Genetics and Inheritance Pattern of Time of Flowering and Quantitative Traits in Cowpea [vigna Unguiculata (L.) Walp].

Genetics and Inheritance Pattern of Time of Flowering and Quantitative Traits in Cowpea [vigna Unguiculata (L.) Walp].

CHAPTER ONE

Objectives of this study

investigate the inheritance pattern of time to flowering and quantitative characters in crosses between short day and day neutral cowpea accessions and
establish the level of crossibility between the two photoperiodic groups of cowpea.

CHAPTER TWO

MATERIALS AND METHODS

The experiment was carried out at the Teaching and Research Farm of the Department of Crop Science, Faculty of Agriculture, University of Nigeria, Nsukka. Nsukka is characterized by low land humid tropical conditions and has a bimodal rainfall pattern with annual total of about 1500 mm. The relative humidity is about 70% during the rainy season and drops to 50% during the dry season. The mean annual temperature does not exceed 30^oC (UNN, 2001). The experimental materials comprised ten cowpea accessions. Six accessions were obtained from Plateau state, north central Nigeria (Latitude 09^o26¢N; Longitude 9^o08¢E, and altitude of 282.2 m above sea level), and four accessions were obtained from Nsukka, Enugu state, south eastern Nigeria (Latitude 06^o52¢N; Longitude 07^o24¢E, and altitude of 447.2 m above sea level).

Characterization and hybridization of the cowpea accessions.

The characterization and hybridization of the cowpea accessions were done between April and November in the 2006 and 2007 cropping seasons. The characterization of the cowpea accessions was done using a Randomized Complete Block Design (RCBD), with the cowpea accessions as treatments replicated three times. The planting was done using an intra- and inter- row spacing of 1m x 1m. The experimental unit was 4m x 4m (16m²). Hybridization of cowpea accessions was carried out using the method of Utuk (1974). Flowers were emasculated and pollinated artificially using a pair of forceps. The forceps were immersed periodically in 70% ethanol between crosses to prevent contamination by unwanted pollens. All the pollinated flowers were carefully tagged. Reciprocal crosses were made between SD and DN cowpea accessions and the F₁s generated were allowed to self pollinate to obtain the F₂. Crossing each F₁ to the respective seed parent (BC₁) and pollen parent (BC₂) was done to generate the backcrosses. The F₁, F₂, BCs and parental populations were evaluated using the randomized complete block design (RCBD) with three replications. The plots were weeded manually to keep weed pressure low. Flower and pod insect pests were controlled using Lamdacylochrim^R at the rate of 600ml in 1000 litres of water ha^-1.

Data Collection

The data collected included days to 50% emergence, number of leaves plant^-1, vine length, number of primary branches plant^-1, days to first flowering, days to 50% flowering, number of flowers plant^-1, number of peduncles plant^-1, number of pods plant^-1, pod length, number of seeds pod^-1, 100-seed weight and grain yield. Vine length measurement and count of number of leaves plant^-1 and number of primary branches plant^-1were carried out at 4, 8, and 12 weeks after planting (WAP). The number of days to first flowering was recorded as the number of days from sowing to first flower production, defined as corrolla colour visible. Days to 50% flowering was monitored as the number of days from sowing to when 50% of the plants flowered. The number of flowers plant^-1, peduncles plant^-1, and seeds pod^-1 were obtained by counting. The number of pods per plant was determined by the total counts of pods in a plot divided by the total number of plants in the plot. The weight of 100-seeds was taken and grain yield plot^-1 was weighed and converted to hectare equivalent.

CHAPTER THREE

RESULTS

The weather data for Nsukka for 2006 and 2007 cropping seasons are presented in Table (1). The mean values of temperature from April-November in 2006 and 2007 were 28.7⁰C and 29.8⁰C, respectively. This temperature is near optimum values for reproductive development of cowpea (Ishiyaku et al., 2005). The photoperiod ranged from 10hd^-1 to 13.4hd^-1.The lower limit of this photoperiod (10hd^-1) was obtained between September and November and it provides the short day condition, while the upper limit (13.4hd^-1) recorded between April and August provides the long day condition. The description of the cowpea accessions used for the study are presented in Table (2).

Parental differences among the 10 cowpea accessions in days to first and 50% flowering for the two cropping seasons are presented in Table (3). The cowpea accessions differed significantly (P<0.05) in days to first flowering. The mean number of days to first flowering for DN cowpea accessions ranged from 40-42 days, while the SD accessions had significant (P<0.05) delay as it took between 56-66 days before flowering. Days to 50% flowering followed the same trend as SD accessions took longer time (ranging from 58-72 days) to flower when compared to the DN accessions (43-46 days). There was however no significant difference between the two cropping years as well as the interactions between the cowpea accessions and years.

CHAPTER FOUR

Correlation

The correlation coefficients of days to flowering and yield components of the parental lines averaged over two cropping seasons are presented in Table (12). Days to first and 50% flowering had significantly positive correlations with number of flowers plant^-1 and 100-seed weight. Grain yield was however, negatively correlated with days to first and 50% flowering. A non significant inverse relationship was recorded when days to 50% flowering was correlated with number of peduncles plant^-1, pods plant^-1 and seeds pod^-1. Significant positive relationships were however, obtained when grain yield was correlated with number of peduncles plant^-1 (0.796**), number of flowers plant^-1 (0.774**), number of pods plant^-1 (0.758**) and pod length (0.728**).

Correlation matrix of days to first and 50% flowering and yield components of F₁ populations of crosses between SD and DN cowpea accessions are presented in Table (13). Though the correlation values for most characters were not significant, a positive relationship was recorded between days to flowering and all yield components. When mean grain yield was correlated with days to first and 50% flowering, inverse relationships were obtained. The number of flowers plant^-1 was however, highly significant (P<0.01) when correlated with days to first (0.889**) and 50% (0.870**) flowering. The result of the F₁ progenies also recorded significant positive correlations between grain yield and number of peduncles plant^-1(r=0.623), number of flowers plant^-1(r=0.672), number of pods plant^-1(r=0.730), pod length (r=0.760) and seeds pod^-1(r=0.601).

CHAPTER FIVE

DISCUSSION

The number of days from sowing to flowering is of great importance in cowpea, as it affects pod set and crop yield. In this study, days to first flowering in SD cowpea accessions was prolonged significantly (P<0.05) when compared to those of DN accessions. For instance, the number of days from sowing to first flowering in Bwa-Tal averaged 61 days, while that of Akidi-ani was 40 days. The 21 days difference between these accessions is greater than the 11 days reported by Ehlers and Hall (1997) for some cowpea genotypes grown under inductive photothermal environments, with temperature of 24-30⁰C and photoperiod of 11h d^-1.

CONCLUSION

The study established the accessions from Plateau state as short day (SD) plants and those from Enugu state as day neutral (DN) plants. The DN cowpea accessions were poor yielding in contrast to the SD accessions with delayed flowering but better yielding potentials. The production of hybrids between these two groups of cowpea would make a mark in the current drive for sustainable crop yield for the teaming population in the sub-saharan Africa. The emerging progenies would flower irrespective of day length with inbuilt endowments for enhanced yield determining attributes.

REFERENCES

Adam, E., L.K. Bognar, C. Kolar, E. Schafer, and F. Nagy (1996). Expression of a tobacco phytochrome B gene. Plant Physiol. 110: 1081-1088.
Adams, S. R., S. Pearson, and P. Hadley (1998). An appraisal of the use of reciprocal transfer experiments: assessing the stages of photoperiod sensitivity in Chrysanthemum cv. Snowdon (Chrysanthemum morifolium Ramato). J. of Experimental Botany, 49:1405-1411.
Adeyanju, A. O. and M. F. Ishiyaku, (2007). Genetic study of earliness in cowpea cowpea [Vigna unguiculata (L.) Walp] under screen house condition. Int. J. Plant Breed. Genet., 1: 34-37
Adeyanju, A.O., M.F. Ishiyaku and L.O. Omoigui, (2007). Inheritance of time to first flower in photo-insensitive cowpea (Vigna unguiculata (L.) Walp.). Asian J. Plant Sci., 6: 435-437.
Amujoyegbe, B.J. and Obisesan, I.O. (1997). Determining alternative pathways toward grain yields in 32 varieties of cowpea (Vigna unguiculata (L) Walp). Ife J. Agric. 19 (1 and 2): 79-91.
Aruah, B. C., Uguru, M. I. and Oyiga, B. C. (2010). Variations among some Nigerian Cucubita species. African Journal of plant Science. 4: 374-386
Awopetu, J.A. and M.O. Aliyu (2000). Genetic diversity in Vigna unguiculata (L.) Walp (Fabaceae). Moor J. of Agricultural Research, 1: 22-31.
Bhor, T.J., N.S. Kute, A.D. Dumbre and N.D. Sorode (1997). Heterosis and inbreeding depression in Cowpea. Indian Journal of Agricultural Research, 31: 122-126.
Biradar,B.D., J.V. Goud and S.S. Pati (1997). Differential expression of pleiotropic genes for pigmentation in cowpea [Vigna unguiculata (L.) Walp.]. Crop Research (Hisar), 14(2): 233-242.
Caspari, E. (1936). Cytoplasmic Inheritance. In: Advances in genetics, volume II. M. Demerec (ed.). Academic Press Inc., New York, pp 1-66
Cha-um, S. and K. Chalermpol, (2007). An alternative protocol for flowering induction of Thai Indica rice (Oryza sativa L. sp. indica) using a short-day photoperiod treatment. J. Agron., 6: 68-74.
Craufurd, P.G., Q. Aming, R.F. Summerfield, R.H.Ellis and E.H. Ro

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