CORN IMPROVEMENT FOR TOLERANCE TO HIGH PLANT DENSITIES

Transcription

1 CORN IMPROVEMENT FOR TOLERANCE TO HIGH PLANT DENSITIES By AHMED MOHAMED RABIE EWIES B.Sc. (Agronomy), Fac. Agric., Cairo Univ., Egypt, M.Sc. (Agronomy), Fac. Agric., Minia Univ., Egypt, THESIS Submitted in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY In Agricultural Sciences (Agronomy) Department of Agronomy Faculty of Agriculture Cairo University EGYPT

2 APPROVAL SHEET CORN IMPROVEMENT FOR TOLERANCE TO HIGH PLANT DENSITIES Ph. D. Thesis By AHMED MOHAMED RABIE EWIES B.Sc. (Agronomy), Fac. Agric., Cairo Univ., Egypt, M.Sc. (Agronomy), Fac. Agric., Minia Univ., Egypt, APPROVAL COMMITTEE Dr. MOHAMED S. M. SOLIMAN.... Head Research of Agronomy, Field Crops Res. Inst., ARC. Dr. MAZHAR M. F. ABDALLA.. Professor of Crop Breeding, Fac. Agric., Cairo University. Dr. MOHAMED REDA A. SHABANA Emeritus Professor of Crop Breeding, Fac. Agric., Cairo University. Dr. AHMED MEDHAT M. AL-NAGGAR. Emeritus Professor of Crop Breeding, Fac. Agric., Cairo University. 2 Date: 23 / 5 / 2012

3 SUPERVISION SHEET CORN IMPROVEMENT FOR TOLERANCE TO HIGH PLANT DENSITIES Ph. D. Thesis By AHMED MOHAMED RABIE EWIES B.Sc. (Agronomy), Fac. Agric., Cairo Univ., Egypt, M.Sc. (Agronomy), Fac. Agric., Minia Univ., Egypt, SUPERVISION COMMITTEE Dr. AHMED MEDHAT MOHAMED AL-NAGGAR Emeritus Professor of Crop Breeding, Fac. Agric., Cairo University. Dr. MOHAMED REDA ALI SHABANA Emeritus Professor of Crop Breeding, Fac. Agric., Cairo University. 3

4 Name of Candidate: Ahmed Mohamed Rabie Ewies Degree: Ph.D. Title of thesis: Corn Improvement for Tolerance to High Plant Densities Supervisors: Prof. Dr. Ahmed Medhat Mohamed Al-Naggar Prof. Dr. Mohamed Reda Ali Shabana Department: Agronomy Approval: 23 / 5 / 2012 ABSTRACT Modern hybrids of maize in North America and Europe exhibit a linear increase in grain yield per unit area by increasing population density up to more than 100,000 plants ha -1, as a result of breeding for tolerance to high density. In contrast, modern Egyptian maize hybrids are adapted to low plant density (ca. 57,000 plants ha -1 ) (the same used for old open-pollinated and synthetic varieties). Thus, a breeding program aiming at developing maize inbred lines and hybrids that possess adaptive traits to high-density, such as prolificacy, erect leaves etc was started. The present study was conducted in 4 seasons during 3 years from 2009 to 2011 at 2 locations, i.e. Bani Sweif and Minufiya. The main objectives were to develop maize inbred lines and hybrids with adaptive traits of high plant density tolerance, so that they can contribute to the enhancement of grain yield from land unit area. Fifty-five newly-developed maize inbred lines in the 3 rd selfed generation, isolated from 12 different sources and 3 testers were used to make 165 testcrosses. These testcrosses were evaluated under low (20,000 plants fed -1 ) and high (40,000 plants fed -1 ) plant density. The highest and the lowest inbreds for some selected adaptive traits to high plant density were chosen based on per se performance and GCA effects to make five diallels. Diallel crosses and their parents were evaluated under low and high plant density. Additive (D) and dominance (H 1 ) variances were highly significant for all studied traits under both high and low plant densities. The magnitude of additive was higher than that of dominance for ASI under high and low plant densities and DTS, PH and LANG under low-density only. Type of dominance was overdominance for EPP, GYPP and GYPF under high and low density and DTS, PH and LANG under high-density and partial dominance for ASI only under high and low density and DTS, PH and LANG under low-density. The highest estimate of narrow-sense heritability under high plant density was shown by DTS (45.25%) followed by GYPP (43.57%), GYPF (43.16%) and PH (42.83%), while the lowest one was exhibited by EPP (29.07%).The highest expected genetic advance (GA) from selection was shown by GYPP (22.66%) under high-density and the lowest one (3.69%) was shown by DTS. Number of ears plant -1, erect leaves and short anthesis-silking interval may be considered good secondary traits for increasing the efficiency of selection for high grain yield under high-density. Correlation coefficients for means vs. GCA effects of inbreds, means vs. heterobeltiosis, means vs. SCA effects and SCA effects vs. heterobeltiosis of F 1 crosses as well as parents means vs. offspring means and breeding values were estimated and discussed. Key words: maize, GCA, SCA, tolerance, high-density, testcrosses, diallel, genetic advance, heterobeltiosis, heritability, prolificacy and erect leaves. 4

5 DEDICATION I dedicate this work to whom my heart felt thanks; TO THE SOUL OF MY LATE MOTHER, AND MY FATHER AND TO MY WIFE and MY CHILDREN for their patience and help, as well as to MY SISTERS and BROTHERS For all the support they lovely offered along the period of my post graduation. 5

6 ACKNOWLEDGEMENT Thanks to ALLAH, the most Merciful and the most Beneficial. I wish to express my deepest gratitude and appreciation to Dr. Ahmed Medhat Al-Naggar and Dr. Mohamed Reda Ali Shabana Professors of Plant Breeding, Agron. Dept., Fac. Agric., Cairo Univ. for suggesting the problem, valuable guidance and constructive criticism throughout the course of this investigation and during the preparation of the manuscript. My deepest gratitude is offered to Mr. Ahmed farid Abd- El- Fattah, Chairman and Managing Director, of Toshka Company for Seed Production and Trade for valuable advice and continuous help throughout the progress of this study. Thanks are also extended to Dr. Hesham T. O. Hassan Researcher, Fine Seeds International SAE Company and Dr. Arafa B. A. El-Fesheikawy, Researcher, Cotton Research Institute at Sids Agric. Res., Station, ARC, for their valuable help during the statistical analysis of this study. Thanks are further extended to the staff members of Toshka Company for Seed Production and Trade for help and providing field and laboratory facilities needed to perform the study reported in this thesis. 6

7 CONTENTS INTRODUCTION... 1 REVIEW OF LITERATURE... 5 Page 1. Role of genotype (G) in HPD tolerance Role of plant density (PD) and G PD interaction Adaptive traits to HPD tolerance Combining ability for maize HPD tolerance traits Genetic parameters for maize HPD tolerance traits 38 MATERIALS AND METHODS RESULTS AND DISCUSSION Per se performance of inbred lines (Experiment # 1) a. Analysis of variance of inbred lines b. Means and ranges of inbred lines 70 c. Superiority of high-pd tolerant over sensitive inbreds.. 75 d. Trait interrelationships for inbred lines Evaluation of lines in testcrosses (Experiment # 2).. 79 a. Analysis of variance of testcrosses. 79 b. Means and ranges of testcrosses c. Superiority of high-pd tolerant over sensitive testcrosses d. Trait interrelationships for testcrosses e. Line tester analysis Analysis of variance of line tester Combining ability variance of testcrosses GCA effects of inbreds in testcrosses SCA effects of testcrosses Genetic parameters for testcrosses The five diallel experiments a. Analysis of variance of diallels. 97 I

8 b. Mean performance of diallel crosses c. Heterobeltiosis in diallels d. Combining ability variance in diallels GCA effects of inbreds SCA effects of diallel crosses e. Parent-offspring correlation 126 f. Gene action, heritability and selection gain from diallels. 130 g. Graphical approach of diallel analyses h. Trait interrelationships across diallel crosses SUMMARY REFERENCES 164 ARABIC SUMMARY II

9 LIST OF TABLES No. Title Page 1. Designation, parental source and place bred of 55 inbred lines (L) and three testers (T) used in this study The best and the worst inbred lines selected under high plant densities for each adaptive trait and /or for yield per se and included in each of five diallel mating designs Form of the ANOVA for line tester for the experiment carried out in 2010 season Expectations of mean squares (EMS) due to females (F), males (M) and females males (FM) from ANOVA of testcrosses Partitioning the degrees of freedom for genotypes into parents (P), crosses (C) and P vs. C and into general (GCA) and specific (SCA) combining ability and their interactions with locations (L) according to Griffing (1956) method II model I Analysis of variance of split- plot design for evaluation of 55 inbred lines under two plant densities at 2010 season Summary of means and ranges for studied traits of 55 inbred lines evaluated under low (LD) and high (HD) plant density in 2010 season The five best and five worst inbred lines for studied traits under low (LD) and high (HD) plant density.. 73 III

10 9. Mean performance of all studied traits averaged for the four highest and four lowest inbreds in GYPF and superiority (%) of tolerant (T) over sensitive (S) inbreds under low and high plant density Genetic correlation coefficients between GYPP or GYPF and other studied traits for inbred lines under low and high plant density Analysis of variance of the split- plot experiments for evaluation of 165 testcrosses under high and low plant densities in Summary of means and ranges for 165 testcrosses evaluated under low (LD) and high (HD) plant density in 2010 season Mean performance of studied traits averaged for the four highest and four lowest testcrosses in GYPF and superiority (%) of tolerant (T) over sensitive (S) testcrosses under low and high plant density Genetic correlation coefficients between GYPP or GYPF and other studied traits for testcrosses under low and high plant density Analysis of variance of line tester experiment for all studied traits under low (LD) and high (HD) plant density General (GCA) and specific (SCA) combining ability variance for studied traits of maize testcrosses under low and high plant density The five best inbred lines and the worst one in GCA effects (ĝ) for all studied traits under low (LD) and high (HD) plant density IV

11 18. The five best testcrosses and the worst one in SCA effects (ŝ ij ) for all studied traits under low (LD) and high (HD) plant density Estimates of additive (δ 2 A) and dominance (δ 2 D) variance, degree of dominance a and broad (h 2 b) and narrow (h 2 n) sense heritability calculated from line tester analysis under low and high plant densities Analysis of variance of split- plot design for seven studied traits of five different diallels among contrasting maize inbred lines under low and high plant density at Bani- Sweif, Minufiya and combined data across locations in 2011 season Analysis of variance of RCBD for seven studied traits of five different diallels among contrasting maize inbred lines under low (LD) and high (HD) plant density for combined data across two locations in 2011 season Means of days to silking (DTS) and anthesis-silking interval (ASI) for parental lines, their F 1 diallels and checks under low (LD) and high (HD) plant density for combined data across two locations in 2011 season Means of plant height (PH) and leaf angle (LANG) for parental lines, their F 1 diallel crosses and checks under low (LD) and high (HD) plant density for combined data across two locations in 2011 season Means of ears plant -1 (EPP), grain yield plant -1 (GYPP) and grain yield feddan -1 (GYPF) for parental lines, their F 1 diallel crosses and checks under low (LD) and high (HD) plant density for combined data across two locations in 2011 season V

12 25. Estimates of heterobeltiosis (%) for days to silking (DTS), anthesis-silking interval (ASI), plant height (PH) and leaf angle (LANG) of diallel F 1 crosses under low (LD) and high (HD) plant density for combined data across two locations in 2011 season Estimates of heterobeltiosis (%) for ears plant -1 (EPP), grain yield plant -1 (GYPP) and grain yield feddan -1 (GYPF) of diallel F 1 crosses under low and high plant density for combined data across two locations in 2011 season Combining ability mean squares for studied traits of five diallels among maize inbred lines under low and high plant density for combined data across two locations in 2011 season Estimates of GCA effects (ĝ i ) of maize parental inbreds of five diallels under low (LD) and high (HD) plant density for combined data across two locations in 2011 season Estimates of SCA effects (ŝ ij ) of three diallels among contrasting maize inbreds for days to silking, anthesissilking interval and plant height under low (LD) and high (HD) plant density for combined data across two locations in 2011 season Estimates of SCA effects (ŝ ij ) of two diallels among contrasting maize inbreds for leaf angle, ears plant -1, grain yield plant -1 and grain yield feddan -1 under low (LD) and high (HD) plant density for combined data across two locations in 2011 season VI

13 31. Rank correlation coefficients among mean performance of inbreds ( p) and their GCA effects and between pairs of mean performance of F1 s ( c), SCA effects and heterobeltiosis (Hetero.) parameters under low (LD) and high (HD) plant density for combined data across locations Parent-progeny correlation coefficients (rop) between per se performance of best and / or worst parents (p) and per se performance of their corresponding offspring (o) under low and high plant density for combined data across locations Breeding values for best and worst parental inbreds under low (LD) and high (HD) plant density for combined data across locations Components of variance and heritability for five diallels among maize diverse inbred lines under low and high plant density for combined data across locations in 2011 season Genetic correlation coefficients (rg) of pairs of studied traits for diallel crosses (1 through 5) across two locations under low (LD) and high (HD) plant density in 2011 season.... VII 142

14 LIST OF FIGURES No. Title Page 1. V r -W r graph of days to silking (DTS) for combined data across locations under low-density V r -W r graph of days to silking (DTS) for combined data across locations under high-density V r -W r graph of anthesis-silking interval (ASI) for combined data across locations under low-density V r -W r graph of anthesis-silking interval (ASI) for combined data across locations under high-density V r -W r graph of plant height (PH) for combined data across locations under low-density V r -W r graph of plant height (PH) for combined data across locations under high-density V r -W r graph of leaf angle (LANG) for combined data across locations under low-density V r -W r graph of leaf angle (LANG) for combined data across locations under high-density V r -W r graph of ears plant -1 (EPP) for combined data across locations under low-density V r -W r graph of ears plant -1 (EPP) for combined data across locations under high-density V r -W r graph of grain yield plant -1 (GYPP) for combined data across locations under low-density V r -W r graph of grain yield plant -1 (GYPP) for combined data across locations under high-density VIII

15 13. V r -W r graph of grain yield feddan -1 (GYPF) for combined data across locations under low-density V r -W r graph of grain yield feddan -1 (GYPF) for combined data across locations under high-density IX

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17 INTRODUCTION Grain yield per unit area of maize is the product of final plant population and grain yield plant -1. As plant density increases, grain yield plant -1 decreases, while grain yield per unit area increases (Gollar and Patil, 2000). According to Duvick and Cassman (1999), average maize grain yield per unit area in the USA increased dramatically during the second half of the 20 th century, due to improvement in crop management practices and greater tolerance of modern hybrids to high plant densities (Tollenaar et al., 1997 and Tollenaar and Wu, 1999). In the USA, hybrids grown during the 1980 era demonstrated that the primary reason for yield gain is the ability of new hybrids to take advantage of higher plant densities (Carlone and Russell, 1987). Duvick (2005) reported that recent maize hybrids yield more than older ones due to continuing improvement in the ability to withstand the stress of higher plant density. Maximum yield per unit area may be obtained by growing recently released hybrids in developed countries, such as USA, France and Italy that can withstand high plant density up to 90,000 plants ha -1 (ca. 38,000 plants fed -1 ) (Huseyin et al., 2003). Modern maize hybrids in North America and Europe are tolerant to high density stress because of decreased lodging and decreased barrenness (William, 1997). Radenovic et al. (2007) pointed out that maize genotypes with erect leaves are very desirable for increasing the population density due to better light interception. An association was found between anthesis-silking interval (ASI) and yield under high plant population density (Edmeades et al., 1993 and Gezahegan et al., 1

18 2006). Prolific genotypes tended to produce fewer barren plants at higher plant densities than non-prolific ones (Russell, 1968; Duvick, 1974; Miller et al., 1995 and Gezahegan et al., 2006). Kamen (1983) reported that early- maturing hybrids at the highest density gave highest grain yields and that early prolific hybrids were the most profitable. Maize genotypes differ in tolerance to high plant density (Duvick, 1974; Prior and Russell, 1975; Troyer and Rosenbrook, 1983; Sangoi and Salvador, 1998; Andrade et al., 1999 and Maddonni et al., 2001). Maize grain yield is more affected by variations in plant density than other members of the grass family due to its monoecious floral organization, its low tillering ability, and its short flowering period (Vega et al., 2001). At lower plant densities, the differences between older and modern hybrids were smaller, becoming greater as plant density increased (Tollenaar 1989, 1991 and 1992). Plant density (PD) resulting in interplant competition affects vegetative and reproductive growth of maize (Tetio-Kagho and Gardner, 1988). An increase in the number of maize plants per unit area within a maize stand will enhance the competition for resources among plants within the maize canopy (Tollenaar and Wu, 1999). Thus, PD was considered as a major aspect in determining the degree of competition between maize plants (Subedi and Ma, 2008). High PD causes increases in stalk breakage, root lodging, barrenness and results in smaller ears (El-Lakany and Russell, 1971; Buren et al., 1974; Edmeades and Daynard, 1979; Troyer and Rosenbrook, 1983 and Tollenaar et al., 1997). High PD also causes increased plant and ear heights, decreased ears plant -1, ear length, ear diameter and kernel 2

19 depth, and cause later anthesis, with silk emergence delayed more than pollen shed (El- Lakany and Russell, 1971). Hybrid varieties currently released by the National Maize Breeding Program (NMBP) in Egypt are selected and grown at low density (24,000 plants fed -1 ca. 57,000 plants ha -1 ), i.e. almost half of the density used in developed countries. This is due to the fact that maize hybrids developed by NMBP of Egypt are not tolerant to high plant densities, because of their tallness, one-eared, decumbent leaf and large size type plants. To increase maize grain yield per unit area, breeding programs in Egypt should be directed to the development of hybrids tolerant to high-density. Thus, an integrated breeding program was initiated by the Dept. of Agronomy, Faculty of Agriculture, Cairo University in cooperation with Maize Breeding Program of the Toshka Seed Co., Egypt, to develop maize inbred lines and hybrids showing adaptive traits for high-density tolerance, such as prolificacy, short plant stature, erect leaves, early silking and synchrony of anthesis and silking, with the ultimate goal of increasing grain yield per land unit area through plant densities higher than presently used densities in Egypt. Since the final evaluation of inbred lines can be best determined by hybrid performance, combining ability plays an important role in selecting superior parents for hybrid combinations and in studying the genetic nature of plant traits (Hallauer and Miranda, 1988 and Duvick, 1999). The line tester analysis developed by Kempthorne (1957) is widely used for evaluating the potential of new inbred lines by crossing them to common testers and evaluating the performance of their testcrosses (Singh and Narayanan 2000). Moreover, the diallel analyses 3

20 developed by Griffing (1956) (Griffing approach), Jinks and Hayman (1953), Jinks (1954) and Hayman (1954 a and b) (Hayman s approach) provide information on the nature and amount of genetic parameters and general (GCA) and specific (SCA) combining ability of parents and their crosses, respectively. The objectives of the present study were: 1. Evaluating the per se performance and combining ability of 55 recently developed maize inbred lines for most important morphological and phenological traits conferring adaptation to high plant density. 2. Providing estimates of genetic parameters of maize traits conferring tolerance to high-density stress in order to identify the proper parents and breeding methods for developing hybrids tolerant to high plant density. 3. Developing maize inbred lines and hybrids tolerant to high plant density that may contribute to the enhancement of grain yield. 4. Identifying maize secondary traits strongly correlated with grain yield under high plant density that may be recommended for more efficient selection of density-tolerant genotypes. 4