Pre-breeding studies on reproductive parameters of papaya
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Date
2023
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Abstract
The research study titled on “Pre-breeding studies on reproductive parameters of papaya” was carried out during 2022-23 at ICAR-AICRP on Fruits Farm, Dr. Rajendra Prasad Central Agricultural University, Pusa, Samastipur, Bihar. The study involved four specific papaya cultivars viz., cv. ‘F1 Red Lady’, cv. ‘Arka Prabhat’, cv. ‘Ranchi Local’ and cv. ‘TNAU Papaya CO-8’, each two as the gynodioecious and dioecious representative, respectively. The experiment was structured in a randomized block design with five replications and the plants were spaced at 2m × 2m. The observations such as, Plant height (cm), Plant girth (cm), Collar diameter (cm), Petiole length (cm), First flowering height (cm) were recorded as pre reproductive parameters and parameters such as, Days taken for bud emergence, Interval between bud emergence to flower bud opening, Sex form, Inflorescence type (single or cluster), Number of anthers per floret, Number of stigmatic lobes, Pollen output per anther, Pollen output per flower, Pollen viability (%), Pollen germination (%), Pollen size (µm), Anthesis (Time), Anther dehiscence (Time), Time span of stigmatic receptivity (hr.), and post fertilization entities were includes, Days taken from bud emergence to ovule maturation, post- fertilization ovule degeneration (%), Days taken for fruit set, Days taken for viable seed set, Percent viable seed set in both the gynodioecious and dioecious cultivars were recorded in the reproductive phase. The present study investigated the sexual diversity and reproductive characteristics of dioecious and gynodioecious papaya cultivars. At 120 days, no significant distinctions were observed in plant height, plant girth, collar diameter, and petiole length between dioecious and gynodioecious cultivars. However, at 160 days, distinct differences emerged, with the dioecious cv. ‘Ranchi Local’ reaching a height of 76.40 cm compared to the gynodioecious cv. ‘Arka Prabhat’ at 65.00 cm. Similarly, plant girth at 160 days ranged from 12.18 cm (cv. ‘Arka Prabhat’) to 15.16 cm (cv. ‘Ranchi Local’), collar diameter spanned from 2.86 cm (cv. ‘Arka Prabhat’) to 4.28 cm (cv. ‘Ranchi Local’), and petiole length varied between 23.40 cm (cv. ‘Arka Prabhat’) and 28.60 cm (cv. ‘Ranchi Local’). First flowering height displayed no significant differences. Notably, bud emergence and flower bud opening time revealed distinctive patterns among cultivars, with dioecious cv. ‘Ranchi Local’ taking 175.20 days for bud emergence and 29.45 days for flower bud opening, gynodioecious cv. ‘F1 Red Lady’ emerging at 160.33 days and flowering at 24.58 days, and gynodioecious cv. ‘Arka Prabhat’ with bud emergence at 166.67 days and flower bud opening at 26.19 days. Anthesis timing demonstrated considerable variability, with the earliest occurrence observed in cv. ‘TNAU Papaya CO-8’ at 17.54, while the latest was recorded in cv. ‘Arka Prabhat’ Carpelloid Pentandria at 21.43. Similarly, anther dehiscence, a crucial stage in pollen release, showcased the earliest timing in cv. ‘TNAU Papaya CO-8’ at 6.34, whereas the Carpelloid Pentandria of cv. ‘Arka Prabhat’ exhibited the latest dehiscence at 9.23. Additionally, the study unveiled the nuanced stages of stigma receptivity, progressing through four distinct phases: absence during bud closure, weakly positive pre-anthesis, strong positivity during anthesis, and very strong positivity post-anthesis. Furthermore, the study delved into pollen characteristics, revealing that dioecious varieties produced pollen within the range of 11,395.60 to 11,801.60 per anther (mean 11,598.60), while gynodioecious varieties ranged from 7,157 to 10,955.80 per anther (mean 9,988.95). Dioecious pollen viability percentages spanned from 71.44% to 75.44%, while gynodioecious pollen viability percentages ranged from 24.17% to 46.80%. Similarly, dioecious pollen germination rates ranged from 62.846% to 67.635%, and gynodioecious pollen germination rates spanned from 22.310% to 40.406%. Additionally, dioecious pollen exhibited sizes ranging from 25.792 to 26.386 µm, whereas gynodioecious pollen sizes fell within the range of 23.802 to 25.842 µm. Similarly, the period from bud emergence to ovule maturation showed slight variations, ranging from 28.57 to 29.13 days for dioecious and 28.32 to 32.09 days for gynodioecious plants. Post-fertilization ovary degeneration rates were observed within the range of 17.94% to 18.11% for dioecious and 16.38% to 26.04% for gynodioecious varieties. The duration for fruit set demonstrated a span of 14.40 to 15.80 days for dioecious and 12.20 to 17.80 days for gynodioecious types. Viable seed set times differed, ranging from 77.80 to 80.60 days for dioecious and 75.60 to 87.40 days for gynodioecious cultivars. Percentages of viable seed set showcased ranges of 58.35% to 61.54% for dioecious and 46.48% to 68.89% for gynodioecious variants. These findings offer comprehensive insights into the temporal dynamics and reproductive patterns of papaya's distinct sex forms