| Results and Discussion On the basis of number of leaves affected and degree of deficiency symptoms, the genotypes were grouped into different ratings of efficiency, viz. Mn-efficient, slightly less efficient, medium efficient, inefficient and highly inefficient (Table 1). Seventeen aestivum and 25 durum genotypes developed very severe Mn deficiency symptoms: 19 aestivum and 15 durum exhibited severe symptoms (rated highly inefficient- and inefficient respectively). Seven aestivum and one durum produced moderate and a similar number mild deficiency symptoms (rated moderately less efficient and slightly less efficient respectively). One aestivum (Nadodores 63) and two durum genotypes viz. ED 2398 and E 2153 did not show any visible deficiency symptoms even up to 70 days of growth and were rated Mn-efficient. Among the aestivum, Chinese spring Lr 9 CS and those with allian genes (lines 2518, 2519, 2956), Spica and a Thatcher (Acc. 1408) showed only slight susceptibility. Similarly the durum RL 3661 showed mild symptoms of Mn deficiency. On the other hand 25 aestivum (including popularly cultivated WL 711) and 41 durum were highly Mn-inefficient (Table 1). The rest had moderate deficiency symptoms. The degree of Mn-inefficiency (susceptivility) did not relate to the time of appearance of sympotoms. In some genotypes, very severe symptoms appeared as late as 40 - 50 days while in others as early as 20 days from the date of planting (Table 2). The deficiency symptoms in most of the genotypes started on the 3rd leaf from below except in highly inefficient ones. The delay in appearance of symptoms may be related to Mn content of grain resulting from variation in sources and capacity to accumulate Mn in the grain. The genotypic efficiency was, however, not related to plant height and number of leaves per plant but was negatively related to number of tillers. The significance of the findings lies in the suggestion that the parents which are susceptible to Mn deficiency should be excluded from the breeding programmes although they may have other desirable characters viz. disease resistance etc. Studies are in progress to determine the mode of inheritance of Mn-deficiency tolerance with respect to number of genes and dominance. References KAUR, N.P. & P.N. TAKKAR. 1987. Effect of Mn stress on the growth and yield parameters in wheat and triticale cultivars. Wheat Information Service 64: 24-33. NYBORG, M. 1970. Sensitivity to manganese deficiency of different cultivars of wheat, oat and barley. Can. J. Plant Sci. 50: 198-200. VOSE, P.B. & D.J. GRIFFITHS. 1961. Manganese and magnesium in the grey speck syndrome of oats. Nature 191, 299-300. |
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