Comprehensive Evaluation of New Maize Varieties for Grain and Fodder Based on Membership Function Method

Chenglin ZOU, Qiongxiang LIN, Kaijian HUANG, Ruining ZHAI, Meng YANG, Aihua HUANG, Runxiu MO, Xinxing WEI, Yanfen HUANG

Abstract To screen new maize （Zea mays L.） varieties suitable for food and fodder dual-purpose in Duan Yao Autonomous County of Guangxi， the agronomic characters， yield and quality indexes of 12 new maize varieties were measured， and the correlation between various indexes were analyzed， and the comprehensive performance of tested varieties was evaluated by membership function method. The results showed that Guidan 671 had the highest grain yield and whole-plant biomass at 10 908 and 49 965 kg/hm2， respectively， and the second was Zhaoyu 215 with a grain yield and whole-plant biomass of 10 086 and 47 175 kg/hm2， respectively. Grain yield was highly significantly positively correlated with ear diameter and 100-grain weight （P<0.01）， and significantly correlated with whole-plant biomass， starch content， ear length and grain number per row （P<0.05）; and the whole-plant biomass was highly significantly correlated with the number of grains per row （P<0.01）， and significantly correlated with starch content， panicle length， plant height and panicle height （P<0.05）. The comprehensive performance scores of the tested varieties from high to low were Guidan 671， Zhaoyu 215， Guidan 669， Guidan 6208， Guidan 666， Guidan 6205， Guidan 660， Guidan 6203， Guidan 6206， Guidan 162， Guidan 668 and Guidan 673. According to the values of membership function and combined with various indexes， Guidan 671 and Zhaoyu 215 had good comprehensive performance， and could be used as the first choice for food and fodder dual-purpose maize varieties in Duan Yao Autonomous County.

Key words Maize; Food and feed dual-purpose; Membership function method; Comprehensive evaluation

Received： December 30， 2022  Accepted： February 28， 2023

Supported by Guangxi Key Research and Development Plan （GK AB21196052）; Guangxi Science and Technology Planning Project （GK AD20297117）; Guangxi Science and Technology Major Project （GK AA17204064-4）; Special Project of Basic Scientific Research Business of Guangxi Academy of Agricultural Sciences （GNK 2021YT015; GNK 2020YM90）.

Chenglin ZOU （1982-）， male， P. R. China， associate researcher， master， devoted to research about genetic breeding and cultivation techniques of maize.

*Corresponding author. Ruining ZHAI（1989-）， male， P. R. China， assistant research fellow， master， devoted to research about genetic breeding of maize. E-mail： 280223000@qq.com.

Maize （Zea mays L.） for both food and fodder purposes means that it can be planted as ordinary maize for harvesting grains in the maturation stage， as cereals or fodder， or as silage maize for harvesting the whole plant in the milk ripe to waxy ripe stage to make silage［1］. In recent years， with the deepening of the countrys supply side structural reform in the agricultural field， especially the continuous implementation of the "grain for forage" and "livestock husbandry" projects， the role of maize with a dual purpose of grain and fodder has become increasingly important， and the development prospects are very broad. The dual-purpose maize for both grain and fodder not only effectively ensures national food security， but also meets the countrys demand for large-scale and standardized cattle and sheep farms. It plays a very important role in effectively promoting the rapid development of Chinas animal husbandry［2-4］.

Scholars have conducted extensive research on how to evaluate the superiority of dual-purpose maize for both grain and fodder. Li et al.［5］ believed that for maize for both grain and fodder purposes in Xinjiang， varieties with more leaves and larger plant heights should be selected for the purpose of biomass utilization， and varieties with thicker stems and better comprehensive ear traits should be selected for the purpose of harvesting seeds. Liu et al.［6］ believed that selecting maize varieties with multiple and heavy green leaves， thick and heavy stems， excellent ear yield， and relatively larger plant height was beneficial for achieving high yield. Meanwhile， they screened out maize varieties Jingke Qingzhu 932 and Weike 106 that were suitable for promoting and planting in Henan Province. Chen et al.［7］ conducted a study on the yields， agronomic traits， nutrient absorption， and economic benefits of six maize varieties for both grain and fodder purposes， and recommended Shengnong 3 as the main recommended variety for both grain and fodder purposes in mountainous regions in Qianxi County， Guizhou Province. Jiao et al.［8］ compared the agronomic traits and production capacities of 20 maize varieties （lines） for both food and feed purposes， and selected varieties Taipingyang 98 and Chuanqing 8 that are suitable for promotion and cultivation in the southwest region. Huang et al.［9］ conducted a comparative experiment on nine introduced ordinary maize varieties and selected suitable grain and fodder dual-purpose maize varieties Zhengda 808 and Zuankababa for cultivation in Yulin City， Guangxi.

Above studies provide a reference basis for selecting suitable grain and fodder dual-purpose maize varieties for local cultivation， and the selected excellent varieties greatly promote the rapid development of the local breeding industry. At present， there is a lack of grain and fodder dual-purpose maize varieties suitable for local cultivation in various parts of Guangxi， and the blind choice of the masses has led to a decrease in maize yield and quality［10-11］， severely limiting the coordinated development of maize and aquaculture industries in Guangxi. As a leading demonstration county for the "grain for forage" project in Guangxi， Duan Yao Autonomous County has Received strong support from the government for the implementation of the "loaning cattle and paying back cattle" and "loaning sheep and paying back sheep" industrial poverty alleviation models， which have led to rapid development of the breeding industry， and there is an urgent need for high-quality maize varieties for both grain and fodder purposes to adapt to it［12］. In this study， in order to solve the problem of the lack of excellent maize varieties for both grain and fodder purposes in Duan Yao Autonomous County， with 12 ordinary maize varieties with silage potential approved in Guangxi in recent years as experimental materials， a comparative experiment was conducted on maize varieties for both grain and fodder purposes in the county to measure agronomic traits， grain yield， whole-plant biomass， and quality traits of the maize varieties， and the comprehensive performance of various tested varieties was evaluated using the membership function method， hoping to screen out suitable grain and fodder dual-purpose maize varieties suitable for cultivation in Duan Yao Autonomous County.

Materials and Methods

Experimental materials

A total of 12 varieties were tested， including Guidan 6203， Zhaoyu 215， Guidan 6206， Guidan 666， Guidan 671， Guidan 660， Guidan 669， Guidan 673， Guidan 6205， Guidan 6208， Guidan 668， and Guidan 162， all of which were selected and provided by Maize Research Insititute， Guangxi Academy of Agricultural Sciences.

Experimental design

The experiment was conducted from February 28 to July 13， 2021 in Guliang Village， Baoan Township， Duan Yao Autonomous County， Hechi City， Guangxi， at 107°51′47″ E and 24°06′02″ N. A randomized block design was adopted. Each plot had six rows and an area of 4.2 m×10.0 m. The plants were planted according to a row spacing of 70 cm and a plant spacing of 50 cm in a manner of single row and double plants with a density of 3 811 plants/hm2. Each variety was set with three replicates. Direct seeding was carried out on February 28， with 3-4 seeds per hole. On March 18， thinning was conducted at the three-leaf stage， with two plants left in each hole. On June 20， when the milk line of seeds reached 1/3-1/2 during the milk ripe to waxy ripe stage， agronomic traits， whole-plant biomass and quality traits were measured. On July 13， ears were harvested during the maturation stage， and the grain yield was measured. Field management was carried out according to local level， and attention was paid to flood and drought prevention， as well as pest control.

Measurement items and methods

Agronomic traits and yield

During the milk ripe to waxy ripe stage， two rows in the middle of each plot were harvested by cutting off plants approximately 5 cm from the roots to the top， and the fresh weight of the entire plant was weighed and converted into whole-plant biomass per hectare. Ten representative plants were selected simultaneously for measuring plant height and ear height， and the average value was calculated. During the maturation stage， fruit ears in the remaining two middle rows of each plot were harvested， threshed and dried in the sun， and weighed， and the weight was converted into grain weight based on a moisture content of 14%， and then into grain yield per hectare. Meanwhile， 10 representative fruit ears were selected for measurement of ear length， ear diameter， number of rows， number of grains per row， and 100-grain weight， and the average values were calculated.

Nutritional quality

During the milk ripe to waxy ripe stage， a plot was selected from each variety， and three maize plants were randomly selected and harvested. The whole plants were dried and crushed， and determined for the contents of starch and crude protein， of which the crude protein content was determined by Kjeldahl method， and the starch content was measured by colorimetric method using a starch content reagent kit purchased from Sangon Biotech （Shanghai） Co.， Ltd.

Membership function values

The membership function values were calculated using the methods of Zhai et al.［13］ and Zhang et al.［14］. First， the specific membership function values （Xu） of various indexes were calculated in different varieties. According to research， the selected index in this experiment were positively correlated with the comprehensive performance of maize varieties［15-18］， so the following formula was used for calculation：

Xu=（X-Xmin）/（Xmax-Xmin）（1）

In the equation， X is the measured value of a certain index for each variety， while Xmax and Xmin are the maximum and minimum values of the index for all varieties， respectively. Next， based on the proportion of the coefficient of variation （CV） of each index in the sum of coefficients of variation of all indexes， the weight of each index was determined， and the comprehensive membership function value of each inbred line was calculated. The comprehensive performance of each tested variety was scored through the comprehensive membership function value.

Data statistics and analysis

Excel 2007 software was used to collate data， and various indexes and membership function values calculated. Analysis of variance and correlation were performed using DPS 16.05 software.

Results and Analysis

Agronomic traits of maize varieties tested

From Table 1， it can be seen that in terms of ear traits， Guidan 671 had the largest ear length and the highest number of grains per row， the second thickest ears， and a relatively suitable number of ear rows. That is to say， various ear traits performed well， and it had an ideal ear type. Guidan 673 had the smallest ear length， the least number of grains per row， and thinner fruit ears. The overall performance of its ear traits was poorer. Other varieties exhibited varying performance in various ear traits and indexes， such as Guidan 6206 and Guidan 669， of which Guidan 6206  ranked first in ear thickness， but lower in ear length and grain number per row， and Guidan 669 ranked second in ear length， but did not perform particularly well in ear diameter and grain number per row. In terms of plant height and ear height， the top three varieties were， respectively， Guidan 6203， Guidan 666 and Guidan 6208， of which Guidan 6203 was significantly higher in plant height than other varieties except for no significant difference from Guidan 666， and significantly higher ear height than all other varieties. The 100-seed weights of various varieties ranged from 34.20 to 40.09 g， with Guidan 671， Guidan 6203 and Guidan 6206 ranking in the top three， significantly higher than other varieties.

Yield and quality of maize varieties tested

According to Table 2， there were significant differences in yield among the 12 tested varieties.  The grain yield ranged from 7 958 to 10 908 kg/hm2， with Guidan 671 being the highest and significantly higher than other 11 varieties， and Zhaoyu 215 ranking second， significantly higher than other 10 varieties except Guidan 671. The lower ones were Guidan 668， Guidan 162， Guidan 673， and Guidan 660， without significant differences therebetween and significantly lower than other 8 varieties. The variation range of whole-plant biomass was from 37 065 to 49 965 kg/hm2， with Guidan 671 being the highest and having no significant differences from Zhaoyu 215 and Guidan 162， but significant increases compared with other 9 varieties. The second-ranked variety was Zhaoyu 215， which was significantly higher than Guidan 6205， Guidan 6206， Guidan 668， and Guidan 673， but had no significant differences from other seven varieties. Guidan 673 showed the lowest value， which was not significantly different from that of Guidan 668， but significantly lower than those of other 10 varieties. There were little differences in quality among the tested varieties， with starch contents ranging from 32.0% to 36.6%， all exceeding 30%. The highest value was found in Guidan 6208， followed by Zhaoyu 215 and Guidan 671. The crude protein contents varied from 7.2% to 9.8%， with the highest value in Guidan 671 and Guidan 6203， both of which were 9.8%， and Guidan 6206 showed the lowest content.

Correlation between various indexes of tested maize varieties

A bivariate Pearson analysis was conducted on yield， quality， and agronomic traits， and the results are shown in Table 3. The grain yield had an extremely significant positive correlation with ear diameter and 100-grain weight， and a significant positive correlation with whole-plant biomass， starch content， ear length， and number of grains per row， but no significant correlation with crude protein content， row number， plant height， and ear height. The whole-plant biomass was in an extremely significant positive correlation with the number of grains per row， and a significant positive correlation with starch content， ear length， plant height， and ear height， but had no significant correlation with crude protein content， ear diameter， number of rows， and 100-grain weight. The trait indexes that were in an extremely significant or a significant correlation with both grain yield and whole-plant biomass were starch content， ear length， and grain number per row， indicating that starch content， ear length， and grain number per row could simultaneously affect grain yield and whole-plant biomass of maize. Moreover， there was an extremely significant positive correlation between plant height and ear height， as well as between ear diameter and 100-grain weight.

Evaluation of maize varieties tested using membership function method

Five indexes including grain yield， whole-plant biomass and starch content， ear length and number of grains per row that were significantly or extremely significantly correlated with the former two indexes were selected. These five indexes were converted into relative values by the membership function method， and the weight of each index was then determined through the coefficient of variation. The relative values of various indexes were multiplied by corresponding weight， and a final membership function value was obtained by adding them， and used to comprehensively evaluate each tested variety. According to Table 4， the comprehensive performance scores of the tested varieties， from high to low， were Guidan 671， Zhaoyu 215， Guidan 669， Guidan 6208， Guidan 666， Guidan 6205， Guidan 660， Guidan 6203， Guidan 6206， Guidan 162， Guidan 668， and Guidan 673. Among them， Guidan 671 had the highest comprehensive score， with a membership function value of 0.986， which was much higher than other varieties， indicating that Guidan 671s comprehensive performance was very outstanding.

Discussion

The comprehensive performance of maize varieties needs to be evaluated through multiple indexes such as yield， quality， and related agronomic traits［15］. The varieties of maize for both grain and fodder purposes should meet both grain and fodder requirements， so the selection of evaluation indexes should take into account the functions of ordinary maize and silage maize. This study focused on two main indexes： grain yield and whole-plant biomass， while simultaneously measuring two quality traits： starch and crude protein contents. Combining agronomic traits such as ear length， ear diameter， ear rows， number of grains per row， plant height， ear height， and 100-grain weight， we jointly evaluated the comprehensive performance of tested maize varieties as a maize variety for both grain and fodder purposes. The results of this study showed that the agronomic traits closely related to grain yield were ear diameter， ear length， 100-grain weight， and number of grains per row， and the agronomic traits closely related to whole-plant biomass were number of grains per row， ear height， ear length， and plant height， which are basically consistent with relevant studies［5，16-18］. Relevant results also provide reference for the selection of different types of maize varieties. If ordinary maize is the main type， the focus should be on examining varieties with larger and longer ears， heavier grains， and more grains per row. If silage maize is the main type， varieties with more grains per row， longer ears， higher ear positions， and higher plants should be selected. In terms of quality， the starch content was in the range of 32.0%-36.6%， and the crude protein content was in the range of 7.2%-9.8%. All varieties were higher than the quality requirements of general high-quality silage maize， with a starch content greater than 28% and a crude protein content greater than 7%［19］. It might be related to the fact that the tested varieties used in this study are all hard-grain maize varieties. Meanwhile， it was found that starch content in quality indexes had a significant correlation with both grain yield and whole-plant biomass， while the correlation between crude protein content and these two indexes was not significant.

In order to screen excellent maize varieties for both grain and fodder purposes， in addition to measuring relevant agronomic traits， yield， and quality indexes， scientific and reasonable methods need to be used for comprehensive evaluation. At present， there are many reports on the comprehensive evaluation of maize yield， quality， and resistance using methods such as principal component analysis， grey correlation degree， and membership function［20-23］. In this study， we selected the membership function method to quantitatively evaluate the comprehensive performance of tested maize varieties for both grain and fodder purposes. Considering that the introduction of some indexes with little or no correlation not only increases the complexity of calculation and analysis， but also sometimes leads to deviations and even erroneous results［24］， when performing membership function calculation， only indexes with significant or extremely significant correlation with grain yield and whole-plant biomass were selected. The comprehensive evaluation results showed that Guidan 671 performed best， with a membership function value of 0.986， followed by Zhaoyu 215， Guidan 669， and Guidan 6208， the membership function values of which were 0.692， 0.656， and 0.627， respectively， all greater than 0.6. Guidan 671 had the highest grain yield， whole-plant biomass， and crude protein content， and a starch content ranking third. It performed well in ear traits and had a relatively suitable plant height and ear height， making it a very ideal maize variety for both grain and fodder purposes. Zhaoyu 215 ranked second in both grain yield and whole-plant biomass， and had a high starch content and moderate performance in other traits. Therefore， it could also be used as a maize variety for both grain and fodder purposes. The performance of Guidan 669 and Guidan 6208 was relatively balanced in all aspects， and they could be used as alternative maize varieties for both grain and fodder purposes. At present， both Guidan 671 and Zhaoyu 215 are key maize varieties developed by Guangxi Zhaohe Seeds Industry Co.， Ltd. The comprehensive evaluation results of this study are consistent with the excellent performance of the two varieties in production practice， further confirming that Guidan 671 and Zhaoyu 215 had good adaptability， stability， and high yield and quality. It provides a reference basis for the large-scale promotion and application of Guidan 671 and Zhaoyu 215 as excellent maize varieties for both grain and fodder purposes.

Although we measured multiple indexes such as agronomic traits， grain yield， whole-plant biomass， and quality in this study， leaf traits such as leaf area and green leaf number that reflect photosynthesis in maize plants were not measured， as well as other two important indexes that reflect the quality of silage maize， namely acid detergent fiber and neutral detergent fiber contents. Therefore， the evaluation results have certain limitations， and further research will be conducted on these contents in the future.

Conclusions

In this study， a screening experiment was conducted on 12 maize varieties with potential for both food and fodder use. Their agronomic traits， grain yield， and whole-plant biomass were measured， and their quality indexes were analyzed， and the performance of the tested varieties was comprehensively evaluated using the membership function method. The comprehensive performance scores of 12 maize varieties intended for both grain and fodder use， from high to low， were Guidan 671， Zhaoyu 215， Guidan 669， Guidan 6208， Guidan 666， Guidan 6205， Guidan 660， Guidan 6203， Guidan 6206， Guidan 162， Guidan 668， and Guidan 673， of which Guidan 671 and Zhaoyu 215 showed excellent comprehensive performance， and thus could be used as preferred maize varieties for both grain and fodder purposes in Duan Yao Autonomous County and surrounding areas for promotion and cultivation.

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