Accumulation of pearl millet downy mildew resistance in Mali--2006 results

Few crop breeding programs today are breeding crops in their areas of diversity and origin. This study reports on a Malian breeding program in an area of genetic diversity. It has the objective to accumulate resistance to major populations of Sclerospora graminicola (= Sg) with modern breeding and selection methods. This study is part of the development of pearl millet top cross hybrids, with a reduced plant height, Sg-resistance (= resistance to pearl millet downy mildew) and 'stay green' at physiological maturity. The parent entries, among other relevant characteristics, were selected for a high level of resistance (good sources of resistance) making use of a combination of artificial young plant screening methods and single location field testing, in 1998. Pedigree selection in F1 to F4 was from 1999 to 2002. Its synthetics and composites were selected for low S. graminicola-levels, in 2003 to 2005 and in 2003 and 2006 tested for S. graminicola-resistance together with 5 checks at two Locations differing in S. graminicola-virulence responses. The 2006 test seemingly indicated the expected quadratic checks, whereby entry 1 is resistant at location 1 and susceptible at location 2 and entry 2 is susceptible at location 1 but resistant at location 2. This quadratic check is indicating differences in virulence between the two S. grominicola-populations and also an adaptation of the pathogen populations on the newly accumulated genes for resistance in the host. It is also indicating that one or more genes for resistance against each of the two populations were accumulated. A good number of synthetics and composites combined low S. graminicola-incidences with relatively high yields and some had 'stay green' at physiological maturity. One too late entry seemingly had immunity. The 2006 results indicate presence of several S. graminicola-resistance genes in the parent entries and accumulation of one or more genes in certain derived entries, and were obtained in combination with reduced plant height and for the first time in pearl millet also with 'stay green' at physiological maturity. The accumulation of S. graminicola-resistance is expected to increase the chance for regional or global 'stay green' hybrids for grain (medium tall) and fodder (tall).