To study the relations of certain morphological and sugar quality characters with sugarcane yield, an experiment was conducted at Wonji and Metehara Sugar Estates, Ethiopia between March 2012 and October 2013. The experiment, comprising of 400 sugarcane genotypes of which 174 were local that were collected from different regional states of Ethiopia and 226 introduced, was laid out in partial balanced lattice design with two replications. Data was collected on cane yield and its components, sugar yield and sugar quality traits. ANOVA, correlation and path coefficient analysis were done. Analysis of variance revealed significant differences (P < 0.01) for all the characters studied. Cane yield showed strong positive and highly significant (P < 0.01) correlation with millable cane number (r = 0.832) , single cane weight (r = 0.528) , stalk height (r = 0.517) and sugar yield (r = 0.987) . There was also positive significant (P = 0.05) correlation of tiller count and cane diameter with cane yield. Path analysis revealed the highest positive direct effect of millable cane number (0.812) on cane yield followed by single cane weight (0.682) and pol percent (0.550) . However, stalk diameter and brix percent had considerable negative direct effects and indirect positive effects through single cane weight on cane yield. Therefore, in view of their significant positive association with cane yield, indirect effects of stalk diameter and brix percent via single cane weight should be considered during selection. Genotypes should be selected on the basis of millable cane number, single cane weight and pol percent for getting higher cane and sugar yield.
Sugarcane is the main source of sugar production in Ethiopia and one of the most important agro industrial crops of the world. It also boosts national economy by providing direct and indirect employment to the people in Ethiopia. Sugar per unit area is determined by the cane yield per unit area and sucrose percent in juice. These two characters are influenced by their component traits. As the demand for white sugar is increasing continuously, the cane productivity and sugar recovery has to be increased accordingly. In sugarcane, complex traits like cane yield and quality are influenced by a number of characters. These characters directly and indirectly contribute to the yield [
Since the start the Ethiopian sugar industry has been totally dependent on importation of varieties. The varieties are of old generation and are contracted with many problems vis a vis deterioration of yield, lack of adaptability to different agro ecologies, susceptibility to disease and insect pests, etc. Currently Ethiopia is in the course of establishing sugarcane breeding program to develop varieties that suit to the different growing conditions of sugarcane growing regions. In any breeding program collection of germplasm is always the first step as it provides plant breeders with sources of useful traits. Especially collecting local germplasm would be crucial as they provide locally adapted genes for better crop improvement. Towards this effort, an exploration and collection work of local sugarcane germplasm in different geographic regions of Ethiopia has been conducted and more than 300 materials were collected [
The study of correlations provides the information that how strongly traits are genetically associated with one another. Thus the estimates of correlations among yield components pave the basis for selection of superior genotypes from the diverse breeding populations.
Path coefficient is an excellent means of studying direct and indirect effects of interrelated components of a complex trait [
Path analysis done by [
Cane yield and sucrose content are two important characters for obtaining high sugar yield [
[
Many component analyses have been performed for complex traits based on morphological and physiological characterizations [
Plant breeders generally select for only a few traits and it is very important to know the effects of this on other important characters as well. Therefore, this experiment was conducted to study the relations of certain morphological and sugar quality characters with sugarcane yield.
The study was carried out at two sugar estates in Ethiopia. Wonji Sugar Estate is located in the Rift Valley of Ethiopia at an altitude and longitude of 8˚31'N and 39˚12'E, respectively, with an elevation of 1550 masl. The area has a mean maximum and minimum temperature of 26.9˚ and 15.3˚C, respectively with mean annual rainfall 800 mm [
Combined ANOVA was done over locations using PROC GLM procedure of SAS software V9. Pearson correlation coefficients were estimated among the variables as suggested by [
The genotypes evaluated showed highly significant difference (P < 0.01) for all quantitative traits considered (see
Correlation coefficients between the different pair of agronomic characters and juice quality parameters were calculated to find the relationship among the various characters studied. The values of correlation coefficient are presented in
From
SPC2MAP | TC4MAP | STC10MAP | MSCHA | SCW | NOI | IL | SH | SD | LL | LW | LA | CYHA | Brix % | Pol % | Purity % | SR% | SY | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
SPC2MAP | 1.00 | |||||||||||||||||
TC4MAP | 0.36** | 1.00 | ||||||||||||||||
STC10MAP | 0.21** | 0.48** | 1.00 | |||||||||||||||
MSCHA | 0.17** | 0.42** | 0.74** | 1.00 | ||||||||||||||
SCW | 0.07** | 0.12** | 0.12** | 0.07** | 1.00 | |||||||||||||
NOI | −0.03 | 0.05* | 0.08** | 0.02 | 0.09** | 1.00 | ||||||||||||
IL | −0.01 | 0.004 | 0.08** | 0.14** | 0.14** | −0.49** | 1.00 | |||||||||||
SH | −0.04 | 0.10** | 0.29** | 0.37** | 0.47** | 0.23** | 0.33** | 1.00 | ||||||||||
SD | 0.07** | 0.08** | −0.02 | −0.01 | 0.56** | 0.07** | 0.04 | 0.19** | 1.00 | |||||||||
LL | −0.04 | −0.06* | −0.02 | −0.03 | 0.16** | −0.07** | 0.07** | 0.10** | 0.09** | 1.00 | ||||||||
LW | −0.02 | −0.06* | −0.10** | −0.11** | 0.31** | −0.01 | 0.07** | 0.08** | 0.33** | 0.24** | 1.00 | |||||||
LA | −0.02 | −0.07** | −0.08** | −0.08** | 0.31** | −0.03 | 0.08** | 0.11** | 0.29** | 0.65** | 0.88** | 1.00 | ||||||
CYHA | 0.16** | 0.40** | 0.66** | 0.83** | 0.53** | 0.05* | 0.17** | 0.52** | 0.26** | 0.06** | 0.06* | 0.09** | 1.00 | |||||
Brix% | 0.00 | 0.06* | 0.08** | 0.13** | 0.20** | 0.04 | 0.05* | 0.21** | 0.19** | −0.13** | −0.04 | −0.10** | 0.20** | 1.00 | ||||
Pol% | −0.01 | 0.04 | 0.08** | 0.12** | 0.20** | 0.07** | 0.05 | 0.22** | 0.18** | −0.13** | −0.04 | −0.10** | 0.20** | 0.96** | 1.00 | |||
Purity% | −0.03 | −0.02 | 0.03 | 0.03 | 0.09** | 0.12** | 0.02 | 0.14** | 0.09** | −0.05* | −0.01 | −0.03 | 0.08** | 0.27** | 0.54** | 1.00 | ||
SR% | −0.03 | 0.02 | 0.07** | 0.11** | 0.19** | 0.10** | 0.04 | 0.23** | 0.17** | −0.12** | −0.04 | −0.09** | 0.18** | 0.89** | 0.99** | 0.67** | 1.00 | |
SY | 0.15** | 0.39** | 0.64** | 0.81** | 0.53** | 0.07** | 0.17** | 0.52** | 0.27** | 0.05 | 0.05 | 0.07** | 0.99** | 0.30** | 0.31** | 0.16** | 0.31** | 1.00 |
SPC2MAP = Sprout count 2 months after planting; TC4MAP = Tiller counts 4 month after planting; STC10MAP = Stalk count 10 months after planting; MSCHA = Millable stalk count per hectare; SCW = Single cane weight (Kg); NOI = Number of internodes; IL = Internodes length (cm); SH = Stalk height (cm); SD = Stalk diameter (cm); LL = Leaf length (cm); LW = Leaf width (cm); LA = Leaf area(cm2); CYHA = Cane yield (qt/ha); Brix% = Brix percent; Pol% = Pol percent; Purity% = Purity percent; SR% = Sugar percent; SY = Sugar yield (qt/ha); *P = 0.05, **P < 0.01.
cant correlation with all agronomic and sugar quality traits except leaf length and width where the association was positive but non significant.
The correlation of cane yield with millable cane number and sugar yield was very strong r = 0.83** and r = 0.99** respectively. In fact the very strong correlation of cane yield with sugar yield is expected as sugar yield is the product of cane yield and sugar percent. A positive and highly significant correlation between cane yield and its components viz single cane weight, stalk length and millable cane number was reported by [
In the present study cane yield was more closely correlated with millable cane number followed by stalk count 10 months after planting, single cane weight and stalk height. This has important implications for selection of varieties to be used as parental material for crossing purposes. The above information indicates that many of the characters affect cane yield but the degree at which each character affects yield is dependent upon the degree of association of that character to cane yield. In this case selecting for the character millable cane number would produce maximum yield as compared with any of the other characters. [
A positive and significant correlation existed between millable cane number and stalk count 10 months after planting, followed by stalk diameter and single cane weight, stalk height and single cane weight, stalk count 10 months after planting and stalk height, stalk count 10 months after planting and single cane weight (
Knowledge of the association of various characters among themselves is important which ultimately gave the indication that selection for one trait will automatically change the other attributes. Therefore, to develop an understanding of association between the component characters is a necessary prerequisite to carry out an effective breeding program. The association between any two characters is dependent upon their inheritance. If they are inherited together, the relationship between them may be observed. The average between genes governing two or more characters, that is, location of genes on the same chromosome or chromosome governing particular character or pair is the cause for association between characters at phenotypic and genotypic levels.
Accordingly as can be observed from the present study the agronomic traits has positive significant association with cane yield, sugar yield, sugar quality parameters and with each other. Only leaf area and its component parts leaf length and width showed negative association with other yield components like sprout count 2 months after planting, tiller counts 4 months after planting, stalk count 10 months after planting, millable cane number, number of internodes, brix percent, pol percent, purity percent and sugar percent.
With regard to the biochemical characters in the present study, sugar percent was closely correlated (P < 0.01) with pol percent, purity percent and brix percent. The three sugar quality characters also had strong positive significant (P < 0.01) association with each other (
Path analysis helps us in identifying the most important characters affecting directly and indirectly through other characters. In the present study, the path coefficient analysis was performed for cane yield as a dependent variate (
Sprout counts 2 months after planting was found to have positive and considerably low direct effect on cane yield. The indirect effect of sprout count was positive through tiller number, stalk count 10 months after planting, millable cane number, single cane weight, number of internodes, stalk diameter, leaf area and brix percent.
Tiller number was observed to have negative and very low direct effect on cane yield. It had also negatively contributed to cane yield indirectly through brix percent (−0.139). The direct effect was counter balanced by the positive indirect effect through millable cane number (0.812), single cane weight (0.125) and pol percent (0.201). Stalk count 10 months after planting showed low positive direct effect on cane yield. However, its indirect effect via millable cane number was positive and high (0.762).
Millable cane number showed the highest direct effect (0.812) on cane yield. On the other hand, it had negative effect on cane yield through tiller number, number of internodes, internode length, stalk height, leaf width and brix percent. A direct effect of millable cane on cane yield was similar to the findings of [
Single cane weight had the next highest positive direct effect (0.682) on cane yield. It showed negative indirect effect on cane yield through tiller number, internodes length, stalk height, stalk diameter (−0.174), leaf area
SPC2MAP | TC4MAP | STC10MAP | MSCHA | SCW | NOI | IL | SH | SD | LL | LW | LA | Brix% | Pol% | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
SPC2MAP | 0.031 | 0.014 | 0.052 | 0.533 | 0.138 | 0.016 | −0.001 | −0.055 | 0.016 | −0.013 | −0.012 | 0.003 | 0.031 | −0.012 |
TC4MAP | −0.008 | −0.054 | 0.066 | 0.812 | 0.125 | 0.010 | −0.003 | −0.067 | 0.054 | 0.023 | −0.020 | 0.002 | −0.139 | 0.201 |
STC10MAP | 0.025 | −0.054 | 0.066 | 0.762 | 0.047 | −0.006 | −0.004 | −0.046 | 0.047 | 0.006 | −0.016 | 0.005 | −0.058 | 0.058 |
MSCHA | 0.021 | −0.054 | 0.062 | 0.812 | 0.022 | −0.012 | −0.005 | −0.052 | 0.052 | 0.006 | −0.016 | 0.004 | −0.076 | 0.071 |
SCW | 0.006 | −0.010 | 0.005 | 0.026 | 0.682 | 0.000 | −0.003 | −0.038 | −0.174 | 0.021 | 0.032 | −0.017 | −0.173 | 0.191 |
NOI | 0.012 | −0.013 | −0.009 | −0.229 | −0.006 | 0.042 | 0.006 | 0.020 | −0.036 | −0.009 | −0.007 | 0.005 | 0.065 | −0.047 |
IL | 0.004 | −0.023 | 0.031 | 0.507 | 0.221 | −0.031 | −0.008 | −0.065 | 0.006 | 0.015 | 0.013 | −0.008 | −0.094 | 0.075 |
SH | 0.021 | −0.046 | 0.038 | 0.529 | 0.323 | −0.010 | −0.006 | −0.080 | −0.022 | 0.010 | 0.002 | −0.003 | −0.112 | 0.119 |
SD | −0.002 | 0.014 | −0.015 | −0.205 | 0.577 | 0.007 | 0.000 | −0.009 | −0.206 | 0.017 | 0.043 | −0.020 | −0.128 | 0.162 |
LL | −0.007 | −0.022 | 0.007 | 0.089 | 0.251 | −0.007 | −0.002 | −0.014 | −0.063 | 0.056 | 0.014 | −0.017 | −0.050 | 0.036 |
LW | −0.006 | 0.019 | −0.018 | −0.227 | 0.372 | −0.005 | −0.002 | −0.003 | −0.151 | 0.013 | 0.058 | −0.025 | −0.034 | 0.043 |
LA | −0.004 | 0.003 | −0.011 | −0.125 | 0.404 | −0.007 | −0.002 | −0.009 | −0.148 | 0.034 | 0.052 | −0.028 | −0.042 | 0.043 |
Brix% | −0.002 | −0.016 | 0.008 | 0.128 | 0.245 | −0.006 | −0.002 | −0.019 | −0.054 | 0.006 | 0.004 | −0.002 | −0.484 | 0.546 |
Pol% | −0.001 | −0.020 | 0.007 | 0.105 | 0.237 | −0.004 | −0.001 | −0.017 | −0.061 | 0.004 | 0.005 | −0.002 | −0.481 | 0.550 |
Residual = 0.0303 *SPC2MAP = Sprout count 2 months after planting; TC4MAP = Tiller counts 4 month after planting; STC10MAP = Stalk count 10 months after planting; MSCHA = Millable stalk count per hectare; SCW = Single cane weight (Kg); NOI = Number of internodes; IL = Internodes length (cm); SH = Stalk height (cm); SD = Stalk diameter (cm); LL = Leaf length (cm); LW = Leaf width (cm) LA = Leaf area (cm2); Brix% = Brix percent; Pol% = Pol percent.
and brix percent (−0.173). Its indirect effect through pol percent was positive (0.191). Significant direct effect of single cane weight on cane yield was also reported by [
Number of internodes showed significantly low positive direct effect on cane yield. However, it contributed to cane yield negatively through millable cane number (−0.229).
Internode length showed negligible negative direct effect on cane yield. However, its indirect effect through millable cane number and single cane weight was positive (0.507, 0.221) respectively.
The direct effect of stalk height on cane yield was negative but low. It had positive indirect effect on cane yield through millable cane number, single cane weight and pol percent. [
Stalk diameter was found to have negative effect on cane yield directly and indirectly through millable cane number. This was counter balanced by single cane weight and pol percent. Similarly, [
Leaf length and width showed positive direct effect on cane yield whereas leaf area showed negative direct effect. The positive indirect effect of all the three traits through single cane weight was moderately higher. Leaf width and leaf area had negative effects through millable cane number and stalk diameter.
Brix percent showed negative direct effect on cane yield, whereas pol percent had a moderate direct positive effect on cane yield. This is in agreement with the findings of [
The traits which had highly significant positive association and negative direct effects on cane yield were viz., tiller count, internode length, stalk height and diameter, leaf area and brix percent. Negative direct effects of positively correlated characters with cane yield were also reported by [
Correlation and path analysis revealed that millable cane number and single cane weight followed by pol percent were the most important for cane yield improvement. The three characters had highly significant positive correlation with each other and with cane and sugar yield. Selection based on these characters can increase both cane and sugar yield. However, stalk diameter and brix percent had considerable negative direct effects on cane yield and indirect positives effect through single cane weight. Therefore, in view of their significant positive association with cane yield, during selection indirect effects of stalk diameter and brix percent via single cane weight should be considered.
The authors are grateful to the financial grant of the Sugar Corporation of Ethiopia. Many thanks are forwarded to Ethiopian Biodiversity Institute (EBI) for its technical advice during collection of the local sugarcane genotypes. Warmly gratitude goes for Dr. Hussien Mohamad at Hawassa University for his overall help and his interest and appreciation of the study. The staff and laboratory technicians at Wonji and Metehara, Sugar Corporation, Research and Training are duly acknowledged for their supports.
Esayas Tena,Firew Mekbib,Amsalu Ayana, (2016) Correlation and Path Coefficient Analyses in Sugarcane Genotypes of Ethiopia. American Journal of Plant Sciences,07,1490-1497. doi: 10.4236/ajps.2016.710141