Correlation of grain characters in rice (Oryza sativa L.)

: Pvlorphological characters of rice grains fO1yz.a. sotivu L.) talciug ~ O L I ~ cultivars each from each of modern and traditional cultivars, growl1 in Bolo season were studied. The length, breadth and thiclrness of grain !unhulled grain). length and breadth of lcernel (hulled grain), embryo length, embryo-endosperm ratio and 1000-grain weight, and their interrelationship were investigated. There were significant differences regarcling values of all parameters except g~.ain thiclcness and embryo len@h among the cultivars. Significant correlatio~is between grain length to kernel length (r=0.9655""'), grain breadth to grain thicltness (r=0.8938:":"), Icernel breadth (r=0.9783:"') and 1000-grain weight (1-=0,7727:~) were found. Embryo length dicl not show any relationship between ot;ber characteristics of grain or Icernel.


INTRODUCTION
Grain shape and size are the most important factors which influence yield and quality of rice (Oryza satiua L.). Morphological characters and their effects on grain quality and yield have been studied by many researc11ers.'-'I The grain characteristics of rice cultivars in Bangladesh have not been thoroughly investigated. Therefore, the present investigation was undertaken to study the morphological characters of rice grain (unhulled grain) and kernel (hulled grain) and their interrelationship.

METHODS AND MATERIALS
Eight cultivars of rice of two types i.e. modern uiz., BR7, BR29, Iratom24-, an.d BR3, and traditional uiz. Hapa, Kaliboro, Kachliboro and Madhabshail-boro, were used for morphological investigation of the grains which were grown in the Boro season (December to May) in Bangladesh. Thirty uilhulled grains were collected from the top of 3 panicles (10 from each) and used for measm.ement of' each cultiv&. The grains were hulled aftelwards and again used for measurement of different parameters. The values for 6 characters i.e. length (mm ), breadth (mm) and tliclu~ess (rnm) of grain, length (mm) and breadth (mm) of lcerr~el and embryo length (mm) were measured with a slide-caliper. The len.gt11 breadth ratio of grain was calculated from length of grain divided by breadth of grain.. The weight of 1000-grains from primary and secondary branches were measured by digital balance. Embryo-endosperm ratio was calculated as ratio of embryo and kernel length.

A.K.M. Golcun Sc~rrunr et al.
The collected data were analysed following ANOVA-technique and means were separated by Duncun's Multiple Range Test (DMRT) using MSTAT computer package. The correlation value among different parameters were calculated from the mean values using Casio fx-100s VPAM scientific calculator.

Length of grain
Data representing the length of the grains (Table 1) showed that BR7 and Kachliboro had significantly the longest (9.81 mm) and the shortest grain (7.49 mm) respectively whereas the others gave intermediate values.
The present results indicated that the modern cultivars possessed longer grain and higher yield potential which supported the previous results reported by Yoshida-"arwar%lso reported that modern cultivars (BR7, BR29, h-atom24and BR3) produced higher yield compared to traditional cul.tivars (I-Iapa, Kaliboro, Kachliboro and Madhabshail boro). This difference in length of grain might be due to the genetic make-up of the culti~ars.'~

Breadth of grain
Data representing breadth of the grain (Table 1) revealed significant variation anlong the cultivars. Madhabshail-boro had the highest breadth (3.55 mm) followed by BR3 (3.17 mm) and Iratom-24 (3.15 mm) while BR7 and ER29 hail lower grain breadth (2.38 mm and 2.58 mm, respectively). All the other cultivai-s had intermediate values.
Madhabshail-boro being the traditional cultivar possessed wider grain and lower yield potential which was in full agreement with the earlier results."' T11is difference in breadth of grain might be due to the genetic make-up of the cultivars. l0

l'l~icki~ess of grain
Data representing thickness of the grain (Table 1) showed that the cultivar Madhabshail-boro had the thickest grain (2.34 mm) followed by BR3 (2.07 mm) while BR7 had the thinnest one (1.82 mm). All other cultivars had intermediate values.
These results indicated that %he yield potential of rice cultivars might not be related to grain thickness. Breadth of grain was sti-ong1.y correlated with grain thickness (r=0.8938:k:!:

Length-Breadth (L/B) ratio of grain
The data representing the L/B ratio (Table 1)  BR7 and BR29 possessed LIB ratio of more than 3 which indicated that these were of slender grains and other cultivars were with long grains." Iratoin 24, Hapa and Madhabshail-boro although possessed relatively .long grains showed lower L/B ratio because of higher breadth. Grai.11 length and breadth had strong positive and negative correlatioi~ (r= 0.8698'F'1', -0.8c437:'::i:) respectively with LIB ratio of grain. This result supported the earlier obse-rvation.:' The grain thickness also had strong negative correlation (r= -0.8465'!"k) with LIB ratio of grain.

Length of kernel
Data representing kernel length (Table 2) revealed that BR7 and J3R3 had significantly higher kernel length (6.93 mm and 6.89 mm, respectively) compared. to the rest. Kachliboro and Madhabshail-boro possessed the lower length (5.20 rnin and 5.21 mm, respectively) and the others showed intermediate lc11@11.

Breadth of kernel
Data on kernel breadth (Table 1) showed that the cultivar Madhabshail-boro had the highest kernel breadth (3.09 mm) followed by BR3 (2.65 mm) and BR7 possessed the lowest breadth (2.12 mm). Other cultivars had the intermediate status.

Length-Breadth (L/B) ratio of kernel
Data representing LIB ratio of kernel ( According to USDA scale for milled rice BR7 and Madhabshail-boro were slender and bold type respectively and other cultivars were medium type.u Bari el al. ':' also reported that linear relationship existed between increased LIB ratio and better quality of grains.

Length of embryo
Embryo length (Table 1)  Though the modern cultivars possessed larger length of kernel than tl-lose of traditional cultivars, the embryo length did not show any special trend and the embryo length did not depend either on length, breadth and thickness of the grain or on length and breadth of the kernel (Table 2).

Embryo-Endosperm ratio
The data representing the embryo-endosperm ratio (Table 1) showed that Madhabshail-boro and Iratom-24 possessed the highest (0.383) and the Iowcst embryo-endosperm ratio (0.267) respectively. Other cultivars had the intermediate status.
The embryo-endosperm ratio varied from 0.383 to 0.267 which was in full agreement with that of Grist."

1000-grain weight
Data on 1000-grain weight presented in Table 1 revealed that there was no clear difference between traditional and modern type of rice but showed significant differences among the cultivars. Weight of 1000-grains obtained from primary branches of BR3 possessed the highest weight (28.60) followed by hatom-21 (27.77 g). Kachliboro possessed the lowest weight (22.50 g). It was also observed that the weight of 1000-grain from the primary branches was 11igl1er than those of secondary branches in all cultivars except Madhabshail-boro (Table 1). Similar result was obtained by Ahnl. Breadth of grain had a strong correlation (r=0.7727") with 1000-grain weight whde there were positive but not significant correlation wit11 pain length and thickness ( Table 2). Jun3 and LirP reported similar observations. Katayama4 also reported that 1000-grain weight was directly related to grain size and might be used as selection and classification characters.