Selection index and activation of seedling growth in mangosteen
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Date
2002
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Department of Pomology and Floriculture, College of Horticulture, Vellanikkara
Abstract
The experiments on "Selection index and activation of seedling growth in Mangosteen (Garcinia mangostana L.) were conducted in the central orchard attached to the Department of Pomology and Floriculture of the College of Horticulture from March 2000 to February 2002 with the broad aims of standardizing selection indices as well as activation of the seedling growth in mangosteen. Two separate experiments, one approach envisaging growth regulators and the .other involving arbuscular mycorrhizal fungi (Glomus mosseae and Glomus fasciculatum and Azospirillum with single super phosphate were taken up. The important results are as follows. Analysis of leaf biochemical characters of the mother plants belonging to different age groups «25, 25-50, 51-75 and >75 years) revealed that nitrogen, phosphorus, potassium and crude protein, were highest in the lowest «25 years) age group and least values were in the highest (>75 years) age group, except sodium, total phenols and total carbohydrates, which were maximum in the age group of 51-75 years.
The number of seedless fruits and almost all the morphological characters of the fruit were highest in the age group of 51-75 years. Number of one seeded, two seeded and three and more than three seeded fruits were also varying among the four age groups. All seed morphological characters and number of ungerrninated seeds showed maximum values in the age group of 51-75 years and >75 years. Seeds obtained from the age group of 51-75 years showed earliness in germination but the percentage of germination was highest in the age group of 25-50 years.
The biochemical characters of seed revealed that nitrogen, phosphorus, potassium, crude protein, total carbohydrates, total sugar and total phenols were maximum in the age group of25-50 years, whereas sodium and abscisic acid were highest in the age groups of less than 25 and more than 75 years, respectively. The morphological characters of seedling such as, height, girth, total number of leaves per seedling, total leaf area, survival rate at twelve months stage and root characters were highest in 25-50 years age group whereas the root and shoot dry weight were maximum in the less than 25 years group.
Nitrogen, phosphorus, potassium, crude protein and sodium levels in the leaves of the seedling were highest in the age group of less than 25 years.
Chlorophyll a, b, total phenols, total carbohydrates and abscisic acid contents were higher in the age group of 25-50 years.
Maximum fruit index was observed in the age group of 51-75 years but seed and seedling index were highest in 25-50 years age group. Most of the seed characters were positively correlated with seedling characters. Though all the fruit characters were positively correlated with seed characters they were negatively correlated with seedling characters. Fruit index, seed index and seedling index were separately predicted using the prediction models fitted by multiple regression equations of principle components one and two with corresponding adjusted R2 values.
Dominant characters among the age of mother plant, fruit, seed and seedling characters separately were found out by figurative plot principal component analysis based on morphological data of the above characters individually.
Using step wise regression major characters contributing to seedling index were identified as age of the mother plant, seed thickness at centre, total leaf area, survival rate, fresh weight of root and plant, root length and total number of roots, which contributed maximum variation to seedling morphological characters and prediction model for fruit index, seed index and seedling index were fitted. To establish the similarities (or dissimilarities) between the four age groups, hierarchical cluster analysis using euclidean distance was performed which revealed that the younger two age groups (less than 25 years and 25-50 years) of the mother plants were the closest groups with respect to all characters.
The four using discriminant functions were fitted to discriminate the four age groups with corresponding D2 values. The criteria and criterion were determined to describe the age groups of selected fruit, seed and seedlings collectively.
By giving equal importance to age of the mother plant, fruit index, seed index and seedling index the selection index was worked out and the best age group of the mother plant for obtaining maximum growth of seedlings was identified as 25-50 years. Based on the correlations between various characters and growth index, the above or below average values with respect to each of the attribute (important and visual) belonging to the fruit, seed and seedling characters were identified. The mid values of the each attribute in the best age group were fixed as the index for selection.
Among the growth regulator sprays for activating the slow growth in mangosteen, the best treatments were GA 150 mg r' followed by IAA 250 mg r'. Biochemical studies on the growth regulators treated plants revealed that the treatment that showed maximum growth also recorded the highest values of nitrogen, phosphorus, potassium, crude protein, chlorophyll a, b, total chlorophyll, total phenols, total carbohydrates and abscisic acid content. The treatment, which showed intermediate growth recorded intermediate values except for sodium, where it was maximum. The least content was observed in the treatments with least growth. The control plant showed intermediate values between the. values of plant with intermediate and least growth. Best treatment for activating the seedling growth among the treatments with arbuscular mycorrhizal fungi and Azospirillum inoculations were identified as, the combinations of Glomus Jasciculatum 5 g + Azospirillum 109 + single super phosphate 109 followed by GlomusJasciculatum 5 g + Azospirillum 20 g + single super phosphate 109.
A rhythmic pattern was observed with the treatments showing best seedling growth also recording higher values of nitrogen, phosphorus, potassium, crude protein, chlorophyll a, b, total chlorophyll, total phenol total carbohydrates and the abscisic acid content, and the treatments showing in intermediate growth recording intermediate values except sodium. The least values were in treatments that showed least growth. The control plant showed intermediate values between the values of the plant with intermediately and least growth.
The highest spore count was observed in the plants inoculated with Glomus Jasciculatum 20g + single super phosphate 109 followed by Glomus Jasciculatum20 g + Azospirillum 20 g + single super phosphate 10 g. With regard to the root infection, plants inoculated with Glomus Jasciculatum 5 g + Azospirillum 20 g + single super phosphate 109. and Glomus Jasciculatum 20 g + Azospirillum 109 + single super phosphate 109 revealed maximum percentage of infection. The Azospirillum population was maximum in the plants inoculated
Glomus fasciculatum 5 g + Azospirillum 109 + followed by Glomus mosseae 20 g + Azospirillum 20 g + single super phosphate 109.
The standard procedure for identification and quantification of abscisicacid (Little et al., 1972) was modified, as clear banding patterns were not obtained. Using the modified procedure, the characteristic-banding pattern corresponding to standard abscisic acid was obtained and confirmed when standards of abscisic acid were also simultaneously run with samples.
Banding patterns and quantification of samples in each of the four age groups, the growth regulator treatments and the treatment with arbuscular mycorrhizal fungi and Azospirillum inoculated plants were also successfully conducted.
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