Stem end rot of mango: Characterizing disease dynamics and fruit quality deterioration from farm to retail in Saurashtra

Introduction

Mango (Mangifera indica L.) a member of the Anacardiaceae family, is an important fruit crop of India as well as tropical and sub-tropical countries of world. With its rich cultural and religious significance spanning generations, the mango stands as a revered symbol, acclaimed as the "king of tropical fruits" (Yadav et al., 2018) [11] . The mango is commercially grown and popular in more than 80 countries worldwide. Among them, India is the largest producer of mango accounting for nearly 50 per cent of the total production of the world (Senjaliya et al., 2022) [8] . India occupies top position among mango growing countries of the world with an area of 2.39 million hectares and annual production of 22.66 million tonnes (Anonomous, 2024) [1] . The mango industry faces significant post-harvest losses, with fungal diseases being a primary culprit. These losses can be as high as 50%, particularly impacting perishable fruits like mangoes more severely than other crops (Eckert and Ogawa, 1985) [3] . During transport, storage and sale, on an average of 17.7% of mangoes rot due to fungal infections (Sharma et al., 1994) [9] . Among the various post-harvest diseases, stem end rot, caused by L. theobromae, is a major concern in India (Johnson et al., 1991) [5] . Globally, stem end rot is considered the second most severe post-harvest mango disease after anthracnose (Dodd et al., 1997) [2] . Stem end rot initially appears as a small, light brown lesion on the mango's skin around the stem. Which later form a circular snuff brown black patch having fringed margin, under humid condition through which a light brown exudation occurred (Pathak and Srivastava, 1967) [6] . This comprehensive approach aimed to understand the progression of the disease from harvest through to retail sale and to identify potential intervention points for disease management. Additionally, the survey intended to assess the pathogenic diversity of L. theobromae, the primary causal agent, across different locations. from both the orchards and markets during survey. Each sample containing 60 fruits. It was collected in paper bags then bring to the laboratory and stored at room temperature for 24 hours. Stored samples were examined every day for post-harvest diseases and fruits showing typical stem end tot disease symptoms were sorted out for the isolation and confirmation of the causal agents. The numbers of infected fruits were recorded and per cent disease incidence was calculated by using following standard formula as given by Gupta (2007) [4] . The fruit weight loss was also calculated by using following formula.

Number of diseased fruits Disease Incidence (%) = x100 Total number of fruits Number of diseased fruits Disease Incidence (%) = x100 Total number of fruits Likewise; to assess the disease severity, observations were taken on area of fruit surface showing symptoms in 0-5 scale as given by Prasannakumar et al., (2002) [7] . Further, per cent disease intensity (PDI) was calculated by using following formula as given by Wheeler, (1969) [10] .

Grade

Results and Discussion

The findings revealed a consistent trend of increasing disease prevalence, severity and fruit weight loss as mango moved from the field to wholesale markets and finally to retail markets in both districts. In Gir Somnath district, the lowest disease levels were recorded at the field level with 10.15% incidence, 4.27% severity and 11.49% fruit weight loss. These parameters increased at the wholesale stage to 19.10% incidence, 14.84% severity and 14.68% fruit weight loss, reaching the highest levels in retail markets with 22.26% incidence, 20.62% severity and 18.38% fruit weight loss.

A similar trend was observed in Junagadh district. At the field level, disease incidence was 9.53%, severity 4.10% and fruit weight loss 11.26%. These levels increased to 17.62% incidence, 11.53% severity and 14.10% fruit weight loss in wholesale markets, peaking in retail markets with 23.99% incidence, 22.51% severity and 19.30% fruit weight loss. Notably, retail market losses in Junagadh district were slightly higher than those recorded in Gir Somnath. This progressive escalation in disease prevalence and fruit deterioration highlights the critical role of post-harvest handling, transportation, storage and market conditions in aggravating stem end rot in mango.

Field survey for stem end rot diseases of mango

A detailed field survey covering 69 villages across eight talukas of Junagadh and Gir Somnath districts revealed substantial variation in stem end rot incidence and severity (Table 1 and Plate 1). The highest disease incidence (30.06%) was recorded in Ramrechi village, while the highest severity (14.28%) occurred in Talala village, both located in Gir Somnath district. In contrast, the lowest disease incidence (1.67%) and severity (0.34%) were observed in Ratang village of Junagadh district. Several villages, including Chhachhar, Ghusiya and Motha in Gir Somnath district and Manpur in Junagadh district, were completely free from the disease during the survey period. Analysis of fruit weight loss data indicated a direct correlation between disease severity and fruit weight reduction. Villages with high disease levels, such as Ramrechi (15.60% fruit weight loss) and Talala (14.93%), recorded significantly greater losses compared to normal physiological levels. Conversely, villages free from stem end rot disease (e.g., Chhachhar -9.50%, Ghusiya -9.95%, Motha -10.05% and Manpur -9.92%) exhibited fruit weight losses within or near the expected physiological range. These findings demonstrate the localized nature of disease prevalence at the orchard level and highlight the influence of disease-free orchards on minimizing post-harvest losses.

Wholesale market survey for stem end rot diseases of mango

The survey of 14 major wholesale mango markets across Junagadh and Gir Somnath districts revealed notable variations in disease incidence, severity and fruit weight loss (Table 2 and Plate 1). Among all the surveyed markets, the highest disease incidence (28.39%) was recorded at APMC Mango Market Yard, Talala, while the highest severity (18.81%) occurred at APMC Market Yard, Kodinar. The Centre of Excellence for Mango at Talala exhibited the lowest disease incidence (11.69%) and severity (7.59%), demonstrating the potential benefits of improved handling and storage infrastructure in reducing post-harvest losses. In terms of fruit weight loss, the highest percentage (18.13%) was observed at APMC Mango Market Yard, Talala, corresponding with high disease levels. In contrast, the Centre of Excellence for Mango recorded the lowest fruit weight loss of 11.71%. These results emphasize the critical role of post-harvest market practices and infrastructure in either mitigating or exacerbating stem end rot losses at the wholesale level. 3. Retail market survey for stem end rot diseases of mango Assessed the incidence and severity of mango stem end rot at the retail level (Table 3 and Plate 1). The significant variations were observed in stem end rot prevalence and severity at the retail level. Among the surveyed retail markets, the highest disease incidence (40.08%) and severity (37.95%) were notably recorded in Vegetable Market, Dhal Road (Junagadh), whereas the lowest disease incidence (15.03%) and severity (14.19%) were recorded at Fruits Market, Sakkarbaug (Junagadh). Furthermore, analysis of fruit weight loss in various retail mango markets as presented in Table 3 revealed that the highest losses were observed at Vegetable Market, Dhal Road (26.35%). The lowest losses were recorded at Fruits Market, Sakkarbaug (13.19%).

Collectively, the surveys demonstrated a clear trend: disease prevalence, encompassing incidence and severity as well as associated fruit weight loss, was minimal at the field level, progressively increasing through the wholesale stage and reaching its maximum at the retail distribution level. This escalating trend is primarily attributed to the cumulative effects of post-harvest handling, transportation stresses, prolonged storage and varying environmental conditions encountered at each stage of the supply chain. These factors collectively favor the development of the pathogen (L. theobromae) and subsequent fruit deterioration, leading to significant economic losses highlighted by the increasing fruit weight reduction due to stem end rot of mango.

Conclusion

A roving survey conducted from May to July during the summer seasons of 2024 across 69 orchards, 14 wholesale and 18 retail mango markets in Junagadh and Gir Somnath districts of Saurashtra, revealed widespread stem end rot. Disease severity significantly increased as fruit progressed from fields to markets: field incidence ranged from 3.34-30.06% (1.65-13.6% severity), escalating in wholesale markets (11.69-28.39% incidence and 7.59-17.82% severity) and retail markets (15.03-40.08% incidence and 14.19-37.95% severity). A similar trend was observed in fruit weight loss, emphasizing the intensification of disease during post-harvest stages. Variations are attributed to differences in horticultural practices, environmental conditions and post-harvest handling and storage across various regions and locations.

Acknowledgement

AcknowledgementThe authors are highly thankful to the Director of Research and Dean, Faculty of P. G. Studies, Junagadh Agricultural University, Junagadh for providing the necessary facilities to conduct the research work.

References

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