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African Crop Science Journal
African Crop Science Society
ISSN: 1021-9730 EISSN: 2072-6589
Vol. 4, Num. 4, 1996, pp. 383-391
African Crop Science Journal,
Vol. 4. No. 4, pp. 383-391, 1996

Heterosis and combining ability for grain yield and yield components in guinea sorghums

A. TOURE, F.R. MILLER^1 and D.T. ROSENOW^2

IER, CRRA-Sotuba BP 438 Bamako, Mali, West Africa
^1 Department of Soil and Crop Science (retired), College Station, Texas A&M University TX 77843
^2 Texas Agricultural Experiment Station, Route 3, Box 219, Lubbock, TX 79401

(Received 29 March, 1996; accepted 16 October, 1996)


Code Number: CS96079
Sizes of Files:
    Text: 34.1K
    Graphics: No associated graphics files    

ABSTRACT

Relatively low yields of guinea sorghums have been a major obstacle for sustained progress in yield improvement of the race in West Africa. In an attempt to determine why guinea sorghums of West Africa display low yield potential, seven converted guinea, four zerazera, and two caudatum sorghums were crossed to three improved A-lines. Parents and hybrids were evaluated for heterosis, general and specific combining at Halfway and College Station, Texas during 1989 and 1990. In general, non-guineas were better combiners than guineas for grain yield and most of yield components. Both additive and nonadditive effects for grain yield were observed among guinea parents. The additive effects of non-guineas for grain yield were higher than those of guinea parents. Guineas showed low additive effects for grain yield, number of seeds per panicle, and seed size. Guinea sorghums seem to maintain a relative low grain yield by reducing the number of seeds per particle and the seed size. Most hybrids of guineas showed positive heterosis over the best parent for grain yield. This is an indication that guineas do possess some genes or factors contributing to high yield expression.

Key Words: Combining ability, guinea, sorghums, yield

RESUME

Les rendements relativement faibles des sorghos guineas ont ete un obstacle majeur pour un progres durable de l'amelioration du rendement de la race en Afrique de l'Ouest. Dans l'intention de determiner pourquoi les sorghos guineas de l'Afrique de l'Ouest ont un potentiel de rendement faible, sept sorghos guineas convertis, quatre zerazera et trois caudatum ont ete croises a trois lignees A ameliorees. Les parents et les hybrides ont ete evalues pour l'heterosis, l'aptitude generale et specifique a la combinaison a Halfway et College Station, Texas en 1989 et 1990. En general, les sorghos non-guineas se sont mieux combines que les sorghos guineas pour le rendement grain et la plupart des composantes de rendement. Les effects additifs et non-additifs pour le rendement grain ont ete observes chez les parents guineas. Les effects additifs des sorghos non-guineas etaient plus eleves que ceux des parents guineas pour le rendement grain. Les parents guineas ont montre des effects additifs pour le rendement grain, le nombre de grains par panicule et la grosseur des graines. Les sorghos guineas semblent maintenir un rendement grain relativement faible en diminuant le nombre de graines par panicule et la grosseur des graines. La plupart des hybrides de parents guineas ont montre des effects positifs d'heterosis pour le rendement de grain compares a leur meilleur parent. Ce resultat est une indication que les sorghos guineas possedent quelques genes ou facteurs contribuant a l'expression de rendement eleve.

Mots Cles: Aptitute a la combinaison, guinea, sorghos, rendement

INTRODUCTION

Sorghum (Sorghum bicolor [L.] Moench) is grown mainly in the semi-arid tropics and subtropics. Many of the traditionally grown cultivars are sensitive to photoperiod. These sorghums have been selected to flower at the end of the wet season, so that the grains ripen under the dry conditions.

The guinea sorghums are the dominant sorghum race in West Africa and tend to predominate throughout the Savannah sorghum belt. The guinea race is characterised by high food grain quality, and withstands weathering and insects, and prolonged storage quite well. The Guineas produce vitreous grain under post anthesis drought stress while under identical conditions, most exotic or introduced varieties fail to adequately fill their grain after flowering. Furthermore, the Guineas have good resistance to head bug (Eurystylus marginatus) damage and to the head bug-grain mould complex. However, the potential yield of Guineas is relatively low though they are very stable producers. The guinea sorghums appear to be well adapted to the harsh climate and poor soils of West Africa.

If guinea sorghums are crossed with other taxonomic groups, the offsprings generally are poor and low yielding and lose most of the desirable grain characteristics of the guinea parents. This problem has been a major obstacle to sustained progress in yield improvement of the guinea race and to improved sorghums adapted to West Africa. Most of the studies concerning guinea sorghums have focused on the taxonomy of the genera. No studies have addressed the generally poor combining ability of guinea sorghums of West Africa when placed in breeding programmes.

MATERIALS AND METHODS

Fifty nine entries were evaluated during 1989 and 1990 in two locations (Halfway and College Station, Texas). Entries included fourteen parents as males and three parents as females (Table 1). Seven converted guinea sorghums (classed as all conspicuums), four zerazera, one subglabrascens, and two caudatum were crossed to three selected improved caffrorum derivative A-line types. The seven converted guinea sorghums were chosen to represent guinea .types from a wide range of environments (five countries in Africa). A total of 42 crosses were made (14 crosses with each female). The 42 hybrids and their parents were grown in performance field trials using a restricted randomised block design with three replications.

TABLE 1. Designation and origin of males and females studied at Halfway (1989, 1990) and College Station (1990)

--------------------------------------------------------------------
Designation                 Taxonomic group          Origin
--------------------------------------------------------------------
SC97E-14E    (IS12602C)    Conspicuum (Guinea)       Nigeria 
SC272-14E    (IS7274C)     Conspicuum (Guinea)       Nigeria 
SC283-14E    (IS7173C)     Conspicuum (Guinea)       Tanzania 
SC265-14E    (IS6705C)     Conspicuum (Guinea)       Burkina Faso 
SC94-14E     (IS2328C)     Conspicuum (Guinea)       Sudan
SC262-14E    (IS3826C)     Conspicuum (Guinea)       Mali
SC603-14E    (IS1168C)     Conspicuum (Guinea)       Tanzania 
SC110-14E    (IS12610C)    Zerazera                  Ethiopia 
SC173-14E    (IS12664C)    Zerazera                  Ethiopia 
SC175-14E    (lS12666C)    Zerazera                  Ethiopia 
RTx7000                    Milo/Kafir                Texas/TAES* 
RTx09                      Caudatum                  Texas/TAES 
RTx430                     Caudatum/Kaura/Zerazera   Texas/TAES 
VG146        (Sureno)      Zerazera                  ICRISAT/Texas
BTx3197                    Caffrorum                 Texas/TAES 
BTx623                     Caffrorum/Zerazera        Texas/TAES 
BTx631                     Caffrorum/Zerazera        Texas/TAES

TAES*: Texas Agricultural Experiment Station.
-------------------------------------------------------------------

At Halfway in 1989, the field experiment was planted on May 24. The soil type was Pullman clay loam. The experiment was fertilised with 224-90-0 preplant, the nitrogen being anhydrous ammonia. Irrigation was applied five times during the growing stages of the plants. The experiment at Halfway in 1990 was fertilised with 179-90-0 preplant and was planted on May 23. Irrigation was applied at preplant and four times during the stages of sorghum growth (before flowering). At College Station in 1990, the experiment was planted on April 3 and fertilised with 100-40-0 at soil preparation and 146-0-0 as sidedressing, the soil was Ship clay loam.

A restricted randomised block design (RRBD) with 3 replications was used to study the combining ability. Measurements were taken on grain yield and yield components. Combining ability analysis was performed using a programme written by Gates in 1991 (unpublished) for line x tester mating system, with 3 females and 14 male lines. The programme does not consider missing plot and assumes residuals are normally and randomly distributed. The expectation for the mean squares were obtained based on covariance of relatives. Assuming no epistasis, the calculations were based on components of variance and based on genetic effects. The general combining ability (GOA) and specific combining ability (SAC) were performed for each location by partitioning cultivars into females (F), males (M) and hybrids (H). Males were divided into Guinea (G) and non-guinea (N) according to taxonomy. Hybrids were classified into two groups; with guinea (G) and with non-guinea males (NIGH).

Measurements were taken on grain yield and yield components. The following data were collected:

    - Grain yield: weight in grams (g) of threshed grains per plot transformed in kilograms per hectare (kg ha^-1).

    - 1000 seed weight: in g based on a 1000-seed sample.

    - Number of primary branches per particle: number of primary branches from panicle tip to the lowest panicle branch.

    - Number of whorls in the panicle: recorded on 3 panicles per plot.

    - Number of seeds per panicle: weight in g of threshed grains of 5 panicles per plot divided per 5 times 1000-grain weight multiplied by 1000.

    - Panicle:stover ratio: 5 plant samples were taken per plot. Panicles were separated from leaves and stems, and dried at 65 c for 5 days, weighed and the ratio panicle:stem+ leaves was calculated.

    - Length of primary panicle branches: measurement in centimeter (cm) recorded from the middle of the panicle on 3 panicles per plot.

    - Length of panicle: distance in cm from the panicle tip to lowest panicle branch, measured on 5 plants per plot.

    - Days to 50% anthesis: number of days from planting to the time when 50% plants have begun to shed pollen.'

    - Plant height: measured in cm from the ground to the panicle tip, on 5 plants per plot.

RESULTS AND DISCUSSION

At Halfway in 1989, guinea and non-guinea combining ability sum of squares were significantly different for all variables studied. Specific combining ability sum of squares for crosses from guineas revealed significance for all variables except for days to anthesis and plant height. Sum of squares for SAC due to crosses from non-guineas showed differences at P=0.01 for all attributes except whorls/panicle, panicle length, and panicle exsertion (data not shown). General and specific combining ability mean squares were significant for all variables. General combining ability (GOA males plus GOA females) accounted for 81% of the variability for grain yield among crosses (Table 2). Thus, additive variance was more important than nonadditive variance in determining grain yield for those crosses. The mean squares for SAC was significant, which indicates that nonadditive gene action did affect grain yield. Guineas accounted for only 14% of the male total variability for grain yield among crosses. This result suggested that additive effects from N were higher when compared with G. The percentage of sum of squares for crosses due to general and specific combining ability for variables studied indicated the preponderance of additive over nonadditive effects. Similar results were found by Atkins and Bueno (1982). Also, the low proportion of GOA of guineas compared to the overall male GOA due to the variability among hybrids were observed with seeds per panicle and 1000-seed weight (measure of the seed size) with 3% and 7%, respectively, suggesting low additive effects for seeds per panicle and seed size. The highest contributions of guineas GOA to the total males GOA were found for primary branches/panicle, whorls/panicle, days to anthesis, panicle length, and exsertion.

TABLE 2. Percentage of the sum of squares for crosses due to general and specific combining ability for eleven variables studied at Halfway 1989

---------------------------------------------------------------------------
Variables               GOA     GOA    SAC    GOA      SAC    GOA     SAC 
                       males  females  fxm   guinea   guinea  non-    non-
                        (m)     (f)                          guinea  guinea

---------------------------------------------------------------------------
                                             % 
Grain yield              78      3      19     14        9     55     10 
1000 seed weight         31     42      27      7       15     21     10
Primary branches/panicle 53      1      46     45       13      7     29
Whorls/panicle           56     13      31     43       17     13      8
Seeds/panicle            64      5      31      3        5     46      3
Days to anthesis         63     25      12     34        4     25      6
Plant height             75      8      17     24        3     50      7
Panicle length           69     14      17     22        9     10      3
Panicle exertion         73      7      20     30       14     23      6

GOA: General combining ability 
SAC: Specific combining ability
---------------------------------------------------------------------------

The males GOA sum of squares were significant at P=0.01 for the following variables studied at Halfway in 1990: grain yield, 1000-seed weight, primary branches/panicle, whorls/panicle, panicle:stover ratio, length of primary branch, and panicle exsertion. The females GOA were significant only for whorls/panicle, length of primary branch, and days to anthesis. SAC sum of squares for all crosses were significant for grain yield, whorls/panicle, panicle:stover ratio, and panicle exsertion.

Guineas GOA sum of squares showed significance for grain yield, primary branches/ panicle, whorls/panicle, and panicle length, while non-guineas revealed significance for 1000-seed weight, seeds/panicle, panicle:stover ratio, plant height, and panicle exsertion. SAC sum of squares for G showed significance for plant height, primary branches/panicle, and whorls/panicle. Sum of squares for SAC due to NIGH were significant for grain yield, whorls/panicle, panicle:stover ratio, days to anthesis, and panicle exsertion. Total general combining ability for parents accounted for 44% of the variability for grain yield among crosses (Table 3). Both GOA and SAC contributed about the same amount to the total variability for grain yield among crosses. Since the GOA and SAC mean squares showed significance at P=0.01 for grain yield, it is suggested that both additive and nonadditive variances were important in grain response. This result is supported by the findings of Rao (1970) and Nagur and Murty (1970) which show that additive as well as nonadditive gene action control the inheritance for grain yield and its components. Guineas GOA accounted for 33% of the male total GOA for grain yield among crosses, and their GOA mean of squares were also significant. Thus, these results indicate that grain yield was controlled by both additive and nonadditive effects as indicated by guineas in the study. The highest average SAC effects were greater for guineas with the females ATx631 and ATx3197.

TABLE 3. Percentage of the sum of squares for crosses due to general and specific combining ability for eleven variables studied at Halfway 1990

---------------------------------------------------------------------------
Variables               GOA     GOA    SAC    GOA     SAC    GOA    SAC 
                       males  females  fxm   guinea  guinea  non-   non-
                        (m)    (f)                          guinea  guinea
---------------------------------------------------------------------------
                                       % 
Grain yield              37      7      56     31      27      6     29
1000 seed weight         62      4      34     27      12     33     20
Primary branches/panicle 55      1      44     47      29      6      9 
Whorls/panicle           28      4      68     19      21      7     38 
Seeds/panicle            36      3      61     15      30      8     31 
Panicle/stover ratio     44      0      56     29      24     13     28
Primary branches length  43     10      47     15      26     15     19
Days to anthesis         23     18      59      5       8     14     46
Plant height             38      2      60     14      39     21     21
Panicle length           55      2      43     35      19     15     23
Particle exertion        38      0      62      5      16     15     43

GOA: General combining ability 
SAC: Specific combining ability
--------------------------------------------------------------------------- 

For the trial conducted in College Station (1990), females and males general combining ability sum of squares were significantly different at 0.05 and 0.01 probability levels for grain yield, respectively. Guineas and non-guineas GOA and SAC sum of squares were significant for grain yield and primary branch length. General and specific combining ability for parents accounted for most of variability among traits studied (Table 4). For grain yield, parents GOA accounted for 61% of the variability among crosses. Both additive and nonadditive gene effects affected grain yield with a preponderance of additive effects. The additive and nonadditive effects for G and N were of equal magnitude. The findings of Rao (1970) have suggested the importance of both GOA and SAC in influencing yield. Again, guinea GOA accounted for only 10% of the male total variability for grain yield among crosses. Low percentage of guineas GOA to the total male GOA among crosses was found with seed/panicle and 1000-seed weight with 9% and 10%, respectively. The results suggested low additive effects for grain yield, seeds per panicle, and seed size.

TABLE 4. Percentage of the sum of squares for crosses due to general and specific combining ability for eleven variables studied at College Station 1990

---------------------------------------------------------------------------
Variables                GOA     GOA    SAC   GOA     SAC    GOA     SAC 
                        males  females  fxm  guinea  guinea  non-    non
                         (m)     (f)                        guinea  guinea 
---------------------------------------------------------------------------
                                           % 
Grain yield              46      15      39    10      19     15     18 
1000 seed weight         31       2      67    10      20     20     42 
Primary branches/panicle 41       5      54    27      22     13     25
Whorls/panicle           56       7      37    38      17     11     18
Seeds/panicle            22       1      77     9      41     12     30 
Panicle/stover ratio     32       5      63    17      24     13     34
Primary branches length  49       1      50    13      26     18     23
Days to anthesis         34       2      64    19      31     14     16
Plant height             28      13      59     9      36     18     22
Panicle length           50       4      46    22      16     24     26
Panicle exertion         26      18      56    10       8     10     24

GOA: General combining ability 
SAC: Specific combining ability
---------------------------------------------------------------------------

The pooled general and specific combining ability sum of squares across environments for parents and crosses were significant for grain yield, whorls/panicle, seeds/panicle, plant height, and panicle exsertion (Table 5). Guineas and their crosses showed significant GOA and SAC sum of squares for grain yield, whorls/panicle, seeds/ panicle, plant height, and panicle length. Male GOA x environment interaction was significant for all attributes studied except for primary branches/panicle. Guineas showed significance across environments for grain yield, primary branches per panicle, days to anthesis, and panicle exsertion.

TABLE 5. Estimates of combining ability of sum of squares for grain yield, and yield components across environments, Halfway (1989, 1990) and College Station (1990)

---------------------------------------------------------------------------
Source          df    Grain yield     1000 seed  Primary branches  Whorls  

                      (kg ha^-1)      weight (g)   /panicle        /panicle 
--------------------------------------------------------------------------- 
Females[GCA]     2    36181511.18**    292.50**       11.59        20.11** 

Env.* F[GCA]     4    7857149.36**     402.69**      218.64        19.71**  
 
Males[GCA]      13    23008625.00**    449.57**     3361.16**     167.84**  
Env.* M[GCA]    26   238291029.30**    438.46**     1714.22        63.34**  
G[GCA]           6    89984878.80**    121.31**     3897.92       140.44**  
Env.* G[GCA]    12    81547389.95**    137.22       1042.14**      25.31   
NG[GCA]          6    90082590.70**    268.02**      453.43        26.47**  
Env.* NG[GCA]   12   134398397.50**    264.82**      512.20        27.66**  
G vs NG[GCA]     1    50019055.50**     60.24**        9.81         0.93   


F x M[SCA]      26   171911851.00**    277.89       2350.63**      87.22**  
Env.* Fx M[SCA] 52   180717026.00**    558.39       3271.44       137.49**  
F x G[SCA]      12    75107487.00**    126.12       1124.60**      37.63**  
Env,* Fx G[SCA] 24    87856244.40**    229.08       1320.67        53.29**  
F x NG[SCA]     12    80953066.00**    140.47**      807.40        44.85**  
Env.* FxNG[SCA] 24   101039750.00**    259.70       1739.43        59.32**  
 
Error          348   545907397.45     3905.90      26513.72       755.95   
--------------------------------------------------------------------------
** Significant at 0.01 level GOA: General combining ability SAC: Specific combining ability F: Female
M: Male
G: Guineas
N: Non-guineas
Env.: Environment
---------------------------------------------------------------------------

TABLE 5. (Continued).

---------------------------------------------------------------------------
Source           Seeds/panicle  
---------------------------------------------------------------------------
Females[GCA]       2294128.11** 
Env.* F[GCA]        669053.45
 
Males[GCA]        21704664.75** 
Env.* M[GCA]      19105787.24*
G[GCA]             4017695.83*
Env.* G[GCA]       1992822.96 
NG[GCA]           10373897.68*
Env.* NG[GCA]     16528858.35*
G vs NG[GCA]       7313071.24*
                  
F x M[SCA]        14557136.55*
Env.* Fx M[SCA]   23671242.67 
F x G[SCA]         5167230.52 
Env,* Fx G[SCA]    9423943.54*
F x NG[SCA]        8840365.52*
Env.* FxNG[SCA]    7586541.41
Error            114062076.47
---------------------------------------------------------------------------
TABLE 5 (continued)
---------------------------------------------------------------------------
Source            df   Days to      Plant       Panicle      Particle 
                       anthesis    height (cm)  length (cm)  exertion (cm)
--------------------------------------------------------------------------- 
Females[GCA]       2    308.35**    8583.54**    121.15**     249.15** 
Env.*F[GCA]        4     45.80       235.43      483.82**     145.81** 
Males[GCA]        13    477.48**   47373.30**   2608.18**    2433.59** 
Env.*M[GCA]       26    351.85     23057.63      920.23**     894.91** 
G[GCA]             6    199.54**   15386.99**   1043.97**     664.05** 
Env.*G[GCA]       12    198.28**    8039.80      312.03       462.06** 
NG[GCA]            6    135.54**   31855.92**    892.20**     324.77** 
Env.*NG[GCA]      12    235.65**   13264.88**    385.84       819.46** 
G vs NG[GCA]       1    142.40**     130.39      672.01**    1444.77** 
F x M[SCA]        26    313.55     23084.09**    661.30       960.44** 
Env.**F x M[SCA]  52    395.54     26645.68**    928.60      1768.03** 
F x G[SCA]        12     74.52     14780.75**    421.20**     118.39 
Env. *F x G[SCA]  24     62.02     11757.61      267.36       773.49 
F x NG[SCA]       12    198.04**    7593.42      194.84       834.43** 
Env.**F x NG[SCA] 24    248.10     11211.02      445.56       650.44 
Error            348   5730.23    248868.32    11407.05     11504.03
--------------------------------------------------------------------------

The percentage of sum of squares for crosses due to GCA and SCA across environments revealed that general combining ability (GCA males plus GCA females) accounted for most of the variability for all traits among crosses (Table 6). Parents GCA accounted for 61% of the variability among crosses for grain yield. Guineas GCA accounted for 21% of the total variability for grain yield in parents. The highest percent contributions for Guineas were found with primary branches/panicle and whorls/panicle. Since pooled GCA and SCA mean of squares were significant for grain yield and the GCA greater than SCA, it is concluded that both additive and nonadditive effects are important in grain yield determination but with a preponderance of low additive effects. A similar pattern was observed by Maim (1968), Harer and Bapat (1982), and De Franca (1990).

TABLE 6. Percentage of the sum of squares for crosses due to general and specific combining ability for variables studied across environments Halfway (1989,1990) and College Station (1990)

---------------------------------------------------------------------------
Traits                   GCA    GCA     SCA   GCA     SCA     GCA     SCA 
                        males  females  fxm  guinea  guinea   non-    non
                         (m)    (f)                          guinea  guinea
---------------------------------------------------------------------------
Grain yield               58      8      39    21      17      21     18 
1000 seed weight          44     29      27    18      12      26     14 
Primary branches/panicle  65      0      35    58      15       7     20
Whorls/panicle            61      7      32    51      14      10     16
Seeds/panicle             62      5      33    38      12      24     20
Days to anthesis          43     28      29    18       7      12     18
Plant height              60     11      29    19      18      40      9
Panicle length            77      4      19    31      12      26      6
Panicle exertion          67      7      26    18       3       9     23

GCA: General combining ability 
SCA: Specific combining ability
--------------------------------------------------------------------------

Heterosis estimates for trials at Halfway in 1989 indicated that most hybrids with ATx631 had positive values for grain yield. Heterotic values ranged from -0.35 to 72.95% for grain. All guinea parental lines showed positive heterosis for grain yield with ATx631 except for SC26214E. This supported the early high SCA estimates observed in guineas hybrid with ATx631, confirming that nonadditive effects played a role in grain yield response. Highest positive values for grain yield were found for SC 173-14E, SC 17514E, and RTx430 with both ATx3197 and ATx623. Ranges in heterosis were -30.57 to 56.60% for 1000-seed weight, -24.58 to 23.35% for primary branches/panicle, -35.71 to 28.57% for whorls/panicle, -56.75 to 56.60% for seeds/ panicle, and -15.11 to -3.98 for days to anthesis. Estimates for heterosis for days to anthesis indicated that hybrids flower earlier than their latest parent.

At Halfway in 1990, ranges in heterosis for grain yield were -39.25 to 98.28%. Guinea parents, SC94-14E, SC28 3-14E, and SC262-14E, had high values for grain yield. Highest positive heterosis values for grain yield were shown with the hybrids derived from ATx3197*RTx09, ATx623*SC173-14E, ATx3197*SC28-14E, and ATx631*SC26214E. On average, the highest positive heterosis effects for guinea parental lines for grain yield were found with ATx3197, with a range of -18.43 to 13.52% for 1000-seed weight, -15.38 to 43.12% for primary branches/panicle, -42.85 to 33.33% for whorls/panicle, -33.09 to 73.45% for seed/ panicle,-19 to -0.90% for days to anthesis, and -27.12 to 47.24 for panicle:stover ratio.

The percentage heterosis for grain yield for F1 hybrids at College Station in 1990 indicated positive heterosis with a range of 9.77 to 60.35%. The highest heterosis values of guineas for grain yield were obtained with the female ATx3197, with hybrids ATx3197*RTx0, ATx3197 *RTx430, and ATx3197*SC283-14E being 60.35%, 37.60% and 34.38%, respectively, over their highest yielding parent. These ranged from -13.13 to 28.50 for 100-seed weight, -21.76 to 35.81% for primary branches/panicle,-31.03 to 28.50% for whorls/panicle, -15.66 to 103.05% for seeds/ panicle, -16.11 to -4.07% for days to anthesis, and -47.46 to 47.91% for panicle/stover ration.

The heterosis estimated across environments revealed that most of the F1 hybrids showed positive values for grain yield. Similar results were obtained by Kambal and Webster (1966) and Patel et al. (1982). Among the 21 GH, only one showed negative values for grain yield across environments with a range between -23.63 and 69.46%. Those results indicated some superiority in performance of guinea hybrids over the superior parent and suggested that some possibilities exist to increase productivity for guineas contrary to current thinking.

CONCLUSION

General combining ability for guineas and non-guineas were significant for most variables. Consequently, guineas as well as non-guineas combined well for grain yield and most variables. However, non-guineas were better combiners than guineas for grain yield. Specific combining ability for hybrids from guinea showed significant differences for most variables. Guineas revealed good combination of genes for grain yield with some females in specific environments, indicating complementarity of favourable genes, a measure of heterotic response between those females and guineas.

Both additive and non-additive effects were observed for grain yield. Guineas GCA contributed less to the male total GCA for grain yield variability among crosses. Additive effects from non-guineas were higher when compared with guineas, thus the latter showed low additive effects for grain yield, number of seed per panicle, and 1000-seed weight. The highest contribution of guineas GCA to the total GCA were observed for primary branches/panicle, whorls/panicle, panicle length, and panicle exsertion. The average GCA effects for guineas was lower than non-guinea effects suggesting a low additive gene effects for the former. Guineas GCA x environment interaction was not significant for seeds/panicle and 1000-seed weight, indicating that guineas were stable with respect to these characters over environments. In general, guinea parental lines showed positive heterosis and high SCA effect for grain yield with the female ATx631. The heterosis study indicated a gain for most progenies over the highest yielding parent. These results indicated the relative superiority in performance of guinea hybrids over the superior parent in selected cases. This study showed that there are complementarities between guineas and some females for grain yield and also indicated that the guineas do possess some genes or factors contributing to grain yield.

REFERENCES

Arkins, R.E. and Bueno, A. 1982. Intercharacter correlations in sorghum in relation to genotypic and environmental variations. Proceeding Iowa Academic Science 89:117-120.

De Franca, J.G. 1990. Studies on Genetic Parameters of Agronomic, Biochemical, and Malting Characteristics in Grain Sorghum. Ph.D. Dissertation, Texas A&M University, College Station, Texas, pp. 24-96.

Harer, P.N. and Bapat, D.R. 1982. Line x tester analysis of combining ability in grain sorghum. Journal Maharashtra Agriculture University 7:230-232.

Kambal, A.E. and Webster, O.J. 1966. Manifestation of hybrid vigor in grain sorghum and the relation among the components of yield, weight per bushel and height. Crop Science 6:513-515.

Maim, N.R. 1968. Exotic germplasm use in grain sorghum improvement. Crop Science 8:295-298.

Nagur, T. and Murty, K.N. 1970. Diallel analysis of heterosis and combining ability in some Indian sorghums. Indian Journal of Genetics and Plant Breeding 30:26-35.

Patel, M.H., Desai, K.B. and Kukadia, M.U. 1982. Note on the manifestation of heterosis in sorghum. Indian Journal of Agricultural Science 52:856-857.

Rao, N.G.P. 1970. Genetic analysis of some exotic x Indian crosses in Sorghum II. Combining ability and components of genetic variation. Indian Journal of Genetics and Plant Breeding 30:362-376.

Copyright 1996 The African Crop Science Society

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