Management of septoria tritici blotch using cultivar mixtures

Septoria tritici blotch (STB) is among the most devastating diseases in European wheat production. In recent years, there has been increased interest in using cultivar mixtures as part of an integrated control strategy against diseases. This study investigated different cultivar mixtures for their ability to control STB across three years and at seven trial sites in Denmark with a range of fungicide strategies, yielding a total of 194 individual cultivar mixture combinations. The mixtures were composed of two, three or four cultivars which were either similar or contrasting in their susceptibility to STB. Across all trials, the cultivar mixtures reduced disease severity significantly, by 14% compared to the component cultivars grown in monoculture. The reductions were larger when the disease pressure was high and when the mixtures included more cultivars. Mixtures composed of four cultivars reduced disease severity significantly, by 24%. Across all trials, cultivar mixtures significantly increased yield by 2% compared to the component cultivars grown in monoculture. The yield increase was significant for plots treated with one or two fungicide applications, and cultivar mixtures increased yield significantly, by 4.4% in untreated plots. The yield increase was smaller for mixtures with a high proportion of resistant cultivars. Based on the results from this study, cultivar mixtures can contribute positively to an IPM strategy, by reducing disease severity for STB and increasing yield. The most pronounced benefits from cultivar mixtures were found in fields with moderate to low fungicide input, under conditions with high disease pressure, when combining four cultivars with varying susceptibilities.

Growing tall and dwarf rice cultivars in mixture for better weed management and higher yield

Growing two or more cultivars of same crop species in mixture reduces intra-specific competition for natural resources and increases competitive ability of crops against weeds and thus enhances crop yield. The objective of this study was to evaluate the potentiality of growing rice cultivars in mixtures for minimizing weed pressure and increasing rice yield. The experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during Aman season (July-December) 2017. Two transplant Aman rice cultivars viz. Binadhan-13 (tall, late- maturing and fine grain aromatic cultivar) and BRRI dhan49 (semi-dwarf, mid-maturing and coarse grain cultivar) were grown following two spatial arrangements viz., alternate row and alternate hill, and nine different cultivar mixture (Binadhan-13:BRRI dhan49) row ratios viz., 1:0, 1:2, 2:1, 2:3, 3:2, 2:4, 4:2,1:1 and 0:1. The experiment was laid out in a randomized complete block design (RCBD) with three replications. Results confirmed the positive influence of spatial arrangement and cultivar mixture ratio on rice productivity. Both the cultivars showed better growth and higher yield when grown in mixture irrespective of ratios compared to their sole culture performances. But cultivar mixture ratio showed no advantages over sole culture in suppressing weeds. Based on the total yield Binadhan-13 and BRRI dhan49 inter-planted in 1:1 row ratio following alternate hill performed the best resulting in 50% and 12% yield advantages over sole culture of Binadhan-13 and BRRI dhan49, respectively. Therefore, growing tall and dwarf rice cultivars in mixture can be adopted as a tool for increasing rice productivity. J. Bangladesh Agril. Univ. 17(2): 133–141, June 2019

Grain and straw yield interactions in barley cultivar mixtures

Cultivar mixtures of winter barley and spring barley, together with their component monocultures, were grown in field trials to assess the effect of cultivar combinations on both straw and grain yield. The overall grain yields for all trials were significantly higher for the cultivar mixtures than for the corresponding component monocultures. Also, significant decreases in rhynchosporium disease severity for cultivar mixtures were recorded for most non-fungicide treatments. The size of these responses was often significantly correlated with the component number of the mixtures. The amount of straw produced in mixtures was sometimes changed significantly, but not always in a positive direction and it was only correlated with increasing mixture component number in two environments. No correlation of straw yield potential of cultivars with performance in mixtures was found. Cultivar × cultivar mixture × environment interactions appeared to affect the relative yield of grain and straw differentially and therefore it was not possible to predict the effect of mixtures on the harvest index.