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The 5 apple viruses, apple chlorotic leaf spot virus (ACLSV), apple stem grooving virus (ASGV), apple stem pitting virus (ASPV), apple mosaic virus (ApMV) and prunus necrotic ring spot virus (PNRSV) and 1 viroid, apple scar skin viroid (ASSVd) are known major viral/viroid pathogens of apple in India. For identification of virus-free elite mother plants, 267 proposed mother plants from Trans-Himalayan region of India were indexed through DAS-ELISA and RT-PCR. Only 20% plants showed typical symptoms of virus/viroid, where as indexing though DAS-ELISA and RT-PCR revealed that, about 95% of apple plants were found infected with the virus/viroid. ASPV was most prevalent virus with 74.91% incidence followed by ACLSV (73.41%), ASGV (45.32%), PNRSV (1.5%) and ApMV (1.5%). Whereas, incidence of ASSVd was 2.62%. In the present study, it was recorded that 24.71% proposed mother plants were infected with a single virus, 38.95% with at least 2 viruses and 31.46% with more than 3 viruses. Only 4.86% plants out of 267 proposed mother plants were found free from virus/viroid infection. For sustainable supply of quality planting material, these virus free elite mother plants were multiplied and distributed to the farmers for establishment of mother blocks.

The wild Malus germplasm is considered as a gene reservoir for various biotic and abiotic stresses tolerance/resistance genes, including important novel horticultural traits. The dwarf vigour is considered an important trait in Malus for promoting high-density plantations and enhancing productivity. Thus, an indigenous and exotic wild Malus species collected in the apple field gene bank were evaluated for their dwarfing potential, based on the diverse traits like stomatal features, photosynthetic pigments and anatomical structures. Among different parameters, inter-nodal length, root bark percentage, palisade: spongy tissue thickness ratio, xylem: phloem ratio, wood: bark ratio, vessel diameter of stem cross-section and photosynthetic pigments exhibited significant variation between dwarf and vigorous Malus species. The indigenous Himalayan crabapple—Malus baccata (L.) Borkh. (Rohru) showed the shortest inter-nodal length (23.82 ± 1.08 mm), low root bark percentage (69.30 ± 0.37), low xylem: phloem ratio (0.43 ± 0.01), low wood: bark ratio (0.49 ± 0.07), smaller xylem vessel diameter (9.67 ± 0.40 µm), and higher palisade: spongy tissue thickness ratio (1.25 ± 0.04) than the vigorous counterparts. These parameters were comparatively at par with the known dwarfing rootstock M.9. The foliar photosynthetic pigments content was significantly higher in M. baccata (Rohru) compared to other studied Malus species. Furthermore, stomatal density showed much dependence on the size of stomata, specifically its length rather than the vigour of Malus genotypes. The study revealed that Malus baccata (Rohru) had several dwarfing attributes which were comparable to the dwarfing rootstock M.9 and thus could serve as an important genetic resource for the development of indigenous dwarfing rootstock.

In vitro haploid production followed by chromosome doubling greatly enhances the production of complete homozygous wheat lines in a single generation. This work aimed to develop wheat doubled haploid genetic stock resistant to yellow and brown rust via intergeneric hybridization with Imperata cylindrica and its further characterization. The wheat doubled haploid (DH) line was developed by crossing wheat F1 (HS 542/China 84-40,022) with I. cylindrica. This DH-1 was tested against eight races of yellow (110S119, 110S247, 238S119, 78S84, 110S84, 111S68, T and P) and eighteen races of brown rust (11,12-5, 12-7, 12A, 77, 77-1, 77-2, 77-5, 77-7, 77-8, 77-10, 77A-1, 104-2, 107-1, 108-1, 162-1, 77-9 and 104-1) at seedling stage and with mix race of yellow and brown rust in adult plant stage (at Dhaulakuan, Bajaura and Shimla). At the seedling stage, DH-1 showed resistance to all the yellow and brown rust pathotypes except for 77-5 race of brown rust. The adult plant response of this DH line also showed resistance to both yellow and brown rust. Based on host pathogen interaction, the DH-1 was postulated to carry leaf rust resistant genes Lr26 + Lr23 + 1 + and yellow rust resistant gene Yr9 + gene. Molecular characterization of the DH line with gene-specific primers showed that the developed DH-1 contains leaf rust resistance genes Lr34, Lr26 and Lr32. The DH-1 has semi-spreading growth habit, erect flag leaf attitude, plant height of 94 cm, have scurs and 1000 grain weight of 36 g. The results highlight I. cylindrica-mediated chromosome elimination technique of doubled haploid production as an effective tool for the development of wheat rust resistant lines in the shortest timeframe. This is the first report of genetic stock development for rust resistance in wheat via I. cylindrica-mediated DH technique.

Development of doubled haploid (DH) plants in wheat is an important technique for establishment of completely homozygous lines in the shortest time frame. In this study, we standardized the in vitro and in vivo variables for the production of wheat DH plants via crossing of three spring wheat genotypes with a wild grass (Imperata cylindrica). The experiment involves testing new treatments and protocol modifications for 2 years. Wheat florets were pollinated with I. cylindrica pollen after 2 days of emasculation, and next day pollinated spikes were injected with different auxin analogues: 100 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) or 100 mg/l 3,6-dichloro-2-methoxybenzoic acid (dicamba) or 50 mg/l 2,4-D + 50 mg/l dicamba. A combination of 50 mg/l 2,4-D and 50 mg/l dicamba was superior to other treatments having maximum haploid embryos and haploid plants developed per emasculated florets. The responsiveness of embryo formation to the addition of silver nitrate (AgNO3) (the ethylene inhibitor) with the auxin treatments showed that the presence of silver nitrate in the medium may not be essential for wheat embryo induction. Time of embryo rescue had a significant effect on embryo and haploid plant production. The most successful time for embryo rescue was 24 days after pollination (DAP) resulting in maximum haploid plants developed (40% in wheat variety AKYK92 and 25% each in variety HD2888 and HS542). The immature embryos were cultured in different media, i.e. Murashige and Skoog (MS), half-strength MS, modified MS media, Gamborg’s B5 and modified B5 media. Maximum number of haploid plants were found in half-strength MS media in all accessions (60.0%) followed by modified MS media (40.00%). For colchicine concentration, during 2016–2017, maximum numbers of DHs with less plant mortality were obtained at 0.08 and 0.06% dose. Taking into account the first year results, refinement of the dose in the second year showed that colchicine doses of 0.08 and 0.075% were the best dose for maximizing DH induction in wheat; however, in this case the number of examined plants was very small. Therefore, we can treat the two doses as a guide for further research on larger samples.

The inadequate information on genetic diversity and population structure of wild Malus genotypes including indigenous Himalayan crabapples [M. baccata (L.) Borkh. and M. sikkimensis (Wenzig) Koehne ex C. Schneider] collected and maintained at different field gene banks of apple necessitated this study. A set of 31 SSR loci covering all the linkage groups of apple genome was successfully used in this study. The average number of alleles at per locus, major allelic frequency, expected heterozygosity, observed heterozygosity and PIC values were 3.29, 0.592, 0.506, 0.271 and 0.438, respectively among the studied SSR loci. The set of SSR loci yielded 8 unique and 11 rare alleles among the wild Malus genotypes. These wild Malus genotypes were grouped into seven distinct clades, where the indigenous Himalayan M. baccata (L.) Borkh. ecotypes were grouped in separate clades confirming them to be genetically distinct. Furthermore, model based population structure differentiated the wild apple genotypes into three populations of which one was indigenous Himalayan M. baccata (L.) Borkh. ecotypes. The high allele-frequency divergence among populations revealed high genetic differences between them. The AMOVA revealed high genetic diversity between populations of wild Malus genotypes; and within; and among the individuals of the populations. The PCoA validated and reconfirmed the three groups of the population as differentiated by model based population structure. The genetic uniqueness of indigenous Himalayan M. baccata (L.) Borkh. ecotypes can further add the new genes in the global gene pool of apple. This study could serve as base information for future exploration and collection of more accessions of indigenous Himalayan crabapples from the region extending to about 7000 km in the Indian Himalayan region. The existing high degree of genetic diversity among the studied wild apple genotypes could be the valuable genetic resource for the apple improvement programmes.

In the present investigation, 32 Malus species including 12 indigenous Himalayan wild apples were evaluated during 2014–2015, for their morphological (14 No.) and biochemical (14 No.) variabilities based on 28 parameters. The leaf related attributes like leaf shape, leaf apex shape, leaf base shape, leaf blade margin and tree attributes like tree habit, suckering tendency, burrknot tendency and presence of lenticels on shoot exhibited considerable variation. The maximum coefficient of variation value was recorded for foliar peroxidase activity (98.18%) followed by catechin (91.32%) content. Principal component analysis (PCA) revealed that the first five principal components (PC1, PC2, PC3, PC4 and PC5) together accounted for more than 50% variation of the total observed variations. The PC1 strongly integrated with the traits like tree habit, leaf blade length, leaf blade width, rutin, phloridzin, chlorophyll a, chlorophyll b, − chlorophyll a:b, total chlorophyll and total phenolics content, which were found to be effective parameters for explaining the natural variability among the studied Malus species. The dendrogram generated based on unweighted Neighbhor-joining method clustered all the Malus species including the indigenous wild apples into three distinct clusters. Scatter plot based on PC1 and PC2 suggested high morphological and biochemical diversity among the Malus species including the indigenous wild apples. The cluster analysis and scatter plot revealed that the indigenous wild apples were quite diverse as observed for the exotic Malus species; though there were no separate groups detected. The higher diversity for endogenous biochemical compounds indicates differential physiological behaviour of Malus species under the prevailing environmental conditions. These findings revealed that there were several biochemical constituents, which could serve as effective indices for indirect selection of potential biotic and abiotic stresses resistance/tolerance Malus species for their potential use in genetic improvement programmes. Similarly, knowledge on graft compatibility with respect to wild Malus could help in exploiting them as new rootstock genotypes. These parameters are known to influence the expression of different traits in scion genotypes upon grafting and thus could help in sustaining the apple production in Indian Himalayan region under changing climate situations The potential genotypes based on their morphological and biochemical parameters identified like M. baccata (Khrot), M. baccata (Kinnaur), M. baccata (Pangi), M. baccata (Rohru), M. baccata (Shillong), M. hilleiri, M. micromalus, M. prunifolia (Maruba), M. prunifolia (Ringo-Assami), M. sieversii and M. spectabilis suggested them to be quite diverse. Besides, some indigenous Himalayan crab apples were also identified, which have inherent potential to serve as valuable genetic resources for rootstock improvement programmes.

Climate change with particular reference to occurrence of warmer winters is a matter of concern to the temperate fruit grower as this means not being able to satisfy the chilling requirement of the fruit trees. There is, therefore, a need to continuously monitor the chill unit accumulation during winters to be able to suggest appropriate corrective measures that the fruit grower may adopt to maintain productivity. Chill unit estimation models are available but they are not applicable universally. Location specific chill unit estimation ready reckoners are needed. In this study, a ready reckoner has been developed for the apple-growing Shimla region (Himachal Pradesh, India). It overcomes some of the drawbacks of the estimation models that have been developed previously.

Strawberries are one of the most popular fruit crops grown in the world. Although it is native of temperate regions, cultivars are available which can be cultivated in mild-tropical and subtropical climates. In India, strawberries are generally cultivated in the hills but in recent years, strawberry is being cultivated successfully in plains also. A wide variation in climate within these regions and a wider adaptation of the strawberry plants permits harvesting and marketing of fruits round the year. Per capita, consumption of fresh strawberries has increased in the past decade and is predicted to continue to rise in the immediate future. Two of the major hazards of strawberry production in mild tropics are diseases that attack the fruits and plants and the lack of superior day neutral cultivars. The cultivated strawberries are attacked by a large number of diseases caused by fungi, bacteria, nematodes, viruses and virus-like organisms. Among these, fungal diseases are the most troublesome worldwide and can reduce the yield and quality of fruits considerably. Grey mold rot (Botrytis cinerea Pers. Ex. Fr.), Rhizopus rot or leak rot [Rhizopus strolonifer (Ehrenb.Fr)], anthracnose (Colletotrichum fragariae Brooks), Verticillium wilt (Verticillium dahliae), red stele, also called red core, red root rot or brown stele (Phytophthora fragariae Hickman), Black root rot (disease complex), leather rot (Phytophthora cactorum) and powdery mildew (Sphaerotheca macularis), are some of the economically important fungal diseases of strawberry. Although farmers systematically attempt to protect the crop from diseases, some of the diseases are much harder to control. This is because of the rainfall and warm weather that prevail during cropping season in mild tropics make the situation an ideal growing condition for pathogenic fungi that attack both plants and fruit. A grower often would apply pesticides eight to ten times or even more during a cropping season and hence, disease control is a major expense in strawberry production. Increased focus on alternative means of disease control with reduced pesticide use are resulting in improved returns to growers, and a better outcome for the environment as well as consumers and hence it is gaining momentum. A more effective and less expensive method would be to develop strawberry cultivars resistant to prevalent diseases. The development and commercialization of day neutral strawberry cultivars (superior production environments) and resistance to some of the above stated diseases therefore should provide a means of reliable, long-term disease control and offer economic benefits by reducing or even eliminating the need for costly spraying. Howard 17, Aroma Dorsett, Rockhill, Fairfax, Fletcher, Trumpet, Sunrise, ‘Earliglow’, Redstar, Tioga, Temple, Catskill, Surecrop, Lassen and Tyee are some of the genotypes with various degrees of disease tolerance are available choices for usage. Hybridization work has already been initiated at Indian Institute of Horticultural Research, Bangalore to develop superior cultivars utilizing some of these lines.

Apple Chlorotic Leaf Spot Virus (ACLSV; family Betaflexiviridae, genus Trichovirus) and Apple mosaic virus (ApMV; family Bromoviridae, genus Ilarvirus) are economically important viruses of apple (Malus × domestica Borkh.). A duplex reverse transcription polymerase chain reaction (RT-PCR) assay was developed for simultaneous detection of both ACLSV and ApMV along with an internal control (NADH dehydrogenase subunit 5 gene). The internal control was used to minimize the risk of getting false negative results. Specific primers were designed against coat protein gene of ApMV while for ACLSV & internal control previously reported primer sets were used. Firstly the uniplex RT-PCR assay was standardized for the detection of each virus independently. Then duplex RT-PCR protocol for simultaneous detection of ACLSV and ApMV was standardized by using primer pairs ACLSV-CP1F & ACLSV-CP1R and ApMV-CP1F & ApMV-CP5R, respectively, along with primer set for internal control. Robustness of the technique was further validated wherein; duplex RT-PCR was carried out to detect both viruses in crab apples, rootstocks and different popular cultivars of apple. Results reveal that the duplex RT-PCR assay has detection sensitivity as that of uniplex RT-PCR assay for respective viruses. This optimized duplex RT-PCR provides a simple, rapid, sensitive and convenient way for simultaneous detection of ACLSV & ApMV by reducing the time and cost of the supplies.

In India, strawberry performs equally well in climates that are characteristically temperate in the northern latitudes, sub-tropical in the plains, or tropical at high altitude. In spite of attract...

A field experiment was conducted on bearing vines of kiwifruit cv. Abbott to find the effect of CPPU (N-(2- chloro-4-pyridyl)-N-phenylurea) and summer pruning on fruit yield, fruit size and quality. CPPU greatly stimulated fruit growth indicating that it can be a powerful tool for improving kiwifruit cropping. Application of CPPU at 10 ppm concentration was done by dipping the fruits for 10 sec in the aqueous solution of compound at petal fall and 30 days after petal fall. CPPU applied fruits increased size by 20-70 g over control. Summer pruning along with CPPU application proved to be more effective in obtaining fruits of high grades with increased fruit weight (95.37 g fruit(-1)) and high quality. Summer pruning, when done by pinching 1/5th at Petal Fall stage + CPPU dipping (10 ml(-1)) and pinching 1/5th continued till harvest, at one month interval resulted in increased fruit yield (54.80 kg vine(-1)), high TSS (17.60 Brix), high total sugar (9.85%), advanced ripening by one week and reduced flesh firmness.

The wild apples (Malus sp.) are important genetic resources for apple improvement programmes. In the present investigation, 32 Malus genotypes including indigenous Himalayan crab apples and exotic wild apples collected and maintained in the field gene banks at different ICAR institutes, were selected for genetic diversity and population structure analysis using the RAPD markers. The mean diversity indices, viz., Rp, PIC, EMR and MI of 18 RAPD markers were 5.829, 0.326, 8.432 and 2.851, respectively among the wild Malus genotypes. The cluster analysis segregated the wild Malus genotypes into two major clusters and the Jaccard's similarity coefficient ranged from 0.66 to 0.90. The first three axes of PCoA explained 40.26% variation and AMOVA explained 2% between the indigenous and exotic wild apple genotypes. The model based population structure studies revealed three major populations in the present set of genotypes. It could be concluded that there was substantial level of genetic diversity and population differentiation among the wild apple genotypes maintained at different research stations. Thus, the available diversity among the present set of wild apples could be explored for the scion as well as for rootstock breeding.

The crab apples (Malus baccata) can play a major role in the improvement of apple through proper utilization of their potential. A number of crab apples have been found growing wild in the Himalayas. An evaluation programme is in progress for utilization of a selection of Malus baccata bio-type from Shillong (Meghalaya, north east India) as rootstock for apple. It is semi-vigorous in nature and has a very good propagation potential. The chilling requirement of this selection is less than that of M 9 and MM106. It has exhibited resistance to woolly aphid, powdery mildew and apple scab. It has been tried as a rootstock for a high density apple planting with tree-densities of 4444, 2500, 1600, 1111 and 625 trees per hectares. Analysis of leaf nutrient content, sunlight interception, photosynthetic efficiency, vegetative growth and yield, leads to the conclusion that the density of 1111 trees per hectare could be the optimum density for stability and sustainability of yield in high density planting.

SummaryThere is a need for a non-destructive and relatively simple technique to measure leaf areas, particularly at locations where leaf area-measuring instruments are not readily available. The use of non-destructive methods, or taking leaf area measurements of attached leaves is required, particularly in situations where area measurements of the same leaf have to be taken at regular intervals throughout growth and development. In this study, a model has been developed with which to estimate apple leaf areas based on the product of leaf length and leaf width. No such model was previously available to measure or estimate apple leaf areas.

Apple chlorotic leaf spot virus (ACLSV; family Betaflexiviridae genus Trichovirus) is one of the economically important latent virus infecting apple (Malus × domestica Borkh.). Reverse transcriptase polymerase chain reaction (RT-PCR) procedures were used to amplify coat protein gene of ACLSV. Among 5 primer sets used, two primer sets (1F1R and 1F2R) amplified fragments of expected size (432 bp). Products visible on agarose gel were produced using templates extracted from apple leaves. The results were further validated by sequencing fragment of 432 bp which was amplified from leaf of apple by using primer set 1F 1R. Comparisons with published sequences indicated that the isolate have very high 91 % identity values to the corresponding region of ACLSV isolate from apple. Selected primer pair (1F1R) was further used for screening 42 elite mother plants collected from apple growing areas of Himachal Pradesh, India, where in 17 were found free from ACLSV. Use of NAD5 gene in mitochondrial mRNA of the apple as an internal control, reduced the risk of false negative results that may occur with routine RT-PCR assays.