COMBINING ABILITY OF MAIZE INBRED LINES RESISTANT TO STRIGA HERMONTHICA

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1 COMBINING ABILITY OF MAIZE INBRED LINES RESISTANT TO STRIGA HERMONTHICA Karaya H. 1,2, Kiarie N. 2, Mugo S. 1, Nderitu H. 2, Kanampiu F. 1, and Ariga S. 2 1 CIMMYT and 2 University of Nairobi 11 th World Congress on Parasitic Plants 7-12 JUNE 2011, MARTINA FRANCA, ITALY

2 Maize in Africa Maize is by far the most important staple food in Africa. It Provides 50% of all diets on average (Vivek, 2009). Lack of food means lack of maize in many parts of Kenya It is no. 1 constituent in livestock feed. The continent most often produces less than it consumes due to many constraints. Among the factors reducing production is Striga weed, an obligate weed parasite affecting many countries in East,West and South Africa.

3 Striga infestation in Africa- (Adapted from Gressel et al.,2004).

4 Striga s Economic impact in SSA In SSA 20-40M ha are infested annually (Kanampiu et al, 2003). Causes on average 40-60% yield loss that could go up to 100% in resource poor farms (Berner et al, 1995). Estimated to cause upwards of 7 billion tons lost annually. Affects livelihood of 110 million people

5 Striga In Africa we have 3 common species. Very prolific - 50, ,000 seeds/plant Seed germination is induced by stimulants from host and nonhost plants Longevity up to 20 years

6 Striga Species and geographic Distribution Striga hermonthica Widely distributed in cereals throughout Sub-Saharan Africa (SSA) Causes the greatest economic losses Purple flowers Striga asiatica Common in East and Southern Africa Attacks cereal crops Flower color varies Striga aspera Attacks cereal crops Common in northern Nigeria Deep purple flower colour

7 Devastating effect of Striga in a maize field

8 Options for striga control Agronomic practices-takes long to accrue benefits Herbicide use- Ethylene, Dicamba and Imazpyr Host plant resistance- Incorporation of more than one mode of Striga resistance offers a better solution to resource poor farmers. Populations resistant to Striga were made and inbred lines extracted. This research was designed to asses the combining ability of these inbred lines for possible use in F1 hybrids.

9 Objectives Goal To increase maize production through Striga control using HPR Specific objectives: 1. To study the combining ability of 20 inbred lines. 2. To identify single cross hybrids that can be: - grown in Striga infested areas by resource poor farmers - Used to develop three way and double cross hybrids resistant to Striga hermonthica

10 Materials and Methods Development of single cross hybrids North Carolina mating design II was used with 20 inbred lines. 14 inbred lines were used as females and factorially mated with six males to make 84 single crosses. The 84 SCs and 6 Checks were evaluated under artificial Striga infestation at 2 locations for 2 seasons.

11 Evaluating the single cross hybrids Artificial infestation with Striga The trial was planted in a 10x9 ά-lattice design at Kibos (0040S, 34480E) and Alupe (0290N, 34020E) in Kenya. An inoculum (10gms of Striga seeds in 5kg of fine sand) was applied per hill using a table spoonful. Good crop husbandry was observed.

12 Data collection & Analysis Data collection Striga emergence counts, 6 th, 8 th & 12 th WAP Striga damage rating-10 th WAP Anthesis silking interval Plant height, ear height, Number of ears per plant and grain yield. Analysis SAS statistical package was used Means were separated using LSD Significant genotype mean square was partitioned into GCA and SCA effects.

13 Results and Discussion The SC hybrids yielded higher (mean 6.7t/ha)- than commercial checks (3.6t/ha) (Table 1). Scs with good scores for Striga resistance traits were identified. Most of the SC hybrids performed well in terms reaction to diseases e.g E.turcicum.

14 Table 1. Field performance of SCs and Commercial checks Variety (Single crosses Grain Yield (t/ha) 50% anthesis (days) Striga damage rating (1-9) Strigacount per M2 (12 WAP) E. turcicum (1-5 4X X X Mean(SCs) Commercial checks-t Commercial checks-hr Commercial checks--s Mean( Checks) Mean CV LSD(0.05) SIG *** *** *** *** **

15 Figure 1. Yield performance of SCs and Commercial checks

16 Results contd. Pooled analysis of variance for combining ability revealed the presence of highly significance mean squares due to GCA for yield, days to anthesis, plant height, ear height, Striga counts, GLS score and E. turcicum scores (Table 2). This was an indication of additive x additive gene action.

17 Table 2: Mean squares for general and specific combining ability for various traits (1) Source Degrees of freedom Grain Yield (t/ha) 50% anthesis (days) Gray leaf spot (1-5) E. turcicum (1-5) REP ** SITE *** *** *** 2.186*** LINE GCA *** *** 1.854*** *** TESTER GCA *** *** 1.295*** SITE*LINE *** 0.564*** SITE*TESTER *** 0.509* LINE*TESTER (SCA) * *** 0.409** SITE*LINE*TESTER ERROR

18 Table 2: Mean squares for general and specific combining ability for various traits (2) Source Degrees of freedom Striga damage rating (1-9) Strigacount per M2 (6 WAP) Striga count per M2 (8 WAP) Strigacount per M2 (10 WAP) Striga count per M2 (12 WAP) REP *** 1.772*** 1.230*** SITE *** 1.374*** *** 8.004*** 8.240*** LINE GCA * 0.381*** 0.787*** 0.999*** TESTER GCA * 0.538*** 1.593*** 1.553*** SITE*LINE ** SITE*TESTER * 0.106** 0.168** LINE*TESTER (SCA) SITE*LINE*TESTER ERROR

19 Results contd. Interaction between site and line was observed for Striga counts 6 WAP, GLS and E. turcicum and site and tester was observed for Striga counts and GLS and E. turcicum leaf diseases Positive and significant SCA mean squares were only observed in the grain yield, GLS and E. turcicum.

20 Results contd. Positive and significant SCA for yield was observed in crosses 7x2, 13x4 and 14x2 (Table 3). The SC 13x4 & 14x2 were also Striga and disease resistant. The GCA/SCA mean square ratio exhibited a predominance of additive gene effects.

21 Table 3: Estimates of specific combining ability effects of some of the best single cross hybrids Crosses Grain Yield (t/ha) 50% days to anthesis (days) Striga count per M2 (6 WAP) Striga count per M2 (8 WAP) Striga count per M2 (10 WAP) Striga count per M2 (12 WAP) Glay leaf spot (score 1-5) Exserohilu mturcicum (score 1-5) 1X ** * 2X *** X ** X ** X2 0.74** * X * 7X * * 7X *** -0.19** ** 8X * * X * 11X * X4 0.83** ** 14X2 0.89**

22 Conclusion and recommendation Additive gene action was observed for the resistance traits Striga resistance & grain yield were found to be controlled by additive gene action Inbred lines 7, 13 & 19 with the highest GCA were identified as best combining Striga resistant lines and can be used in development of new maize varieties

23 Conclusion and recommendation Single crosses 13x4 & 14x2 exhibited good SCA for yield,striga and foliar disease resistance and can be multiplied and availed to farmers for direct use. Inbred lines 3,4,5,6,9 7 &11 were identified as good combiners both for GLS and E. turcicum

24 ACKNOWLEDGEMENTS CIMMYT University of Nairobi Kenya Agricultural Research Institute (KARI) International Institute for Tropical agriculture (IITA) IPPS European Weed Research Society (EWRS)

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