Crop genetic diversity is the most important factor for a long-term sustainable production system. Breeding and production strategies for developing and growing uniform and homogenous varieties have created many problems. Such populations are static and very sensitive to unpredictable stresses. In Nepal, more than 80% of the seed system is informal, which has contributed greatly to creating and maintaining genetic diversity within the field. This paper aims to assess and present the approaches and advantages of increased crop genetic diversity in the fields, based on the experiences of implementing on-farm conservation activities carried out in Nepal for last two decades. Some of the evidence has been derived from an ongoing evolutionary plant breeding (EPB) project being implemented in Nepal. The information is supplemented with field assessments, focus group discussion, and a literature review. The major approaches to increase crop genetic diversity are evolutionary plant breeding, cultivar mixture, landrace enhancement, informal seed systems, the bulk method, diversifying the seed sources, participatory plant breeding, open pollination, etc. EPB and cultivar mixture are very simple and effective approaches to increase crop genetic diversity at field level. The involvement of farmers in these approaches helps to accelerate the population improvement, maintaining the higher degree of genetic diversity. The major advantages of increased crop genetic diversity are seed maintenance by farmers themselves, minimal risk of crop failure, resilience to unpredictable stresses, increased amount of diversified nutrition, production increment, ease of producing organically, etc. However, there are some issues and problems associated with mixtures and intra-varietal diversity; for example, not being able to harvest by machine, maturing at a different date, difficulty in maintaining seeds and registration, etc. Crop genetic diversity should be considered as a sustainable approach for a climate-resilient and self-dependent production system. The higher the genetic diversity in farming land, the more chance of receiving multiple benefits in the agriculture system.

Field trials of rice and bean dynamic mixtures were carried out in low input and hill farming systems of Nepal from 2019 to 2021 to improve productivity and resilience. The rice trials were conducted in two locations (Jumla and Lamjung) and those on bean in Jumla, using a randomized complete block design with three replications. Dynamic mixtures were constructed from landraces, improved varieties and breeding lines for both crops. A total of 48 bean entries were used in Jumla, whereas 56 and 66 rice entries were used to make location-specific dynamic mixtures in Lamjung and Jumla, respectively. They were formed by mixing diverse varieties as a strategy to maintain a broad genetic base. Farmers (men and women) and technicians selected from the most complex mixture and the selections were added to the trials starting from second year. In rice, some mixtures and selections from the mixtures gave grain yield comparable to the improved check and higher than the local checks. In the case of bean, differences between entries were not significant but some of the selections received a high preference score. Overall, the dynamic mixtures appear as a reliable material for sustainable increase in yield in the low input and hill farming system of Nepal.

Maize (Zea mays L.) is one of the most productive crops worldwide. As a heterotic crop predominantly grown as F₁ hybrid, maize exhibits challenges for genetic studies of complex traits, since homozygous genotypes, which are largely used in these studies, may not accurately reflect what happens in cultivated conditions. To map Fusarium Ear Rot (FER) resistance to Fusarium verticillioides and traits with potential impact on yield, including phenology, we constructed a recombinant intercross (RIX) population. This was achived by crossing pairs of recombinant inbred lines (RILs) derived from a multi-parent maize population. We characterized the RIX population over two growing seasons, employing artificial F. verticillioides inoculation. The heterozygous background of the material enabled the identification of QTL and candidate genes through in silico reconstruction of RIX genotype probabilities. A total of 37 loci were identified using single-year BLUPs while 29 with joint-year BLUPs. These, included several known QTL associated with days to tasseling, kernel row number and a QTL on the chromosome 9 associated with FER resistance. In this region, we could identify candidates based on their predicted functions and potential roles in plant-pathogen interactions and/or resistance mechanisms. These QTL represent potential breeding targets to FER resistance and yield components in commercial maize varieties.