Screening of grapefruit cultivars for mutagenesis, fruit quality and micropropagation

Grapefruit (Citrus paradisi) is consumed worldwide and is popular for its flavour and good juice quality. In the first experiment, fruits of 'Shamber', 'Rio Red', 'Red Blush', 'Pink Ruby', 'Star Ruby' and 'Flame Seedless' were harvested and subjected to different physico-chemical analysis including fruit shape and base shape, weight, diameter, length, no. of segments, seeds per fruit, ratio of fruit length and fruit diameter and polyembryony. Chemical parameters were total soluble solids, titrable acidity, TSS/TA, vitamin C, anthocyanins and sugars. Experimental layout was according to completely randomized design (CRD). Results showed that in 'Flame seedless' maximum fruit length (87.71mm), fruit diameter (105.17 mm), rind thickness (1004 mm), number of segments (13.6) and fruit weight (455.5 g) was observed whereas, 'Shamber' showed maximum ratio of fruit length and fruit diameter. Highest TSS value (8.87 %) was found in 'Star Ruby' whereas maximum TA (1.89%) was observed in 'Flame seedless' and maximum ratio of TSS/TA was calculated in 'Pink Ruby' (7.8). Fruit shape and base shape were observed as (Spheroid) and (Convex) respectively in all cultivars. Highest vitamin C value (73.85 mg/100g) was recorded in 'Red Blush' whereas maximum value of anthocyanins (0.82 mg/100g) was recorded in 'Pink Ruby'. Maximum value of total sugars and reducing sugars was observed in 'Flame Seedless' (5.67%) and (2.85%) respectively. Non-reducing sugars were highest in 'Pink Ruby' (2.9%). In mutation induction experiment, grapefruit cultivars (Red Blush, Rio Red, Flame Seedless, Pink Ruby and Star Ruby) were exposed to different gamma-irradiation doses 0 (control), 40, 80, 100, 110 and 140 Gy. Irradiated wood was grafted on rough lemon rootstock. Data was collected regarding number of leaves, number of shoots, leaf area, shoot length, inter-nodal distance and irradiated bud sprouting percentage. The experimental layout was two factors Factorial experiment under randomized complete block design (RCBD). It has been observed that number of leaves, leaf length, leaf width, leaf area, internodal distance and shoot length showed a significant decline in irradiated treatments (T1-T5) compared to untreated controls (T0). However, number of branches showed non-significant differences among gamma radiation doses. In the third experiment, explants from 'Foster' and 'Shamber' were cultured in MS media supplemented with BAP 0, 0.5, 1, 1.5, 2, 2.5 and 3 mg/L and BAP+IAA 0, (0.5+0.1), (1+0.2), (1.5+0.3), (2+0.5), (2.5+0.5) and (3+0.1 mg/L). The experiment was laid according to completely randomized design (CRD). No. of shoots, roots and plant survival percentage were studied. Results did not come as no shoots or roots were produced. However, plants survived to produce callus. This research was carried out in University of Agriculture, Faisalabad during 2015-2016.