PBZ or Put alone or in combination also reduced the accumulation of both Na+ and Cl− ions in leaves and roots in NaCl stressed seedlings. A combined application of 250 mg L−1 PBZ and 50 mg L−1 Put proved to be more effective in improving proline and Ca2+ content and restricting accumulation of Na+ ions in leaf tissues.

Effect of NaCl in the irrigation water on growth, anti-oxidant enzyme activities, and nutrient uptake in five citrus rootstocks

Summary Seven–month-old, uniform-sized seedlings of five citrus rootstocks [sour orange (Citrus aurantiam), Attani-2 (C. rugulosa), Troyer citrange (C. sinensis × Poncirus trifoliata), billikhichlli (C. reshni), and RLC-6 (C. jambhiri)] were irrigated to 70% of field capacity with water containing 0, 50, 100, or 200 mM NaCl for 180 d. Growth, in terms of plant heights and the numbers of leaves, decreased with increasing levels of salinity in all five rootstocks. The decrease in plant height was greatest in the salt-susceptible Troyer citrange and billikhichlli at higher levels of salinity. However, in the salt-tolerant sour orange and Attani-2, NaCl caused only a slight decrease in plant height. Defoliation was maximum in the salt-susceptible Troyer citrange and billikhichlli. The maximum increases in superoxide dismutase (SOD) and peroxidase (POD) activities were found in the salt-susceptible Troyer citrange at higher levels of salinity. Leaf proline contents increased most in Attani-2, sour orange, and RLC-6 at higher levels of salinity.The concentration of Na+ ions in leaf tissues increased to a maximum in Attani-2; while, in root tissues, RLC-6 and Troyer had the highest Na+ ion contents. The maximum increase in leaf Cl– ion levels occurred in Troyer citrange, and the minimum was in RLC-6, at 200 mM NaCl. These data suggest that higher levels of proline accumulation and leaf abscission could be used as indicators for screening citrus rootstocks for resistance to NaCl stress. Sour orange and Attani-2 were able to exclude Cl– ions, whereas Troyer citrange appeared to exclude Na+ ions at lower levels of NaCl. Further studies are required to observe the translocation of harmful and beneficial mineral elements to scion cultivars grafted onto sour orange and Attani-2 and grown under NaCl stress. Overall, salt-tolerance increased in the following order: Troyer ì billikhichlli ì RLC-6 ì Attani-2 ì sour orange.

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

ABSTRACT The 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.

Gametophytic self-incompatibility causes seedlessness in ‘Kagzi Kalan’ lemon (Citrus limon)

ABSTRACT The present study aimed to study the flower and pollen structure, pollen viability, in vitro pollen germination of ‘Kagzi Kalan’ lemon (Citrus limon (L.) Osbeck), and in vivo pollen tube growth in self- and cross pollination to understand the mechanism of seedlessness. The results revealed that Kagzi Kalan had tetra-colporate spherical shaped pollen of uniform size. The results of Acetocarmine and FDA test and in vitro germination indicated normal pollen viability and germinability in Kagzi Kalan. In vivo pollen tube growth showed > 50% pollen germination on stigma in all treatments though a greater number of pollen tubes at the mid style, base of the style, and near the ovule was found in cross pollination. Contrary to this, despite optimum pollen germination (53.51–70.37%) in self-pollination treatments, none of the pollen tubes reached the base of the style due to abnormal growth of pollen tubes, viz. curvatures, inhibition of pollen tube growth, and callose deposition. The inhibition of pollen tubes at the mid style under self-pollination treatments, and production of seeded fruits under cross pollination treatments, indicate the presence of self-incompatibility and the site of inhibition of pollen tubes. Thus, gametophytic self-incompatibility (SI) caused seedlessness in Kagzi Kalan by blocking fertilization in the ovary.

Effect of polyembryonic rootstocks on leaf mineral composition of five cultivars under Inceptisol

The leaf macro- and micro-nutrient concentrations of five mango scion cultivars grown on three polyembryonic rootstock genotypes were studied during 2012–13 and 2013–14. Among the cultivars, Pusa Arunima appeared be the good accumulator for most of the nutrient elements except leaf N. Though, Amrapali seems to be the good accumulator of N and Mg but poorest accumulator of P, K, and Zn. Whereas, Mallika was good accumulator of N and Mg but poorest accumulator of Mn, Zn and Cu. Among rootstocks, Kurakkan was found potential for higher accumulation of leaf N, Ca, Mg and Zn concentrations in scion cultivars. Among different rootstock-scion combinations, leaf nitrogen (1.25%) and K (0.54%) in Pusa Arunima was observed higher on K-5 rootstock, while higher leaf N in Amrapali (1.36%) and Mallika (1.37%) were estimated on Kurakkan rootstock but Pusa Surya tree on Olour had higher leaf N (1.26%). In most of the cultivars, leaf K was higher on K-5 rootstock. Besides, higher leaf Ca in Pusa Arunima, Mallika and Dushehari were observed on K-5 rootstock, while in Amrapali and Pusa Surya, trees on Kurakkan had higher leaf Ca concentration. Similarly, leaf Mg concentration was also found higher on K-5 rootstock in Pusa Arunima, Amrapali, Mallika and Dushehari. The Pusa Arunima and Pusa Surya on Kurakkan proved its ability for leaf Fe and Mn concentrations, whereas, K-5 rootstock found superior over other rootstocks for the highest accumulations of Fe and Mn in Dushehari and Mallika. Both Kurakkan and Olour were equally effective for higher accumulation of Zn in Amrapali. Based on present study, it can also be inferred that metabolism of Kurakkan and/or K-5 is better adapted for N, K, Ca, Mn, Fe and Zn accumulation for most of the mango cultivars tested.