Physio-Anatomical Study of Polyploid Watermelon Grafted by Different Methods

Mohamed Omar Kaseb,Wenge Liu,Weinan Diao,Muhammad Jawad Umer,Hongju Zhu,Shengjie Zhao,Eman El-Remaly,Nan He,Eftekhar Mahmud,Pingli Yuan,Muhammad Anees,Xuqiang Lu

doi:10.3390/agronomy11050913

Abstract

Watermelon is one of the most desirable vegetable crops in the world. Recently, grafting is common in watermelons worldwide, but not all grafting methods are compatible with polyploids. In this study, diploid, triploid, and tetraploid from one watermelon variety, “Mi Mei”, were grafted on the “Xijiaqiangsheng” squash rootstock to study the effect of genome duplication on graft compatibility. Three grafting methods (splice, hole, and tongue) were used to determine graft compatibility. Significant differences in survival rates, hormones, antioxidants (AOX), sugars, and starch contents were observed between compatible/incompatible combinations. Compatible combinations with high survival rates showed high levels of hormones, AOX, carbohydrates, and low hydrogen peroxide H2O2 compared to incompatible plants. The hole grafting method was more efficient with diploid, while splice was efficient with a tetraploid, and both methods can be used for triploid. Compatibility is a combined effect of hormone, carbohydrate, and antioxidant activities. We predict that compatibility is a complex process and that further molecular studies must be performed to dig deep into this phenomenon.

Highlights

Seedless watermelon cultivars (Citrullus lanatus L.) are the most desirable by consumers and have a high price and more excellent quality than seeded watermelon [1]
The most critical time in the healing process is 2–3 days after grafting (DAG) during the healing stage [55], there is the highest rate of stress, and the highest increase of hormones and antioxidants leads to graft compatibility [56]
Our results showed high compatibility in Tetra grafted with splice method and high content and higher increment rates of hormones than Di, especially at 3 DAG and 15 DAG

Summary

Introduction

Seedless watermelon cultivars (Citrullus lanatus L.) are the most desirable by consumers and have a high price and more excellent quality than seeded watermelon [1]. Seedless watermelons are triploids (3n = 33) produced by crossing a tetraploid (4n = 44) seed parent with a diploid (2n = 22) pollen parent [2,3]. One of the main advantages of the polyploidy in the watermelon is triploid (seedless) fruits; another benefit, conferred by gene redundancy, is diversifying gene function by altering redundant copies of important or essential genes [7,8,9]. After genome doubling, the artificially induced autopolyploids always exhibit new characters, such as DNA contents, high secondary metabolite organisms, large tissues and organs, improved yield, higher contents of chlorophyll, lycopene, fructose, and glucose, and higher tolerance to both abiotic and biotic stress, than diploid, all of which are distinct advantages of polyploidy [2,3,5,10,11,12,13]

Methods

Results

Discussion

Conclusion