No abstract

A novel cropping system for potato was tested for two consecutive years under normal Dutch agronomic conditions. Seedlings from two experimental genotypes of hybrid true potato seeds were produced in a greenhouse nursery and transplanted into the field 5 weeks after sowing to assess tuber yield levels and to study effects of hilling on tuber yield and number, tuber size distribution and tuber greening. Field experiments had a split-plot design with hilling treatments as the main plots and genotypes as the sub-plots. Final harvest was at 122 and 132 days after transplanting in 2017 and 2018, respectively. Hybrid seedlings were transplanted into small initial ridges and irrigated straight after planting. Three hilling treatments were applied between transplanting and 100% canopy cover. Treatment ‘zero hilling’ did not receive any additional hilling after transplanting. Treatments ‘double hilling’ and ‘triple hilling’ received two and three additional hilling treatments, respectively. Total tuber yields at final harvest in both years were not affected by the hilling treatments. Yields for the respective genotypes were 26 and 30 Mg/ha in 2017 and 25 and 32 Mg/ha in 2018. Total tuber numbers were only affected by hilling treatments in 2017, where under hilled conditions, plants produced more tubers compared with plants under zero hilling. Plants under zero hilling yielded more tubers in size class > 40 mm compared with triple hilling in 2017. In 2018, no significant effects of hilling on tuber numbers were found, but the trend was similar to that in 2017.

We integrated recent research on cardinal temperatures for phenology and early leaf growth, spikelet formation, early morning flowering, transpirational cooling, and heat- and cold-induced sterility into an existing to crop growth model ORYZA2000. We compared for an arid environment observed potential yields with yields simulated with default ORYZA2000, with modified subversions of ORYZA2000 and with ORYZA_S, a model developed for the region of interest in the 1990s. Rice variety ‘IR64’ was sown monthly 15-times in a row in two locations in Senegal. The Senegal River Valley is located in the Sahel, near the Sahara desert with extreme temperatures during day and night. The existing subroutines underestimated cold stress and overestimated heat stress. Forcing the model to use observed spikelet number and phenology and replacing the existing heat and cold subroutines improved accuracy of yield simulation from EF = −0.32 to EF =0.70 (EF is modelling efficiency). The main causes of improved accuracy were that the new model subversions take into account transpirational cooling (which is high in arid environments) and early morning flowering for heat sterility, and minimum rather than average temperature for cold sterility. Simulations were less accurate when also spikelet number and phenology were simulated. Model efficiency was 0.14 with new heat and cold routines and improved to 0.48 when using new cardinal temperatures for phenology and early leaf growth. The new adapted subversion of ORYZA2000 offers a powerful analytic tool for climate change impact assessment and cropping calendar optimisation in arid regions.

No abstract

Genetic gain in potato is hampered by the heterozygous tetraploid genome of cultivated potato. Converting potato into a diploid inbred-line based F1-hybrid crop provides a promising route towards increased genetic gain. The introduction of a dominant S-locus inhibitor (Sli) gene into diploid potato germplasm allows efficient generation of self-fertilized seeds and thus the development of potato inbred lines. Little is known about the structure and function of the Sli locus. Here we describe the mapping of Sli to a 12.6 kb interval on chromosome 12 using a recombinant screen approach. One of two candidate genes present in this interval shows a unique sequence that is exclusively present in self-compatible lines. We describe an expression vector that converts self-incompatible genotypes into self-compatible and a CRISPR-Cas9 vector that converts SC genotypes into SI. The Sli gene encodes an F-box protein that is specifically expressed in pollen from self-compatible plants. A 533 bp insertion in the promotor of that gene leads to a gain of function mutation, which overcomes self-pollen rejection.