Dead Heart Percentage Research Articles

Some effects of plant densities and carbofuran on the damage byDiopsis thoracicaWest, andMaliarpha separatellaRag. and yield of rice in Nigeria

Abstract In a field study of the effects of plant densities and carbofuran on damage by Diopsis thoracica Westwood and Maliarpha separatella Ragonot, significant increases were recorded in the percentage of dead hearts and bored stems in widely spaced rice plants. Carbofuran treatments resulted in significant control of borers, the best treatment being that covering early growth up to 40 days after transplanting. There was a significant depression of yield components and total yield with closer spacing. Yield increases of 59%, 32% and 55% for the 1983 planting, and 55%, 35% and 50% for the 1984 planting, were recorded when carbofuran was applied to cover the periods 0 to 40, 40 to 80, and 0 to 80 days after transplanting, respectively.The percentage of dead hearts and bored stems increased with increasing seedling density. The yield components, however, did not show any significant differences.

Trichomes in Segregating Generations of Sorghum Matings. II. Association with Shootfly Resistance1

The shootfly (Atherigona soccata Rond.) is a major seedling pest of sorghum in Asia and Africa. To determine whether the presence of nonglandular trichomes on the leaf lamina was associated with resistance to shootfly, trichomed, segregating, and trichomeless F2— derived lines in the F3 and F4 from four trlchomed ✕ trichomeless sorghum matings and their parents were studied at ICRISAT Center, Patancheru, India. Trichomed lines had significantly lower percentages of plants with shootfly eggs 18 days after emergence and of deadhearts (killed central shoot) at both 18 and 23 or more days after emergence. The ratio of the difference between the means of trichomed and trlchomdess lines for the percentage of deadhearts to the corresponding difference between the parents ranged from 0.16 to 0.92 and exceeded 0.32 in seven of nine comparisons. Thus, trichomes were clearly a major factor, but not the only factor, involved in resistance. Means of the parents and trichomed, segregating, and trichomeless offspring were regressed on four possible genetic models. The results indicated that at least two additional loci that interact with each other were involved in resistance. Trichome density was examined as a possible factor in resistance, but correlation of deadheart percentage with the density of trichomes was low and nonsignificant.

Ovipositional preference and antibiosis in relation to resistance to a sorghum shoot fly.

In greenhouse tests of ovipositional preference by Atherigona varia var. soccata, the Indian varieties M35-1, IS2123, IS8315 and IS5470 and the foreign variety IS3691 were used. The above Indian varieties, except IS8315, and CSH2 (the male parent of which is the foreign variety IS3691) were also examined in the field for ovipositional preference. Antibiosis was measured by larval survival and by adult emergence on the Indian varieties M35-1 and IS2123 and on the foreign variety Swarna in greenhouse tests. When adults of A. varia var. soccata were given a choice between foreign and Indian varieties in both field and greenhouse tests, the former were highly preferred for oviposition. Damage, as measured by the percentage of dead hearts (damaged growing points), was significantly higher in foreign than in Indian varieties when there was a choice for oviposition; when there was no choice, foreign and Indian varieties were damaged equally. Some degree of antibiosis was observed; larval survival was around 90% on Swarna compared with 77% and 80% on IS2123 and M35-1, respectively. Adult emergence was about 54% on M35-1 compared with 71% and 66% on Swarna and IS2123, respectively.ADDITIONAL ABSTRACT:Greenhouse and field studies in Andhra Pradesh, India, indicated that, when given a free choice, adult females of Atherigona soccata Rond. (varia soccata) greatly preferred to oviposit on exotic varieties of sorghum than on native ones; preference was judged by the mean number of eggs per plant and the percentage of plants infested. Although damage (measured as the percentage of dead hearts) was significantly higher on exotic varieties in free-choice tests, the two types of varieties were equally damaged in no-choice tests. Larval survival and adult emergence differed with variety