Breeding for resistance to grain mold, an economically important disease of sorghum, has been only partially successful. Hybrid technology is well developed in sorghum due to availability of the cytoplasm male sterility (CMS) system and at present almost all commercial hybrids are based on the A(1) CMS system. To compare the available alternate CMS systems for grain mold resistance, 72 hybrids were produced by crossing 36 A-lines (six CMS systems; A(1), A(2), A(3), A(4(M)), A(4(G)), A(4(VZM)) each in six nuclear backgrounds) with two common restorers, and were evaluated during the 2006 and 2007 rainy seasons in grain mold nursery at ICRISAT. Data analyses indicated influence of cytoplasm on the responses of hybrids to grain mold infection as measured by panicle grain mold resistance (PGMR) score. The A(1) cytoplasm seemed to contribute to grain mold resistance followed by A(4(VZM)) and A(2) cytoplasms. The A(4) (M) cytoplasm had superior general combining ability (GCA) effects while the A(1) and A(4(VZM)) cytoplasm based hybrids had superior specific combining ability (SCA) effects on the PGMR score. Almost all hybrids had significant mid-parent heterosis. The A(1) cytoplasm is the best suited for the development of sorghum hybrids for the rainy season adaptation with grain mold resistance. However, use of alternate cytoplasms (A(2) and A(4(VZM))) for hybrid development will not increase susceptibility to grain mold in commercial grain production. (C) 2011 Elsevier Ltd. All rights reserved.

Grain mold, the most important and widespread disease of sorghum worldwide, is a major constraint to sorghum productivity. Grain mold development is particularly severe in the shortduration hybrid cultivars and varieties that are grown during the rainy season under warm and humid conditions. It is caused by a number of unspecialized fungal pathogens that severely affect grain mass, seed viability, grain quality and market price. A large volume of literature is available on studies related to various aspects of grain mold, including biology, epidemiology, association with mycotoxins and management methods. In this bulletin, attempts have been made to briefly describe the important findings of research done at ICRISAT and elsewhere, and to emphasize some of the recent developments on management of grain mold, including refined screening techniques, sources of resistance, genetics and mechanisms of resistance, resistance breeding and other management options, including an integrated management approach. Cover: Moldy sorghum grains on different types of panicles, and a mold-free panicle on the extreme right. Copyright© International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), 2006. All rights reserved. ICRISAT holds the copyright to its publications, but these can be shared and duplicated for non-commercial purposes. Permission to make digital or hard copies of part(s) or all of any publication for non-commercial use is hereby granted as long as ICRISAT is properly cited. For any clarification, please contact the Director of Communication at icrisat@cgiar.org >. ICRISAT’s name and logo are registered trademarks and may not be used without permission. You may not alter or remove any trademark, copyright or other notice.

Sprinkler irrigation was used to provide high humidity during the flowering to grain maturity stages. The experiment used a completely randomized block design with two replications. Each entry was sown in two rows of 4 m with a spacing of 75 cm between rows and 10 cm between plants within a row. The hybrids and their parents were scored for grain mold severity (panicle grain mold rating, PGMR) at physiological maturity on 10 tagged panicles in each plot using a 1-9 scale, where 1 = no mold, 2 = 1-5%, 3 = 6-10%, 4 = 11-20%, 5 = 21-30%, 6 = 31-40%, 7 = 41-50%, 8 = 51-75%, 9 = >75% grains colonized by grain mold fungi. The threshed grain mold rating (TGMR) was also taken on bulked grains from the same 10 tagged panicles per plot using the same 1-9 scale. Statistical analysis. The computed mean PGMR and TGMR scores were used for analysis of variance (ANOVA) and for estimation of the general combining ability (gca) of the parents, and the specific combining ability (sca) and mid-parent heterosis of the crosses (Kempthorne 1957). The cytoplasmic differences for gca of A-lines and per se responses and sca effects of hybrids for PGMR and TGMR were tested for critical difference (CD). The difference between A1- and A2-based hybrids for mid- parent heterosis was tested using the paired t-test.