Barley lesion mimics,supersusceptible or highly resistant to leaf rust and net blotch

Lesion mimic mutants of plants have the feature of spontaneously displaying necrotic spots or bands on their leaves. Lesion mimics have often displayed enhanced resistance to biotrophic pathogens whilst showing increased susceptibility to necrotrophs. This paper identifies three novel, non‐allelic mutants of barley (Hordeum vulgare), which spontaneously form necrotic leaf lesions: Necrotic leaf spot 9.3091 (nec9.3091), Mottled leaf 8.1661 (mtt8.1661) and Mottled leaf 9.2721 (mtt9.2721). The Necrotic leaf spot 8.3550 mutant (nec8.3550), formerly known as bst1, was included in the study because it is a lesion mimic mutant belonging to the same original pool. The reactions of the mutants to the biotroph Puccinia hordei and the necrotroph Pyrenophora teres f. sp. teres were investigated. Mutants nec8.3550 and mtt8.1661 were more resistant than the parental Bowman near‐isogenic line with the Rph3.c gene (Bowman Rph3.c, NGB 22452) to leaf rust, caused by P. hordei. Mutants nec8.3550, mtt8.1661 and mtt9.2721 were more susceptible than Bowman Rph3.c to net blotch, caused by P. teres f. sp. teres. Autofluorescence was detected in leaf tissues of all mutants. Based on the high expression of the PR1 and Hv‐HIR genes, combined with the low susceptibility to P. hordei, nec8.3550 appears to have entered a state of systemic acquired resistance, which is quite distinct from the resistance expressed in mtt8.1661. The latter mutant has low or no expression of PR1 and Hv‐HIR genes, yet it is highly resistant to rust. It is also extremely susceptible to net blotch. These mutants can serve as genetic sources of novel disease resistance for barley improvement.     

Optimising quality-parameters of apple cv. ‘Pigeon’ by adjustment of nitrogen

To improve the productivity and quality of the apple cultivar ‘Pigeon’ the influence of 5 fertigation levels (14, 42, 70, 112, 224 mg N/l) and 3 widths of herbicide strip (0.2, 0.5, 1.0 m) were investigated on growth, yield and post-harvest quality/colour development of fruit. ‘Pigeon’ apples are picked when ca. 20% of the fruit skin has turned red, the fruit are then exposed to a sunning period on the orchard floor of 2–3 weeks to enhance red colour development (80% red skin); however the internal quality deteriorates during this period. Fruit drop occurs if fruit are left on the tree to develop colour. This study focused on how to reduce the length of the post-harvest sunning period to maximise both colour development and fruit quality. It was demonstrated that 14 mg N/l resulted in a low yield, small fruit, low vegetative growth, and low N content in leaf dry matter, but good fruit colour development. Excessive N fertigation (224 mg N/l) did not produce the significantly highest yield or the largest fruit, but it did enhance vegetative growth and resulted in less fruit colouration. N fertigation influenced optimal picking date; higher N fertigation delayed the time of picking, and increased the incidence of green fruit. Fruit from the high-N treatments required more days of post-harvest sunning to obtain the comparable red skin colour than fruit from the lower N-treatments. However, when all treatments were picked at ca. 20% fruit coloration it was not possible to reduce the length of post-harvest sunning period by N-supply. Most of the post-harvest colour development occurred within the first 6–9 days following harvest; colour developed on both sides but was enhanced on the shade side of the fruit. The shade side of the fruit had a greater potential for better red colour development than the blush side of the fruit.