Anirudh Thakur

Organic amendments influence growth, buddability and budding success in rough lemon (Citrus jambhiri Lush.)

The influence of organic amendments [cocopeat, vermicompost, farmyard manure (FYM) and neem cake] in growing media on growth and buddability of rough lemon seedlings was studied. Cocopeat and vermicompost improved seed germination. The growing media having cocopeat or vermicompost and FYM were more effective than cocopeat alone in increasing the growth, buddability and budding success. Poor seed germination and growth were recorded in media with neem cake. Greatest seedling height, stem diameter, number of leaves, leaf area and root–shoot ratio were recorded with soil+FYM+cocopeat (2:1:1). Soil+FYM+cocopeat (2:1:1) also resulted in the highest proportion of early buddable seedlings (85.9%) and budding success (93.2%). Cocopeat and vermicompost have the potential to improve the proportion of Kinnow mandarin plants ready for sale within 1 year of sowing rootstock seed.

Mulching and herbicides in peach: Weed biomass, fruit yield, size, and quality

An experiment was conducted to study the effect of mulches and herbicides on weed population, fruit yield, and quality in peach cv. ‘Earli Grande.’ Covering soil with black polythene mulch (100 μm) resulted in 100% control of weeds at six weeks after treatment (WAT) during both the years of study. However, guinea grass, which had emerged out of the black polythene mulch, reduced the weed control efficiencies (WCE) to 96.3 and 98.5% in 2009 and 2010, respectively, at 12 WAT. Application of straw mulch (8 cm, 15.5 t ha− 1) resulted in higher weed control efficiencies at 6 WAT during 2009 and 2010 (98.4 and 98.2%, respectively). At 12 WAT, this decreased to 90.7 and 93.1% in 2009 and 2010, respectively, due to the emergence of bermuda grass and guinea grass from the mulch. The weed control efficiencies with treatments having diuron as pre-emergence herbicide did not differ significantly from black polythene at 6 WAT. Atrazine and pendimethalin were the next most efficient and did not differ significantly from each other. At 12 WAT, diuron followed by fb glyphosate resulted in higher WCE, and it did not differ significantly from atrazine fb glyphosate. In both years, highest fruit yield (69.3 and 67.9 kg tree− 1, respectively) was recorded with straw mulch (8 cm). Straw mulch (8 cm) also resulted in a 20 and 19% increase in fruit weight (81.9 and 81.4 g during 2009 and 2010, respectively) over manual weeding. Straw mulch (8 cm) did not differ significantly from straw mulch (6 cm), black polythene mulch, and diuron treatments for fruit yield during both years. Conclusively, plastic and straw mulches can be used as an effective chemical-free alternative to manual or chemical weed control in peach.

Benzaldehyde dehydrogenase-driven phytoalexin biosynthesis in elicitor-treated Pyrus pyrifolia cell cultures

Pyrus pyrifolia (Asian pear) cell cultures respond to yeast extract (YE) treatment by accumulating benzoate-derived biphenyl phytoalexins, namely, noraucuparin and aucuparin. Biphenyl phytoalexins are defense-marker metabolites of the sub-tribe Malinae of the family Rosaceae. The substrates for biphenyl biosynthesis are benzoyl-CoA and malonyl-CoA, which combine in the presence of biphenyl synthase (BIS) to produce 3,5-dihydroxybiphneyl. In the non-β-oxidative pathway, benzoyl-CoA is directly derived from benzoic acid in a reaction catalyzed by benzoate-CoA ligase (BZL). Although the core β-oxidative pathway of benzoic acid biosynthesis is well-understood, the complete cascade of enzymes and genes involved in the non-β-oxidative pathway at the molecular level is poorly understood. In this study, we report the detection of benzaldehyde dehydrogenase (BD) activity in YE-treated cell cultures of P. pyrifolia. BD catalyzes the conversion of benzaldehyde to benzoic acid. BD and BIS activities were coordinately induced by elicitor treatment, suggesting their involvement in biphenyl metabolism. Changes in phenylalanine ammonia-lyase (PAL) activity preceded the increases in BD and BIS activities. Benzaldehyde was the preferred substrate for BD (Km=52.0μM), with NAD+ being the preferred co-factor (Km=64μM). Our observations indicate the contribution of BD towards biphenyl phytoalexin biosynthesis in the Asian pear.

Bio-inoculants enhance growth, nutrient uptake, and buddability of citrus plants under protected nursery conditions

ABSTRACT Bio-inoculants have been used for enhancing plant growth in horticultural crops even in nutrient-limited soils. The present research evaluated the effect of inoculation of two growing media with six biofertilizer consortia on the growth and buddability of ‘Rough lemon’ rootstock subsequently budded with ‘Kinnow’ mandarin variety. Soil + FYM + Cocopeat (SFC) with Azospirillum (Azo) + AM fungi consortium improved seed germination, seedling growth, chlorophyll, P, K, root growth, root epidermis, and cortical region thickness; xylem and phloem diameter in rough lemon; budding success and growth in Kinnow mandarin saplings. It also increased OC, P, and K levels in growing media. AM spore count and AM root colonization showed a positive correlation with budding success, root P and soil P content. SFC fortified with Azo + AM fungi resulted in better growth and buddability of rough lemon seedlings along with better growth of Kinnow mandarin saplings.

Morphological and genetic diversity in citrus genotypes to substantiate rootstock breeding for root rot resistance

Investigations were conducted on six citrus rootstocks, viz., rough lemon (RL), trifoliate orange (TO), Swingle citrumelo (SC), X 639 (X), Rangpur lime (RA) and Gou Tou (GT), to assess the morphological and genetic variability; and reaction against Phytophthora. Smooth trunk surface was recorded in all the genotypes. Three genotypes had erect growth habit, while it was spreading in Gou Tou (GT), Rangpur lime (RA) and rough lemon (RL). The leaves of GT, RA and RL were of unifoliate, while trifoliate orange (TO) had trifoliate leaf and Swingle citrumelo (SC) and X 639 (X) had multifoliate leaf division. No variation was recorded with respect to flowering season in all citrus rootstocks, i.e. mid February to last week of March. Fifty-five SSR markers were used for evaluation of genetic diversity amongst the six rootstocks. Twenty markers exhibited high polymorphism and showed wide allelic diversity. Capacity of each SSR to show polymorphic loci, varied from 0.29 (F98) to 0.83 (CCSME46 and CCSMEc4) with an average PIC value of 0.61. The resolving power (Rp) was highest for the primer CCSME43 (8.33) and was lowest for F90 (1.33). Significant differences were observed in the value of MI and were found to be the highest for primer F40 (9.25), while minimum MI was recorded for F98 (0.38). The PIC values of a marker vary with the crop and the set of the genotypes used. The reduction in the number of sporangia and lesion size in trifoliate orange and Swingle citrumelo indicated their tolerance against Phytophthora nicotianae var. parasitica. The number of sporangia counted after 48 h of incubation showed that all leaf baits of each rootstock were attacked by large number of sporangia. The number of sporangia on each leaf disc of rootstocks decreased after 48 h as the sporangia germinated into mycelium on the edges of leaf discs.

Effect of training system and in row spacing on yield and fruit quality of peach in the sub-tropical regions

Information on the use of different training systems in peach under the sub-tropics is inadequate. Trees of Shan-i-Punjab peach were planted at two spacings, viz., 5 m x 2 m and 5 m x 3 m and were trained to four training systems, viz., Y shaped, Hedge row, Espalier and V trellis. The fruits harvested from Espalier and V trellis trained trees were superior in fruit quality in terms of fruit size, weight, colour and TSS as compared to fruit harvested from other training systems. Fruit yield was found to be maximum from V trellis trained trees. Trees planted at 5 m x 3 m gave higher fruit yield and better quality fruits as compared to 5 m x 2 m planted trees irrespective of training systems.

Summer stratification and germination: A viable option for recovery of hybrid seedlings in low chill peach and nectarines

In-vitro embryo rescue; and summer stratification and germination under controlled conditions was tested for recovering hybrid seedlings in crosses involving low chilling peach and nectarines. The embryos from all the cross combinations showed very high in vitro embryo germination (>85%) on basal MS medium, which can be effectively performed at hard mature or full ripe stage. The stratification period of the hybrid seed varied from 36.3 days in Shan-i-Punjab × Florda Prince to 44.7 days in Tropic Beauty × Florda Grand. At the end of four weeks of transfering the cultures to culture room, maximum plant height (33.7 mm) was recorded in Shan-i-Punjab × Tropic Beauty, which did not differ significantly from the cross Florda Crest × Tropic Beauty. The fruit development period of the seed parent varied from 78.3 days in Shan-i-Punjab × Tropic Beauty and Shan-i-Punjab × Florda Prince to 104.7 days in Tropic Beauty × Florda Grand. Stratification media of cocopeat + vermiculite + perlite (2:1:1) resulted in the highest seed germination but, the actual germination percentage varied with cross combinations. Highest germination (81.5%) was recorded in the cross FlordaGlo × Tropic Sweet, which did not differ significantly from Tropic Beauty × Florda Grand. It was followed by seed germination (68.0%) in Florda Grand × Tropic Beauty. Under high density nursery system, the hybrid seedlings of FlordaGlo × Tropic Sweet showed highest growth (160 cm) and branches (13). The germination of hybrid seeds was positively correlated (0.86) with fruit development period of the seed parent (FDP) and negatively correlated (−0.85) with chilling requirement of seed parent. The proportion of rosseted seedlings was negatively correlated with FDP (−0.61) and positively correlated (0.39) with chilling requirement of the seed parent. The cross combinations with higher FDP of seed parent resulted in higher seed germination of hybrid seed. Hence, controlled climate stratification and germination after harvest can be a viable option for recovery of hybrid seedlings and reducing the breeding cycle in crosses involving seed parents with higher FDP.

Morphological and Floral Characterization of Some Citrus Rootstocks

The study was carried out on five different citrus rootstocks viz. rough lemon (Citrus jambhiri Lush.), trifoliate orange [Poncirus trifoliata (L.) Raf.], rangpur Lime (Citrus limonia Osbeck.), Carrizo citrange [Citrus sinensis (L.) Osbeck. x Poncirus trifoliata (L.) Raf.] and Swingle citrumelo [Citrus paradisi Macf. x Poncirus trifoliata (L.) Raf.] at Punjab Agricultural University, Ludhiana. The plants were evaluated for 20 quantitative and 11 qualitative characters as per Descriptor of Citrus. Variability was observed among different genotypes for tree, leaf and flower characters. Trifoliate orange, Carrizo citrange and Swingle citrumelo were deciduous where as rough lemon and rangpur lime were evergreen. Tree shape was obloid in rangpur lime and ellipsoid in all the other rootstocks. Tree growth habit also varied from erect in trifoliate orange, Carrizo citrange and Swingle citrumelo and spreading type in rough lemon and rangpur lime. Spine shape was curved in case of trifoliate orange and straight in all other rootstocks. Leaf division was unifoliate in rangpur lime and rough lemon where as it was trifoliate in case of trifoliate orange, Carrizo citrange and Swingle citrumelo. Leaf lamina shape was observed lanceolate in Swingle citrumelo, ovate in Carrizo citrange and trifoliate orange; and elliptic leaf lamina was observed in rangpur lime and rough lemon. Maximum leaf lamina length and width (76.33 mm and 44.47 mm, respectively) were recorded in rough lemon and minimum leaf lamina length (45.64 mm) and width (21.92 mm) was recorded in Carrizo citrange. The spine length ranged between 13.33 to 46.67 mm in all the rootstocks. Among the different rootstocks, Swingle citrumelo was the earliest to flower (February 24) while rangpur lime was last to flower (March 17). Swingle citrumelo was the earliest to attain full bloom (February 28 to March 4) among all the rootstocks. While rough lemon and rangpur lime was the last to reach full bloom (March 22 to 26). The rootstocks also differ with respect to end of flowering. Among different rootstocks the flowering season terminated earliest in Swingle citrumelo (March 19) whereas, in rough lemon flowering ended at the last on 24th April.

In vitro plantlet formation in Carrizo citrange: A promising citrus rootstock

The shoot tip and nodal segment explants from three-year-old plants of Carrizo citrange were exposed to mercuric chloride (0.1%) for different durations. In case of nodal segments, maximum survival (39.00%) and minimum microbial contamination (60.80%) was observed with mercuric chloride treatment for 10 min., whereas, shoot tips failed to establish. The explants were established on Murashige and Skoog (1962) medium supplemented with different concentrations of BAP, NAA and IBA. Maximum culture establishment (97.20%) was observed highest on MS medium supplemented with BAP (2 μM) + NAA (1 μM). Season of culturing also effected the establishment of shoot cultures as maximum establishment (96.60%) was observed during April-May followed by August-September. The highest shoot proliferation (3.64 per explant) and shoot length (3.71 cm) were also recorded on MS medium supplemented with BAP (2 μM) + NAA (1 μM). The micro-shoots were rooted on half-and full-strength media supplemented with different concentrations of IBA and NAA. Earliest root induction (10.60 days) and maximum rooting (53.89%) were observed on MS medium supplemented with IBA (10 μM) + malt extract (500 mg/l). Maximum number of roots per shoot (1.37) and root length (5.0 cm) were observed on half-strength MS medium containing IBA (2.5 μM) + NAA (2.5 μM). The maximum ex vitro plantlet survival (81.4%) was observed in potting mixture consisting of cocopeat + vermiculite + perlite (2:1:1).