Disease management factors influencing yield and quality of sorghum and groundnut crop residues

Supported by the CGIAR System-wide Livestock ProgrammeCrop residues from groundnut and sorghum constitute important fodder resources for dairy production and fodder trading on the Deccan Plateau in India. This paper addresses the effect of important diseases of groundnut and sorghum on pod and grain yield and crop residue yield and quality. In four genotypes of groundnut, late leaf spot (Phaeoisasariopsis personata) and rust (Puccinia arachidis) are the two major foliar diseases that together could reduce pod and haulm yield by 70% and in vitro digestibility of haulms by 22%. Two genotypes (ICGV 9202 and 92093) were highly resistant to these foliar diseases maintaining high pod and haulm yield as well as high in vitro digestibility of haulms (>62.3%) even under highest disease pressure. Important diseases in sorghum investigated were a viral disease caused by maize stripe virus (MStV) and anthracnose caused by Colletotrichum graminicola. MStV reduced grain yield by 30%, stover yield by 42% and digestible stover yield by 45%. Effects of MStV were highly genotype-dependent and grain and stover were affected in different ways in different varieties. The choice of appropriate genotype for a given farming situation will depend on trade-off scenarios for benefits from grain and stover. Similarly, anthracnose could reduce grain yield by 47% and stover yield by 23% but effects on stover quality were variable. As observed for MStV, effects of anthracnose were highly genotype-dependent and genotypes were identified that maintained high grain and stover yield under high disease pressure

Prevalence of major foliar and panicle diseases of Sorghum (Sorghum bicolor [L.] Moench) in the Deccan Plateau of India

Extensive on-farm disease surveys were conducted from August 1999 until March 2001 in four sorghum-growing states of the Indian Deccan plateau. A total of 965 fields were surveyed covering 228 fields in Andhra Pradesh (AP), 406 in Karnataka (KAR), 290 in Maharashtra (MH) and 41 in Tamil Nadu (TN). Among 14 foliar diseases observed, maize stripe virus (MStV), a tenuivirus transmitted by the delphacid plant hopper (Peregrinus maidis), and among five panicle diseases, ergot or sugary disease (Claviceps sorghi and C. africana) were the most destructive diseases. MStV was prevalent in 28.4% and ergot in 13.4% of the fields surveyed in two years across four states. Yet, the mean incidence of MStV in AP was 6% with 85% mean severity. The values in KAR were 12% incidence and 83% severity, in MH 5% and 67%, and in TN 12% and 76%, respectively. The mean incidence of ergot in AP was 34% with 67% mean severity. The values in KAR were 41% and 79%, in MH, 30% and 67%, and in TN 100% and 100%, respectively. Variation in frequency of occurrence of MStV was observed between 1999 and 2001. Variations in frequency could be due to weather factors, vector survival, cropping pattern, and host specificity. The frequency of ergot also was varying among years, locations, seasons and cultivars. An ergot epidemic was observed during the 1999 rainy season in Maachinenipalli village (16°35′N; 78°3′E), Andhra Pradesh. In September 2000, the disease had spread to 13 neighboring administrative zones damaging about 130,000 ha. This paper elucidates the distribution of diseases observed between 1999 and 2001 but does not imply that the diseases are restricted necessarily to a particular zone or location

Effect of temperature and humidity regimes on grain mold sporulation and seed quality in sorghum (Sorghum bicolor (L.) Moench)

Grain mold, induced by a number of non-specific fungi, causes substantial loss to seedgrain yield and quality in sorghum (Sorghum bicolor (L.) Moench). Fungal sporulation and grain mold severity are greatly influenced by temperature and relative humidity (RH) levels. We studied the effects of three incubation temperatures (25, 27 and 288C) and two sets of RH levels (first set: 85, 90, 95, 98, and 100%, second set: 95, 96, 97, 98, 99 and 100%) on sporulation and grain mold severity in three major mold fungi (Curvularia lunata, Fusarium moniliforme, and Bipolaris australiensis) and on four each of resistant, moderately resistant and susceptible sorghum genotypes for sporulation and mold severity of major fungi. Results indicated that both fungal sporulation and grain mold severity increased on most sorghum genotypes with increasing incubation temperature from 25 – 288C and RH levels from 95 –98%. A linear relationship was observed among RH levels, grain mold severity and fungal sporulation. The highest sporulation of all the three fungi occurred at 288C and 98% RH after 5 days of incubation. Among the three fungi, C. lunata grew and sporulated faster than B. australiensis and F. moniliforme, in that order. Among the sorghum genotypes, IS 25017 supported the least sporulation and had the lowest mold severity, followed by IS 8545 and PVK 801. Seed quality parameters, such as seed germination, seedling vigor index, field emergence potential, dehydrogenase and þ-amylase activities declined significantly with increasing temperature and RH levels that supported heavy sporulation and grain colonization