Elsevier

Field Crops Research

Volume 137, 20 October 2012, Pages 268-271
Field Crops Research

Short communication
Image analysis of grain shape to evaluate the effects of high temperatures on grain filling of rice, Oryza sativa L.

https://doi.org/10.1016/j.fcr.2012.08.003Get rights and content

Abstract

High temperatures during ripening of rice (Oryza sativa L.) cause the conditions “immature thin grain” and “chalky grain”. Immature thin grain reduces yield and lowers milling quality due to deep creases on the surface, which hinder removal of the bran. We investigated the effects of high temperatures during ripening and of cultivar on the crease depth in field and growth chamber experiments. To avoid the influence of grain size, we calculated the inflection of the grain perimeter (from polar coordinates) at 50–60° away from the ventral ridge, which corresponded to the deepest crease. We used the mean inflection in this range (Iravg50–60) to evaluate the effect of high temperature on grain creases in the heat-tolerant rice cultivar ‘Nikomaru’ and heat-susceptible ‘Hinohikari’ at high and normal temperatures during ripening in a growth chamber and in the field in 2007 (hot summer) and 2008 (average summer). The grain creases were deeper under high temperature in the growth chamber and in the field (P < 0.001). Nikomaru had shallower grain creases than Hinohikari under both high and normal temperatures in the growth chamber and in hot weather in the field. Iravg50–60 was negatively correlated with final grain dry weight in both sets of experiments. These results confirm that Iravg50–60 is a suitable parameter for the evaluation of creasing on rice grains, which reflects grain filling under high temperatures during ripening.

Highlights

► High temperature during ripening deepens creases on the rice grain surface. ► The inflection point of the grain perimeter was measured by image analysis. ► The inflection at the deepest crease indicates the effect of high temperature. ► Heat-tolerant ‘Nikomaru’ had shallower creases than ‘Hinohikari’.

Introduction

High temperatures during ripening reduce rice grain quality, causing the conditions “chalky grain” (Yoshida and Hara, 1977, Tashiro and Wardlaw, 1991), “fissured grain” (Nagata et al., 2004), and “immature thin grain with deep creases” (Nagato and Ebata, 1965, Morita et al., 2005a, Morita, 2009). This last effect is more serious because it causes not only lower grain quality, relating to lower milling efficiency, but also lower grain yield by reducing grain weight (Morita et al., 2005b). The physiological mechanisms underlying this problem are unclear, so there is little information about how to prevent it.

Research has been hindered by the lack of a high-throughput method for evaluating crease depth. Sasaki and Magoshi (1933) proposed a method based on microscopic analysis, but this method is too time-consuming to have been taken up. Breaks and cracks responsible for fissured grain have been assessed by image analysis of parboiled rice (Courtois et al., 2010), but creases formed along the junction of the lemma and palea have not.

We have proposed a method based on image analysis and have used it to assess the effects of growing condition (Morita et al., 2005a, Morita, 2009) and cultivar (Morita, 2009). We found that high temperatures during ripening promote creasing, and that the heat-tolerant cultivar ‘Nikomaru’ (Sakai et al., 2007, Morita and Nakano, 2011) creases less than the susceptible cultivar ‘Hinohikari’ under high temperatures during ripening, especially with low solar radiation (Morita, 2009). However, our pot experiments provided little information about the factors relating to the depth of creases on the grain surface.

Here, we elucidated the effects of high temperature during ripening and of cultivar on crease depth using data from growth chamber and field experiments at high and normal temperatures (Morita, 2009), and confirmed an appropriate index for immature thin grain with deep creases.

Section snippets

Pot experiment

We grew two cultivars: the heat-tolerant ‘Nikomaru’ (Sakai et al., 2007) and the heat-susceptible ‘Hinohikari’ (Yagi et al., 1990), a leading cultivar in western Japan. Ten seedlings of each cultivar were transplanted on 17 June into plastic pots (16 cm across, 20 cm tall) containing Gray Lowland soil (a Typic Endoaquept), the field soil at the National Agricultural Research Organization (NARO) Kyushu Okinawa Agricultural Research Center (KARC), in 2004. Tillers were removed periodically to

Results and discussion

Higher temperatures decreased r by similar amounts at both the dorsal (180°) and ventral (0°) ends in the pot trial (Fig. 2A); it also decreased grain weight in the pot trial (Fig. 3) and 1000-grain weight in the field trials (Fig. 4). Nagato and Ebata (1965) reported that the effects of temperature on grain growth differed between the ventral and dorsal sides: the dorsal radius, which develops early during ripening, was longer at higher temperatures, and the ventral radius, which grows later

Acknowledgments

We thank Mr. Hisashi Kitagawa, Dr. Hiroshi Nakano, Dr. Hiroshi Wada, Mr. Akitoshi Honbu, Ms. Kumi Matsufuji, and Ms. Emi Hashimoto, NARO/KARC, for their help and cooperation.

References (16)

  • F. Courtois et al.

    Assessing breakage and cracks of parboiled rice kernels by image analysis techniques

    Food Control

    (2010)
  • S. Chowdhury et al.

    The effect of temperature on kernel development in cereals

    Aust. J. Agric. Res.

    (1978)
  • Y. Ishiyama et al.

    Labeling board based on boundary tracking

    Comput. Vision

    (1990)
  • S. Morita

    Eco-physiological analysis for the high temperature effects on rice grain ripening

    Bull. Natl. Agric. Res. Cent. Kyushu Okinawa Reg.

    (2009)
  • S. Morita et al.

    Nonstructural carbohydrate content in the stem at full heading contributes to high performance of ripening in heat-tolerant rice cultivar Nikomaru

    Crop Sci.

    (2011)
  • S. Morita et al.

    Effects of topdressing on grain shape and grain damage under high temperature during ripening of rice

    Rice is Life: Scientific Perspectives for the 21st Century. Proc. World Rice Res. Conf., Tsukuba, 4–7 November 2004, Japan

    (2005)
  • S. Morita et al.

    Grain growth and endosperm cell size under high night temperatures in rice (Oryza sativa L.)

    Ann. Bot.

    (2005)
  • K. Nagata et al.

    Effect of air temperature during the early grain-filling stage on grain fissuring in rice

    Jpn. J. Crop Sci.

    (2004)
There are more references available in the full text version of this article.

Cited by (12)

  • Application of hyperspectral imaging technology to discriminate different geographical origins of Jatropha curcas L. seeds

    2013, Computers and Electronics in Agriculture
    Citation Excerpt :

    However, shells and kernels of samples were separated in the above researches, which is a drawback for breeders who require non-invasive techniques to determine the qualities of seeds. Machine vision is a promising non-destructive method for rapid and automatic identification in many research areas (Ahmed et al., 2012; Alvarenga et al., 2010; Brescia et al., 2007; Choudhary et al., 2008; Courtois et al., 2010; Ercisli et al., 2012; Hu et al., 2012; Wu et al., 2012b; Yonemaru and Morita, 2012). Near infrared hyperspectral imaging is a fast, simple, and non-contact technique which combines spectroscopy and digital imaging simultaneously to acquire spectral and spatial information.

  • Heat Stress and Grain Quality

    2022, Thermotolerance in Crop Plants
View all citing articles on Scopus
1

Both authors contributed equally.

View full text