Effects of the number of pollen grains on cold tolerance at the booting stage in rice lines with QTLs for cold tolerance

Akira Fukushima,Takami Hayashi,Hisatoshi Ohta,Ryota Kaji,Narifumi Yokogami,Naoto Tsuda

doi:10.1080/1343943x.2016.1245103

Abstract

This study was conducted to clarify the relationship between the number of pollen grains per anther and spikelet fertility under low temperature conditions in the rice cultivars and lines including lines with quantitative trait loci (QTL) for cold tolerance, adapted to the Tohoku region of northern Japan. Cold-water treatment decreased anther length, the number of pollen grains per anther, and spikelet fertility in all cultivars and lines. The number of pollen grains was proportional to anther length in all cultivars and lines and under all temperatures. Spikelet fertility decreased with decreasing the number of pollen grains in cold-water treatments at 18.5 and 19.3 °C. ‘Ouu 415’, with the qLTB3 QTL for cold tolerance, had 28% more pollen grains and 9% higher spikelet fertility than the recurrent parent, ‘Hitomebore’, in the 18.5 °C cold-water treatment, suggesting that qLTB3 increased both parameters. Lines with the qCTB8 QTL for cold tolerance had significantly more pollen grains in two of the three years and significantly higher spikelet fertility in all three years in the 19.3 °C cold-water treatment, suggesting that qCTB8 reinforced cold tolerance. Ctb1, a proposed cold-tolerance QTL, had no effect on the number of pollen grains or spikelet fertility. In conclusion, the cultivars and lines with more pollen grains had a higher cold tolerance. Some of QTLs were inferred to increase the number of pollen grains and reinforce cold tolerance.

Highlights

Rice yield is often decreased by spikelet sterility caused by low temperatures at the booting stage in northern Japan’s Tohoku region
One promising method of breeding cold-tolerant cultivars is the introduction of quantitative trait loci (QTLs) for cold tolerance into elite cultivars by taking advantage of DNA marker-assisted selection
We used four elite cultivars from the Tohoku region as the control cultivars:‘Masshigura’,‘Akitakomachi’,‘Hitomebore’, and‘Fukuhibiki’. We compared their performance with the following cold-tolerant cultivars and lines: ‘Ukei 898’ and ‘Ukei 965’, indica lines derived from crosses among cold-tolerant indica cultivars (Figure 1, Yamaguchi & Yokogami, 2003); ‘Lijiangxintuanheigu’ (‘LTH’), a local cultivar from China’s Yunnan Province;‘Ouu 415’(‘LTH’/‘Hitomebore’× 4), with QTL qLTB3 for cold tolerance, derived from ‘LTH’; and ‘Ukei 855’ (‘Kunmingxiaobaigu’ [a cold-tolerant local cultivar from Yunnan Province]/‘Hitomebore’ × 2)

Summary

Introduction

Rice yield is often decreased by spikelet sterility caused by low temperatures at the booting stage in northern Japan’s Tohoku region. Many QTLs for cold tolerance have been detected, including qCT-7 (Takeuchi et al, 2001), Ctb and Ctb (Saito et al, 2004), qCTB8 (Kuroki et al, 2007), and qLTB3 (Shirasawa et al, 2012) Their role in cold tolerance is not fully understood, and their introduction into elite cultivars in the Tohoku region has not always reinforced cold tolerance. Nakamura et al (2000) pointed out that cultivars with more pollen grains had higher fertility under low temperatures All of these studies suggest that the number of pollen grains is an important indicator of cold tolerance. Genetic diversity in the number of pollen grains produced under

Objectives

Methods

Results

Conclusion