The Responses of Physiological Characteristics and Flowering Related Gene to the Different Water Stress Levels of Red-Flesh Pummelo Cultivars (Citrus grandis (L.) Osbeck) Own-Rooted by Air Layering Propagation under Two Growing Conditions

Prawit Thammatha,Suchila Techawongstien,Chanon Lapjit ,Tanyarat Tarinta

doi:10.3390/horticulturae7120579

Abstract

One of the major problems in the fruit production of citrus, including pummelo (Citrus grandis) is controlling flowering induction. Water stress is known to be related to flowering induction via physiological responses related to the flowering gene. However, reports on the mechanisms underlying floral induction by water stress in pummelo are limited. Thus, this study aimed to determine the physiological characteristics and the expression of genes related to flowering induction, CiFT (Citrus Flowering locus T), in pummelo at different levels of water stress. Experiments were conducted under two growing conditions: field and container conditions, each using a 2 × 5 factorial experiment in a randomized complete block. Factor A consisted of two red-flesh pummelo cultivars while factor B consisted of five levels of water stress based on the leaf rolling index. Among the seven characteristics studied, only the data of total nitrogen, CiFT, and flower number were combined for analysis due to their results in a homogeneity test. Although a consistent tendency was not observed for the interaction among environments, genotypes, and water stress levels of all characteristics, ‘KKU-105’ grew more flowers under higher water stress conditions (225 flowers). This result may imply that decreases in total nitrogen (1.48%), stomatal conductance (50.53 m−2s−1), chlorophyll fluorescence (0.30 Fv/Fm), and upregulation of CiFT mRNA level (13.95) may induce flowering in the pummelo cultivar ‘KKU-105’.

Highlights

In Thailand, Pummelos (Citrus grandis (L.) Osbeck) are divided into two kinds based on the color of their flesh: white-flesh pummelos and red-flesh pummelos [1]
The genotype-bywater stress (G × S) interactions were significantly different among the four characteristics studied (Table 1)
This study revealed that the number of flowers and CiFT mRNA level for floral in‐

Summary

Introduction

In Thailand, Pummelos (Citrus grandis (L.) Osbeck) are divided into two kinds based on the color of their flesh: white-flesh pummelos and red-flesh pummelos [1]. The red-flesh pummelo is popular among consumers due to its richness in lycopene, anthocyanin, and beta carotene [2,3,4]. The red-flesh pummelo cultivars (‘KKU-105’, ‘KKU-101’, and ‘Manee Esan’) are some of Thailand’s newest and most promising pummelo cultivars, and can be found in Baan Bung 14, Tambon Nonthong, Amphoe Kasetsomboon, Chaiyaphum province in the northeast. Red-flesh pummelos grown in tropical and sub-tropical areas are frequently susceptible to climate change, which causes their flowers to fall off owing to high relative humidity and rainfall [5]. Stress related conditions can directly and indirectly decrease the expression of genes which are responsible for floral induction or flowering, which is one of the most crucial events in a plant’s lifecycle [6,7].

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