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Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia



D. Ruswandi, J. Supriatna, N. Rostini and E. Suryadi
 
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ABSTRACT

Objective: Sweetcorn/chilli pepper intercropping is commonly applied to increase yield and profit by farmers in West Java, Indonesia. Methodology: An experiment was set up in Kutamandiri-Sumedang, West Java from January up to April, 2015 to select new sweetcorn hybrid and their parental lines for intercropping with chilli pepper. To evaluate the genetic materials, they were arranged by split plot design. This was replicated twice with the main plot consisting of four cropping systems, whereas, the subplots were 38 sweetcorn genotypes. Results: The result showed that parental line of MSR 17.2.3 is the best combiner for plant height, while SR 17 is the best combiner for maturity and ear weight per plant. The best combinations for high yield in both sole cropping and intercropping are MSR 12.6.7xSR 4 and MSR 25.5.1xSR 17. However, MSR 17.6.7xSR 17 were the best hybrid for intercropping based on land equivalent ratio, competitive ratio and stress tolerance index analysis. Conclusion: It is also identified that MSR 17.6.7xSR 17 was suitable for sweetcorn/chilli pepper intercropping for the following aspects including higher yield than sweetboy check variety both in sole and intercropping system, moderately level of competition ratio against chilli pepper, low tolerance index to chilli pepper and higher productivity in 2:1 sweetcorn/chilli pepper intercropping system.

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  How to cite this article:

D. Ruswandi, J. Supriatna, N. Rostini and E. Suryadi, 2016. Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia. Journal of Agronomy, 15: 94-103.

DOI: 10.3923/ja.2016.94.103

URL: https://scialert.net/abstract/?doi=ja.2016.94.103
 
Received: March 03, 2016; Accepted: May 12, 2016; Published: June 15, 2016



INTRODUCTION

Sweetcorn and chilli pepper are two important horticulture products, which could be cultivated either in sole cropping system or in intercropping system1,2. Sweetcorn is an alternative food instead of rice, baby’s food, agro industrial product for ethanol and high fructose corn syrup, whereas chilli pepper is among the most importance spice having high economic values and among the importance spicy in Indonesia.

Management of two commodities in particular intercropping system is the right strategy that can be developed in Indonesia to increase production of the two commodities involved. The characteristic of farming system in Java island the most populated island in Indonesia, shows a dependence on lands that are small in area with poor land management and does not yield optimal results. The purpose of this planting system is to decrease the risk of harvest failure due to biotic stress. Thus, in case one crop fails to harvest good yield, the other crop can still be harvested and hopefully the loss will be less than when only one crop is planted. Midmore et al.3 reported that sweetcorn/chilli pepper intercropping reduced viral infection in pepper plants. Further he mentioned the advent of sweetcorn/chilli pepper cropping system including: (i) The cropping system improved the efficiency of cropping due to the ability to catch more sunlight than by growing alone as indicated by Land Equivalent Ratio (LERs) of sweetcorn/chilli pepper greater than unity and (ii) The pepper can be benefitted if intercropped with taller plants because of wind break effects. The taller plants help reduce evapotranspiration, aphid infestation and virus spread.

Among the factors that need to be considered when determining the intercropping strategy is the kind of crop and the cultivar that will be planted4. The kinds of cultivars that will be planted depend upon their characteristics. The cultivars should not compete with each other so that the harvest will be maximal for each cultivar. Most of the cultivars of sweetcorn available in the market are usually grown as a single crop. In a study by O’Leary and Smith5, they found out that when corn/clover or corn/bean intercrops are desired, corn monoculture is not desired. Also, selection in intercrops determines the genotype adapted to the other.

Plant breeding programs are very important in developing cultivars of sweetcorn that suitable into an intercropping system. According to Koutsika-Sotiriou and Karagounis6, the choice of the genetic resources are priority in the development of cultivars specially in obtaining cultivars that have high yields according to the specific conditions. So far, it had developed corn-inbred lines by hybridization and mutation7. These inbred lines divers for morphological and yield components in a sole cropping system8. However, the information on combining ability of these inbred lines and the performance of their hybrids in sweetcorn/chilli pepper intercropping system were not yet explored.

MATERIALS AND METHODS

Genetic material and evaluation site: Genetic material to be evaluated in the study were 38 genotypes included 8 SR unpad inbred lines of sweetcorn, 28 F1 developed through diallel mating design by Griffing II and two commercial sweetcorn hybrids (Sweetboy and Jamboree). In addition unpad chilli pepper was used for sweetcorn/chilli pepper cropping system. Evaluation was performed from January up to April, 2015 in Kutamandiri, West Java, Indonesia at 784 m a.s.l. (above sea level), which represents climate type of C3 classified by Oldeman.

Statistical analysis: A split plot design was done with 2 replications to evaluate inbred lines. The intercropping systems, which consisting the main plot were sweetcorn sole cropping system, sweetcorn/chilli pepper, sweetcorn/chilli pepper/sweetcorn and chilli pepper/sweetcorn/chilli pepper; whereas, the subplots were 38 sweetcorn genotypes. The traits to be observed are plant height, maturity and ear weight per plant.

Data analysis covered estimation of combining ability and evaluation of sweetcorn hybrid in intercropping system with chilli pepper and otherwise. The ANOVA was done for the average data for split plot design. Diallel crosses were analysed based on Griffing II method9, which estimates General Combining Ability (GCA) of sweetcorn inbred. Specific Combining Ability (SCA) was estimated to determine superior hybrids. The significance of hybrids, GCA and SCA mean squares were estimated using F test. The GGE biplot is also used for diallel cross analysis. This was done by utilizing GGE biplot software10.

Evaluation of adaptive sweetcorn hybrid performance in intercropping with chilli pepper was estimated using least significant increase following by Petersen11. Thus, productivity of hybrid in intercropping with chilli pepper was determined based on Land Equivalent Ratio (LER) according to Willey12 and competitive ratio of sweetcorn hybrid following by Dhima et al.13. On contrary to the evaluation of sweetcorn hybrid performance, evaluation of tolerant chilli pepper to sweetcorn under sweetcorn/chilli pepper cropping system was estimated based on Stress Tolerance Index (STI)14.

RESULTS AND DISCUSSION

General and specific combining ability of sweetcorn: Table 1 shows the ANOVA testing for significance of the studied traits. The source of variation for the genotypes was divided into two: General Combining Ability (GCA) and Specific Combining Ability (SCA). Significant differences for GCA and SCA were seen in all the studied traits. This shows the importance of additive and dominance genetic variance15.

Combining ability analysis helps assess potential inbred lines. They also help identify the kind of gene action taking place in various quantitative characters, as agronomy, yield component and yield16-18. Abdel-Moneam et al.19 mentioned that the effects of combining ability are important indicators in determining potential inbred lines as parental of superior hybrid in maize. This implies that in determining high yield hybrids, the parents genetic structure and their combing ability play important roles. Differences in GCA effects reflected additive and epistatic genetic effects in the observed population, whereas variation in SCA effects associated to non-additive genetic variance including dominance and epistatic genetic effects16. Sprague and Tatum15 proposed that GCA was relatively more important than SCA for unselected inbred lines. On the other hand, SCA played a more important role for selected lines. The values for combining ability effects showed that none of the parental line showed desirable GCA effects for all the traits studied (Table 2 and Fig. 1 and 2). Hussain et al.20 and Ruswandi et al.17 also observed similar results to this finding. In the present study, line b (SR 17) had the highest positive and highly significant GCA effect for grain yield. This parental line also had high mean value. This shows that the performance of the line can be useful as index for combining ability. The SR 17 and MSR 25.5.1 parental lines exhibited highest negative and significant GCA for maturity, therefore these lines are good combiners for early maturing. In addition, MSR 17.2.3 showed highest negative and significant GCA for plant height, which indicates that it is a good general combiner for this trait. In crossing programs for maximum genetic variability, it is reconsidered to use lines with desirable GCA as for synthetic cultivar development21.

The SCA for plant height, maturity and ear weight per plant was estimated based on Griffing II and GGE biplot and they are presented in Table 3 and 4 and Fig. 1 and 2. Based on SCA estimate using Griffing II and GGE biplot (Table 3 and 4 and Fig. 1 and 2), hybrid SR 43xSR 17 showed greatest SCA for plant height, maturity and ear weight per plant. This indicated that hybrid would perform short plant, early maturity and high ear weight per plant comparing to their parents. MSR 25.5.1xSR 17 hybrid also possessed high SCA for maturity and ear weight per plant. In addition, MSR 25.2.6xMSR 17.2.3 had great SCA for ear weight per plant. Some researchers also reported high positive SCA together with a high yield performance and their component17-22. These hybrids showing high performance for yield and early maturity would be potentially useful in sweetcorn breeding programs to obtain high-yielding hybrids for intercropping in the same climate of West Java, Indonesia.

Evaluation of sweetcorn hybrid performance in sweetcorn/chilli pepper intercropping: Table 5 showed means of ear weight per plant from 30 sweetcorn hybrids planted in different cropping system.


Table 1: Analysis of variance (ANOVA) of genotype and combining ability
Image for - Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia
*Significant based on F-test at 5%

Table 2: General Combining Ability (GCA) estimates and means of observed traits
Image for - Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia
*Significant based on F-test at 5%

Image for - Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia
Fig. 1(a-c):
Average Tester Coordination (ATC) view of the biplot based on diallel. The arrow represents the average tester. Parental lines as entry is presented as small letter, whereas parental lines as tester is showed as capital letters. A/a: SR 4, B/b: SR 17, C/c: SR 24, D/d: SR 43, E/e: MSR 17.2.3, F/f: MSR 17.6.7, G/g: MSR 25.6.7, H/h: MSR 25.5.1., (a) Plant height, (b) Maturity and (c) ear weight per plant

Image for - Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia
Fig. 2(a-c):
Scatter plot view of the biplot based on diallel. The arrow represents the average tester. Parental lines as entry is presented as small letter, whereas parental lines as tester is showed as capital letters. A/a: SR 4, B/b: SR 17, C/c: SR 24, D/d: SR 43, E/e: MSR 17.2.3, F/f: MSR 17.6.7, G/g: MSR: 25.6.7, H/h: MSR 25.5.1., (a) Plant height, (b) Maturity and (c) Ear weight per plant

Table 3: Selected crosses based on GGE biplot and Griffing II
Image for - Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia

Table 4: SCA and mean of days to harvest and ear weight per plant
Image for - Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia
*Significant based on F-test at 5%, **Significant based on F-test at 1%

The results from this study showed that sole cropping yielded higher than all the sweetcorn/chilli pepper intercrop. However, there were 7 sweetcorn hybrids possessing higher ear weight per plant than commercial hybrid sweetboy. Those hybrids were SR 43xSR 4, MSR 17.2.3xSR 4, SR 43xSR 17, MSR17.6.7xSR17, MSR 25.5.1xSR 17, MSR 25.2.6xSR 24 and MSR 25.5.1xMSR 17.6.7.

Land Equivalent Ratio (LER) for sweetcorn hybrids was shown in Table 6. The highest LER were in sweetcorn/chilli pepper 2:1 intercropping. There were 4 hybrids possessed LER more than 1 in intercropping sweetcorn/chilli pepper 2:1 (P 2:1) including MSR 17.6.7xSR 4 (LER 1.01), MSR 17.6.7xSR 17 (LER 1.01), SR 43xSR 24 (LER 1.04) and MSR 17.6.7xSR 43 (LER 1.02). Similar result also reported by Muraya et al.23 explaining that maize/bean intercropping had high economic advantage. He studied that everton synthetic maize showing higher LER than check varieties KTS and H 614.

Table 5: Means of ear weight per plant of 30 sweetcorn hybrids
Image for - Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia
P1: Sweetcorn sole planting, P1:1: Intercropping sweetcorn/chilli pepper 1:1, P2:1: Intercropping sweetcorn/chilli pepper 2:1, P1:2: Intercropping sweetcorn/chilli pepper 1:2, S: Hybrid better than commercial check hybrid sweetboy based on LSI at 5%, J: Hybrid better than commercial check hybrid Jamboree based on LSI at 5%

He explained the characteristic maize for intercropping including modification of canopy geometry and photosynthetic apparatus aside of yield and its components.

Sweetcorn hybrid adapted for intercropping with chilli pepper should be selected based on its land productivity as shown by its LER. Li et al.24 explained that the LER more than one indicating the high economic advantage of particular intercropping. This intercropping index indicates that intercropping is more advantageous than sole cropping in terms of the efficiency of using environmental resources for growth or by increased plant density25,26. Furthermore, Willey and Reddy27 explained that yield advantages in intercropping occurs due to differences in their use of resources and its stability greater than in sole cropping system. Evans and Wardlaw28 reported that shading and reduced assimilate production have least effect on yield in intercropping, while competition prevails during vegetative periods.

Table 6: Land Equivalent Ratio (LER) of 30 sweetcorn hybrids in intercropping sweetcorn/chilli pepper
Image for - Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia
P1: Sweetcorn sole planting, P1: 1: Intercropping sweetcorn/chilli pepper 1:1, P2:1: Intercropping sweetcorn/chilli pepper 2:1, P1:2: Intercropping sweetcorn/chilli pepper 1:2

Some researchers also showed similar LER value exceeding one when they applied maize intercropping. Some maize based intercropping includes maize/bush bean29, maize/cowpea30, maize/dwarf bean31, cereal/legume intercropping32, legume/cereal intercropping33 and maize/soybean intercropping34,35.

Competitive ratio of sweetcorn hybrids cultivated in sweetcorn/chilli pepper intercropping system: The competition between sweetcorn and chilli pepper in intercropping was predicted by Competitive Ratio (CR) index and is presented in Table 7. The result showed that CR sweetcorn/chilli pepper (CRj) was higher than CR chilli pepper/sweetcorn (CRc) in all-intercropping system. This indicated that sweetcorn hybrids have higher competitiveness than chilli pepper and this is the reason why sweetcorn hybrid is stable under different intercropping pattern with chilli pepper. The CR sweetcorn/chilli pepper was greater than 1.00 but CR chilli pepper/sweetcorn was less than 1.00 suggesting that chilli pepper is a mild competitor and it is suitable crop in all sweetcorn base intercropping.

Table 7: Competitive Ratio (CR) of 30 sweetcorn hybrids in intercropping sweetcorn/chilli pepper
Image for - Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia
P1: Sweetcorn sole planting, P1: 1: Intercropping sweetcorn/chilli pepper 1:1, P2: 1: Intercropping sweetcorn/chilli pepper 2:1, P1: 2: Intercropping sweetcorn/chilli pepper 1:2. CRj: Competitive ratio sweetcorn/chilli pepper, CRc: Competitive ratio chilli pepper/sweetcorn, Yellow show selected hybrid based on CR

Ghosh et al.36 justified that there is a positive advantage when competitive ratio was less than one and the crop can be grown in intercropping, but there was negative benefit when greater than one. Willey and Rao37 showed that CR index measures competitive ability of the crops. It is also an advantageous index over relative crowding coefficient and aggressivity.

An exceptional occur in intercropping sweetcorn/chilli pepper 2:1 pattern, in which 3 hybrids showing CRj lower than CRc. The hybrids were MSR 17.6.7xSR 4, MSR 17.6.7xSR 17 and MSR 17.6.7xSR 43. An increase of chilli pepper yield higher compare to sweetcorn hybrids yield in this pattern was the important factor to explain why CRc is higher than CRj. This result suggesting that these hybrids could be developed as suitable hybrid in sweetcorn/chilli pepper intercropping system.

Tolerance of chilli pepper against sweetcorn hybrids cultivating in intercropping: The tolerance of chilli pepper in sweetcorn/chilli pepper intercropping was predicted by Stress Tolerance Index (STI). The STI used to identify high-yielding genotypes in both stress and non-stress conditions14. He categorized particular crop to be tolerance if STI value is high in which the mean performance of particular crop under stress condition would perform high or similar to one in optimal condition. In this research, STI of chilli pepper was estimated based on its fresh fruit weight, since its growth is under stress in intercropping with sweetcorn as indicated by its low CRc value.

The STI value of chilli pepper in intercropping with 38 sweetcorn hybrids under different pattern of sweetcorn is presented in Table 8. There is some hybrids show high STI including 13 hybrids and 4 hybrids for sweetcorn/chilli pepper 1:1 and 1:2 intercropping pattern and for sweetcorn/chilli pepper 2:1 intercropping pattern, respectively. Those hybrids were selected since it gives less stress to chilli pepper to yield higher than other non- selected hybrids.

Over all, stress due to cropping system reduced significantly the yield of chilli pepper and difference of STI suggests the genetic variability in sweetcorn hybrids for cultivating in intercropping with chilli pepper.

Table 8: Stress Tolerance Index (STI) of 30 sweetcorn hybrids in intercropping sweetcorn/chilli pepper
Image for - Assessment of Sweetcorn Hybrids Under Sweetcorn/Chilli Pepper Intercropping in West Java, Indonesia
P1: Sweetcorn sole planting, P1: 1: Intercropping sweetcorn/chilli pepper 1:1, P2: 1: Intercropping sweetcorn/chilli pepper 2:1, P1: 2: Intercropping sweetcorn- chilli pepper 1:2, STI: Stress tolerance index, Yellow show selected hybrid based on STI

With a careful selection of parents used in hybridization and with application of an appropriate selection method in segregating populations, it could be possible to obtain intercropping tolerance lines.

CONCLUSION

Parental line of MSR 17.2.3 is the best combiner for plant height, while SR 17 is the best combiner for maturity and ear weight per plant. The best combinations for high yield in both sole cropping and intercropping are MSR 12.6.7xSR 4 and MSR 25.5.1xSR 17. The MSR 17.6.7xSR 17 was the best hybrid for intercropping based on land equivalent ratio, competitive ratio and stress tolerance index analysis. Thus, MSR 17.6.7xSR 17 was suitable for sweetcorn/chilli pepper intercropping for the following aspects including high yield both in sole and intercropping system, moderately level of competition ratio against chilli pepper, low tolerance index to chilli pepper and higher productivity in 2:1 sweetcorn/chilli pepper intercropping system.

ACKNOWLEDGMENT

The authors would like to put into words their appreciation to the Directorate General Higher Education, Ministry of Culture and Education, Republic Indonesia and Universitas Padjadjaran for the study April 25, 2016 funding through Competency Grant (Hibah Kompetensi) 2015 No. 1348/UN.6.R.1/KP/2014 and to University of Padjadjaran for Travel Grant 2015 No. 1565/UN6/R/KP/2014 to the 1st author.

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